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Need new air conditioners?


saflyer

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'05 Holiday Rambler Ambassador

I have 2 Dometic DuoTherm 13,500 BTU ducted air conditioners with heat pumps.  Last week while on our first hot weather trip in some time we left the coach in the morning with temperatures inside and out in the lower 70's.  The A/C's were set in the lower 70's also.  The blinds were closed.  When we returned in late afternoon the outside temp was 99-100 with moderate humidity.  The living area temp was almost 90 degrees.

I'm wondering what I should do.  Is there a test for cooling performance other than what I described?  I have been told these units cannot be recharged with coolant and the only thing to try to service them is clean the cooling coils.  Is this correct?  Are there any other options for service?

My shop told me if that didn't work the only option is purchase a new A/C.  My units, like so many are terribly noisy.  I've even thought in the past of getting new units in the hope the noise could be reduced.  That being said, are the new units known to be quieter than the ones from the early 2000's?  Replacing them would be an easier pill to swallow if I got the secondary benefit of quieter operation but I read on some forum recently that a poster replaced his with a newer model and it was louder.

How difficult is it to replace an A/C?  How heavy are they?  I'm handy enough so if it's not too complicated I could do it with a little help.  My shop can't get to me until late July and we want to take a trip before then.

Any thoughts are appreciated.

Edited by saflyer
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It would be unusual for both units to fail at the same time I would think.

I have3 of the originall in my 99 Signature.

Andtwo of them running will keep the temps at 72 most of the time. Seldome does the third one kick on.

If your units are running at all ?

What is the temperature of the air coming from your registers ??? 40 something???

Do you show a full 220 on your 50 amp system ?

 

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My understanding is that at best, most of the older motorhomes should expect the cool to about 20 degrees below outside ambient temp, so if 100deg, inside of coach would be about 80.  We experienced this last summer.  So, the obvious things should help: shady spot, blinds closed, sun deflectors, etc...  I have looked into the ceramic coating for my windshield,  but havent done it yet.  My 06 Dip has 2 15k rooftop heat pump units for comparison.  

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I’m going to clean mine and test them next week and check the temps when it should be in the mid-90’s again.  Will check the air temp out of the register.

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It was 92 yesterday afternoon so after I read your post I tested the roof registers air temp.

 

It was reading 44 to 52 depending on how I aimed the gun.

 

Many in the campground s have told me that they cant get the inside temperatures below 80 or 90 

When its 90 plus and humid outside.

Im comfortable at 74 to 78. With front window curtains open.

With 2002 or newer coaches.

We came to conclude that it has to do

with construction quality and insulation. 

My coach was manufactured in Oregon in 1999.

 

Visone in Kentucky says cut a few Monaco signature,  H.R. s Diplomats into ???

 

Oregon manufactured or Indiana manufactured.??? 

 

Big, big difference. 

 

 

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Guest Tim503

You said you returned late afternoon. Were they on and both blowing cold air when you entered? The thermostat needs to be checked to see if both zones are active. If they both come on and cool or say they do you can go up and remove 4 screws and hose off the units they can have wasps nests etc. That is a job to do with a total roof check and it may be time to replace the rubber if you have that. My rubber looked good and I kept it clean then one year while gone it failed with microscopic holes in the membrane. 15 years is a maintenance time but the AC should still work. Go out there at night and see how cold you can get it and understand the zones in your rig.

I know what you mean on the noise it is a shame we have had to deal with this design for the last 50 years. The shrouds disintegrate, the wasps, dirt, wind drag, in the sun while cooling and sometimes you can only operate one depending on your power. They need to make split units that have a soft start. Just like home fridge we need current tech on AC units and put them in the basement.

Edited by Tim503
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4 hours ago, Tim503 said:

You said you returned late afternoon. Were they on and both blowing cold air when you entered? The thermostat needs to be checked to see if both zones are active. If they both come on and cool or say they do you can go up and remove 4 screws and hose off the units they can have wasps nests etc. That is a job to do with a total roof check and it may be time to replace the rubber if you have that. My rubber looked good and I kept it clean then one year while gone it failed with microscopic holes in the membrane. 15 years is a maintenance time but the AC should still work. Go out there at night and see how cold you can get it and understand the zones in your rig.

