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Old 09-01-2010, 01:06 PM   #1
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Can I upgrade the compressor in my RV roof AC unit?


Hello all,

Here is my situation.

I have a large older 1985 model RV (33') it has 2 roof AC Units (110 volt 13,500 btu each)

1 unit is in a bedroom which is 8'x8' (overkill)

1 unit cools an area about 8'x15'

Due to the power consumption Winnebago installed a switch which limits you to only 1 unit when you are running off the generator.

Last year the compressor on the bedroom unit went out. So I bought a 5000btu window unit and mounted it in the old shroud and wired and ducted it through the existing roof hole. It works beautifully and cools the small area perfectly.

What I would like to do now is take the old unit and replace the dead compressor with a newer/smaller/more efficient (10,000btu) compressor and then switch it out with the old front (13,500btu) unit so I can run both units at the same time.

I have called local HVAC companies but they all act like RV roof AC units are alien technology and they dont want to mess with it.

I called the local appliance supplier and they have plenty of 10,000btu window type compressors for less than $100 but I have to give them a part #. I asked if I could bring the old one in and see if they had something generally similar but they to run screaming if it doesnt show up on their computer when they pres a button.

Its like auto parts, years ago you could walk into a parts store holding your broken part and before you open your mouth the guy behind they counter would say "1972 vega fuel pump? same pump fits about 15 other GM cars and a few Volvos. pretty sure we have one in stock but if not we have a few other similar ones that will work with a little tweakin"
Any more you have to tell them everything but your underwear size and if it it doesn't show up on their computer you might as well just walk away.

Sorry, I'll step of the soap box and get back to my question.....

1. Is it possible to replace the 13,500btu compressor with a similar smaller 8-10,000btu one and......
2. does anyone have any model # they would suggest?
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Old 09-01-2010, 05:55 PM   #2
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Can I upgrade the compressor in my RV roof AC unit?


A 5000 and 10,000 starting at the same time may still stall your generator.
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Old 09-01-2010, 10:28 PM   #3
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Can I upgrade the compressor in my RV roof AC unit?


I was trying to locate a compressor for one of those last month. Ended up replacing the whole unit.
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Old 09-02-2010, 07:09 AM   #4
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Can I upgrade the compressor in my RV roof AC unit?


I understand your problem, here's a thought , have you checked the amp readings on the RV air conditioners today ? Remember a lot has changed in 25 years maybe you can replace it with 1 today that has lower amperage. Keep looking.
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Old 09-02-2010, 10:18 AM   #5
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Can I upgrade the compressor in my RV roof AC unit?


The problem with an undersized compressor is that your entire evaporator might not be live. I've seen this with undersized condensing units (or oversized evaporators) in homes.

When the refrigerant enters the evaporator, the "flash" may be over before it gets to the other end of the evaporator, leaving you with a coil that is only cold at the bottom 2/3rds or 3/4ths. This leaves you with a a/c that's blowing semi cool air. High effeciency usually means more condensing coils.
just a thought.
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Old 09-02-2010, 10:19 AM   #6
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Can I upgrade the compressor in my RV roof AC unit?


Quote:
Originally Posted by beenthere View Post
A 5000 and 10,000 starting at the same time may still stall your generator.
Quote:
Originally Posted by Marty S. View Post
I was trying to locate a compressor for one of those last month. Ended up replacing the whole unit.
Quote:
Originally Posted by COLDIRON View Post
I understand your problem, here's a thought , have you checked the amp readings on the RV air conditioners today ? Remember a lot has changed in 25 years maybe you can replace it with 1 today that has lower amperage. Keep looking.
Thanks Guys!

I did check the amp ratings. The combination of newer units (10,000 + 5000) is about 75% of what the single older (13,500 ) unit was requiring.

I didn't think about the double start hit but the generator max output is pretty high so I hope when they do both start simultaneously it could handle it.

I priced new complete units and an 11,000btu unit is around $900 (upper/lower/hardware/tax/shipping)
a 13,500btu unit is actually cheaper, around $700 but the amps would max out my generator.

$100 new compressor and some elbow grease is more in my price range.

I have even considered buying a 10,000btu window unit (seasonal clearance price is about $175) and switching out the guts.
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Old 09-02-2010, 10:22 AM   #7
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Can I upgrade the compressor in my RV roof AC unit?


Quote:
I didn't think about the double start hit but the generator max output is pretty high so I hope when they do both start simultaneously it could handle it.
This is easy to fix. A simple time delay relay on one of them will keep them from starting at the same time.
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Old 09-02-2010, 12:38 PM   #8
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Can I upgrade the compressor in my RV roof AC unit?


If the compressor is the wrong size you get incorrect freon pressures,bad oil return etc and it probably won't last long. Probably uses R12 which is mostly obsolete. Sounds like a waste of time to me.
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Old 09-02-2010, 04:16 PM   #9
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Can I upgrade the compressor in my RV roof AC unit?


Quote:
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This is easy to fix. A simple time delay relay on one of them will keep them from starting at the same time.
If he runs them both off the same thermostat.
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Old 09-02-2010, 04:38 PM   #10
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Can I upgrade the compressor in my RV roof AC unit?


Quote:
If he runs them both off the same thermostat.
You're right, and if they aren't on the same thermostat the odds of them starting in the exact same instant would be slim I'd hope. I wouldn't think it would take more than a split second for a good compressor to switch to the run winding on start up.
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Old 09-02-2010, 04:43 PM   #11
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Can I upgrade the compressor in my RV roof AC unit?


Amp draw can remain high for several seconds or even a few minutes, depending on outdoor conditions.

Bit of a flip of the quarter. As to how well it will work. Lots of people set the main unit high when they go to bed, so shouldn't have both units on at same time too often.
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