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Author Topic: Refrigerator not cooling well on LP  (Read 266 times)

happyhiker

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Refrigerator not cooling well on LP
« on: August 18, 2020, 09:05:23 PM »
I am wondering if anyone has any ideas to help me get my Dometic RM 2554 refrigerator working better on gas.  My camplite DB14 is a 2014 and I had problems after the first few years with it cooling.  I took it to a dealer and he told me the space between the box and the refer was too big and I didn't have any ventilation.  I put two 12 volt fans in the back and that helped but a few years ago the entire cooling unit failed.  It was replaced under warranty and has worked ok for the past couple of years.  Recently, it stopped cooling on LP.  It works on AC (cools to around 37).  I changed the LP regulator (at the tanks) and it now cools down to about 47 on gas but that is it.  I have cleaned the orifice, the burner tube and the flue tube but is still not cooling properly.  Also checked the board and the termistor and they appear to be functioning.  I haven't checked the LP pressure at the refer, but the flame is burning hot and is noticeably better since I changed the LP regulator. I am kind of at a loss at this point short of taking it to a service tech.  Any ideas would be appreciated.  I am kind of wondering if I have the baffle in the right position.  The service manual states that the baffle is supposed to be 1 15/32 above the burner.  It is kind of hard to determine if I have it right.  I have attached a picture of the baffle placement although I don't think that is the problem.  Any suggestions would be appreciated.  Oh, I should state that I am trying to test it in Florida and it is hot and humid and never really cools well down here, but it should get colder than 47 on gas.   Thank you.

ps I am starting to think this was just a poor design on the refer layout.  Probably should have a roof vent for all of that heat.  Has anyone installed a roof vent for their refer?
« Last Edit: August 19, 2020, 08:26:48 AM by happyhiker »

Apollo

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Re: Refrigerator not cooling well on LP
« Reply #1 on: September 15, 2020, 12:24:26 PM »
My fridge wouldn't cool very low either and I found a piece of insulation blocking the vent under the roof cover. Fridge works perfect once I removed that piece of insulation. 

This may not be your problem but you'll want to make sure the heat can get out.

Maybe adding a fan to the top vent blowing out will help, I saw a guy do that once he used zip ties to hold the fan to the vent cover.

Keep in mind an LP fridge can only cool like 50 degrees below ambient so if it is 100 degrees out and the sun is shining on the fridge side of the camper you are going to have decreased cooling.
« Last Edit: September 15, 2020, 12:25:57 PM by Apollo »

happyhiker

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Re: Refrigerator not cooling well on LP
« Reply #2 on: September 15, 2020, 04:25:12 PM »
Unfortunately, when Livin Lite installed the refrigerator they did not provide a roof vent, but relied entirely on the two side vents.  I have attached a picture of the inside of the cabinet.  As you can see the top of the cabinet is the bottom of an inside cabinet.  There is no vent.  It is all non-vented. 

When they installed it they also left over a 1 inch gap on both sides and the top.  I put some mineral wool on the sides and top since I posted the last picture.   That has helped a bit but not much.  The fans have been there for awhile and usually get the temps down, but not this year.  I have been measuring temps and it was never able to achieve a 50 degree variance between ambient air on gas and the inside box temp.  The best spread on gas was 43 which wasn't bad, but not great.  On electric, it would get below freezing in the box and would achieve between 48-53 difference with the ambient air.   In my most recent outing, I couldn't get the temperature in the box while on gas below 45 degrees with an outside temp between 80-90.

At this point, I am not sure how to proceed.  Probably the best option is to install a roof vent, but I have no idea how to do that so I am a little bit uncertain.  Perhaps others have encountered this problem?   Maybe the fans are pointing in the wrong direction?  Should they push the hot air out or force air over the coils?  I have seen pictures both ways.

