Quincy Compressor Motor Overheating

[wbrian63]

I've got a Quincy QV41C60VC model compressor. Tag on the unit says 15.6scfm@100psi, 15.2scfm @ 175psi. 5hp single phase motor.

The pressure switch cuts out at about 175psi. I've got a regulator on the outlet of the unit limiting the shop air pressure to about 100psi.

I've just added a media blasting cabinet using the TP Tools foot-operated gun (http://www.tptools.com/Build-Your-O...oot-Pedal-Operating-System,7190.html?b=d*8040), which states that it should work OK in shops with 10-15scfm available.

I've got the regulator on the blast cabinet set at about 90psi.

As I'm using the blaster, I can hear the compressor come on after a few minutes usage. It runs for a while, even while I'm using the blaster, then cuts off.

It will do this cycle 3 or 4 times - maybe 5 max - then the temp overload on the motor cuts out and I'm done blasting for a long time.

I've checked the input voltage to the unit - 240v. I've also checked the voltage while the unit is running - 240v.

After a single cycle of the compressor, I'm seeing approx 200f head temps on the low pressure cylinder, and 230f on the high pressure cylinder - using an IR thermometer.

Motor temps are about 140 through the rear casing holes at the rear end of the setup (opposite the pulley), and 160-170 through the front casing holes.

After the temp switch has tripped, the front #'s are about 180-195, rear #'s are 165-170.

The compressor is mounted in a closet that has a vent fan pulling 100cfm out of the closet. Feed air is about 85f.

When this happened the first time, the closet door was shut, and I'm sure ambient in the closet was 100f.

Second attempt, I left the closet door open - still got the same results.

Am I going to have to provide conditioned air from the HVAC in the shop into the closet, or is something wrong with the motor?

I've not checked the specs on the motor - it's a Baldor unit, and I'd assume it's continuous duty rated.

Suggestions are appreciated. I've checked the Quincy site for information and all I can find directs me to my "local Quincy reseller" - which I've not contacted.

Thanks and regards

 

[A_Pmech]

The major problem is probably the closet. 100CFM air exchange doesn't seem anywhere near sufficient to support a compressor in an enclosed space per the calculations in my head.

I would begin by using a clamp-on ammeter to see what the motor is pulling just before the compressor shuts off. It should be less than nameplate FLA.

195F with an IR thermometer suggests a core temperature in the mid 200's. That's sufficent to trigger the internal thermal overload on a class B insulated motor.

 

[wbrian63]

I thought the same thing re the closet. Leaving the door open made a big difference in internal temps, but the motor still overheats.

When you say "just before the compressor shuts off" - I'm assuming you mean with a normal cycle, not the cycle when the overload trips.

Also, I'm thinking about relocating the intake for the compressor to outside the closet. I'll use iron pipe for the first few feet and then switch to PVC. Wouldn't compressing lower ambient intake temps be easier than higher? If nothing else, I understand a remote located intake makes for a far quieter compressor...

 

[G_P]

Sounds like the compressor is cooking in that closet. You need more airflow around it.

Also, have you checked the oil in the pump? Could it be low or have turned to sludge putting extra load on the motor?

I've run my 3hp single stage until head temp was nearly 300 degrees and have never tripped the motors thermal protection.

Sent via carrier pigeon.

 

[A_Pmech]

When you say "just before the compressor shuts off" - I'm assuming you mean with a normal cycle, not the cycle when the overload trips.

Correct. The motor is under maximum load just before the pressure switch trips.

 

[wbrian63]

Sounds like the compressor is cooking in that closet. You need more airflow around it.

Also, have you checked the oil in the pump? Could it be low or have turned to sludge putting extra load on the motor?

I've run my 3hp single stage until head temp was nearly 300 degrees and have never tripped the motors thermal protection.

Sent via carrier pigeon.

The compressor has <50 hours on it. I did check the oil first thing - it's still clear-ish, and right at the full mark.

 

[71goldss]

I have the same compressor as yours mounted in a somewhat soundproof closet that I made for it. I mounted a 1540 CFM attic exhaust fan in the ceiling of the closet and cut a large rectangular air inlet opening in the lower portion of the solid core door near the floor (where the slightly cooler air is drawn from) and then covered the inlet opening with a household AC filter. When the compressor is on, the fan is on. I don't run a blast cabinet, but I have run my DA while sanding for hours at a time in 100F temps, and I've never experienced on overheating issue as of yet (knock on wood!). Even with the large inlet and outlet openings, it's still very quiet while running in the closed closet. It may be that your small 100 CFM fan isn't drawing enough air through your closet. I believe that the draft that my fan creates over the compressor is far better than simply leaving the door open in a still somewhat confined area with no circulation around it.

The fan that I have:
http://www.homedepot.com/p/Master-F...Mount-Vent-in-Mill-PG2/100014195#.UhL1eErn-ic

 

[zkling]

Does it hesitate to start at all? Possibly a non working check valve? I don't think that pump has underloaders on it, does it? I might try pulling off the belt(s) and seeing of either the pump or motor have a lot of internal resistance.

 

[MTW]

Compressor tips,
About the closet, the closet is normally used to reduce noise, but there are other ways to reduce noise, without suffocating the unit. Most folks locate their unit in a corner to save space, bad idea for noise. The corner acts as an amplification chamber and always makes it louder. A straight wall is much better for noise, as is some vibration isolation pads under the unit.

Most of the noise from a compressor is due to the air intake, you hear the suction inside the cylinders. You can reduce noise significantly by installing a intake muffler that is twice the pipe size of the intake to your head. Keep the pipe size large until it gets right next to the head then reduce to fit. This also has the added benefit of having to change or clean the element half as often, more surface area. A larger muffler slows the velocity and has more volume, so less noise. Similar to a large muffler on an engine. If you can pipe it to an exterior location then you export most of the noise. But be sure to keep a large pipe size to reduce velocity and restriction. The bad thing about putting the intake outside is increased humidity pickup and giving the neighbors your excess noise.

