Is this air compressor plumbed correctly? What else could be wrong?

[King Chrome]

I have a second hand air compressor which had a another pump installed on it.

Starting it with an empty tank and empty transfer tube, the motor barely runs the compressor to 15psi before struggling to build pressure. The unloader also keeps venting when I turn it off. When I open the tank to vent to atmosphere or remove the transfer tube the compressor picks up speed and spins freely.

Here is a look at the unloader... is it even plumbed correctly? From what I've seen online it seems like it should go to a port on the check valve or a port on the pump head but here it's tied in with the pressure relief valve.




This is what the check valve looks like. It doesn't resemble the aftermarket check valves where there is some casing over the assembly. Is it bad? Did something break off? It also doesn't have an unloader port, neither does the pump head.



While I'm at it, does anyone know what this silver fastener in the center is? Looks like it may have had a wire in it once but idk.

 

[Rockable]

It sounds like you don't have enough horsepower for that pump. More information required. Electric motor horsepower, pulley diameters, pump size. Max pressure, etc.

 

[Bert_]

Unloader needs to be before the check valve. Yours is after. That won't cause the motor to stall if it's already running

If that's a 3450rpm motor then the pulley looks very big.

 

[seber]

It's hard to tell from that photo but it looks like the unloader is plumbed to the tank. If so, then venting of the tank will occur when the motor is shut off instead of venting the fill line. As far as struggling to turn the pump, you will need to check the spec on the pump and see if the motor is powerful enough to run it.

 

[The Cobbler]

is that the check valve on the the tee with the unloader line?
the check valve needs to be at the tank, and everything gets unloaded but the tank.
if that is the check valve, and it's venting the tank , it's either on backwards or more likely leaking

 

[The Cobbler]

that silver thing might be a low oil switch?
also, what HP motor,rpm of motor, what size pulleys, is it wired for 240 & trying to run on 120?

 

[Jswain]

Unloader definitely is not plumbed in correctly, place a T after the check valve and hook the unloader in there to bleed off the compressor discharge line.

Sounds like your next issue could be the check valve isn't sealing, or it could be a number of other things with the pump and or motor/wiring.

 

[King Chrome]

It sounds like you don't have enough horsepower for that pump. More information required. Electric motor horsepower, pulley diameters, pump size. Max pressure, etc.

1) The motor is 5hp spl, 3150 rpm, 230v.
2)The motor pulley is single groove around 4-1/2 inches. The compressor pulley is 2 groove and about 8-1/2 inches.
3) The distance from the centers is about 13-15/16 inches.
4) It's a dewalt pump but I can't find specs for it. I think I found the model number but there are no results online.

I have another pulley laying around that is 2 groove and 3-7/16 inches that I can put on the motor.

that silver thing might be a low oil switch?
also, what HP motor,rpm of motor, what size pulleys, is it wired for 240 & trying to run on 120?

It's 5hp spl on a 240v 30amp outlet, 35 ft of 10/3 to the pressure switch with 14/2 whip from the switch to the motor. I haven't measured voltage at the motor yet.

is that the check valve on the the tee with the unloader line?
the check valve needs to be at the tank, and everything gets unloaded but the tank.
if that is the check valve, and it's venting the tank , it's either on backwards or more likely leaking

That is the pressure relief valve on the tee. The check valve already sits under the transfer tube and inside the tank. (check valve is not pictured installed.) The current check valve doesn't have an unloader port.

I think someone tried to save the compressor with a new compressor pump but didn't know how to plumb the unloader.

My current plan is to order a new check valve with an unloader port, and put a smaller pulley on.

 

[Citation]

Yeah, I agree with the others, the unloader is in the wrong place. I mean I guess as plumbed it would unload all the air in the tank...

There is a line going from the pump to a check valve mounted on/in the tank

The unloader line is usually a small line going from the side of the check valve to the pressure switch. The idea is when the pump turns off the unloader vents the air in the line from the pump to the check valve. That gets rid of any compressed air in the pump.