I know what you mean on the noise it is a shame we have had to deal with this design for the last 50 years. The shrouds disintegrate, the wasps, dirt, wind drag, in the sun while cooling and sometimes you can only operate one depending on your power. They need to make split units that have a soft start. Just like home fridge we need current tech on AC units and put them in the basement.

Yes they were both blowing cold air, just not cold enough. Coach was only 11-12° colder than outside temp.  I went up and checked the coils.  Appeared to be mostly clean but had a little film covering less than 5% on the front A/C unit. Cleaned that and will do a check tomorrow to see if any improvement.  Will report back.

As to the zone issue.  We have always struggled with getting the temps set in the coach.  I think the thermostat swing is too great.  We find ourselves constantly resetting the thermostat.  Gets too warm and we drop the setting down 2° then it gets too cold so set it up a degree or two. Back and forth, back and forth.  I think the placement of the thermostat temperature sensors is part of the problem, especially the front one.  If the coach faces East or West the morning or evening sun shining in the windshield causes havoc with it especially with the windshield curtains drawn.

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Regardless of the thermostat. 

If the air conditioning system is functioning. 

 

You will be putting out 40 to 45 degree air.

That comes first .

 

Then coach insulation

Awnings 

Double pane windows ?

Curtains closed up when its 80 plus degrees.

Coach humidity.

Operator error and understanding how to manage the thermostat 's

 

 

 

 

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I don't see where anyone has mentioned this so I will. If the weather is hot don't run your fan on auto and place the fan on the highest speed and leave it there. Let the compressor cycle via the thermostat.

 

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Guest Tim503

I'm afraid it is sitting in the sun then. That will ruin the efficiency of these roof units. There is not as much insulation in my ceiling as I would have thought and the AC duct work in the ceiling is a quarter of an inch thick and seams could have opened in it. I had a mice problem where they went up behind the fridge into the ceiling and used that material to make nests. You could take off a vent and use a mirror and flashlight to see your venting. Even put the light in the back and look inside at the front. The front cap on mine is opened to the attic area and hot air from the roof can come down from there. Open different cupboards to get an idea and also them keep then closed as a barrier to the skin of the motorhome. Buy a thermometer that uses infrared to see the temperature of your walls and ceiling etc. You will notice an increase where the metal frame is. That is the problem with the steel frame it transports heat and cold very well from outside to inside. There is insulation between the steel members. There is no insulation on the front cap or the firewall. Bottom line your AC units do not need to be replaced in my opinion.

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Guest Tim503

Just to add a couple more comments. I use 90 as my temp for using AC otherwise I would use the attic fan or a box fan in front of a bedroom screen blowing out and have two windows in front on each side for incoming air.and take off more clothes. That is quieter and the air blowing in over your skin works for me. Of course sweating in your chair is not fun but I've even used beach towels if the weather is soon to cool down.Make sure when using AC that all vents are shut and the barrier is in your attic vent. They will keep transferring air and remember that every window has weep holes that allow air in so seal them up with your window blinds etc. It kind of makes double pane windows moot, considering the window is surrounded by 1 1/2" steel. You really need to batten the hatches even more than on a cold night.

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2 hours ago, Tim503 said:

Just to add a couple more comments. I use 90 as my temp for using AC otherwise I would use the attic fan or a box fan in front of a bedroom screen blowing out and have two windows in front on each side for incoming air.and take off more clothes. That is quieter and the air blowing in over your skin works for me. Of course sweating in your chair is not fun but I've even used beach towels if the weather is soon to cool down.Make sure when using AC that all vents are shut and the barrier is in your attic vent. They will keep transferring air and remember that every window has weep holes that allow air in so seal them up with your window blinds etc. It kind of makes double pane windows moot, considering the window is surrounded by 1 1/2" steel. You really need to batten the hatches even more than on a cold night.

