Dometic disappointing 15k a/c

[smt0954]

I have a 2016 Jayco 317RLOK Eagle fifth wheel with (2) 15k units. Cooling off a hot box is a real problem. Here's what I did:
a) installed a 2nd 50AMP inlet on fifth wheel hitch (could have just used a 30AMP)
b) installed a 2nd transfer switch
a + b cost about $1000
c) purchased a Champion Digital Hybrid portable generator model 100302 from Home Depot shipped free to my house - cost $643
d) purchased a 20ft 30AMP male to 50AMP female cord

the genset sits dead middle of truck bed in front of my PullRite fifth wheel hitch. I crank it up, connect 50AMP female to inlet to fifth wheel hitch, then connect 30AMP RV male to genset, go inside, turn 1 AC fan to 'ON', then turn AC to Cool, then go back to genset and put in Econ mode.

I could probably also run my Norcold on 'Electric', but haven't chanced it yet. Now when I get to a campsite, the interior is about 18 to 20 degrees cooler than the outside ambient temperature.
works great.

[jloco]

I guess it's mainly dependent on humidity levels. My 2016 38FDDS, has a single, Coleman Mach 15K along with the thermal package. I think the key is to turn it on BEFORE it get hot. I do this and our 38 foot box stays pretty cool with the single unit. Then again, I'm 1/4 mile from the ocean so it really never get too hot and there's always a breeze, which is exactly why I opted for the aluminum siding with sliding windows over the fiber glass siding with tilt windows.

[Farris7]

Have you cleaned the coils and or the screens? Ducts? They work much better when cleaned

[Sandy5288]

Originally Posted by o2silverado

Anybody else disappointed with their Dometic 15k air conditioners. First hot day in the new trailer and I am really disappointed with the performance of this unit. It's about 86° here and mild humidity thermostat is set at 72° and this baby is barely keeping up. Really glad I opted for the 2nd a/c & thermal package. Maybe my expectations were to high.

Yes... The same problem.. it struggles to even do 20 degrees under outside temp. We bought a new 2018 White Hawk plagued with poor workmanship, faulty equipment and no support from other Jayco dealers... As quoted to me by one Jayco dealer, they are too busy getting new units ready and do not have time to do warranty work. They suggested calling an RV mobile company who will charge me for the service call and cost of material... which they state I will get back when they get paid by Jayco... there are no guarantees, Jayco will pay them back, based on their experience in the past. One Jayco dealer told me if I could wait for 8 weeks they might be able to get to me and it may take another 3 weeks to fix the problems. I am now replacing faulty thermostats, a none working Microwave unit, fixing wiring and poor construction work on my own time and money. Not only are these units below "acceptable" quality but their Warranties are totally useless especially when you are out on the road thousands of miles away from where you purchased the unit.

[sinnott4]

Originally Posted by o2silverado

So after further investigation I found that about 3/4 of the duct opening at the a/c is filled with caulking because they missed the side of the unit with the duct....leaving the main part of the trailer with minimal air flow.

Sounds like more Jayco poor workmanship! I found that they put one of the screws that were supposed to hold on the rear license plate holder into the hole that the taillight wire runs through, therefore not holding the bracket.


George in Mi Jayco Hummingbird, Chrysler Pacifica

[Inglysh]

See attached.

Take the cover off the interior part your air conditioning unit.

There should be a copper sensor somewhere just above the air filter.

If it is located on the evaporator? it is in the wrong spot. It needs to be relocated to where the air goes into the AC unit, essentially right above the filter (so it read something close to ambient). How you see it in the attached is how the unit is shipped from the manufacturer. Whoever installs it is supposed to relocate it. Ours was not and it was causing the AC unit to short cycle... To the point where the compressor would almost never run.

It took two years and threats of legal action to finally find this out.

