roh roh compressor motor thermal overload is tripping

shannonw · May 1, 2012

Hi All,

Quick background, it's an ssl5 i picked up a couple of years ago for pretty cheap 100 bucks, it had a bad motor. Picked up a new baldor 5hp on ebay awhile back (so you know YMMV on those deals) it sat awhile but i got it put together a while back. All in all a YMMV deal so ...

http://www.garagejournal.com/forum/showthread.php?p=1978237#post1978237

Yah i know no belt guard (that's an older post) have one now.

Anyways I've been using it but not really working it heavy. Last couple of days been working it more running some 5" sanders for 30m or so at a time. But today the motor thermal overload is tripping on me. Once it cools and resets Its good for about 3-4 cycles then trips again a bit after starting that last cycle. It's not the breaker but the motor thermal protection that kickin in.

Anyclues on where to start why it's getting so hot?

I did some basics double checked the belt tightness all is good there.

Obviously the pump turns as it cycles several times....wouldn't trip unless the long run time. Could it be the pressure switch cutting on too early or late working the motor longer?

I'll pull the belt off later but not really sure what i'd be looking for except to make sure things turn.

Steevo · May 1, 2012

Is that really a 5HP motor?
What model of Baldor motor is it?
How many amps does it say it draws at 230v?
A true 5HP motor will be 23A or better at 230v.

A compressor duty motor should also have a service factor rating of at least 1.15

Thermal overload is just that, overload.
It means the motor is not up to the task of running the pump under the load you need from it.

shannonw · May 1, 2012

Steevo, thx for the reply. The stats on the motor look to be 5Hp running to me, 21 amp @ 220 on the motor which from research was the same as the original emerson one...but I'll double check that stuff tonight to be safe. The motor number i'll have to check it was actually a quincy part number from research which i imagine is for one of their 60 gallons.

Maybe it's pulling too many amps? I'll put an amp meter on it tomorrow.

shannonw · May 1, 2012

Also the rpm's and everything matched up to the original. The only thing i had to order a pully but i did the calculations on those to get the right size.

Should it be pulling right at 21 amps? or is a bit higher running possible? One thing I thought was wierd i did put an amp meter on it quickly awhile back and it seemed high...26 amps when it was running.

shannonw · May 1, 2012

Also..i did have the motor tested on a bench at a winding shop close by when i got it, it was only pulling 2amps with no load.

RECox286 · May 1, 2012

The motor is pulling too many amps. You need to use a "compressor

duty" motor for compressor duty applications.

You can try replacing the motor pulley for a smaller diameter one.

It may help. Also, you could rig a fanblade on the motor pulley to

help pass cooling airflow over the motor, but I think you need to

change the motor type to get the results you desire.

Uncle Bob

larry_g · May 1, 2012

back to the basics,
Are you getting a full 240vac at load? Is the wiring up to snuff?
If your pulling 26a then your on the high side, Why? Are you geared wrong running the compressor to fast? Are you running to high of pressure? Is there adequate air flow to cool the motor and pump? Is there good oil in the pump head? Oil helps to cool.

You said in your other post that you did the math for the drive pulley, can you post the pump speed spec and what speed it is really turning at? Most pump heads have a speed range and where in the range it should run for the given power of the prime mover. In a quick look I could not find the spec for your pump head.

I'm suspecting that your running the system to a high pressure with a pulley that is just on the high limit of acceptable size. Try a smaller motor pulley or reduce the cutout pressure till the motor runs within its FLA spec.

lg
no neat sig line

In your

shannonw · May 1, 2012

i just put my amp meter on it, it pulls 20 amps when there's about 40-50 lbs pressure in the tank, increases to 26 amps before the pressure switch cuts it off at 120 or so.

So it should be pulling around 21 on the high side? Maybe i got the pulley calculation wrong...i've got those specs around here somewhere here maybe i screwed that up, i'll dig it up after dinner.

i'm pretty sure the motor is compressor duty it was a quincy part number from what i remember but who knows i could be wrong there, i'll double check that stuff.

Thanks for the help!