As to the motor overheating and tripping. Most manufacturer compressor designs overload the motor at the end of the pressure cycle. In other words the first part of the pumping cycle the motor draw is below nameplate, but near the end of the cycle as the pressure increases the motors draw go's well above the nameplate value. The philosophy here is that it is not run at 100% maximum capacity and therefore the motor is only temporarily overloaded and will have a chance to cool before the next cycle. It also lets the manufacturer claim a higher CFM flow rate for advertising their product.

Being that you have a single phase motor with internal overload protector (klixon switch), the latent heat buildup on the internal klixon switch doesn't get enough time to cool between cycles. If you keep running this way for long the klixon switch will take a poop and then you will be headed to your local motor shop for a repair job, as overloaded motors will not be covered under a warranty. Most commercial or industrial compressors have a remote mounted motor starter with overload protection, and this helps with dissipating the heat from the overload assembly, between cycles to prevent nuisance tripping.

Things you can due to alleviate the heat build up: Slow down, blasting or blow gun use consumes copious amounts of air, give the unit some down time to cool off. Like you stated at the 5th cycle it makes you do this anyway, damaging your motor in the process.

The next thing to do is reduce the pressure switch setting. You don't need 175 PSI to blast with (or any other tool for that matter) and this is the region where the unit is operating in the overloaded condition. Reduce to somewhere around 140 PSI or less to keep the load below the nameplate amp value. This will have the effect of less storage capacity, but the motor won't cycle as often, it just keeps running, when heavily loaded. This is a good thing though, when it stays running at or below nameplate amp values, the cooling fan inside the motor keeps running and dissipating the heat much faster than when it's not spinning, same goes for the cooling fan blade on the compressor pulley. It also has the added benefit of less starts on the motor, and less dry starts on the compressor crankcase especially on units with splash lubrication. The start switch and capacitor on a single phase motor is the weakest link and will almost always fail first.

And for others out there, when selecting a compressor, always look for a unit with a 1750 RPM motor versus a 3450 RPM unit. Half the speed means half the wear and half the noise. Just get a larger sized unit to make up for the slower delivery, all industrial units are built this way, most homeowner units are high speed, high noise and high wear.

Quincy and Baldor brands are some of the top of the line names as far as I'm concerned, but they need to be applied within their ratings. Most Quincy pumps have pressure lubrication which is rare among most other manufacturers of small pumps.

One last note if you must run it full out with no breaks, changing the motor pulley to a smaller size will reduce the load on the motor and slow the pump a little, to make it a more continuous duty type setup. Industrial units often come setup this way, they have a continuous run cycle and a built in unload-er on the head, that prevents the pump from pumping air into the tank until the pressure switch requires it.

Hope that help you and others... MTW

 

[wbrian63]

Does it hesitate to start at all?

It doesn't start because the thermal overload on the motor has tripped.

Possibly a non working check valve? I don't think that pump has underloaders on it, does it?

The pump has an overloader. When the pressure switch reaches the cutoff, it depresses a plunger on a one-way valve that's attached to the pump and vents the head pressure. If I'm blasting continuously, there's probably at least 3 or 4 minutes between each cycle - even without an unloader, the head pressure would likely bleed off to zero during that interval.

I might try pulling off the belt(s) and seeing of either the pump or motor have a lot of internal resistance.

As noted previously, this setup has less than 50 hours on it. The oil in the compressor is clean. I would think that high cranking resistance on the pump would have shown itself much earlier if it was a manufacturing defect.

 

[wbrian63]

MTW - Thanks for taking the time to respond in such an informative fashion.

Compressor tips,
About the closet, the closet is normally used to reduce noise, but there are other ways to reduce noise, without suffocating the unit. Most folks locate their unit in a corner to save space, bad idea for noise. The corner acts as an amplification chamber and always makes it louder. A straight wall is much better for noise, as is some vibration isolation pads under the unit.

The last compressor I had wasn't as big as this one, and I thought I had vented the closet enough to allow full load work like this. Good point about the corner magnifying the noise.
I did install vibration pads under the unit - so that's not an issue for noise, at least for me.

Most of the noise from a compressor is due to the air intake, you hear the suction inside the cylinders. You can reduce noise significantly by installing a intake muffler that is twice the pipe size of the intake to your head. Keep the pipe size large until it gets right next to the head then reduce to fit. This also has the added benefit of having to change or clean the element half as often, more surface area. A larger muffler slows the velocity and has more volume, so less noise. Similar to a large muffler on an engine. If you can pipe it to an exterior location then you export most of the noise. But be sure to keep a large pipe size to reduce velocity and restriction. The bad thing about putting the intake outside is increased humidity pickup and giving the neighbors your excess noise.

I plan on relocating the intake. I'll probably just run it up through the ceiling of the closet into the loft above - I don't work in the loft, so I don't care how loud it may be up there. Good point on increased pipe diameter.

I'm assuming if I get a good quality automotive style filter and fashion an assembly to use it, that would be sufficient for filtering the incoming air.

As to the motor overheating and tripping. Most manufacturer compressor designs overload the motor at the end of the pressure cycle. In other words the first part of the pumping cycle the motor draw is below nameplate, but near the end of the cycle as the pressure increases the motors draw go's well above the nameplate value. The philosophy here is that it is not run at 100% maximum capacity and therefore the motor is only temporarily overloaded and will have a chance to cool before the next cycle. It also lets the manufacturer claim a higher CFM flow rate for advertising their product.

I'm somewhat disappointed to hear this about Quincy products. I had a Husky (Home Depot) unit before, and it was very obvious when I tried to use a pneumatic drill that the stated CFM capacity of the unit was far below what was printed. The drill only needed about 75% of the stated 90psi cfm of the unit, but the drill was completely unusable - quickly exhausted the reserve of the compressor and slowed down further after that.

APMech did suggest getting the at-shutoff amp load for the unit. Now I just have to find my amp clamp...