[nynethead]

You should check to see if you really have a 15K AC unit. I had the same issue with my last trailer and I was told it was a 15K unit. I could never get the temperature below 80 until the sun went down. After many years I took off cover of roof unit and cleaned fins and took down information. When i searched the Internet i found it was actually a 13.5K unit.
When i purchased my 2018 Jayco i got the two 15K units, but the main one worked all by itself last year sitting in the sun at the beach it could cool the trailer to 65 with no issue. It is faster with both units on, but one works.

[Cheaperrooter]

ALL air-conditioners, wether for your house, business, car or RV, by nature of their design, will only lower the outside ambient temperature by 20°.

It’s a BIG misconception amongst homeowners if not a wives tale that think they can get the house down to 65° by putting the thermostat on 65 regardless of the outside temperature.

Then depending on the size of the unit you have other factors, which is how fast it will get the house down that 20° and depending on the insulation how long it will stay there before it kicks on again. So if it’s 100° outside don’t plan on it getting cooler than 80°

And that’s why it’s a big waste of money to put your thermostat lower than 20° because the unit will just run 24 / 7 and the house will never get cooler.

35 year retired plumber

[BJR]

Originally Posted by Inglysh

See attached.

Take the cover off the interior part your air conditioning unit.

There should be a copper sensor somewhere just above the air filter.

If it is located on the evaporator? it is in the wrong spot. It needs to be relocated to where the air goes into the AC unit, essentially right above the filter (so it read something close to ambient). How you see it in the attached is how the unit is shipped from the manufacturer. Whoever installs it is supposed to relocate it. Ours was not and it was causing the AC unit to short cycle... To the point where the compressor would almost never run.

It took two years and threats of legal action to finally find this out.

Do you have more info? My copper wire is on the output side not the intake.

[TakerEasy]

This simply is not true.

You mean to say, the AC duct temps should be 18-20 DegF cooler than the Filter Inlet temp. It has nothing to do with outside temp.

Outside temp has to do with the heat rejection on your structure and how well it is insulated. If your structure is insulated, you would drop initially 20 degrees from outside ambient temp, but now the air in your house is 20 deg cooler. As you recirculate air, the house and duct temp should continue to drop until you reach a certain point where the AC simply can't remove heat any faster than it's coming in (from outside or other heat sources).

It's 101F outside right now. My office is a cozy 68F. I also have very good insulation in my office and the AC is cycling!. I can drop it into the lower 60's if I wish.

Richard

Originally Posted by Cheaperrooter

ALL air-conditioners, wether for your house, business, car or RV, by nature of their design, will only lower the outside ambient temperature by 20°.

It’s a BIG misconception amongst homeowners if not a wives tale that think they can get the house down to 65° by putting the thermostat on 65 regardless of the outside temperature.

Then depending on the size of the unit you have other factors, which is how fast it will get the house down that 20° and depending on the insulation how long it will stay there before it kicks on again. So if it’s 100° outside don’t plan on it getting cooler than 80°

And that’s why it’s a big waste of money to put your thermostat lower than 20° because the unit will just run 24 / 7 and the house will never get cooler.

35 year retired plumber

[2edgesword]

We had some concerns when we picked up our 28RLS over the Memorial Day weekend. Our first few days camping the temperature got up to 90F with 70RH. Thankfully the 13.5K Dometic unit cooled things down relatively quickly (we use quick cool venting) and it kept up with the heat and humidity throughout the long weekend. This is a new unit so it remains to be seen if the good performance is long term.

[TakerEasy]

Originally Posted by BJR

Do you have more info? My copper wire is on the output side not the intake.

If you have the Mach 15k ac with control knobs on the AC ceiling assembly then when you remove the entire ceiling/filter assembly by removing the 4 screws, you will see the temp control knob. Out of that control knob (thermostat) there is a copper capillary tube and it should be away from the coils and sitting in the suction air flow right above the filter.