If nothing is connected to the unloader connector on the side of the check valve then instead of the air from the pump going into the tank it will vent out the unloader connection. Since the unlaoder valve is open when the motor is off, any air that did make it into your tank is then vented by the unloader.

Anyway, line from pump to check valve. Small line out of check valve to unloader valve on the side of the pressure switch. Based on your picture you will need to cap the extra line on the T or just add a second air connector.


The thing on the side of the pump looks like a crank positive pressure vent. I presume it's not supposed to have anything connected to it.

 

[King Chrome]

I put the 2 groove 3-7/16 pulley on and got new belts and plumbed in a milton check valve. Everything sounds healthier. The unloader doesn't leak when the compressor is off anymore but it does leak when running. The compressor takes what seems like too long to fill but it now makes 80 psi before the thermal overload trips on the motor. Which is great for airing a tire but not for doing a day's worth of work.

May have to create another topic for that problem.

 

[Tools4Me]

After casually looking at this thread, it seems like your pump/motor/pulley combo is very mismatched. Your existing pulleys are much better suited for a 1725rpm electric motor instead of the faster rpm motor you have. Also, are you sure you don't have a 3450rpm motor? You said 3150rpm, but I don't think I've seen a motor with a 3150rpm spec before.

If your motor is a 3450rpm motor, that means you are currently spinning your pump at around 1400rpm with the 3-7/16" diameter motor pulley installed. All the belt driven air compressors I have worked on and/or used in the past had pump specs of around 600-900rpm, with 800-850rpm being the most common spec I have seen. I just took a look at the current Dewalt 5hp 2-stage compressors for sale online and it appears that they have pumps that spin at 850rpm, so that's the number you should likely aim for with your unknown model Dewalt pump. That would explain why your motor is overheating from too much load when your air tank reaches 80psi. You would need a 14" pulley on your pump to get your pump down to 850rpms. You could alternately make the motor pulley smaller, but it would need to be around 2-1/8" diameter to get you close to 850rpms. Depending on the type of v-belt you are using, you might not be able to go that small without belt slippage becoming an issue or the minimum bending radius of the v-belt itself being exceeded. You would have to look up a few specs to see if making the motor pulley smaller is an option for you or not, but in general I only see motor pulleys that small on fractional horsepower motors, so you will likely have to either make your pump pulley much larger or change out your 5hp motor to a 1725rpm model to get things working properly once the other issues are resolved.

 

[Citation]

I put the 2 groove 3-7/16 pulley on and got new belts and plumbed in a milton check valve. Everything sounds healthier. The unloader doesn't leak when the compressor is off anymore but it does leak when running. The compressor takes what seems like too long to fill but it now makes 80 psi before the thermal overload trips on the motor. Which is great for airing a tire but not for doing a day's worth of work.

May have to create another topic for that problem.

The unloader is supposed to "leak" when the motor is off. It shouldn't leak when the compressor is running. That said, it sounds like your check valve is leaking/bad.

 

[Citation]

After casually looking at this thread, it seems like your pump/motor/pulley combo is very mismatched. Your existing pulleys are much better suited for a 1725rpm electric motor instead of the faster rpm motor you have. Also, are you sure you don't have a 3450rpm motor? You said 3150rpm, but I don't think I've seen a motor with a 3150rpm spec before.

If your motor is a 3450rpm motor, that means you are currently spinning your pump at around 1400rpm with the 3-7/16" diameter motor pulley installed. All the belt driven air compressors I have worked on and/or used in the past had pump specs of around 600-900rpm, with 800-850rpm being the most common spec I have seen. I just took a look at the current Dewalt 5hp 2-stage compressors for sale online and it appears that they have pumps that spin at 850rpm, so that's the number you should likely aim for with your unknown model Dewalt pump. That would explain why your motor is overheating from too much load when your air tank reaches 80psi. You would need a 14" pulley on your pump to get your pump down to 850rpms. You could alternately make the motor pulley smaller, but it would need to be around 2-1/8" diameter to get you close to 850rpms. Depending on the type of v-belt you are using, you might not be able to go that small without belt slippage becoming an issue or the minimum bending radius of the v-belt itself being exceeded. You would have to look up a few specs to see if making the motor pulley smaller is an option for you or not, but in general I only see motor pulleys that small on fractional horsepower motors, so you will likely have to either make your pump pulley much larger or change out your 5hp motor to a 1725rpm model to get things working properly once the other issues are resolved.