Being that you have a single phase motor with internal overload protector (klixon switch), the latent heat buildup on the internal klixon switch doesn't get enough time to cool between cycles. If you keep running this way for long the klixon switch will take a poop and then you will be headed to your local motor shop for a repair job, as overloaded motors will not be covered under a warranty. Most commercial or industrial compressors have a remote mounted motor starter with overload protection, and this helps with dissipating the heat from the overload assembly, between cycles to prevent nuisance tripping.

I would assume the klixon switch would "poop safe" and fail to relatch after tripping - apparently not.

Things you can due to alleviate the heat build up: Slow down, blasting or blow gun use consumes copious amounts of air, give the unit some down time to cool off. Like you stated at the 5th cycle it makes you do this anyway, damaging your motor in the process.

Not an option, far as I'm concerned. I purchased (I thought) a quality product that was rated for continuous duty. The gun in the cabinet requires 10-15cfm, per the TP Tools website. That being said, if their requirements are understated the same way compressor manufacturers are overstating capacity, we've got a problem.

Quality product means ZERO if I've installed it in an environment that becomes hostile to continuous operation after a period of heavy usage - I need to solve the environment issues.

The next thing to do is reduce the pressure switch setting. You don't need 175 PSI to blast with (or any other tool for that matter) and this is the region where the unit is operating in the overloaded condition. Reduce to somewhere around 140 PSI or less to keep the load below the nameplate amp value. This will have the effect of less storage capacity, but the motor won't cycle as often, it just keeps running, when heavily loaded. This is a good thing though, when it stays running at or below nameplate amp values, the cooling fan inside the motor keeps running and dissipating the heat much faster than when it's not spinning, same goes for the cooling fan blade on the compressor pulley. It also has the added benefit of less starts on the motor, and less dry starts on the compressor crankcase especially on units with splash lubrication. The start switch and capacitor on a single phase motor is the weakest link and will almost always fail first.

I've thought about reducing the pressure before. Most days, the compressor cycles exactly one time - when I come into the shop. I don't typically use a lot of compressed air, so when I leave for the evening and turn the unit off, the dump valve releases all of the pressure in the tank, effectively wasting most of the electricity consumed to fill it in the first place.

And for others out there, when selecting a compressor, always look for a unit with a 1750 RPM motor versus a 3450 RPM unit. Half the speed means half the wear and half the noise. Just get a larger sized unit to make up for the slower delivery, all industrial units are built this way, most homeowner units are high speed, high noise and high wear.

Good point - I wish I had found a lower speed unit. I thought this was one of them (all blue two-stage compressors look alike in the ads - must remember to read the details)

Quincy and Baldor brands are some of the top of the line names as far as I'm concerned, but they need to be applied within their ratings. Most Quincy pumps have pressure lubrication which is rare among most other manufacturers of small pumps.

This unit does not have pressure lubrication.

One last note if you must run it full out with no breaks, changing the motor pulley to a smaller size will reduce the load on the motor and slow the pump a little, to make it a more continuous duty type setup. Industrial units often come setup this way, they have a continuous run cycle and a built in unload-er on the head, that prevents the pump from pumping air into the tank until the pressure switch requires it.

I'll look into this if I can't solve the issues I've got now with the following modifications:
1) Relocate the intake - this will help when the closet ambient temps climb - at least the compressor will be sucking in cooler air, not hotter.
2) Do a comparative analysis of blast cabinet performance as I reduce the pressure of the gun - currently running it about 90psi - how will it work at 75psi. Lower gun demand = fewer compressor cycles = longer potential cool down period between cycles.
3) Check the at-cutout amp draw of the motor for 175psi cutout.
4) Reduce the cutout pressure to 140psi.
5) Repeat step 3 - see if the max draw is below the rated capacity of the motor.
6) Relocate free-standing A/C unit from loft to compressor closet. I don't need the A/C in the loft anymore. This should greatly improve the temps in the closet and hence lower the running load on the compressor.

Regards

 

[wbrian63]

For what it's worth, here's the tag from the motor on the compressor:

The rating section shows 40C AMB-CONT. From this I take it the motor is rated to run continuously at 40C (104F).

I'm fairly certain that when the overload pops on the motor that it's over 100F in the closet.

If I read the rest of the tag correctly, with Insulation Class F, the windings should be rated for 190C (375F) before the overload kicks in. There's no way for me to get true winding temps, but when I checked the spots on the motor where I could get a laser point from my IR meter, I was seeing temps approach 200F. Not unreasonable to believe the internal winding temps might be far higher than what I can see on the outside.

I think that correcting the environmental issues the compressor is facing and reducing the cutout pressure to 140psi will go a long way towards curing my overload problem.

I'm also assuming that the AMPS 21 indicates the full load amp rating of the motor, and ideally, I should see less than that at the cutout of the pressure switch.

Thanks for all the replies.

 

[wbrian63]

I have the same compressor as yours mounted in a somewhat soundproof closet that I made for it. I mounted a 1540 CFM attic exhaust fan in the ceiling of the closet and cut a large rectangular air inlet opening in the lower portion of the solid core door near the floor (where the slightly cooler air is drawn from) and then covered the inlet opening with a household AC filter. When the compressor is on, the fan is on. I don't run a blast cabinet, but I have run my DA while sanding for hours at a time in 100F temps, and I've never experienced on overheating issue as of yet (knock on wood!). Even with the large inlet and outlet openings, it's still very quiet while running in the closed closet. It may be that your small 100 CFM fan isn't drawing enough air through your closet. I believe that the draft that my fan creates over the compressor is far better than simply leaving the door open in a still somewhat confined area with no circulation around it.

The fan that I have:
http://www.homedepot.com/p/Master-F...Mount-Vent-in-Mill-PG2/100014195#.UhL1eErn-ic

I'm sure there are temperature issues at play with this problem. I had failed to consider how hot it will get in the closet when I'm using the blaster cabinet. I don't have an option to install a unit like you've got - the closet is in the center of the rear wall of the shop, underneath the loft - there's no way to duct the output of the fan outside.