If it's touching the coils it will be cycling the ac based on coil temp and not inside air temp. If it's really in the discharge then it's measuring the discharge air temp and not the inside air temp. I didn't think it would reach far enough inside to be on the discharge side but I hadn't looked at mine in awhile.

[BJR]

Originally Posted by TakerEasy

If you have the Mach 15k ac with control knobs on the AC ceiling assembly then when you remove the entire ceiling/filter assembly by removing the 4 screws, you will see the temp control knob. Out of that control knob (thermostat) there is a copper capillary tube and it should be away from the coils and sitting in the suction air flow right above the filter.

This makes total sense and I am somewhat baffled. No wonder it struggled to get cool.

Edit: Christ, you were right. It says in the instructions under Attaching the Ceiling Grille:
1. Gently position the thermostat capillary so as to be in the return air stream.


Here's mine after I taped it. (ducted Mach 3) You can't see the wire because it's on the other side of the foam. That changes now!

[MLaffoon]

2 AC units is a must. And if 1 is a heat pump for the winter it is worth the investment.

[robert9999]

True if driving through the summer Desert for hours and than setting up the place is so heat soaked that the a/c will run for hours to get cool. I was inTucson AZ in July 105 degrees and the 15k was on for hours during the day,almost non stop. It was about 78 inside. The problem isn’t the a/c but the cheap thin under insulated walls & ceilings topped with single pane widows that make these rolling boxes so hot. I leave the cabinet doors open on the sunny side where food & meds are stored as they are mini ovens also.

[TakerEasy]

Wow, let us know how it goes. Please report back!

Originally Posted by BJR

This makes total sense and I am somewhat baffled. No wonder it struggled to get cool.

Edit: Christ, you were right. It says in the instructions under Attaching the Ceiling Grille:
1. Gently position the thermostat capillary so as to be in the return air stream.


Here's mine after I taped it. (ducted Mach 3) You can't see the wire because it's on the other side of the foam. That changes now!

[BJR]

Originally Posted by TakerEasy

Wow, let us know how it goes. Please report back!

Will do. I fixed mine and will report back after the weekend. We have had the camper two years but they replaced the roof under warranty a few months ago. I don't know if it was always that way or if they did it when they r/r the unit for that.

Hopefully the OP has success, as well.

[vcbice]

We feel lucky if our inside temps are in the 70's when the outside is over 105F (in full sun) and that is with TWO 15k AC running almost all day.

The cheaper RV's (which is what we have) are just not insulated that well. Ours is certainly MUCH better than our two previous RV's. Still, they are not like a house or any other building. Walls and roof are THIN. They can only do so much.

So, you need much more AC capability to keep your RV cool compared to similar size building.

Yes, if you only have one AC in a 30ft or larger RV it will be tough to keep your trailer cool in desert daytime temps over 100F.

You can do things to help. Put some sun protection tinted film on your windows, or, just cover the windows. Some use the Al bubble wrap in their windows and in skylights. Keep window shades closed on sun side. Use your awning if the wind is not blowing bad.

If you know you are going to be using your trailer in higher temps, then take that into consideration when purchasing (do not rely on sales talk). Get double pane windows, slide toppers. Look for units with better insulation. Yes, you will pay more.

[jpolito]

Just retired after just short of 40 years of ac repair work. I also noticed the same, ac units do not cool very well. To me it seems like low freon charge? can't tell about the charge without getting into the sealed system and I am not going to touch that until warranty is up. since the supply air is not cool enough even coming right out of the unit not going through the ceiling duct work makes me think that is the problem. But in hearing other peoples posts doesn't make sense that it would be that widespread. Will post if I check further.

[TCNashville]

Although I haven't read this entire thread but have any of you ever pulled [unscrewed] any of your ceiling vents to make sure you aren't having AC air escaping into the attic? Common problem. I pulled all my vents, removed the plastic ring and aluminum taped between the ceiling and the main AC vent, reinstalled the vent w/o the ring and saw a big improvement. Just a thought.