7.5 HP Compressor Shutting Off - 3 Capacitor Testing & Identifying & Grease Fitting Question

[mm08822]

2 mag started and the same results, time to start considering it's not the issue IMHO.

I'm with ya on that thought but they haven't properly been eliminated through rational troubleshooting. None of the q's directly answered. Some of the next steps taken are impulsive. What's next......change out the entire compressor?

How many ss o/l blocks have you seen spit sparks? Arcing, sparking and hissing usually occurs at the last place in a ckt to close and/or the weakest location.

Take the o/l out of the ckt and observe....... then decide next steps.

 

[mm08822]

So just to refresh. New mag starter installed. Two blue dials on the heat pack set to previous settings. The heatpacks are H2014B and set to M (manual) and D. Today started up twice to test. Both tests, HUGE amount of sparks, more then the old one. Both times. First time, sparked but tank filled and pressure switch set point hit of 175psi. Second time, sparked and tank psi got to about 172 and the thermal overload kicked on and shut it off. Pressure switch air release didn't kick off obviously. It did kick off when I turned it off. I can see arching on the far right heat pack, more then the old box.
.
@mm08822 (1) I checked all the connections, but I will double check tomorrow. (2) You're saying to bypass the heater packs. (3) What could we hope to learn from that? (4) That would bypass the thermal protection that the heat packs provide right? (5) Thinking about that, could the power coming from the subpanel be causing any issues?

1 - How?
2 - Yes
3 - If no spark when out of circuit, then it is the source of the problem.
4 - It's a temporary situation for troubleshooting purposes, not permanent.
5 - Not sure how 4 creates this thought, but everything leading up to it is sight-unseen, so my $$ is still on the compressor.

 

[PCustoms]

How many ss o/l blocks have you seen spit sparks? Arcing, sparking and hissing usually occurs at the last place in a ckt to close and/or the weakest location.

Take the o/l out of the ckt and observe....... then decide next steps.

Brand new electronics, properly used and wired, typically don't just blow sparks. Considering the old one suddenly stopped working, seems to me that clearly isn't the issue.

I'm with you on the troubleshooting. Parts swapping as sole diagnosis a major pet peave of mine.

 

[mm08822]

Brand new electronics, properly used and wired, typically don't just blow sparks. Considering the old one suddenly stopped working, seems to me that clearly isn't the issue.

I'm with you on the troubleshooting. Parts swapping as sole diagnosis a major pet peave of mine.

Properly wired is the question, still not proven. (In this case - assembled. Think about the minimum wage labor told to operate a screwdriver in a factory. After the 10th one is assembled with 90 more to go, their brain is in the clouds and feeling entitled just b/c they showed up to work.)

The old one didn't stop working IIRC, it was changed out iinstead of being properly evaluated.

 

[walta]

.
@walta the 100k question is what is causing the fireball

Let me expand on what I said in post 64.

The chances of having the exactly the same fault in the replacement overload is almost zero. The fire ball coming out of the overload is not the fault it is the symptom. My guess is the winding in the motor have been overheated to the point that the insulation on the windings has turned black and is allow current to flow between the wires bypassing the coil of wire with a very low resistance this allow hundreds of Amps to flow the overload is more sensitive than the breaker. The overload sees the current and is doing it job and stopping stop the flow.

If you want a test disconnect this motor and connect a known good 240 Volt motor.

Or take the motor apart and inspect the winding my guess is they will look burned.

A brand new 7.5 HP motor will cost less than 100K more like a 1K.LOL



Walta

 

[cloves]

Sorry couldn't troubleshoot this weekend with work. Hopefully, today I'll get a look.
.
@mm08822
(1) Before I changed out the old mag starter box, I checked all the connection for tightness. All connects including the heatpacks, basically everything that I could put a screw driver on.
...
(2) I'll try the bypass today after checking and straightening out the heat packs. (3) Got it, no spark then its the source of the problem
...(4) Here is my thought process Power comes into the mag switch from the sub panel. The mag box powers the pressure switch and the electric motor. The motor has the caps. The function of the heat packs is to protect the motor from a short circuit, overload, or overheating correct? So what's to say the motor or bad caps are causing a short and setting off the heat packs? Would I be able to see the amps shooting up if something like a short was happening? BTW you mentioned your money was still on the compressor, what do you mean?
..
@walta So if the motor is actually failing, would bypassing the heatpacks for a test be a bad idea? You mentioned inspecting the motor. Can that be seen by just taking out the outside back end (as in the pic?) Are worn windings possible after light usage over the last few years?
..

