| Author |
Message |
Craig (Ceieio)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 09, 2005 - 12:30 am: | |
I was reading another thread about AC, and yet another one about a low cost battery charger (AC motor running a car alternator).
Combining the two thoughts, has anyone used an AC motor to drive something like an aftermarket automotive AC unit to provide dash air? There is the problem of where to put the packaging and all that, but has anyone tried the basic idea? |
Sean Welsh (Sean)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 09, 2005 - 1:19 am: | |
Craig,
We used a 120vac refrigeration compressor to run our dash air, instead of an engine-driven compressor. All the other components (evaporator, condenser, condenser fan, passenger blowers, etc.) are standard automotive units, made by Red Dot for heavy trucks.
The only issue we had was that we had to have the hoses custom made, since automotive refrigeration uses a different set of couplers than commercial and household refrigeration.
We did away with all our engine-driven AC stuff, as well as refrigerant hoses running 40' up and back, plus we can run the cockpit air now when parked. For us, this was a big issue since our cockpit is downstairs, where our roof airs can't reach it.
The refrigeration compressor is small and easily fit under the dash. It is also refrigerant-cooled, so it needs no air flow around it, and can be insulated for noise reduction.
We thought about coupling an automotive-type compressor to a 120vac motor, but the integrated compressor was more compact and did not need external cooling.
-Sean |
Jim Bob
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 09, 2005 - 9:09 am: | |
That must be a pretty big refrigerator compressor! The dash air in our Eagle is 24,000 btu. (getting ready to remove the main air & keep the dash air) How many amps does it draw? Can you post mfg info? Are you using R-22? It would be great to have the dash air 120V.
Jim-Bob |
Doug Dickinson (Dougd470)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 09, 2005 - 9:09 am: | |
What size refigerant compressor did you use? Source? I am interested in this approach as I want to keep the existing coil and duct under teh dash, and don't want an engine driven solution for the same reasons as you.
Doug
St Louis MC9 |
Craig (Ceieio)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 09, 2005 - 10:13 am: | |
Sean - that sounds very "cool" if you will pardon the pun! This sounds like what I have in mind. I want something I can control from the drivers seat and provide more air up front. I also like the idea of being able to run the dash air when teathered.
Thanks for the ideas.
Craig |
Brian (Bigbusguy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 09, 2005 - 10:47 am: | |
Sean,
I would like to know also what size and model you used. I was looking in to using home window AC and taking the parts out of them to do about the same thing.
Brian 4905 Klamath Falls Oregon |
Sean Welsh (Sean)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 09, 2005 - 12:35 pm: | |
Wow -- I had no idea this would be such a popular topic...
First, let me say that, while I understand how it all works, refrigeration is definitely not my specialty. So I went to a refrigeration expert to help me size the system. He also did the evacuation, charging, and testing.
What we did was to start with the dash unit itself. The factory stuff was in poor condition, and was too hard to retrofit. So we pulled it out and found a Red Dot unit to fit where it had been. This unit was the R8500-0-24, which is what they call a "back wall" unit, even though we put it under the dash. This has ductable output, a heater core, an AC evaporator, and 24 volt blowers.
We hooked the heater core up, with an appropiate volume valve, to the stock heater lines from the engine. We got the BTU/hr rating from the evaporator, and selected an appropriate condenser from the Red Dot catalog that would match the capacity, and also fit behind our front "bumper" trim (due to our unique coach design -- on a standard coach, the spare tire compartment would be a good choice). That was mated with a 24 volt condenser fan, for when we are not moving fast enough to get good air flow over the condenser. I'm sorry, but I don't remember the part numbers on the condenser or fan.
We next went to our refrigeration people with the BTU/hr and volume capacity ratings of all these parts, and they sized out a compressor unit, which turns out to be the Copeland RR81C1EIAA. This is a 115vac, R134A sealed compressor unit (meaning the motor is completely internal). A Red Dot "trinary" pressure switch and a nice looking dash control completed the kit.
We went to a commercial hose shop to get hoses made with the correct fittings on the ends and hooked everything together. I wired the R8500, controls, condenser fan, and Trinary just like you would for a straight automotive application. However, the wire that would normally go to the AC compressor clutch instead goes to a 24vdc relay rated at 20amps/125vac, and this relay switches the power to the 115vac compressor on and off. The compressor is then fed from a 20 amp circuit off my SW4024 inverter.
The refrigeration guy came back in, evacuated the system, tested the vacuum, and filled the system with R134A until his gauges read the magic numbers, and we got cold air out.
The most expensive part of the system was the compressor, which I was able to get at a discount for around $400. In most states, mere mortals without a refrigeration license can't get these, so I had to do some sleight-of-hand.
We ended up spending around $2k on the whole system, but, then again, we needed to replace all the dash stuff and the condensers and condenser fans (which were originally in the back, near the engine-driven compressor). If you have good dash blowers, condensers, etc. you will not need to spend this much.
Last caveat -- your mileage may vary. The compressor we used was sized by a pro for the specific evaporator/condenser setup we chose. You may need a different size based on your other components.
HTH,
-Sean |
Ron Leiferman (Ron_in_sd)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, March 10, 2005 - 10:54 am: | |
Here are some specs I found on the Red Dot R8500 unit.
BTU's: Heating-22,000 BTU/Hr @ 100° F Air Temp. Rise
Cooling-15,200 BTU/Hr with 36°F Refrigerant Temp. and 80° Wet Bulb Entering Air
Air Flow: 205 CFM
Weight: 24 Lbs |
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