Window unit compressor overheat - Contractor Talk - Professional Construction and Remodeling Forum

protechplumbing · 01-05-2009, 10:59 PM

I've got a window unit at my brother's house that is tripping off. It cools then shuts off. Pulled the cover and there are service ports on it. Checked the pressures. Lo side =50-70psig and the high side starts out at 350psig and climbs to 400+ until the thermal switch kicks the compressor off. The sticker on the side says the L.S. 150 and H.S. 350. Is it possible that there is moisture in the system that is clogging the capillary tube and causing to high of a pressure differential or is it something else?

flashheatingand · 01-05-2009, 11:40 PM

Odds are that the condenser coil is very dirty. If you can, pull out the unit, and give it a good washing with a garden hose (wash from inside out). It is possible that there is moisture in the refrigerant, but, try the simple stuff first.

protechplumbing · 01-06-2009, 10:36 AM

Condenser coils appear clean and are rejecting heat adequately. The liquid line coming out of the condenser is mildly warm.

flashheatingand · 01-06-2009, 10:11 PM

Did the suction pressure drop as the high side increased or did it stay relatively constant? If the suction dropped significantly while the high side pressure climbed, then it is likely that there is a restriction (moisture or something else) and you are on the right track. Has somebody messed around with the refrigerant circuit? Or has it been untouched. If it has been untouched, the likelihood of moisture is not high. You would be surprised how much a difference a good washing of the coil will help even if the coil appears clean. I would put a sprayer on a garden hose and give the coil a good washing first (inside to outside). Another possibility is that the fan motor is going bad (lower rpm's) after ten minnutes of run time. That also could account for a high discharge pressure.

Even if the moisture was the culprit, do you have tools to reclaim the refrigerant, purchase a new cap tube, and weigh in the charge...etc. It's a lot easier to wash the coil before messing around with the refrigerant circuit.

Good luck, I know you are a pretty sharp guy based on that electrical question you posted a few months ago and you will get to the bottom of this. Let us know the final outcome.

protechplumbing · 01-07-2009, 11:52 AM

I cleaned the coil though I don’t think it needed it.

The pressure on the low side does drop as the high side goes nuts. I do have a stinger and recovery tank but I'm pretty inexperienced with HVAC and am self teaching myself. I was thinking if it is moisture that I could just pull a vac then put just a little fresh r22 in and vac again. Weigh out a fresh charge the do s.h./s.c. check and it should work. Could there be actual solid debris in the line some how clogging the cap tube? I would think the filter would catch any solids if they some how got into the circuit. Another thing I'm not clear about would be how to replace the cap tube entirely. I would assume that the brazing would have to be done under nitrogen to keep any copper oxides from flaking off after brazing and re-clogging the tube. I've never tried to braze onto such a tiny copper tube either. It's about as thin as medium sized spaghetti noodle.

flashheatingand · 01-07-2009, 08:50 PM

Does the system frost immediately after the cap tube or at the filter? I think the spaghetti tube you are talking about is brazed into the evaporator. You would heat that joint and pull out the "spaghetti" there (spaghetti is the male and the evap coil is the female). and re-insert the new piping...etc. You are on the right track. But, its vac then recharge. Not vac, recharge, and vaccum again. Also, you might as well replace the filter as well. As for the nitrogen, use it if you have it, but I wouldn't go out of my way to pick up a tank.

This is a project for a learning experience right? Also, did you rule out the fan motor as a culprit? I am not saying you are wrong, and this would be good hands-on practice. It's just that I would want to make sure everything else is good. Like I said, it would be cool to know how things turn out.

protechplumbing · 01-07-2009, 08:57 PM

Pretty much.

It does frost up right after the cap tube.

Quote:

Originally Posted by flashheatingand

Does the system frost immediately after the cap tube or at the filter? I think the spaghetti tube you are talking about is brazed into the evaporator. You would heat that joint and pull out the "spaghetti" there (spaghetti is the male and the evap coil is the female). and re-insert the new piping...etc. You are on the right track. But, its vac then recharge. Not vac, recharge, and vaccum again. Also, you might as well replace the filter as well. As for the nitrogen, use it if you have it, but I wouldn't go out of my way to pick up a tank.

This is a project for a learning experience right? Also, did you rule out the fan motor as a culprit? I am not saying you are wrong, and this would be good hands-on practice. It's just that I would want to make sure everything else is good. Like I said, it would be cool to know how things turn out.

MALCO.New.York · 01-07-2009, 09:04 PM

Never seen a REALLY successful R & R on ANY window unit nor a Refrigerator. Successful meaning lasting much more than 1 more season.

But if there truly exists King Valves, maybe it will last.