To the OP,
Looking at this comment above had me thinking it might be good to share some additional pictures of the over all compressor as well as the motor plate and pump model number of possible.

 

[Hohn]

The unloader line is usually a small line going from the side of the check valve to the pressure switch. The idea is when the pump turns off the unloader vents the air in the line from the pump to the check valve. That gets rid of any compressed air in the pump.

This is why you generally get a brief "PSSST" on shutdown for most compressors. The unloader vents the discharge line upstream of the check valve.

 

[MacMcMacmac]

That check valve looks like a Load Genie, which is a self unloading check valve. If it is you should see a very tiny orifice on one of the flats. They are a good idea which seldom works that well. Just over tightening the valve is often enough to render it useless. I'm not sure that's a Dewalt pump. That silver fitting looks like a temperature probe that has broken off. It looks.like the wrong flywheel for it as well, and based on the pulley sizes it is very near turning 1700rpm.

You will need a new check valve, then plumb the unloader line from the pressure switch to the port on the side of the check valve, or into a bleed port on the discharge side of the cylinder head.

 

[King Chrome]

Depending on the type of v-belt you are using, you might not be able to go that small without belt slippage becoming an issue or the minimum bending radius of the v-belt itself being exceeded.

The belts being run are 4L480W. So far I only seen as small as 2.5 inch 2 groove pulleys online.

 

[isb cornbinder]

That looks like a total mess. Start over and do it right.

 

[King Chrome]

The unloader is supposed to "leak" when the motor is off. It shouldn't leak when the compressor is running. That said, it sounds like your check valve is leaking/bad.

Should have said the unloader no longer continuously leaks when off. It now only leaks briefly when turned off but it's always leaking when on. Didn't quite specify but the Milton check valve I installed is brand new and correctly plumbed. Surely it's not bad already.

I'll take pictures of the pump from every angle in a few hours. There's also a guy online in this comment section who is able to identify them sometimes.

 

[King Chrome]

That looks like a total mess. Start over and do it right.

It looks like a mess
but it also cost 150 for the tank pump and 2 motors.

 

[Tools4Me]

The belts being run are 4L480W. So far I only seen as small as 2.5 inch 2 groove pulleys online.

4L series belts are lighter duty v-belts designed for fractional horsepower applications (less than 1hp), so that belt needs to go. You will need to switch to a type A v-belt (I found a source online that said they require a 3" minimum pulley diameter or you will have belt delamination issues) or a type AX v-belt which is cogged and might be able to reliably handle a smaller than 3" pulley. Note that type A and AX belts are measured differently than 4L belts. There is a 2 inch difference as a result, so the 4L480W belt you are using right now would translate to a AX46 cogged belt to have a belt with the same total outside length.

I can't seem to find the website I've used in the past for calculating belt slippage and minimum pulley diameter. It calculated slippage based on the wrap angle (angle of the pulley that has direct contact with the v-belt around the circumference of the pulley). Maybe someone else on GJ knows the site I am referring to or knows of another one that would have the info.

I'm not very experienced working with higher horsepower setups, so I don't know when it becomes necessary to have a dual v-belt setup vs a single belt, but my attached chart seems to indicate that you should be fine carrying the full 5hp load with a single A or AX series v-belt as long as your faster spinning pulley (the motor pulley) is spinning at a minimum speed of 450rpm, which it definitely is. It looks like all the new 5HP air compressors I see available for sale online also only use a single belt, so a single belt pulley setup should be fine as long as you upgrade to the correct type of v-belt for your application.

