Dometic A/C

[Thurman]

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?

[5picker]

Originally Posted by Thurman

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 +-20º

[Bama Rambler]

I was about to type the same thing. With a Delta-T of 34ºF 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 FT² and our 15k BTUH unit does a good job of keeping the RV cool.

[ben31]

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.

[Thurman]

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

[Bama Rambler]

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.

[SeaDog]

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.

[Thurman]

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.

[Thurman]

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

[325BH]

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.

[l001952119]

Originally Posted by Thurman

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

A/C's have a manufacturers stated cooling of 15-20 degree's below the ambient outside temperature. You should expect a reduction of 15 degree's, IF the humidity outside is not high. 20 degree's reduction is not common, per my 43+ years of RV experience. May need a second AC? Put one on my 34' and can hang meat!

[Bama Rambler]

Thurman -- You may be on to something about the thermostat. I actually hate those new digital thermostats! But that's for another day.

Since the unit cooled the RV down to setpoint with the blower on Hi but wouldn't when it was in Auto, I'd say that the Auto fan setting by the thermostat is the problem.

Unfortunately there's no easy replacement for that thermostat. The problem is that you will have to replace the thermostat and control board in the A/C, AND you'll have to replace the 3-wire thermostat cable with a 5 or 6 wire cable, and that may or may not be a problem.

You could try replacing the thermostat on the wall with a new unit, but that's taking a chance that it will work the same as your current unit.

I think that the thermostat is supposed to switch fan speeds at about 4ºF below setpoint. You might want to test it to see if it's actually doing that.

That 3-wire thermostat cable is also a problem when changing brands.

[Thurman]

Well it's nice to have friends in certain places, businesses. After talking with Steve (Authorized Dometic Service Person) and doing all that he suggested, Steve takes the time to come to my house. With outside temp at 84, the A/C unit set to 72, the fan on AU, the inside temp of the TT was at 79 with the unit having been running for hours. Steve checked and recorded the outside ambient temp (84), the inside ambient air temp (79), the air going into the A/C (79), the temp coming from the A/C at the dump on the grill (67), the cooled air temp from the registers farthest from the A/C unit (front 67) and rear (68), and checked that amp draw on the unit ( white 11 amps, black 11.3 amps) then stated "You have a problem". The delta being 12 degrees was what he was referring to. Steve's opinion is that this unit has probably lost some freon and is starting to show a failure. Being as my warranty runs out January 17 he agreed with me that something needs to be done ASAP. Steve also told me that when this A/C problem started showing up all he had to do was call Dometic, tell them he had a unit under warranty with an A/C failure and they would ship him the core ASAP. But, Steve says lately that Dometic is asking many questions and wanting many answers such as the amperage draw, the temp readings as he took them, where was the TT parked (sun, shade, partial) etc. Steve also told me that the Dometic digital thermostat lacked a lot to be desired and could have been telling the fan to run on LO when it needed to be on HI. So Steve is going to call today (Fri) to ask Dometic about a new unit or advice on what to do next. Steve also told me that he has about a dozen of these units at his shop waiting to be returned to Dometic. He says at first Dometic did not want the units back but started asking for the return of failed units somewhere around late June. He is going to palletize all the units at once for shipment. Why doesn't Dometic own up to this problem and do some type of PR work? It seems that at first Dometic wanted to do the proper thing and replace the units but as time went on and more units were failing Dometic took a stand and started making it harder for an authorized service person to get the bad units exchanged. I'm not at a point as some others who have posted on this forum in that I would like Dometic to refund me some monies so I can invest in another brand unit. It sure was odd this past weekend that my two friends TT's were cool and comfortable sitting one each side of mine in the direct sun also. Both of these units have Coleman A/C's. Until I hear back from Steve I will go out and take readings every four hours or so, recording them, and see what I get.

[Thurman]

Well a new plan now. Steve says Dometic wants him to have the TT at his business to record temps. Don't understand that one. So Monday A.M. the TT goes to his shop. Meanwhile the temps here have nosedived. The high Saturday was 83* and the A/C preformed like a champ. The ten (10) day forecast calls for high's in the mid 80's so I bet the A/C performs as well at his place. It would be nice to get a freak 90+* weather day right now. I'm concerned that the A/C will perform as normal and Dometic will not replace it. With my warranty expiring mid-January it will more than likely not perform well when the weather warms up down here.

[Thurman]

I'm leaving this problem alone for a few days or so. Steve has it at his shop and wouldn't you know it we are having a cool spell here in S. Ga. Today's hi was 83* and tomorrow's hi is expected to be 84*. Bet that A/C sucker will cool as it should with these temps.

