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Old 10-18-2016, 12:52 PM   #1
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Dometic A/C

NOT happy with this #3 (installed in August) Dometic A/C. Four day trip this past weekend with daily high's in the mid 80's. Saturday was 88 and my inside temp was 77 under the shade of tall pines with the A/C running wide open set on 72. We were with two other couples/campers and both of their units were at 72. Both of those were Colman units also. Today at high noon at home, no shade, 82 outside temp, the t'stat set to 72 and the inside temp was 76. Air into the A/C at 76 with air out at 42. Amp measures at 11 amps white wire, 11.3 on the black wire. The unit is a Coachmen 310BHDS. With the two slides I'm figuring about 295 sq. ft. to cool with the 15k unit. Is this 15k A/C too small for my unit or do I maybe need to change brands?
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Old 10-18-2016, 12:58 PM   #2
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Quote:
Originally Posted by Thurman View Post
NOT happy with this #3 (installed in August) Dometic A/C. Four day trip this past weekend with daily high's in the mid 80's. Saturday was 88 and my inside temp was 77 under the shade of tall pines with the A/C running wide open set on 72. We were with two other couples/campers and both of their units were at 72. Both of those were Colman units also. Today at high noon at home, no shade, 82 outside temp, the t'stat set to 72 and the inside temp was 76. Air into the A/C at 76 with air out at 42. Amp measures at 11 amps white wire, 11.3 on the black wire. The unit is a Coachmen 310BHDS. With the two slides I'm figuring about 295 sq. ft. to cool with the 15k unit. Is this 15k A/C too small for my unit or do I maybe need to change brands?
Is this a typo?
You should have an icebox for a camper if this is true.
The norm is +-20
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Old 10-18-2016, 04:20 PM   #3
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I was about to type the same thing. With a Delta-T of 34F it's doing more than expected.

If that's not cooling your coach, you've got something else going on.

You're not running the furnace at the same time are you???

I don't think changing brands is going to help if that's correct.

We're at about 275 FT and our 15k BTUH unit does a good job of keeping the RV cool.
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Old 10-18-2016, 04:54 PM   #4
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One thing I have found with my Dometic A/C is the temperature sensor is about 2 degrees off. We have to set our Zone 2 at 70 degrees to get it to go down to 72. It took a little trial and error to find this, using a known, good electronic thermometer.

Also, we found we have to set the fan on high, instead of using the auto. The auto couldn't keep up with the temps.
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Old 10-18-2016, 04:59 PM   #5
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Gentlemen I assure you that there was a 34 degree delta when I checked it today. I don't have "Harbor Freight" equipment either. I worked industrial maintenance for 38 years and consider myself to have great equipment and knowledge of what I was doing. Yes, the numbers surprised me. A lot. This past weekend was a mystery to me as far as cooling the camper. Friend "A" has a 32 ft. Jayco with a 15k Coleman unit and his was cycling on/off with his t'stat at 72 and outside ambient air at 88. Friend "B" has a 26 ft. Jayco with a 13.5k Coleman and his t'stat was at 72, his unit was cycling on/off with the same 88 degree outside ambient air temp. While at the campsite I shut my unit down, cleaned the filter and climbed up on the roof to inspect for anything that would interfere with my units operation. Nothing odd found. I haven't parked the camper in the back yard yet, it's still in the driveway set up so I can check anything with the A/C that may be a problem. Part of today I had the t'stat set at 72 with outside temp at 84 and the unit ran continuously with an inside temp of 76. I called the local Dometic service guy, whom I've known for years, and told him about all of this. He also agrees that with that delta T I should be good to hang beef in the camper. He's backed up right now so we will talk later about taking it out to him so he can look into it. "ben31" I had not thought about changing the fan speeds to see if there could be a difference, it's set on automatic at this time. I'll change it to HI tomorrow morn and see what happens. You probably are not that far from me so you know the crazy warm weather we are having for October. Thanks for the replies
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Old 10-19-2016, 09:21 AM   #6
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I never meant to doubt you. It's just odd that someone posts a delta-T of that much.