 

[MTW]

The rating section shows 40C AMB-CONT. From this I take it the motor is rated to run continuously at 40C (104F).

Yes this is correct

I'm fairly certain that when the overload pops on the motor that it's over 100F in the closet.
Yes well over 100F

If I read the rest of the tag correctly, with Insulation Class F, the windings should be rated for 190C (375F) before the overload kicks in. There's no way for me to get true winding temps, but when I checked the spots on the motor where I could get a laser point from my IR meter, I was seeing temps approach 200F. Not unreasonable to believe the internal winding temps might be far higher than what I can see on the outside.
Not correct 190C is the max allowable temp of the winding insulation. the internal temp of the winding will be much hotter than what you could read on the end of it where it is exposed to the air

I think that correcting the environmental issues the compressor is facing and reducing the cutout pressure to 140psi will go a long way towards curing my overload problem.
Correct, or get rid of the closet and use other sound mitigating ideas

I'm also assuming that the AMPS 21 indicates the full load amp rating of the motor, and ideally, I should see less than that at the cutout of the pressure switch.
Partially correct, 21A * 1.15SF(service factor) = 24.15A for the maximum value, best to keep it below 21 due to your extreme heat. Running at SF values will reduce life expectancy

For the filter you should use an intake muffler instead of just a filter to reduce noise. The filters in them are reinforced with expanded metal to resist deformation with the pressure pulsations.

Something like this.
http://www.grainger.com/Grainger/SOLBERG-Intake-FilterSilencer-4Z681?Pid=search

 

[MTW]

Quincy is a quality brand, but you purchased their bottom end model, high speed with splash lube. And you are murdering it in a super high ambient, and trying to run it at maximum capacity.

Get rid of the enclosure, reduce the pressure a bit, and it will work as advertized.
Just my 2 cents,

Did your husky unit suffer the same fate, or didn't you punish that one as hard?

 

[MTW]

Another tip on the leakdown issue. Install a ball valve at the tank outlet, and close it before you leave, when shutting down the power. The compressor should not leak down when in storage.

If it does you have a leak somewhere, pipe fittings, tank plugs, improperly adjusted unloader valve, tank check valve, or possibly exhaust valves in the head. My Quincy unit is left on 24/7 with the piping attached and pressurized, and it only cycles once per day due to my small hose coupler leak. I hate waiting for it to fill a 120Gal tank to blow off an item quickly when needed. Air leaks are expensive, and cause unnecessary wear on the machine. My machine is older than dirt and I got it second hand, but I refurbished and installed it with great care to eliminate leaks.

 

[zkling]

It doesn't start because the thermal overload on the motor has tripped.

I am talking about the 3-4 times that it does start before it starts overheating and tripping the thermal cycle.

It will do this cycle 3 or 4 times - maybe 5 max - then the temp overload on the motor cuts out and I'm done blasting for a long time.

The pump has an overloader. When the pressure switch reaches the cutoff, it depresses a plunger on a one-way valve that's attached to the pump and vents the head pressure. If I'm blasting continuously, there's probably at least 3 or 4 minutes between each cycle - even without an unloader, the head pressure would likely bleed off to zero during that interval.

That is different than a unloader. I have a 270 which is from the higher end (no offense, but much better quality line of quincy than the pump you have) I was wondering if it was having trouble from that start which would cause a pretty good heat build up. Add in a few cycles and the build combined with high ambient temps could cause to motor to take all it can.

As A_Pmech said, monitoring your amps would be a good start.

As noted previously, this setup has less than 50 hours on it. The oil in the compressor is clean. I would think that high cranking resistance on the pump would have shown itself much earlier if it was a manufacturing defect.

Here's the question. Did it work fine before, has this setup ever worked properly? If so, what did you change since then?

Ultimately the motor is being worked too hard. Whether it be from ambient conditions and high surrounding temp or an increase over normal operating resistance, which is causing an increase in internal temp. For some reason, I think you have a bigger issues than just high ambient temps that that is causing it to trip.

 

[wbrian63]

Another tip on the leakdown issue. Install a ball valve at the tank outlet, and close it before you leave, when shutting down the power. The compressor should not leak down when in storage.

If it does you have a leak somewhere, pipe fittings, tank plugs, improperly adjusted unloader valve, tank check valve, or possibly exhaust valves in the head. My Quincy unit is left on 24/7 with the piping attached and pressurized, and it only cycles once per day due to my small hose coupler leak. I hate waiting for it to fill a 120Gal tank to blow off an item quickly when needed. Air leaks are expensive, and cause unnecessary wear on the machine. My machine is older than dirt and I got it second hand, but I refurbished and installed it with great care to eliminate leaks.

Sometimes my visits to the shop are weeks part - it's not located at my home. As such, I prefer to dump the entire contents of the tank when I leave.

When I installed the compressor, I set up a remote control contactor to allow me to turn the unit on and off from the entry door, which is 50+ feet from where the compressor is located.

I added a 1/4" electric valve after the ball valve on the bottom of the tank. When the power is on to the contactor, the valve is closed. As soon as I turn off the system, the valve opens and vents the tank. I have an elevated floor in the shop (see this post: http://www.garagejournal.com/forum/showpost.php?p=989428&postcount=57 ) and I just vent the air under the floor.

 

[wbrian63]

I am talking about the 3-4 times that it does start before it starts overheating and tripping the thermal cycle.

That is different than a unloader. I have a 270 which is from the higher end (no offense, but much better quality line of quincy than the pump you have) I was wondering if it was having trouble from that start which would cause a pretty good heat build up. Add in a few cycles and the build combined with high ambient temps could cause to motor to take all it can.

As A_Pmech said, monitoring your amps would be a good start.

Here's the question. Did it work fine before, has this setup ever worked properly? If so, what did you change since then?

Ultimately the motor is being worked too hard. Whether it be from ambient conditions and high surrounding temp or an increase over normal operating resistance, which is causing an increase in internal temp.