 

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Today’s test. Ran ACs all night.  Front AC had the quick cooling vent open all of the time. My bedroom unit has a Wacko noise reducer. (BTW I obtained no measurable noise reduction after adding it, just a better quality of sound).  About 90° outside temp. Inside temp made it to 77°.  Taped a digital thermometer to the quick cooling grill and it showed 54.5°.  This was a few days after checking the cooling fins a removing a slight amount of coating, less than 5% on the front unit and closing a gap where the there is foam rubber between the cover and the perimeter of the box that directs air through the condenser On the bedroom one.

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So your AC works, 77 degrees in an 54 out, more than 20 degrees drop is what you are looking for. House insulation can't keep up or there is an outside air coming in somewhere. For us, outside winshield cover made a noticeable difference, still just an equivalent of a huge single pane glass but helped.

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I recently switched control boards in my air conditioners when installing a new thermostat, and took the time to blow the dust out of the coils. The front AC unit had very dirty coils, both external condenser and evap coils. Previously I had thought that AC unit was must be running low on freon, since it didn't cool very well compared to the rear unit, but now it works pretty well.

I also installed new foam strips that press against the cover. The old ones were stuck to the cover, I just stuck the new ones to the top of the coils and they stayed in place. You can find the 1" high expanding foam weatherstrip in the weatherstrip section at Lowes, it installs easily. It curves well enough to follow the curve of the condenser coils with no problem. 

For cooling when it's hot, we have a curtain behind the driver/passenger seats that keeps a lot of hot air up by the windshield. We also have a screen we put up on the windshield that dramatically reduces the solar heating. Shade also helps a lot.

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I’d consider replacing the front AC with a 15000 BTU unit but have seen posts that say (1) it will need a new 10 button thermostat and (2) that may or may not be doable if I don’t change the bedroom AC.  Any insight?

Edited by saflyer
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18 hours ago, Tim503 said:

Just to add a couple more comments. I use 90 as my temp for using AC otherwise I would use the attic fan or a box fan in front of a bedroom screen blowing out and have two windows in front on each side for incoming air.and take off more clothes. That is quieter and the air blowing in over your skin works for me. Of course sweating in your chair is not fun but I've even used beach towels if the weather is soon to cool down.Make sure when using AC that all vents are shut and the barrier is in your attic vent. They will keep transferring air and remember that every window has weep holes that allow air in so seal them up with your window blinds etc. It kind of makes double pane windows moot, considering the window is surrounded by 1 1/2" steel. You really need to batten the hatches even more than on a cold night.

Wow, I wouldn't sit around in 90 degree air. That's the reason I have A/C, to be comfortable.

I usually leave the bedroom unit on during the day, and turn on the front unit at night.  If really hot I'll run both.

It helps that my unit doesn't have slideouts, as they're a source of a lot of air leakage and also increase the exterior surface area.

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  • 2 weeks later...

I was am having issues with my roof ac keeping the coach cool. My temporary answer is a portable mini split, My roof units put out cold air but I believe it is a issue with air movement just does not replace the air in the coach fast enough. 

i have a feeling the coils are not clogged all the way but enough to slow the air flow. To hot in AZ to open up the units and look right now. 
I would check the coils it could also be a issue with your ducs and that’s why it worked with the quick cool open,

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On 6/14/2020 at 6:13 AM, saflyer said:

I’d consider replacing the front AC with a 15000 BTU unit but have seen posts that say (1) it will need a new 10 button thermostat and (2) that may or may not be doable if I don’t Chang the bedroom AC.  Any insight?

You have a choice (sort of).  The AC control board version must match the thermostat version. 

If you install only one new A/C unit, then you can install a retrofit control board in the new A/C unit and still use your older 5 button Comfort Control thermostat to control both the new and the old A/C.  

If you decide to replace both A/C units, then instead of purchasing two retrofit control boards for your older thermostat, you can just install the newer CC2 programmable thermostat.  

The new CC2 thermostat is not compatible with your old A/C unit and will only work with the new design A/C or heat pump from Dometic.  