Have you looked in your ducts to see if they're collapsed anywhere? Collapsed ducting would reduce the airflow and that would also account for the high delta-T. The less air you're moving the higher the delta-T, to the point that it freezes up.
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Old 10-19-2016, 09:33 AM   #7
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In the HVAC world 20* Delta T is considered great. I do see your stat is set to 72* but you read 77 or 76* in the unit may be the stat is not correct.
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Old 10-19-2016, 11:01 AM   #8
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I didn't take any comments as to doubting me, I doubt me also until I check things twice or more. Approximately two months ago I pulled the grill off of the unit and found that the "baffle" between the ambient air and cold air was not properly in place. There was about a 3/4" gap at the top allowing cooled air to go back into the return, I fixed that. Then I check each register in the ceiling of the TT and found that all six of them had gaps between the duct and the ceiling. This was allowing air to go into the attic area of the TT. I fixed all of those. After those two major fixes I believe I could tell that I had more air flow coming from the registers. This TT has had a problem, IMO, with the A/C not cooling the unit since day one. The unit was purchased in January of '15 and the Dometic 15k A/C unit quite cooling on March of '15. The second A/C unit was replaced with the third one in August of '16. This third unit just has not impressed me as far as being able to cool this TT. I pulled the grill off yesterday to check anything I could see and confirmed that this unit is a 15K unit. As far as a possibility that the t'stat could be not working correctly, that is certainly a possibility. Yesterday with the t'stat set on 70 degrees the thermometer I have in the TT and an electronic unit I own read the same as the temp reading on the t'stat--76 degrees with the unit running wide open. Last Friday at the campground I closed the door to the bunk room and the two doors to the front bedroom, I had the dump open on the grill and the main living area did cool down more. Today I'm going to pull the shroud off of the unit and inspect anything I can see. I'll also try the idea of putting the fan on HI manually and see if that helps.
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Old 10-19-2016, 05:35 PM   #9
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I hope that I am not being overbearing with all this info on my A/C unit. I believe that there is a problem and it is not the actual cooling unit part of the whole system. I feel that this is what this forum is for, to help each other so I am posting all this info hoping that someone out there will post back that "Ah, Ha" answer for me. Interesting discovery: Today with the outside temp at 88 degrees I set the fan manually on HI (Thanks ben31 for the suggestion) then turned on the A/C setting it to 72 degrees. About two hours later I went in to check in it and the inside temp was 72 degrees, the compressor was not running but the fan was running on HI, of course. I then set the fan back to AU (auto) leaving the t'stat on 72. An hour later when I went in the inside temp was 77 and it sounded as if the compressor and fan were running. O.K. shut everything down and let everything stop. Set the fan only to HI and listen to the sound. Set the fan only to LO and listen to the sound. Yes there is a difference between them and the LO setting sounds more like what my A/C has been sounding like. So I get the paperwork for the Dometic fancy, dancy digital t'stat and read it. The fan is automatically set by the t'stat to either HI or LO based on the difference between the ambient air temp within the TT and the temp setting on the t'stat. Now I'm wondering if the t'stat is telling the fan to run on LO when it really needs to be running on HI. It seems that maybe I have a bad t'stat in that it will not set the fan speed to HI when it really needs to be. My previous TT had a manual Dometic t'stat and I changed it out to a Honeywell that helped tremendously. So, does anyone know of a t'stat that I can change out with the Dometic that may solve this problem? Thanks
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Old 10-19-2016, 06:42 PM   #10
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The delta is good, but it takes a lot of airflow to keep your camper cool. You may need another ac unit.

I have two units in mine but have problems with the back bunkhouse. I'm going to install a 3rd unit which will be dedicated for that room. Will be overkill, but I can turn them down or off when need be.

My camper has a lot of dark colors (especially the front cap), has slide outs and an outdoor kitchen. My bunkhouse probably has very little insulation in it. The closest ac unit to the bunkhouse is still 10+ feet away, so airflow is lacking back there. My kids will love having their own ac unit. The bunkhouse has its own door for privacy, so having its own ac will allow for that door to be closed when wanted.
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