No offense taken - I paid what I paid and you paid what you paid. This isn't a commercial installation - it's my hobby gone horribly wrong

Now that I think about it, that line with the plunger is only activated when you manually switch the unit off.

However, I do hear a distinct hiss noise when the compressor reaches full pressure and shuts off.

I also added a electric valve inline with the output of the compressor that's energized closed as long as power is applied to the controlling contactor (see here: http://www.garagejournal.com/forum/showpost.php?p=960267&postcount=38). If the power is removed from the contactor, the valve opens and dumps all the pressure out of the output line. I don't have this operating with the cycling of the pressure switch, just with the main power coming into the unit from the contactor.

I've never heard it start any different when cycling during use than it does when I first fire it up when I get to the shop in the afternoon (the system is completely empty at that point - I've got another electric valve on the tank drain that dumps the tank when I cut the power off).

I certainly could adapt this setup to be triggered when power is sent to the motor from the pressure switch, then each time the unit reaches cutoff pressure, the valve would open and dump the line feeding the tank.

As I understand it, an unloader actually vents the pressure chambers on the pump, so this isn't that good, but it would be far better than nothing if the unit is cycling a lot.

Plus, as I noted previously, the intervals between cycles are 3-4 minutes if I'm constantly using the cabinet. If I pause - obviously the intervals are longer. From start with a full tank, I can probably blast for 3-4 minutes before the compressor comes on. If I keep blasting, the compressor will run for 5+ minutes before cutting off. Then it's another 3-4 minutes before it will need to run again.

I've never had any issues with this system until I started using the new blasting cabinet I built. I've done some furniture/cabinetry finishing using a SATA HVLP-type gun, but the air demands are small for that effort compared to the demands of the blasting cabinet.

 

[wbrian63]

Quincy is a quality brand, but you purchased their bottom end model, high speed with splash lube. And you are murdering it in a super high ambient, and trying to run it at maximum capacity.

Get rid of the enclosure, reduce the pressure a bit, and it will work as advertized.
Just my 2 cents,

Did your husky unit suffer the same fate, or didn't you punish that one as hard?

My Husky unit is happily inflating tires and running a few pneumatic tools (impact wrench, etc) at home. I knew it wasn't up to the task of anything like a blasting cabinet, so I upgraded to this unit when I built the shop.

I have no intention of shortening the life of this unit. I will get the operational environment issues solved and the unit should be good to go for as long as I care to use it. The blasting is a high demand process right now because I'm restoring a car, but it will subside as I move from area to area in that process. Right now, it's front-end work - lots of suspension pieces to blast in prep for powder coating.

There is an option to get a smaller nozzle for my blasting gun, but I think I can improve things with the compressor to limit the abuse to a more normal workload without having to resort to that modification.

 

[zkling]

No offense taken - I paid what I paid and you paid what you paid. This isn't a commercial installation -

Don't get the wrong idea, I only have ~$250 into my 270 setup, including 2 tanks, motor and controls Not many folks are fond of the large single stage units so they tend to go pretty cheap. How much did you pay?

The unit you have is built quite a bit different than the common quincy QR series. A unloader allows the motor to spin the pump without putting air in the tank, so basically it is only fighting the internal resistance of the pump, not the additional force added by the pressure on the pistons. Ultimately it reduced the startup torque and thus amps needed to get it going. The reason I brought it up was to see if your pump is being pressurized while trying to start, which would cause a heavy start up current and thus initial heat buildup.

However, I do hear a distinct hiss noise when the compressor reaches full pressure and shuts off.

That is just the pressure switch doing its thing and bleeding out the line.

I certainly could adapt this setup to be triggered when power is sent to the motor from the pressure switch, then each time the unit reaches cutoff pressure, the valve would open and dump the line feeding the tank.

I think I would try that. Set it back to the way it came from the factory and see if that has any change on what you are experiencing. I don't fully understand why you have it setup the way you do. I understand the part about how you have it discharge and bleed down, but why? Why not just kill power to the unit when you leave? If it bleeds down so what when you come back it will start up again.

I've never had any issues with this system until I started using the new blasting cabinet I built. I've done some furniture/cabinetry finishing using a SATA HVLP-type gun, but the air demands are small for that effort compared to the demands of the blasting cabinet.

In that case it definitely sounds like you have a duty cycle issue. After looking at the closet, it doesn't look THAT small. I would call quincy and ask if they think you should be experiencing those problems with the ambient temps you recorded in the closet. Compressors are installed outdoors all the time, in sheds, in the sun, in un cooled buildings. 100°F ambient shouldn't be that big of an issue for it.

IIRC that pump / motor should be designed for 100% duty cycle.

 

[blaperle]

As with most induction motors it is rated continues duty provided the Full load amps plus service factor are not exceeded (although I do not recommend getting too far into the service factor). A 5 horsepower motor is realistically only good for about 13.5scfm for continuous duty. As suggested check the amp draw on the motor throughout the cycle I suspect you will see a max of about 26 to 27 amps. Looking at the motor data plate full load amps is 21 with a service factor of 1.15 giving a total max amp for the motor 24.15 I would try to stay at the low end of the service factor.
Reducing the tank pressure and the ambient temperatures will not have a large impact. If the compressor is cycling as you say while using the media blaster it means the compressor is providing more air flow than is needed so you can do as MTW suggested and reduce the motor pulley circumference by about 12%. Or install a larger motor (expensive).

Brian

 

[larry_g]

r.
Reducing the tank pressure and the ambient temperatures will not have a large impact. If the compressor is cycling as you say while using the media blaster it means the compressor is providing more air flow than is needed so you can do as MTW suggested and reduce the motor pulley circumference by about 12%. Or install a larger motor (expensive).