Start talking about Bullet Valves and replacing tubing..............Never a good scenario on such a Compact Systems.

protechplumbing · 01-07-2009, 11:05 PM

I never said anything about king valves

Are you referring to the service ports? If so, I'm not sure you’re using the proper terminology (I could be wrong as this is not my trade and I'm basically doing this out of books). I believe a "king valve" is an actual valve located close to, and usually on top of, the compressor.

What I was referring to was simple service ports (1/4 flare fitting with a Schrader valve inside of it)

Plumber, not A/C tech. Please forgive my ignorance if I'm mistaken.

MALCO.New.York · 01-07-2009, 11:13 PM

Quote:

Originally Posted by protechplumbing

I never said anything about king valves

Are you referring to the service ports? If so, I'm not sure you’re using the proper terminology (I could be wrong as this is not my trade and I'm basically doing this out of books). I believe a "king valve" is an actual valve located close to, and usually on top of, the compressor.

What I was referring to was simple service ports (1/4 flare fitting with a Schrader valve inside of it)

Plumber, not A/C tech. Please forgive my ignorance if I'm mistaken.

OK if there are actually High and Low Schraders, your success rate WILL be greater than a Bullet Tap!

I may have used the wrong term, but if I recall, the larger style valves, as one would see on a Home A/C unit and on a car, are called "King Valves".

I am not HVAC. Just seen and heard lots of different stuffs concerning lots of different stuffs.

protechplumbing · 01-09-2009, 12:11 AM

Update: Pulled vacuum and heated everything with a space heater while under vacuum for about 20 min. Recharged with fresh r-22 to factory spec. Fired it up and she doesn't over heat

. The low side was a bit lower than what was on the sticker but it was cold when I finally fired it back up so that's proly why. High side is dead on though.

OK, so what do I do with the old r-22 that is most likely tainted with moisture?? (I'm into doing the right thing environmentally)

Thanks for your guidance flash

MALCO.New.York · 01-09-2009, 12:27 AM

Quote:

Originally Posted by protechplumbing

Update: Pulled vacuum and heated everything with a space heater while under vacuum for about 20 min. Recharged with fresh r-22 to factory spec. Fired it up and she doesn't over heat

. The low side was a bit lower than what was on the sticker but it was cold when I finally fired it back up so that's proly why. High side is dead on though.

OK, so what do I do with the old r-22 that is most likely tainted with moisture?? (I'm into doing the right thing environmentally)

Thanks for your guidance flash

Huff it man!!!

NO!! Do not Huff it!

IF you were certified...............You would KNOW what to do!

(

Just thinkin' like you........Concerning Plumbing!!! Gotta get my licks in when I can!!!

)

protechplumbing · 01-10-2009, 04:09 PM

I am EPA certified. Just because I know that I have to recycle Freon doesn't mean I know WHERE to take it to recycle it and what that costs (if anything) as none of that information was in the books I had to read to take the EPA test. I have not taken Freon out of a circuit up until this point so I have no idea where to take it.

MALCO.New.York · 01-10-2009, 04:13 PM

Quote:

Originally Posted by protechplumbing

I am EPA certified. Just because I know that I have to recycle Freon doesn't mean I know WHERE to take it to recycle it and what that costs (if anything) as none of that information was in the books I had to read to take the EPA test. I have not taken Freon out of a circuit up until this point so I have no idea where to take it.

Just bustin' yer Cajones!!

SLSTech · 01-10-2009, 04:21 PM

Quote:

Originally Posted by protechplumbing

I am EPA certified. Just because I know that I have to recycle Freon doesn't mean I know WHERE to take it to recycle it and what that costs (if anything) as none of that information was in the books I had to read to take the EPA test. I have not taken Freon out of a circuit up until this point so I have no idea where to take it.

Try here
http://www.co.pinellas.fl.us/bcc/uti...ofit/freon.pdf (most counties have something similiar)

From another site

Quote:

For more information concerning the proper handling of freon, contact the Florida Department of Environmental Protection, Bureau of Solid and Hazardous Waste (http://www.dep.state.fl.us/waste/categories/shw/default.htm) or the Florida Center for Solid and Hazardous Waste Management (http://floridacenter.org). This information is offered only as guidance. Specific requirements may vary with individual processes and/or businesses.

protechplumbing · 01-10-2009, 04:38 PM

Thanks slstech.

flashheatingand · 01-11-2009, 10:29 AM

There is a local supply house that takes our reclaimed refrigerant. If I were you, I would call one of the supply houses to find the nearest drop-off point. It isn't free. By the way, glad to hear things worked out, and good job on the diagnosis.

I don't mean to sound creepy, but I would bet that hvac would be a good career path for you. Are you still doing something with electrical?

protechplumbing · 01-11-2009, 12:35 PM

here and there. I got slammed with plumbing work so I don't have much time right now to dabble around in electrical and hvac. When things slow down a bit I'll get back on the horse.