I have been given a 24000 BTU window unit. I need this in a bad way for my shop. It blows cold, but the motor cuts out within a few minutes.

I have the motor out, it's 230/208 volta, looks like 1 HP Fan Duty, thermally protected motor. Appears to be made by RMR, corporation.

Can I rebuild this beast affordably. Note, I think I can get a replacement for around $120. What parts are most likely failing? I'd rather not spend too much, I can get an 18,000 BTU window unoit new for around $365.

I can feel some grindin when I spin the shaft. but it does spin. Bearings?


There are 2 big capacitors in this AC unit. My basic understanding of caps, is that they do not have an in and out (pos and neg). Does that sound right?

Sorry for all of the questions, any help appreciated.

It's hot here in Texas :-)

 

Replace the bearings, you may even be able to get them at the auto parts store, -just remove them and see

Is this unit made for three phase or just single phase?

 

It's single phase.

Do you think bad bearings would heat up and trip any thermal protection? Soinds like a possible failure mechanism, given that it runs for a bit.

 

When the bearings are bad the motor will draw excess current and can trip the overload devices. Replace the bearings b4 you burn out the motor.

 

Men forget that old motor, pop in a blown 460! Should cool that shop down to minus 100 degrees in no more than 4.6 seconds

 

You may be wasting your time. If you can spin the motor freely, then the bearings are probably not causing the motor to trip, even if they need replacing.
If it runs for a few minutes, it probably is not the caps.
It may be damaged windings, but you need a megger to test them.

Without proper test equipment you can not determine what the actual cause is.

My advice is take it to a rebuilder and get them to test it for you.

Mind you.....my advice is worth exactly what you paid for it

 

Have you determined that the problem is the motor? Is it tripping the protecter right on the motor? I am no expert on such things but can generally repair all my own appliances with my dvom and a little head scratching. Is the motor noisy when it runs? A small scraping sound may just be the brushes. If you deem it the motor then by all means tear into it. What have you got to lose?
Now being fairly new to Texas, how do I get rid of these darned sand fleas that have taken over my house?

 

I have fixed up a few window units in the past for extra money, and it sounds to me that either the caps are bad or the bearings are creating enough load and heats up that it trips a load switch.
If the windings were bad then it would probly not work hardly at all.
Good luck.

 

FYI, the larger outside a/c units have start and running caps. And you mention that your small window unit has two caps, so I'd venture that it's the same setup. It is possible that your running capacitor is dying. If you knew which one was your running cap you could use the part number and call the local a/c supply houses to find out the cost of a new running cap.

You could probably find the window a/c unit's manufacturer website to get some basic help. Some companies will even sell you the component schematics for a reasonable fee if you want to fix it yourself.

Can you tell us what brand, model number, etc it is?

 

the motor gets quite warm. Too hot to maintain contact for very long with a bare hand. Is that typical?

Caps: well, there are 2. Ones a bit larger, would that be the starting cap or running cap?

Thanks for all the help.


On a good note, te AC n the 67 is now blowing cold :-) Only needed $150 on hoses and freon, yikes. Labor was free, for some work I did on N'Laws PC :-)

 

My two cents....
generally a bad or failing bearing will do one of two things.
1) seize or be hard to spin
2) lose contact and allow you to wiggle the shaft
Any strong electric motor is going to have resistance when you try to spin it. Try taking your altenator and turn it. All electric motors use magnetism.
I would note on either a bad capacitor or carbon tracking in the motor. Carbon tracking is when the brushes in the motor leave carbon deposits on the rotor. This causes a low volt high resistance short. Such a short would allow an appliance to operate until the thermal breaker tripped. Try hosing the thing down with electric component cleaner.
Good luck

 

There are no brushes in an AC induction motor of the type found in appliances like the AC unit we are discussing. The universal motors found in hand tools will have brushes in them. Universal motors will operate from AC or DC.

 

Capacitors are used in single phase AC motor applications to provide a phase differential for motor action (this is required in all single phase operations but is sometimes provided by a shaded pole). Not to be off-color but think of riding a bicycle using only one leg (that is the effect of NOT having a phase differential). If the running capacitor? was degraded I would say that the motor would continue to slow after the starting capacitor cut out until the rotor would stop. I would NOT think that a bad running capacitor could cause a thermal overload since ANY capacitor in an AC circuit is virtually shorted and its capacity decreasing would ONLY shift the phase angle closer to unity. The slight grinding/sluggishness you mentioned is most likely the bearings and would most likely be your culprit. Has the motor been exposed to harsh conditions? If so, try blowing any debris out with 20# air and try running it again. BTW AC motors CAN have brushes however this application is most likely a squirrel-cage induction motor and would NOT have brushes. Oh yeah, the thermal overloads have been known to degrade over time and since they are cheap (and of cheap manufacture) I would look at getting a new one to try out. Even if that doesn't fix it you may get through the rest of the summer with it! But do not use a larger amperage overload (or remove it)! It may be hot now, but working outside when the garage burns down will be even hotter! If you have access to a multimeter PM me and I will give you advice on troubleshooting your motor.

 

at work we have 3 46hp 3 phase hydraulic pump motors. one of them burned up a few months ago. i mean burned up, flames smoke... we sent it out to get repaired. they had to rewind it and replace the bearings. bearings probably wouldve been fine if we noticed it sooner