Brian

I disagree with your statement "Reducing the tank pressure ...snip... will not have a large impact"

Reducing the max operating pressure will have the same load reducing effect on the motor as going to a smaller pulley. If the OP has a current probe I would suggest that he monitor the current draw. Monitor current and pressure and reset the cutout pressure to where the current draw is a bit less than the max rated current of the motor. This is the easiest thing to do as it only involves the turning of a screw.

lg
no neat sig line

 

[wbrian63]

Don't get the wrong idea, I only have ~$250 into my 270 setup, including 2 tanks, motor and controls Not many folks are fond of the large single stage units so they tend to go pretty cheap. How much did you pay?

I paid a WHOLE lot more than you... about $1300 if I recall...

The unit you have is built quite a bit different than the common quincy QR series. A unloader allows the motor to spin the pump without putting air in the tank, so basically it is only fighting the internal resistance of the pump, not the additional force added by the pressure on the pistons. Ultimately it reduced the startup torque and thus amps needed to get it going. The reason I brought it up was to see if your pump is being pressurized while trying to start, which would cause a heavy start up current and thus initial heat buildup.

Gotcha - typical of industrial installations, the motor runs all the time and the compressor loads up and unloads as required to provide air.

That is just the pressure switch doing its thing and bleeding out the line.

What's the advantage of bleeding off that line?

I think I would try that. Set it back to the way it came from the factory and see if that has any change on what you are experiencing. I don't fully understand why you have it setup the way you do. I understand the part about how you have it discharge and bleed down, but why? Why not just kill power to the unit when you leave? If it bleeds down so what when you come back it will start up again.

After I finished installing the valve at the top, I thought about it and figured it was really a waste of effort. It only helps if I start the compressor and while it is pressuring up, turn off the control circuit, and immediately turn it back on again, which is typically something I wouldn't do.

I do turn off the power to the unit when I leave. That's the purpose of the remote-controlled contactor. The switch for the compressor is adjacent to the light switches for the space - when I turn off the lights, I also switch off the compressor. The dump valve opens and all of the pressure in the tank, including any built-up moisture is dumped (takes several minutes, I don't have the valve ball valve ahead of the electric valve open all the way). If I don't want to dump the tank, all I have to do is close the ball valve. That being said, I don't think there's much of an arguement against dumping the tank every time I turn the compressor off. True, I'm spending $ on electricity to refill the tank when I return, but that return might be weeks later, depending on many factors. There's also a small amount of additional wear on the compressor and motor, but I don't think a few extra zero-to-cutoff runs are going to accelerate the eventual demise of the unit by a large factor.

In that case it definitely sounds like you have a duty cycle issue. After looking at the closet, it doesn't look THAT small. I would call quincy and ask if they think you should be experiencing those problems with the ambient temps you recorded in the closet. Compressors are installed outdoors all the time, in sheds, in the sun, in un cooled buildings. 100°F ambient shouldn't be that big of an issue for it.

IIRC that pump / motor should be designed for 100% duty cycle.

The closet is 4' x 6', IIRC. It has a 9' ceiling. There's a hole in the wall behind the compressor near the floor where I've got 3 2" PVC pipes that allow intake air to be pulled from the adjacent room at floor level. They open up above the height of the compressor. The air comes through a A/C return air grill 12x12" in dimension, with a filter that I keep clean. The idea is that the cooler air near the floor will dump down on the compressor, rather than pooling on the floor.

The reason for all this nonsense is that the closet that houses the compressor is inside the room where I do all my woodworking finishing work, including spraying finishes. The room has a ventilation fan that pulls air from the main shop and through some special filters before exiting the building through the side wall in the loft. I don't spray any volatile/flammable chemicals - everything is water-based.

Anyway - I don't want the compressor ingesting any of that stuff - even a small amount of the lacquer I use will clog the inlet filter very quickly. Keeping the door closed and allowing the compressor to pull air from the adjacent room prevents it from taking a snort of stuff it doesn't need. Path of least resistance, etc.

The motor tag says 40AMB CONT. I'm pretty sure the closet is > 100F when the overload trips. I've got a small vent fan (type you see in a small bathroom) that's controlled by a line-voltage thermostat. The LV thermostat has a thermometer on it - only shows to 90f, and the needle is almost always pegged during the summer.

I have a small refrigerator in the same closet (dorm-room sized) and I like to keep the closet as cool as possible to lessen the load on the fridge when I'm not there. I'm sure this adds to the heat load, but not nearly so much as the compressor itself.

 

[wbrian63]

I disagree with your statement "Reducing the tank pressure ...snip... will not have a large impact"

Reducing the max operating pressure will have the same load reducing effect on the motor as going to a smaller pulley. If the OP has a current probe I would suggest that he monitor the current draw. Monitor current and pressure and reset the cutout pressure to where the current draw is a bit less than the max rated current of the motor. This is the easiest thing to do as it only involves the turning of a screw.

lg
no neat sig line

I've missplaced my amp clamp, so I'm going to try reducing the tank pressure today to 140psi and see what that gets me. If the limit switch pops again, then I'll have a look at what the true ambient temps are in the closet when this occurs.

I don't really care what the cutout pressure is set to, so long as I don't have to stop using the media blaster for lack of pressure, which is what's happening now when the overload pops. None of my pneumatic tools need 175 or even 140psi anyway and I have a regulator on the main line that limits the shop air pressure to 100psi as well.

The HVAC unit for the shop is in the room adjacent to the compressor - it wouldn't take too much effort to add a small (4") rigid duct into the plenum just above the evaporator (vertically installed unit) and run it into the closet. Add an inline butterfly damper that I can open when I need a little extra cooling and that will have a huge impact on the closet temps - the AC runs constantly when I'm there in the afternoon this time of year.

Thanks for all the replies to date.

Regards

 

[zkling]

Gotcha - typical of industrial installations, the motor runs all the time and the compressor loads up and unloads as required to provide air.