Replacing A/C units is fairly easy once you get it onto the roof.   They weigh about 100#.   I used a long ladder and a rope to drag it up onto the roof (still in the protective shipping box).   It is held on by 4 bolts accessed from inside.  All the wiring is also accessed from inside.   You will need to set the control board dip switches according to the instructions and it's a good idea to install a new foam gasket.  

Below are pictures of the  A/C unit on the ladder.  It takes two to drag it up.  Next is the retrofit control board.  Install this on the ground.  Last is a picture of our new 15,000btu A/C.  

Hope this helps.

AC unit on ladder.jpg

AC retrofit control board.jpg

AC unit installed.jpg

Edited by vito.a
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7 hours ago, vito.a said:

You have a choice (sort of).  The AC control board version must match the thermostat version. 

If you install only one new A/C unit, then you can install a retrofit control board in the new A/C unit and still use your older 5 button Comfort Control thermostat to control both the new and the old A/C.  

If you decide to replace both A/C units, then instead of purchasing two retrofit control boards for your older thermostat, you can just install the newer CC2 programmable thermostat.  

The new CC2 thermostat is not compatible with your old A/C unit and will only work with the new design A/C or heat pump from Dometic.  

Replacing A/C units is fairly easy once you get it onto the roof.   They weigh about 100#.   I used a long ladder and a rope to drag it up onto the roof (still in the protective shipping box).   It is held on by 4 bolts accessed from inside.  All the wiring is also accessed from inside.   You will need to set the control board dip switches according to the instructions and it's a good idea to install a new foam gasket.  

Below are pictures of the  A/C unit on the ladder.  It takes two to drag it up.  Next is the retrofit control board.  Install this on the ground.  Last is a picture of our new 15,000btu A/C.  

Hope this helps.

AC unit on ladder.jpg

AC retrofit control board.jpg

AC unit installed.jpg

Thanks.  That helps a lot.

Ed

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Guest Cruzbill

My recent hot weather experience with new (2 year old) Penguin 15k heat pumps. Could not get inside temp below 77 with outside at 89. Bedroom  AC would keep  temp in bedroom cold, but front AC could not keep living room cold. Thought it might be bedroom AC shutting off too soon (due to temp sensor placement) so set bdrm tstat to 60, closed all ceiling vents but the one in living room so bdrm AC pushes more air thru ducts. Now that worked! So the trick was to keep the AC on in the bedroom ( it get down to 64 with tstat set to 60). If its not quite as hot outside, I can raise the bdrm AC to 64 or 66 and the front AC will keep up. Our new ACs both have new control boards and the CCC2 tstats. Good luck!

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On 6/14/2020 at 8:13 AM, saflyer said:

I’d consider replacing the front AC with a 15000 BTU unit but have seen posts that say (1) it will need a new 10 button thermostat and (2) that may or may not be doable if I don’t change the bedroom AC.  Any insight?

We just replaced our front A/C with a Brisk Air II 15000 unit and still use our old thermostat and we didn't change the bedroom A/C.

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1 hour ago, sheena154 said:

We just replaced our front A/C with a Brisk Air II 15000 unit and still use our old thermostat and we didn't change the bedroom A/C.

The tech who installed the Brisk Air II probably removed the control board from your old unit and installed it in the new unit. That would allow the new unit to work with the 5 button thermostat. I hope he gave you the board from the new unit because if you later decide to upgrade the rear unit and the thermostat you will need to put that board back in the front unit. Of course there is always the option of putting the control board from the rear unit in a future unit ans staying with the 5 button thermostat. That is a shame because the new 10 button thermostat is fantastic.

 

 

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Sounds like your  A/Cs are working. RVs have very poor insulation some starting with none.  Fix all air leaks. Cover all windows and doors with reflective bubble foam so you now live in a cave. Don't use uncecessary heat like HW etc.  Awnings out for shade. Some add shade protection for the refer.

My A/Cs will cool to 75F when it's 115F in full AZ sun and only window shades. 

But your best option is move where  it's cooler as that is what wheels are for.

 

 

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