[Thurman]

This thread is getting way too long but I have to have an answer to my problem of the A/C unit not cooling the camper. The local authorized service guy has had my TT at his place since Tuesday of this week. He has checked the temps regularly and is getting the delta temps within Dometic's specs, 12 to 15 degrees, those are the specs Dometic told me also in an email I printed and saved. The amperage draw on the unit when running with compressor has been a steady 11.0-11.3 amps. Steve called this afternoon to tell me he thinks he understands my problem better as the unit is within Dometic's specs but is not cooling the TT. Today's high temp was 87* and Steve says the inside of the TT never got below 78* and the air coming from the unit, at that time, was 58*. He is now wondering, as I did initially, IF the unit is not moving enough air even with the fan on HI. Steve says he called Dometic to ask about a spec for the CFM of the air as it leaves the cooled air discharge outlet, with the dump open. I am going to call a local HVAC company Monday and talk to one of their long time service techs whom I know to see if they might have a tool to measure the CFM of air coming from the discharge side of the A/C unit in the TT. But I had a thought: Does anyone on this forum know of any spec the air flow, measured in CFM, might be from a Dometic 15K unit? Thanks

[Super 8]

This is the latest and greatest from Dometic, 350 CFM
Blizzard NXT - Dometic Corp
I am in the same boat as you, camping with other brands with Colman brand AC units that work very well compared to my newly recharged Dometic 15K unit.
Our campers are suppose to have R9 in the walls,R11 insulation in the ceiling and floor. I am thinking that we do not have this good of insulation or the other manufacturers have better?

[Thurman]

Thanks for the link Super 8, that new unit does look nice and it gives the output of the fan @ 350 CFM. Makes me wonder IF the unit on my TT has the same output. As far as having R11 insulation in the ceiling--definitely NOT in my camper. Some time back I pulled the skylight over the tub and the fan in the bath in order to pull some wires to add a light over the tub, which by the way is a great idea. I could, and did, stick my head up into the area where the skylight had been mounted just to see what was up there and I assure you there is not any R11 rated insulation. What was up there was insulation approximately 1/2" thick and did not fit between the rafters as it should, there was at least 1" of empty space between the sides of the insulation batts and the rafters. I have given some thought as to blowing in extra insulation. The problem is that I cannot get to all of the attic type space but I'm thinking that any added insulation would help way down here in S.Ga. where we don't have winters. This past week the temps were in the high 80's each day. Perfect weather to run my A/C and try to figure out why it won't cool the TT. The service guy had it for four days and says he can't figure out any problem as the A/C unit meets Dometic specs. When I asked him what he had the t'stat set on he told me 76*. That's not a good temp to me to try and figure out why and A/C unit is not preforming correctly. I now have the TT set up at home where I get the most sunshine during the day and have the t'stat set on 72* which is as low as the t'stat will go for cooling. I'm charting the temp readings of outside air, inside temp, temp at A/C intake, temp at the dump of the grill, and temps at the front and back registers for ducted air. I also found out that the infrared thermometer I paid high bucks for 22 years ago is not accurate at all anymore. So new digital really good A/C service guy type thermometer. The unit has delta temps now of between 8-16 degrees depending on what time of day you check it. Barely within Dometic's quoted specs to me via an email. Dometic is stating delta temps between 16-20 degrees with an amperage draw of 10-12 amps when running with fan on HI. The amps are fine but the temps are not what Dometic states. One thing I have noticed is there are times when I go in to check the temps the fan is running on LO and not much air is moving. The specs for the thermostat state that the t'stat monitors the ambient air in the TT and the set point and tells the fan to run on either HI or LO. In the AU (auto) mode the fan is supposed to run on HI if the differential between ambient air and set point is greater than 5*. The fan is supposed to run on LO if the differential is less than 4*. That ain't happening with my TT. It seems the t'stat tells the fan to run on LO when it is warm inside the TT. I did set the fan to manual HI yesterday about 1:00 p.m. and let the A/C unit run. I get much better results as far as maintaining a set temp within the TT. With yesterdays high at 90*, sitting in full sun, the TT stayed at 74* which was comfortable. At this time the outside temp is 89*, at 3:27 p.m., the unit is running with the fan on AU and the inside temp is 76*. Not exactly where I want it and not as good as my former TT with a Dometic Brisk Air unit did. I'm certainly leaning now towards a defective t'stat in that it allows the fan to switch to LO during the hottest part of the day. I wonder what hoops I will have to jump through to get the t'stat replaced under warranty?

[Super 8]

If I am understanding this right, your thermostat only adjust down to 72F in the cooling mode?

[northstar1960]

How many slides ? slides are bad for cooling and heat loss . my 15000 btu dom knock on wood has ran great for the last 18 months . in Fl now and it has no problem keeping unit cool during the day i set at 71 and it stays there at night down to 66 . i have put some foil bubble insulation over one side of the slide to help reduce heat gain . the slide sides are black and really absorb the heat of the sun in my TH . also most all the windows have the insulation also that also helps a lot . sound like to me your problem is more with keeping the cool in and the heat out and not so much the AC unit . Dom has had issues with some units but not all.