NO, the comp does not run all the time. You are using the word loaded and unloaded in a different context. When compressors talk about being loaded they are referring to the back pressure that is put on the pistons from the compressed air. When you get large displacement pumps this can be a good amount of force, which translates to torque which needs motor torque to over come it. On larger and heavy duty compressors they start without building pressure, it gives the system a chance to build oil pressure and get a running start before it has to actually work fighting the compression of the air. On smaller, home owner type compressors like yours, they use a check valve so the entire tank pressure is not constantly being held against the pistons and valves. Hence I asked initially if you may have a check valve problem. Because when they go out they tend to cause the motor to work harder because every stroke is hitting against full tank pressure.

Here is a good video of one in operation. You will have to listen to it. Those two tower looking things on the head are hydraulic unloaders. You will hear when they kick in and start to divert the pumped air to the tank to build pressure.

What's the advantage of bleeding off that line?

There is really no advantage, just a by product of how it works. When you go to adjust cut in and cut out pressure which are just spring preloads these are what determine where your compressor will start and stop. More spring compression --> More force needed to open the valve --> Higher activation pressure.

The motor tag says 40AMB CONT. I'm pretty sure the closet is > 100F when the overload trips. I've got a small vent fan (type you see in a small bathroom) that's controlled by a line-voltage thermostat. The LV thermostat has a thermometer on it - only shows to 90f, and the needle is almost always pegged during the summer.

If I was having issues with a comp like you are. I would return the compressor to stock configuration, not adjust the cut out pressure and then see how it works. If it still has a problem overloading at high duty cycle I would get an accurate ambient temp reading and call quincy. That way they know how your compressor is set up. As soon as you say you "improved this" or "modified that" they are going to be highly suspicious of your mods. In my experience they are very helpful and willing to solve small customer problems.

I've missplaced my amp clamp, so I'm going to try reducing the tank pressure today to 140psi and see what that gets me. If the limit switch pops again, then I'll have a look at what the true ambient temps are in the closet when this occurs.

I don't think reducing the pressure is going to help that much. Especially if you are running the stock pulleys. Going from 175psi to 140psi cutout is going to be a ~20% decrease in torque and thus power required to turn over the compressor. I would be more curious if you ran it at ~120psi for an extended period of time and see if it still overheats.

 

[71goldss]

I'm sure there are temperature issues at play with this problem. I had failed to consider how hot it will get in the closet when I'm using the blaster cabinet. I don't have an option to install a unit like you've got - the closet is in the center of the rear wall of the shop, underneath the loft - there's no way to duct the output of the fan outside.

I should have been more clear on my closet design. The fan doesn't exhaust outside. It exhausts into the open rafters of my garage. Very little sound, if any, comes through the inlet and outlet openings, and the fan doesn't create a turbulence in my garage either. Also, the fan can hardly be heard, so I'm not replacing one noise with another. I did line the inside closet walls with 3/4" soundproof material I picked up at HD, and also use a solid core door. I'm assuming the soundproof material deadens the sound before exhausting out the opening.

I made this over a year and a half ago and have used it for hours at a time over the last two 100F summers. I've never had an overheating issue, and I'm extremely happy with the sound deadening results. Still need to finish the outside with moldings and paint.

 

[71goldss]

I'm nearly certain your issue is overheating from your closet. I would pull it out of the closet and run it out in the open air and see what it does. First step in the process of elimination.

 

[PT Doc]

Some good recommendations.

Estanlish if the compressor works as intended. Pull it put of the closet and return to stock mode. Run it. If good , return it to outrun modded style. Run it. If works, then back into the closet with a higher cfm fan .

According to quinct for the qt series, comtinuous duty is 6on off cycles per hour. Call them to verify what continuous means in the compressor industry. I think you will be surprised. 80 gallon should've the minimum for your application. The special rating on the motor plate to means its not a 5hp motor.

Good luck.

 

[71goldss]

The special rating on the motor plate to means its not a 5hp motor.

I discovered that info about the special rating on the plate on my Baldor motor shortly after purchasing mine. There's a formula for figuring the actual hp (can't remember it now) and it turned out that mine was actually closer to 5 1/2 hp, so it doesn't necessarily mean that it's less than 5hp.

 

[zkling]

I discovered that info about the special rating on the plate on my Baldor motor shortly after purchasing mine. There's a formula for figuring the actual hp (can't remember it now) and it turned out that mine was actually closer to 5 1/2 hp, so it doesn't necessarily mean that it's less than 5hp.

It's a very shady and far fetched way of rating motors. There have been lawsuits and what not about this. That is one of baldor's lower end motors. Give awya's are a.) It is marked spl and b.) It is a 3450rpm on a compressor. Not trying to rag on this guys compressor, but there have been a few reports of those motors going out.

 

[71goldss]

It is a 3450rpm on a compressor. Not trying to rag on this guys compressor, but there have been a few reports of those motors going out.

Having the same compressor as the OP's, I am overall happy with my purchase. It fits my needs very well and it fit my budget at time of purchase. The Baldor motor is very loud and is my only complaint, but so far I'm very happy with the compressor's overall performance. I'm just a home DIY'er and don't really need anything bigger, badder or more expensive, and unfortunately I probably won't outlive this compressor at the age that I am now.

That said, would I purchase this model again? Probably not. Not because it hasn't performed to my satisfaction, but because I tend to suffer from GJ addiction that so many of us suffer from on this forum. If I always did what my addiction wanted me to do, I would own a "double the price" Champion Advantage series just to piddle around with in my garage on weekends. Fortunately I've been able to fight this addiction most of the time, well except for the overall $1500.00 investment in my Miller 211 with accessories, just to do a couple of patch panels on the front fenders of my El Camino. It did do a great job on my panels and was very easy to use the one time that I've used it (trying to justify here!). Oh well, it's nice to know I have a nice mig in the event I come up with something else to weld in the future.

My point is, purchasing up or "top of the line" doesn't always make for a good value, just overkill in many cases.

 

[wbrian63]

Finally had to break down and purchase an amp clamp - never could find my existing tool.