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Re: Refrigerator not cooling well on LP
« Reply #3 on: September 16, 2020, 02:49:23 PM »
I have a 2014 14DB as well. It wasn't long before I became frustrated with antiquated absorption fridge technology. Like many, I added the usual the computer fan(s) to the fridge exhaust vent. Cooling improvement was marginal at best. Finally, I took the advice from https://www.arprv.com/ and mounted a squirrel cage fan to the lower vent pushing air in, and another to the upper vent exhausting the air, all controlled by a temp relay. IMO, this is the way to go. Setting the fridge at level 3 is now adequate to keep the temp hovering between 35F and 40F. Also, the fridge cools much more rapidly after door open/close.

For a long time, venting thru the cabinet above the fridge and out the roof was on my list of mods, but thankfully that's no longer on the list. (Why couldn't CL have done that at the factory?) Back to the present and tech has improved. 12V compressor fridges now sip so little battery power that I'll be installing one once the current beast croaks or even before if I can convince my LSW that our 14DB deserves one! There is even a company that sells a compressor retrofit for absorption fridge cabinets https://jc-refrigeration.com/. Regards, GK


Merlin

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Re: Refrigerator not cooling well on LP
« Reply #4 on: September 16, 2020, 05:26:52 PM »
Iím very impressed with the current iteration of DC compressor cooler/freezers. My Waeco cooler (now Dometic) runs a long time on one Group 27 battery and would run indefinitely if hooked up to solar too. If an RV fridge could be made with that same quality and efficiency, compressor technology is a viable alternative to absorption. The problem is that I have found most RV appliances are made to be cheap with no consideration to efficiency or longevity. Everybody wants low prices instead of quality.  :-\
Michigan

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Re: Refrigerator not cooling well on LP
« Reply #5 on: September 16, 2020, 05:48:02 PM »
My experiences with absorption fridges have generally been good, and I have quite a bit of experience with 12V high efficiency (Danfoss) compressor fridges in boats, so here is my take.

My absorption fridge has never given me a problem and cools the fridge compartment to about 40F and the freezer to below 10F even on a warm day. But warm days in the NE are not the same as warm days in the south. It uses little propane. Many years ago we had a 5th wheel with a fridge like is in our 16TBS and could go at least a month on a 20# propane cylinder.

DC fridges are great when you absolutely cannot use absorption such as on a boat that rocks and rolls. Small efficient ones can use as little as 30-40 amp hours daily like the Waeco but a 6+ cu ft one like is in our 16TBS will use at least 60 Ahs daily. That will soon tax a G27 battery.

Soon, when this crazy RV market cools and the CV abates, we will probably buy a short Class A motorhome. It will definitely have an absorption fridge since we almost exclusively dry camp. I may have to fiddle with it and add fans as GK and others suggest. I hope not.

Refilling a propane tank every month or so is a lot cheaper and easier than adding lithium batteries, a big solar panel or running the genset every day to keep up with a DC fridge.

David

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Re: Refrigerator not cooling well on LP
« Reply #6 on: September 17, 2020, 01:24:11 PM »
For a long time, venting thru the cabinet above the fridge and out the roof was on my list of mods, but thankfully that's no longer on the list.

My solution to this same issue was to use some Dollar Store cheap tin baking pans placed above and to the sides of the fins forcing air out the top wall vent.  This was in addition to adding fans below the fins drawing/forcing air up through them - and a thermostat.  I haven't had an opportunity to measure effectiveness yet, but I expect it will only be marginal at best. 

......David
« Last Edit: September 17, 2020, 01:38:22 PM by PDX David »

DaveL

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Re: Refrigerator not cooling well on LP
« Reply #7 on: September 18, 2020, 02:51:43 PM »
I had a similar problem where the fridge cooled well on electric but not well on gas.  This was in contrast to a trip out west earlier in the year where it operated fine on gas.  After cleaning, checking the flame, etc. I noticed that some online videos showing how to troubleshoot the flame... mine was a beautiful blue but not as robust as the video.  The Dometic manual also has you check gas regulator pressure as one of the first steps.  I could have went down to Home Depot and bought the materials to make a home made manometer ($20 and a hour of effort) ... however I had previously noted that it seemed to take 3 - 4 tries to light our stove.  Decided to just go ahead and buy a replacement 2 stage regulator.  Installed it and there was a noticeable difference: stove  now lights first try and the fridge flame is more robust.  Two day check of fridge temps running on gas indicated it is now cooling very well equivalent to electric.