 

[walta]

..
@walta So if the motor is actually failing, would bypassing the heatpacks for a test be a bad idea? You mentioned inspecting the motor. Can that be seen by just taking out the outside back end (as in the pic?) Are worn windings possible after light usage over the last few years?
..

I do not like the idea of bypassing the overloads. If you want to substitute with a fuse I would be OK with that.

It is a risky game without the overload and if there is a short circuit you will find the next weakest link in the circuit. That should be the breaker in the panel. Did you say it was 50Amps? If the short is present the next fire ball will be larger. If the fire ball gets big enough a plasma ball can form and the air becomes conductive. When that happens, things get very ugly very fast.

If you can get a bright light in the vents, you may be able to see the winding without disassembly. Taking the motor apart while horizontal should not be hard putting it back together in the horizontal seems unlikely as you are fighting gravity getting the bolts back in the holes will be a trick. A common failure is a stuck start switch that deenergizes the start winding after the motor gets moving. If the switch sticks and the winding stay energized the overload should trip before and damage is done. If someone should reset the overload several time in a few minutes the winding will get overheated and be destroyed





Walta

 

[mm08822]

Screw alignment caution......

As she said, "....firmaly mounted"

 

[micromind]

Post #58 states the the motor current is within nameplate specs. If the motor had any sort of problem, the current would be higher.

Bypassing the overloads is a temporary thing aimed at troubleshooting. Not permanent. If the unit starts with no sparks while the overloads are bypassed, then the problem is the overload block. It doesn't matter if you test 100 of them, if they all spark, they are all bad.

In my experience as an industrial electrician, this type of overload is prone to failure much more often than most others. It doesn't surprise me that 2 failed.

 

[cloves]

Hey guys, so update from this weekend. Turns out my friend's buddy has the exact compressor. He did me the favor and took out all three of his capacitors for me to test. His model must be newer. I noticed that both startup caps have 1 resistor on them vs mine that has 1 double. So we put in his caps. I also replaced the outside (right side) heatpack, checked all screws for tightness. I also double checked all the heatpacks. The new one had arched the far right side one so bad that even the washer where the copper lines hooks to the top starter had gapped and was loose. The middle one was also loose. That one had light arching. So I tightened the middle copper line bolt and replaced the far right heat pack.
..
Started up the compressor no sparks! So we figured probably the startup caps. Then took out his caps and put the old ones back in. Started up to confirm bad caps but I got no sparks. We did a total of three run cycles and haven't gotten sparks. Today I did a fourth startup and no sparks.
..
@mm08822 thanks for the video, that helped me confirm that the heatpack back plate is actually suppose to be slightly angled and not flat on all 3 heat packs. Helped me screw and angle my philips.
...
@micromind thanks for sharing that, do you think the failure point are the heatpacks themselves?
...
So as of right now 3 run cycles and no arching. Here's something which is weird, I put the amp clamp on the GREEN ground wire coming from the electric motor into the Mag starter box. When the compressor is on the amp clamp is showing amps. Does that make sense? (Photo below)
...
(this is with the compressor running)

 

[u3b3rg33k]

@walta So if the motor is actually failing, would bypassing the heatpacks for a test be a bad idea? You mentioned inspecting the motor. Can that be seen by just taking out the outside back end (as in the pic?) Are worn windings possible after light usage over the last few years?
..

don't take those nuts off without removing belt tension, the back cover holds the bearing (and rotor) in place.

 

[cloves]

don't take those nuts off without removing belt tension, the back cover holds the bearing (and rotor) in place.

Thanks for mentioning this. I attempted this over the weekend. I loosened the nuts but the plate wouldn't move. Barely put any force on it, the middle def looks like its got stuff holding it (thought it was those grease fittings possibly) So I just put the nuts back on.

 

[mm08822]

@mm08822 thanks for the video, that helped me confirm that the heatpack back plate is actually suppose to be slightly angled and not flat on all 3 heat packs. Helped me screw and angle my philips.
...

So as of right now 3 run cycles and no arching. Here's something which is weird, I put the amp clamp on the GREEN ground wire coming from the electric motor into the Mag starter box. When the compressor is on the amp clamp is showing amps. Does that make sense? (Photo below)

I think you actually got the screw threads to engage the threads in the receiving hole by angling the screwdriver.

0.49A is rather large for a stray field. Try and take other readings by moving the clamp-on to different positions along the green conductor. Can you also wrap the green wire through the tongs so there is only 1 conductor turn inside the tong "cavity"?
Don't touch any steel while doing this. If the readings don't lower, measure the incoming leads. They should be equal in value. If one is different by ~0.49A, then you have a ground fault brewing.