[edit] wiring should be fine i'm like 6 feet from the box. I'll double check voltage on both legs and under load.

larry_g · May 1, 2012

Can you get a picture of the motor data plate? It should have the FLA data on it. If not look up the motor data on the Baldor site. http://www.baldor.com/products/prod...ily=Single+Phase|vw_ACMotors_SinglePhase&hp=5

Can you find your motor number in the above link? If so click it and then read the spec sheet.

If your pulling 20a at 40-50 psi I think your running to fast, or have some other problem that is increasing the load. If you look at some of the motors linked above they are all in the 20a range and you are reaching that at only half pressure.

wiring should be fine i'm like 6 feet from the box. I'll double check voltage on both legs and under load.

Don't discount poor connections, undersized wire, and low voltage coming from the pole. Trust but verify at the compressor.

lg
no neat sig line

shannonw · May 1, 2012

Hi Larry,

yeah something odd there with the load, i remember looking at the curve charts before now that you mention it.

http://www.aire.ws/HOJA ING SS3.pdf

So pump should be turning 950rpm,

the motor is 3450 rpm

This was IR's docs on the pulley for the original motor according to the dealer (unfortunately i did not have the original pulley so i'm going by what they quoted me):

SET, SHEAVE 1A4.0X0.875 AK44H X .875

This is the pulley i'm running:

http://www.surpluscenter.com/item.asp?item=1-BKH50&catname=powerTrans

Which on the order showed as:

4.75 O.D. H-BUSHING SINGLE GROOVE PULLEY
SET, SHEAVE 1A4.0X0.875 AK44H X .875

Does that make sense to anyone else? It seemed right to me.

On the motor specs, i could never find them on baldors website because it was a SPL and googling showed it was a replacement for a quincy 60 gallon so seemed it would be comparable. Unfortunately i don't have that number but i'll dig it up here shortly and take a picture of the motor plate.

shannonw · May 1, 2012

hrmmm maybe that number should be a 4 inch pulley instead of 4.75?

shannonw · May 1, 2012

ok i remember now

So the pulley i'm running is:

Belt Type A (1/2") Datum Diameter 4.00"
Belt Type B (5/8") Datum Diameter 4.40"

Which i took belt type A to be the correct one comparible to the IR specs:

SET, SHEAVE 1A4.0X0.875 AK44H X .875

iirc (i'm not expert on this i remember looking up the belt types), but maybe the original IR pulley is 4.0 OD and i'm running a bit too large like larry thinks.

larry_g · May 1, 2012

well according to my math

3600rpm motor
950 pump speed
14.5" pump pulley (pitch dia)
= 3.8" motor pulley

http://www.surpluscenter.com/pages/Catalog285-117.pdf

It would seem to me that you would want a 3.95 or a 4.25" od max pulley per the above link depending on whether you have an A or B section belt. If you run your current, amps, ratio's you will see that you need to be at ~75% (20a/26a) of what your running now or ~3.5" od (.75x4.75") pulley. So you decide. Me I would probably go 3.5 or 3.75"od to be safe and run a bit slower, quieter and some longer life.

lg
no neat sig line

shannonw · May 1, 2012

Hi larry,

yep, I think zero'd in right on it and i'll bet that's it....that's where i messed up.

Thanks all for the help! I'll let you know how it goes

Kevin54 · May 1, 2012

Is there anyway that you could do like mentioned above and put a fan on it to help cool? I know the motor on my IR has a plastic fan inside the motor at the pulley side to pull air in and cool it.