Found what others have suggested might be happening - while allowing the compressor to cycle from 0 psi to the 175 cutout, the 21amp-rated motor pulled a maximum of 22.9 amps just as the pressure switch shut the motor off. That's under the 24.15 amps technically allowed by the 1.15 service factor, but one can easily see that repeated demands beyond the 1.0 value will likely cause problems.

So, I reduced the cutout pressure on the unit to 140psi, and still saw a peak amp draw in excess of 21amps. So, I reduced it further to 120psi, and even after 4 cycles back-to-back, max amp draw peaked at just above 19amps.

That's the only change. I used the media blaster for over an hour - 5 or 6 cycles of the compressor and no overload tripping.

After the last cycle before I left for the day, I checked the closet temps - they were WAY lower than what I'd seen previously when the overload problems were occurring.

I've got the output of the compressor running into the shop through a regulator set at 90psi, so having 175psi in the tank was really overkill, and obviously (to me) more than this "continuous duty" compressor was capable of generating.

Would I have encountered this problem if the compressor was not installed in the closet? Maybe, maybe not, but the compressor IS installed in the closet, and that is where it needs to remain. Solving the problem by reducing the cutout on the system to a number that is still more than adequate to provide air for my needs is a solution I can live with.

Thanks for all the input and for the education.

Regards

 

[cnc-me]

Could it be the thermal protector itself?
Have seen these trip prematurely.

Just put a fan blowing over the motor, and make sure most of the air flow is going
over the thermal protector.

 

[MTW]

wbrian63,

I'm glad to see that you got it figured out. It's nice that you posted your final results so others could see the case closed conditions. For future reference and for others, anytime you see a SPL (special rated) tag on a motor, be suspicious. What this usually means is cost savings for the manufacturer, and short life for the consumer. The motor will be designed to the absolute minimum to handle the specific load it is connected to. As compared to a standard motor, they generally have smaller bearings and frame sizes, and worst of all an inflated HP rating. As an example you can find vacuum cleaners rated at 5HP @ 120V, they legally get away with this false advertizing due to the PEAK HP. Meaning at start-up it develops enough torque to get near the advertized rating for a second or two.

In your case, with the compressor, the unit is rated at 5HP 230V 21FLA, and you stated you got it to run successfully at 19A without overheating. According to the table from the NEC your setup is running at a little better than 3HP which is listed at 17FLA. And a full 5HP rated motor would be rated at 28FLA.

And before the other members dispute this, a clarification. This chart is for average values of belted motors, with normal torque characteristics, and is manufacturer agnostic. The code requires you to size the circuit based on this chart (*1.25 min) so that when the motor is replaced, any manufacturer unit will function correctly and safely.

If you see a portable compressor advertized at more than 1HP and see a 115V 15A chord pigtail on it you will know it is BS.

I have a old Emglow portable with a real 1.5HP motor that I retrofitted from a 5HP gas engine. It's a Dayton motor with a 19FLA @120V tag and a belted load of exactly the same, at full head pressure. It's difficult to even get it started on a dedicated 120V 20A circuit. Usually it will only start if the outlet is less than 5' from a service panel. For field use I installed a dual voltage switch to allow use at 120/240V depending on power conditions at the jobsite. At 208/240V it runs without issue all day long.

 

[zkling]

My point is, purchasing up or "top of the line" doesn't always make for a good value, just overkill in many cases.

The sad thing with those compressors, is that (IMHO) Quincy is trying to live off of their reputation built on their other industrial series. They want you to think you are purchasing "top of the line" because of the name, but honestly it is not. Again not trying to rag your compressor, just putting it out there. All the large industrial compressor manufactures have tried (and many failed) to provide a high quality product to the average DIY guy at a somewhat resonable price point. Amazingly I personally think the one company that succeeded at this was CH, followed by IR. Are they the best? No, but for the price point they are very hard to beat.

 

[Climber]

Wow!!! ..., so much info. Thanks Guys!

 

[wbrian63]

Update -

The remote intake is installed. Made some, but little difference in noise. I chalk that up to the 3450rpm motor and high speed compressor operation. Still, it is better to have the intake out of the area where the compressor is running. If I get dust or overspray mists into the closet with the compressor, I don't have to worry about clogging the intake filter.

However, heavy demand (extended media blaster usage) still causes the thermal overload to trip.

I've reduced the pressure switch to top out at 120psi, and that keeps the peak load amps below the 21a indicated on the motor tag (around 19a at cutout), but my measurements were only taken on the first 0 to 120psi fill.

I'm going to add a 4" vent line from the A/C into the closet to see what effect dropping the closet temps WAY down will have. Dumping 50+/- air into the closet should have a positive effect...

 

[scw1991]

First, I'd measure the amperage on each leg. The compressor is designed so that the motor should never draw more amps than what is shown on the nameplate. In addition, motors are designed for a certain number of maximum starts-per-hour or duty cycle. The problem with 2-pole motors (3600 RPM) for compressor applications is they develop half the torque of a 4-pole (1800 RPM) motor. Unfortunately, you need that starting torque to get the compressor up and running. The reason compressor manufacturers use 2-pole motors is because they are more economical to manufacture. Plus manufacturers are cramming more horsepower into smaller and smaller motor frame sizes. I think what is happening in your application is the motor is simply cycling on/off too frequently which is causing severe heat build up. A motor has to be able to dissipate heat effectively and the combination of having a small frame size motor in a restrictive environment is not allowing the motor to adequately cool before the next cycle on period. Another thing I see a lot on GJ is folks shove their compressors right up against a wall which is not ideal. The compressor flywheel also acts as a fan blade to draw air past the compressor fins to assist in cooling. The same applies to the motor.

 

[Milton Shaw]

I haven't seen anybody mention this but have you checked the voltage under load. If you have any voltage drop under load, that might be what is causing your overheating problem. Most motors are rated at 230 which is less than the 240 volt normal home voltage. That rating gives motors a little leeway on slight voltage drops but check it so that you can eliminate any electrical problems being the reason for your overheat. Low voltage will make all about all motors run hot.