 

[isb cornbinder]

It looks like a mess
but it also cost 150 for the tank pump and 2 motors.

BUT, it does not work.

 

[Bert_]

BUT, it does not work.

Yet

 

[isb cornbinder]

My Ingersoll did not arrive here as a working compressor. I collected parts for more than 10 years. I cruised Craigslist many times a day with my list of many wants. I have/had lots of good luck and met some nice sellers. On one visit to a shop that had a new Ingersoll 80 tank for $250, I found another person who was selling a Baldor polisher.($400) Another guy in the complex sold me a Baldor 5hp compressor motor. ($200). The compressor component came from an auction. I was the only bidder at $25 for a box of parts mixed with leaves. The parts included a rebuild kit, new pistons, bearings, the crank-case and the cylinders
I can identify with the "YET".

 

[MacMcMacmac]

Should have said the unloader no longer continuously leaks when off. It now only leaks briefly when turned off but it's always leaking when on. Didn't quite specify but the Milton check valve I installed is brand new and correctly plumbed. Surely it's not bad already.

I'll take pictures of the pump from every angle in a few hours. There's also a guy online in this comment section who is able to identify them sometimes.

That's probably me.

 

[King Chrome]

4L series belts are lighter duty v-belts designed for fractional horsepower applications (less than 1hp), so that belt needs to go.

Rip $22. Idk if it matters for the belt but it's not a true 5hp it's peak 5hp

I guess 8.5 flywheel is going to have to stay since all the 14 inch ones are pricey enough to just buy a whole 'nother harbor freight pump. Maybe an air compressor graveyard around here has a 12 or 14in.

On ebay I a found 2"- 2grv... a 2.15"- 2grv...and a 2-1/8, 1grv. Don't know if one single AX46 belt cares about the extra weight of a single/double or double/double grove pulley config. Might buy both types of pulleys.

By the way, it was 3450 motor there was just crud covering the 4.

 

[King Chrome]

That's probably me.

If so I hope you can work your dark magic on this one.

 

[MacMcMacmac]

Well, it's definitely a DeWalt... Seriously, I can't find a spec of info on this thing. I don't know why they didn't just stick with the Emglo pumps they inherited, they were some of the best you could get for their size. The silver probe may be the remains of a low oil shut down system. Worth having, since it looks like it was probably running pretty hard given the tiny flywheel and fan blades galore.

If the unloader is blowing off while running, it either has a perished o-ring inside it, or i might need to be adjusted slightly. Sometimes you can bend the little metal tang that presses on the needle valve so that it is farther away from it while running. Sometimes you can move the entire valve. If not, you will need a new needle valve, if you can find one. I used to be able to source them individually back in the day. If not, a whole new switch isn't that expensive.

I think you have the ingredients for a decent machine, but it might not come as cheaply as you would like.

I need to read more before posting sometimes, you obviously have the new check valve and plumbing installed properly.

 

[seber]

4L series belts are lighter duty v-belts designed for fractional horsepower applications (less than 1hp), so that belt needs to go. You will need to switch to a type A v-belt (I found a source online that said they require a 3" minimum pulley diameter or you will have belt delamination issues) or a type AX v-belt which is cogged and might be able to reliably handle a smaller than 3" pulley. Note that type A and AX belts are measured differently than 4L belts. There is a 2 inch difference as a result, so the 4L480W belt you are using right now would translate to a AX46 cogged belt to have a belt with the same total outside length.

I can't seem to find the website I've used in the past for calculating belt slippage and minimum pulley diameter. It calculated slippage based on the wrap angle (angle of the pulley that has direct contact with the v-belt around the circumference of the pulley). Maybe someone else on GJ knows the site I am referring to or knows of another one that would have the info.