Measure the ground wire back in the panel right where it comes out of the cable jacket.

For a ground fault, you need to shut the circuit down if you have to get in contact with any steel on the compressor for whatever reason.
Use gloves and dry cardboard on the floor is a good idea also.

 

[cloves]

I think you actually got the screw threads to engage the threads in the receiving hole by angling the screwdriver.

0.49A is rather large for a stray field. Try and take other readings by moving the clamp-on to different positions along the green conductor. Can you also wrap the green wire through the tongs so there is only 1 conductor turn inside the tong "cavity"?
Don't touch any steel while doing this. If the readings don't lower, measure the incoming leads. They should be equal in value. If one is different by ~0.49A, then you have a ground fault brewing.

Measure the ground wire back in the panel right where it comes out of the cable jacket.

For a ground fault, you need to shut the circuit down if you have to get in contact with any steel on the compressor for whatever reason.
Use gloves and dry cardboard on the floor is a good idea also.

Never knew stray current would come from the negative of the electrical motor. I decided to check it after reading into how electric motors can start failing and grounding out
..
Ok, let me see if I am understanding correctly. First try to move the clamp to another spot on the green wire while its running. If I am still seeing .49A, then see if the green wire has enough slack so I can make a loop into the clamp and back to the ground screw on the box correct? Right now there is no other wire inside the clamp.
..
When you said "measure the incoming leads" do you mean the two hot wires coming from the electrical motor into the mag box or do you mean the leads coming from my sub panel?
..
I have some thick electrical rated gloves, I knew they would come in handy someday .

 

[mm08822]

Never knew stray current would come from the negative of the electrical motor. I decided to check it after reading into how electric motors can start failing and grounding out
..
Ok, let me see if I am understanding correctly. First try to move the clamp to another spot on the green wire while its running. If I am still seeing .49A, then see if the green wire has enough slack so I can make a loop into the clamp and back to the ground screw on the box correct? Right now there is no other wire inside the clamp.
..
When you said "measure the incoming leads" do you mean the two hot wires coming from the electrical motor into the mag box or do you mean the leads coming from my sub panel?
..
I have some thick electrical rated gloves, I knew they would come in handy someday .

This possible stray current could be from a minor knick in the winding to ground. I am however initially doubting the reading and thinking it is from other wires in proximity to the meter's tongs. That's the reason to move it to different locations and see if the 0.49 A is constant or approaches 0.0A.
Measure each incoming lead of the power source at the compressor individually. If one reading shows 12A and the other showed 11.5A and the grd wire still shows 0.5A then you have a ground fault present and it will get worse over time and eventually trip while probably destroying the winding. (Numbers are for example purposes only.)
You could measure each motor lead just as easily. Do whatever you can to keep the meter tongs away from other conductors picking up possible magntic field from other conductors. I would expect Klein to have branded a decent meter but I've only used Flukes and never had that problem.

 

[micromind]

If you measure current on both power wires (not including the ground wire) in the opposite direction (like both at the bottom of the starter), they should balance out and the reading will be zero. If the reading of both wires and the reading of the ground wire are the same, them you have an actual ground fault.

This is basically how a GFI works.

 

[cloves]

Hi guys, sorry for lack of updates been away for work. So I retested the green wire coming from the motor to the mag starter box again. This time I picked a few different spots and turned off autorange. I also tested the other two and they had amp but the ground was tiny fraction so it was 40+00 amps vs my photo 0.49. I should have tested all three wires and that would have let me seen all the numbers. So for now the compressor is working. Occasionally I see a bit of electricity inside the motor through the holes. Sometimes I do sometimes I don't.
.
So as of right now, looks like replacing the heatpacks and resitting them has resolved the issue. I tested things out with the mag box cover off to make sure I wasn't seeing sparks.
.
Thanks again to all who shared their knowledge and experience!

 

[wyliesdiesels]

There shouldn't be any current on the ground wire

 

[cloves]

Hi all, so my compressor has been running well for at least 6 weekends where I was working. Last week, it shut off again before full cycle. So I took off the mag cover and tightened snugged the heat pack screw and then reset and ran (no sparks) and it filled to correct psi.
.
That got me thinking, when the compressor turns on, that mag switch box shakes like crazy. I believe the vibration maybe causing the junky eaton screws to loosen. So I am going to move the mag switch box to my wall, to eliminate that. I went to lowes and picked up some SOOW cord one is a 12-3 and the other a 8-3, 6 foot in lenght (so I can reach my wall).
.
When I picked up the cable at the store (online order), both cords looked thin. Sure enough today when I was starting to hook it up I realized the wires is the correct awg but the insulation on the wires and the outside jacket is way thinner. Now the question is whether this is a problem and I am not even sure I can return since its custom cut. (2 pics below)