What you may want to do is try your compressor while running a box fan or some type of fan blowing on the motor

RangerDaleXp · May 1, 2012

Did you watch the voltage when it was at 26 amps? You may have excessive voltage drop on that outlet and as the motor loads down, the voltage drops. the motor then will pull more amps.

shannonw · May 1, 2012

You know...that's where i messed up I remember using this:

http://www.surpluscenter.com/techhelp/motorpulleycalc.html

Which gave me a 4 , being clueless on this, i assumed that was not the OD measurement but the datum diameter (which seems now to be more related to belt). You know...i remember now thinking i'm probably doing this wrong...uggg

here's the funny thing, i didn't order it from IR as it was like 60-70 bucks which just seemed nuts for a pulley. I ordered the first one from SC...and promptly dropped it the next day and broke it. Ordered the 2nd one which of course we now know is the wrong size. And i'm going to order a 3rd which will put me when shipping is all accounted for at the price of the IR one to begin with!

lol you win some and you loose some.

shannonw · May 1, 2012

Kevin, that baldor motor has tons of cooling fins in it, i don't think it's air...I was wondering the same..it's cooled from those not the pulley as the on the pully side there are no vents on the front, it's all pulled in with the internal fins and the side vents.

Ranger I didn't get a chance to check voltage when i was doing amps, (side tracked with a pan of oil on the oven setting the fire alarm off while i was putzing with the compressor).

But i'm going to do that tomorrow to double check there's no voltage drop, and after that plan on the pulley as it does seem like i'm running one too large.

Kevin54 · May 1, 2012

shannonw said:
Kevin, that baldor motor has tons of cooling fins in it, i don't think it's air...I was wondering the same..it's cooled from those not the pulley as the on the pully side there are no vents on the front, it's all pulled in with the internal fins and the side vents.

Ranger I didn't get a chance to check voltage when i was doing amps, (side tracked with a pan of oil on the oven setting the fire alarm off while i was putzing with the compressor).

But i'm going to do that tomorrow to double check there's no voltage drop, and after that plan on the pulley as it does seem like i'm running one too large.

I didn't mean the pulley itself cooling it, just the end of the motor that is on the pulley side of the motor.

The motor on my IR has a cooling fan built inside the motor. It's a white plastic fan inside.

shannonw · May 1, 2012

I think the way these work or at least this one, it has a metal fan on the shaft inside (pulley side). That should pull air in from the rear and out the side vents (or visa versa) so it's got a good bit of air flow. But right if you're not rotating fast enough it would make sense heat would build up.

I was able to figure out roughly by process of elimination which quincy model this motor is off of (the cheaper 60 gallon ones sold at some outlets,etc is my best guess), the partnumber that was on the box led me to google which while not pinpointing a model pointed me to a 60 gallon, given it's an SPL motor it's probably off one like this (which looks identifical from the rear):

http://www.northerntool.com/shop/tools/product_200350475_200350475

So should be fine for this compressor, similar specs as all these other type.

I ordered a smaller pulley tonight...can't get here fast enough. I'm not going to run it more until i get that on there and can check the amps then i'll look at these other suggestions. My money is on my screw up.

Hope i didn't screw anything up if that's it, but i've probably only got 30-60m runtime on it since i got the motor on. It just started kicking today because i really began using it so it had to cycle.

Steevo · May 1, 2012

Should be fine once you reduce the motor pulley size and lessen its load.

larry_g · May 1, 2012

Can you do one test on the existing setup for my curiosity. Can you test fill time on the existing set up and then do the same test with the smaller pulley? I'm curious if the ratio of old to new fill time is directly proportional to the pulley ratio change.

lg
no neat sig line

RECox286 · May 2, 2012

After reading the back and forth:

I would suggest a 3.5" od motor pulley, and the addition of a fan blade attached to it

not to push air thru the motor, which already has an internal blade, but to push air

over the outside of the motor. I also never use a 3450 rpm motor for a compressor.

(much too fast to begin with) I prefer to keep the speed down by using a 1750 rpm.

I'm of the opinion that a compressor should sound "thunk-a-thunk", and not "bzzzzzzz".

Uncle Bob

shannonw · May 2, 2012

Hi,

Yes I took larrys advice and went with the 3.5.

Larry yes I'll do a fill test and compare the two. I'm not even going to pretend I understand the math around all this as it was always my worst subject.

Howver on a completely uneducated hunch i'm going to guess same or less fill time, i'm guessing the smaller pulley will turn less rpms so you'd think fill time would be more, but on the other hand i'm guessing that since the motor is overheating it's laboring against the load and likely not turning the correct rpms to begin with?

