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Topic: Original dometic ac replacement options (Read 1440 times) previous topic - next topic

Re: Original dometic ac replacement options

Reply #25
OK, lets look at what happens with a "constant run" evaporator fan:

It runs (as it should) when cooling is needed.  It continues to run when cooling is not needed.  When that happens, the water that has condensed on the evaporator (YES, this is very important in humid climates, not so in dry ones) is then returned to the interior as the fan blows air over the WET evaporator. 

Not sure this works for humid areas.  Please convince me.
Yes Brett a continuous operation of the evaporator fan sets up a vicious cycle just as you stated. You pay dearly to condense water on the coil, but as soon as the compressor cycles off the evaporator fan only blows that moisture back into the space be it an coach or any other building or space. Most residential units will also run the fan for a few minutes (sometimes adjustable on the control board) to bleed off the pressure on the ref. liquid line or "high side" to prevent compressor damage when it short cycle's. Increasing the unit size will make matters worse, as the compressor is off more and humidity levels rise and you feel clammy. The only good way to prevent this is to allow the compressor to run and reduce the evaporator airflow so that coil surfaces remain below dew point. They good news is that running compressors continuously adds to there lifespan as starting is done on somewhat oil dry bearings. Just found out yesterday, when I ask a vendor how much extra a variable evaporator air volume packaged HVAC unit would be because I'm working on an exercise facility where humidity is a major issue and they wanted cheap, cheap, cheap. New DOE requirements make this standard. BTW I run my 1800 sqft house on 2 tons and it was built in the 50's and not super insulated. 1990 Compressor runs pretty much 24/7 for 4 months and house temp will climb to 80 when it 110 outside but it's a dry heat inside and totally comfortable
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: Original dometic ac replacement options

Reply #26
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Re: Original dometic ac replacement options

Reply #27
We have been running the Attwood units for about 3 years now in the high humidity Gulf Coast area and have had no problems with humidity in the coach, in fact, much less so than with the old Dometic units.  I have had absolutely no problems with the units and would not go back to the other noisy brands.
Current coach 1996 U320 40'
Previous coach, 1990 36' U280

Re: Original dometic ac replacement options

Reply #28
I replaced my front unit with a Atwood heatpump 15k don't really need the heatpump but the a/c works great. No complaints.
91 GV U300 Unihome 40' Build 3811
6V92TA Detroit

Re: Original dometic ac replacement options

Reply #29
Adventure rv is not an issue for me due to my location. Scratch and dent guy is local small guy. Gonna get back on the roof today while little one is napping I hope.
Toby a 94 u280
Cummins 8.3
6 speed Allison
Exhaust brake


Adopted by Derek and Annabelle

Re: Original dometic ac replacement options

Reply #30
Update:

During nap I scrambled back up on the high wire and reinstalled the capacitors. No circuit board there.  Following the wires I had the remove the interior panel to follow them and screwed to the top of the inner half of the clamp was a box for the circuit board. I bumped the wires and Alice was the beast. Cleaned the connector and squeezed the terminals and all is well bringing an end to my flying walindas career.
Toby a 94 u280
Cummins 8.3
6 speed Allison
Exhaust brake


Adopted by Derek and Annabelle

Re: Original dometic ac replacement options

Reply #31
Forgot to add pictures.  And thank you everyone for your help.
Toby a 94 u280
Cummins 8.3
6 speed Allison
Exhaust brake


Adopted by Derek and Annabelle

Re: Original dometic ac replacement options

Reply #32
Toby,

Looks like they moved the board to a diffrent location than what was on our '92 the board looks somewhat diffrent as best as I can remember. Great that you kept hunting and troublshooting as a lot of A/C units have been replaced due to simular problems. Persistance has saved you a $ or 2.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Original dometic ac replacement options

Reply #33
Good thing on saving the money, I kind of spent it on a new invertor last night that I found of Kijiji (like craigslist). This board had a relay but appears to be soldered in and no serviceable fuse. Will have to keep an eye out for a used one for parts.
Toby a 94 u280
Cummins 8.3
6 speed Allison
Exhaust brake


Adopted by Derek and Annabelle

 

Re: Original dometic ac replacement options

Reply #34
Brett,

No noticeable difference on our Attwood over the old Dometic as far as humidity is concerned.

Keith
Keith, Joyce & Smokey the Australian Cattle Dog
1995 U320 SE Extreme 40' WTBI Build # 4780, with a Honda CR-V hopefully still following behind.
Motorcade # 17030
FMCA # F422159