 

[PCustoms]

Hi all, so my compressor has been running well for at least 6 weekends where I was working. Last week, it shut off again before full cycle. So I took off the mag cover and tightened snugged the heat pack screw and then reset and ran (no sparks) and it filled to correct psi.
.
That got me thinking, when the compressor turns on, that mag switch box shakes like crazy. I believe the vibration maybe causing the junky eaton screws to loosen. So I am going to move the mag switch box to my wall, to eliminate that. I went to lowes and picked up some SOOW cord one is a 12-3 and the other a 8-3, 6 foot in lenght (so I can reach my wall).
.
When I picked up the cable at the store (online order), both cords looked thin. Sure enough today when I was starting to hook it up I realized the wires is the correct awg but the insulation on the wires and the outside jacket is way thinner. Now the question is whether this is a problem and I am not even sure I can return since its custom cut. (2 pics below)

#12 seems light for 7.5ho, but I'd have to give this more thought when I'm awake...

You sure you're comparing apples to apples?

 

[micromind]

looks ok to me.

The motor cord is ok, the control cord could have been smaller but #12 is ok too.

 

[cloves]

I should have mentioned that the awg was what the manual stated (and the cord when I took it out). So insulation and thickness on the wires and the outside jacket isn't a problem? I feel like I got screwed, the electrical supply was way cheaper per foot too over Lowes. But I wanted to get it started today after work.

 

[wyliesdiesels]

#12 cordage is too small for a 40a load. SOOW #12 2 CCC(current carrying conductors) is rated for 25a. You need #8/3

https://www.controlbooth.com/attachments/table_400-5-a-1-pdf.9386/

 

[cloves]

Sorry I should have put more details. The 2 SOOW cords I got (as per manual):
1. Electric motor to the mag switch box = 794464 - 8-3 SOOW Cord
2. Pressure switch to mag switch box = 794465 - 12-3 SOOW Cord

So yup @wyliesdiesels you got that right

 

[mm08822]

Pull the screws out and add a drop of Loc-tite to each.

What is the condition of the belt? Any ribbed sections missing?

 

[walta]

.
When I picked up the cable at the store (online order), both cords looked thin. Sure enough today when I was starting to hook it up I realized the wires is the correct awg but the insulation on the wires and the outside jacket is way thinner. Now the question is whether this is a problem and I am not even sure I can return since its custom cut. (2 pics below)

Your new wire has been value engineer to meet the same SOOW spec while using less materials it shood be fine.

Walta

 

[Bigbandguy]

My compressor is a cheapo HF 24 gallon vertical. It was doing EXACTLY the same thing turning off before it got pressure up. A minutes wait and pressing the reset button got it started again.

I replaced caps, same. No change. I was considering the dump since as old as it is it doesn't owe me a thing. Then the light dawned. Ordered a new RESET button switch of the same size.

Complete cure. YMMV but worth checking.

 

[cloves]

@mm08822 the dual belts looks good. It had just about 1/2 of play which is the max as per manual. So today I was like, might as well tighten it up since I am waiting on a crimp connector. I'll say this to whoever wants to get a northStar compressor, dont! Horribly engineered. Anyways, I loosened the electrical motor, hoping I could get a screw driver into a center slot, so I can move the motor 1/8 to tighten the slack.
.
Nope, the engineers decided not to put a slot in the center of the hold down section. So then I tried to sneak in a long screw driver to the holes where each bolt was, too tight. Then I tried using tie straps on the outside to pull the electrical motor. Even ended up using a piece of 2x4 horizontally and a tie straps and another 2x4 to pry it outward. While that somewhat worked, the electrical motor was then slightly 1/16th not on the same plain with the motors flywheel. So I loosened it and gave up for the night. Easily just spent 3 hours on this thing again.
.
Pardon the drawing, I was so ticked off forgot to take a photo. The green is the tie down strap, looping under the base plate of the electrical motor. I used 2 2x4 shown in yellow.
.
This thing has 2 belts, I just can't figure out how to pull the motor to take up the slack without cocking the motor off.
.
Thought about using inverse clamps, just don't have room to place them.
Dual belts, look good.

Motor and leverage idea: (didn't work)Too much tension from both belts I believe

 

[mm08822]

Since the belt condition is fine, is anything else loose letting the enclosure vibrate?

Are the feet making solid contact with the floor.......no teetering?

Don't forget the mild lock-tite.