ReCox, yes i've read the threads on here about the lower rpm motors and the noise/cooler running advantages,etc. My intention was to find an compressor that ran at a lower rpm, but ran across this awhile back and i'm not a heavy enough user for it to bother me too much.

That's intriguing though, I didn't think much about using a smaller pump pulley and finding a 1750 motor even though i know that's how some work and this is the budget setup.

i'd love to turn less rpms, i wouldn't mind keeping my eye out for a 1750 motor..i know those are typically pretty darn expensive, would that work? I'd wonder about cooling cause the pump would be turning the same rpm but presumably you'd have a smaller pump pully (8") pushing less air?

Milton Shaw · May 2, 2012

One other thing is make sure the check valve/unloader is working all the time. You could ge getting at leakback from the tank and trying to start at full load - stalled compressor and tripping the overload. I had one that was sticking and unless you were right next to the compressor when it cut off you could not hear the pressure release when it shut off.

shannonw · May 4, 2012

Update!

while i haven't ran it continuously i'm pretty sure larry nailed my mistake right off the bat.

Now i'm turning ~14 amps at empty, at peak of fill a hair under 21 with the 3.5 pulley!

fill time difference

2.48 vs 4:13 with the 3.5 pulley..not bad. The motor is *noticably* cooler just by touch. I could touch it on run 1 with the wrong pulley and that was the first run of the day and it was noticably warm. After it cooled and I got around to installing the 3.5 I really couldn't feel much heat.

So while i haven't ran it continiously i'm pretty sure you fixed it. Larry I thank you much sir!

shannonw · Feb 13, 2013

Oh boy well this compressor deal isn't working out. Win some loose some.

I noticed recently the thermal limit was tripping after runtime from sanding.

Today i ran it then put my amp meter on it, at 50+ lbs it's pulling 20+ amps..was pulling over 21 at 100. So i removed the belt, let it cool, the motor now by itself is pulling 18-19amps. So something is pooched with the motor. Any ideas? I'll probably run it down to the electrical shop who checked it out to see if they may have an idea if it can be saved at a reasonable cost.

shannonw · Feb 13, 2013

Yeah something fried. I checked voltage running on the 2 legs at the motor and it's ok. After cooling a few hours it's still pulling 15 amps no load. So something is fried.

caper150 · Feb 13, 2013

I have the same problem with my IR if I'm blasting, I tok it to a motor repair guy who told me that this is common for these IR compressors and he see's a ton of them come in. He suggested sitting a fan in front of it whenever I am using it.

shannonw · Feb 13, 2013

I'm going to check out the run capacitor, it's either that or something else. The motor with no load drew 2amps awhile back so something isn't right.

larry_g · Feb 13, 2013

Well it seems you can't catch a break here. I'm glad this thread came up again though as I missed your post #26. That was about the time father went in the hosp and I fell out of the group for awhile. If you have serious motor problems then this may be the time to go with a 1750 rpm motor.

lg
no neat sig line

shannonw · Feb 13, 2013

*whew* i think that's all it is.

The start capacitor is around ~324uf (on the cap) my meter has capacitance range of Range: 1 nF to 9999 µF it reads right around 324 give or take on that cap. I presume the higher is the start capacitor.

I put it on the other (which i presume is the run)...it's a 40uf and meter shows 0.

No electrician, and have never even used this function but i'll call that a correct diagnosis. I already replaced the start awhile back before i even had this compressor back together. I'm thinking since the motor was a quincy part number maybe it was old stock.

I'll be happy if that's it as those are only couple bucks.

shannonw · Feb 13, 2013

Opps hi larry! sorry i didnt see your reply above.

Sorry to hear about the hospital, I had thought i hadn't seen you around. Hope all is well!

i remember a thread popped up awhile back about changing to a 1750 and don't recall seeing much input on it but I've been pretty busy as well to keep up much here.

I sure appreciated your help that last time, was educating as well.