I'm not very experienced working with higher horsepower setups, so I don't know when it becomes necessary to have a dual v-belt setup vs a single belt, but my attached chart seems to indicate that you should be fine carrying the full 5hp load with a single A or AX series v-belt as long as your faster spinning pulley (the motor pulley) is spinning at a minimum speed of 450rpm, which it definitely is. It looks like all the new 5HP air compressors I see available for sale online also only use a single belt, so a single belt pulley setup should be fine as long as you upgrade to the correct type of v-belt for your application.

That chart assumes a smooth running load. Air compressors have a pulsating load. Which is why you will normally see two belts for any compressor over 3 hp.

 

[King Chrome]

It works now.

I used a 2" single groove pulley with 46" - AX44 v-belt. Though, it seems like there is more belt noise when I use a single belt.

Spinning around 811 rpm, it takes 7 minutes to reach the cut off pressure of 105 psi, which according to a pump up calculator means is making 8.19 cfm ... Wish it at least filled in 5 minutes. I could prolly run 2.15" pulley and knock off 30 seconds. The air filter is shot. Replacing it could save time.

The filter is full of paint dust, and when I took off the head and it was splattered with paint goo everywhere too. The reed valves look intact. I wiped the paint off the pistons and used my hand to check for suction/compression and threw it back together.

Someone may have actually slapped a 30 gallon tier pump on it which typically do around 8 cfm. Anyway, this setup enables a few more applications than my previous 8 gallon hot dog. Down the road I might sell the pump/motor as coupon for one of those fancy 15cfm pumps.

With the knowledge I have now I could have got it to pump air with $20. But as it were, I overspent on a lot of belts. So remember to double check belt type for pulleys and recalculate the needed belt length.

 

[Citation]

It works now.

I used a 2" single groove pulley with 46" - AX44 v-belt. Though, it seems like there is more belt noise when I use a single belt.

Spinning around 811 rpm, it takes 7 minutes to reach the cut off pressure of 105 psi, which according to a pump up calculator means is making 8.19 cfm ... Wish it at least filled in 5 minutes. I could prolly run 2.15" pulley and knock off 30 seconds. The air filter is shot. Replacing it could save time.

The filter is full of paint dust, and when I took off the head and it was splattered with paint goo everywhere too. The reed valves look intact. I wiped the paint off the pistons and used my hand to check for suction/compression and threw it back together.

Someone may have actually slapped a 30 gallon tier pump on it which typically do around 8 cfm. Anyway, this setup enables a few more applications than my previous 8 gallon hot dog. Down the road I might sell the pump/motor as coupon for one of those fancy 15cfm pumps.

With the knowledge I have now I could have got it to pump air with $20. But as it were, I overspent on a lot of belts. So remember to double check belt type for pulleys and recalculate the needed belt length.

Do keep in mind that other things can affect pump rate. If you are not at sea level then you can expect slower fill times. For not much money on clearance the Harbor Freight "3hp" pump is a very good value. It's a true 10cfm 145 psi pump. Not too noisy with the stock filter.

 

[King Chrome]

My elevation is 270ft to 300ft. So it's probably not of a big effect. I want the 5hp pump from HF. It costs the same money and looks like it pushes more air but it's not measured in scfm for whatever reason. Also never in stock so I'd wheel and deal with manager

Some people say it works with their peak 5hp. Others say have had to dip it to 700/750 rpm to avoid thermal overload.

 

[Citation]

My elevation is 270ft to 300ft. So it's probably not of a big effect. I want the 5hp pump from HF. It costs the same money and looks like it pushes more air but it's not measured in scfm for whatever reason. Also never in stock so I'd wheel and deal with manager

Some people say it works with their peak 5hp. Others say have had to dip it to 700/750 rpm to avoid thermal overload.

One of my brothers has the 3hp HF pump. Another has the 5hp. However, the 5hp pump was paired with a "4.7" hp motor (at 18.5 amps) so it was run at less than full capacity to avoid overloading the motor. Both seem happy enough with their respective setups. I think the 5hp claims something like 17cfm. That would put it in real 5hp range.