I hope even with my measly skills i may have figured this out. Motor sounds fine aside from the rpms and i haven't ran it that much...but i remembered awhile back reading on the start vs run capacitor's and this evening it just rang a bell that I had read that would cause overheat and more amp draw. So if my brief read of this capacitance function on this fluke is correct it looks bad.

shannonw · Feb 13, 2013

Caper150 i'm not sure about that may want to check it out again, i wouldn't say i use it much but run it pretty good for an hour when sanding on/off, quite a few members on here with these I've read use them pretty heavily. It's pretty tough to tell much i've found out without testing with a clamp meter while it's on load, off,etc.

As an aside this clamp meter is one of those things I said man when will i ever use this? boy was i wrong has it come in handy...i've diagnosed pool pump overamp, dishwasher overamp and now hopefully compressor overload with it.

shannonw · Feb 14, 2013

Put the new run cap in, and it's like normal, pull 14 amps at empty, at peak full 19 amps...seems even slightly better than the original time i measured after changing the pulley! I ran it a good 10 minutes leaving the air open at running peak it stayed right at 19amps.

I didn't run the motor down, just took the cap, he did say a bad motor can make them go bad as well but i didn't have much time to discuss. Seems ok and normal now from what I'm measuring so just hoping it was that cap and nothing is wrong with the motor.

Will see next time i got to run a sander.

shannonw · Feb 14, 2013

Though now that I think.. i do wonder about the motor, see i can't remember but i seem to recall long ago when i had it bench tested that it pulled 2 amps when off the compressor...it doesn't do that today. But i'm going by memory which may be wrong and never tested that myself. So we'll see if the new cap goes bad.

nehog · Feb 14, 2013

shannonw said:
Though now that I think.. i do wonder about the motor, see i can't remember but i seem to recall long ago when i had it bench tested that it pulled 2 amps when off the compressor...it doesn't do that today. But i'm going by memory which may be wrong and never tested that myself. So we'll see if the new cap goes bad.

What would cause a motor to damage a capacitor is a shorted winding. And a sorted winding will cause over heating under no-load conditions. A quick test might be to run it from cold for about 15 minutes with no belt on--if the motor is reasonably cool (perhaps a slight noticeable warmth, but clearly not hot) you're probably good to go.

shannonw · Feb 19, 2013

Looking good. i sanded today and ran the compressor about as much as usual when it would trip. This time i left my amp meter on it, it never went above 20amps the entire time, usually hovering around 19. so that's looking pretty good and within specs! Motor was tons cooler. Hopefully this will be it for awhile!

shannonw · Sep 1, 2013

Welp i'm back resurrecting this old thread

compressor overheated month ago sanding (sure florida summer it was hot).

But today i got around to putting my amp meter on it. pulling close to 17 amps with no belt/load. Under load at 100+psi it's pulling 23-24 amps which is too much for this 21 amp motor.

Anyhoo...pretty sure it's this 3450 21amp SPL motor, they're just not meant for long run periods. It's running but will trip the thermal if i run a sander a lot. So until it gives up the ghost..

What do you guys think?

Put a 1750 rpm motor on here and starter (single stage ingersol ss5l5 pump)

or wait for a deal on another compressor. Unfortunately can't go 80 gallon which is going to nix a lot of craigslist deals, and this one keeps up with my sander so i may think about looking for a 1750 motor and larger pulley.

Anyone think changing the motor and pully to a lower rpm one will be a problem? Can't see how...pump would still be turning at same rpm.

shannonw · Sep 4, 2013

Yeah i think i was ignorant on motors and steevo was right on back then, this thing needs a 23 fla motor as at 100% load the pump pulls 21.5, these SPL motors you see on compressors assumes time spent over fla will be brief.

I'm thinking a L1410 fla 23 is the way to go on this, i imagine this is what eaton is using on theirs and it's 1750

http://www.baldor.com/products/spec...Phase&hp=5&winding=36WGW849&rating=40CMB-CONT

That should cover the pump full 21.5 without getting above 1.0 sf

http://www.aire.ws/HOJA ING SS3.pdf

But that will mean motor + starter switch + pulley.

roh roh compressor motor thermal overload is tripping

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