ADR

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Re: Refrigerator not cooling well on LP
« Reply #8 on: September 24, 2020, 05:37:47 PM »


Soon, when this crazy RV market cools and the CV abates, we will probably buy a short Class A motorhome. It will definitely have an absorption fridge since we almost exclusively dry camp. I may have to fiddle with it and add fans as GK and others suggest. I hope not.



I'd rethink that- I have a 4Wheel popup truck camper that has a marine 12V compressor fridge- I also use a 12V compressor ARB in my van.
Now for the good part- with a compressor fridge you have no need at all to park even close to level, which of course is a requirement to not ruin an absorption fridge.
The ability to stop anywhere at anytime in my 2 with DC compressor fridges is priceless to me.


At one time Dometic had a fridge that had BOTH technologies in it- that sounded great- must not have worked out though as it was short lived.
« Last Edit: September 24, 2020, 05:40:12 PM by ADR »

DavidM

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Re: Refrigerator not cooling well on LP
« Reply #9 on: September 24, 2020, 06:38:14 PM »
Thanks for your comments but I have thought about this long and hard.

The typical small upright DC fridge is 6 cu ft and draws about 40 Ah daily (50% cycle time at 3.5 amps). Our other DC loads add up to about 20 Ah daily, so a total of 60 Ahs. Even with 200 Ahs of lithium batteries that load will draw down the batteries in three days. With an absorption fridge the load will be 25 Ah if I cut off the frost heater and I can go at least double the number of days without charging.

In so far as leveling is concerned, my Dometic fridge in my current 16TBS specs say 6 degrees fore and aft and 3 side to side is allowable. I routinely level the trailer to less than a degree using stepped ramps and leveling blocks.

So I can live with leveling an absorption fridge for its much lower amp draw. BTW a 20# propane cylinder lasts for at least a month with continuous fridge use, coffee and an occasional dinner cooked on board (rather than on the grill outside) and with most small Class As having 45 lbs minimum on board, propane should be no problem.

I have thought about it and those are my conclusions.

David

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Re: Refrigerator not cooling well on LP
« Reply #10 on: September 24, 2020, 07:42:07 PM »
No problem- I respect your decision of course. 

I was mostly referring to stopping while traveling- as in oh look- there is a place we'd like to stop- maybe for hours- but there is nowhere near level enough to park and keep the fridge going... 

Sure wish someone had a fridge that would do both- LP for efficient long term motionless stays and a compressor for quick cool down and parking off level.

happyhiker

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Re: Refrigerator not cooling well on LP
« Reply #11 on: September 25, 2020, 12:29:40 PM »
I appreciate all of the comments.  At this point, I am going to try to fix the Dometic RM2554. I will however, give serious consideration to a DC compressor frig if I have to replace the entire unit.

 I am usually out West in the Summer at high elevations, with low humidity and low nighttime temps so the gas has worked better.  As stated, the cooling unit failed three years ago (under extended Dometic warranty) and they replaced that (i.e. cooling unit)  but not the control board, thermistor or any other components.  I added the fans after the cooling system failure and used the fans to vent hot exhaust gas out the top.  It has generally worked ok.  Never great but usually will stay below 45 degrees on gas.

This year, when I tested for our initial road trip inspection (pre Covid lockdown) it wouldn't cool on gas below 47 in Florida.  I cleaned the flue burner tube, the orifice and the baffle tube.  Still no improvement.  Next, I considered the Manonometer test and decided to simply replace the regulator.  I wasn't comfortable either building or buying a monometer and testing.  I do note that Dometic states that there must be 11" Water Column of pressure at the refer test port.  So I changed the old single regulator with a dual tank regulator up front.

I took several vids and a picture to compare the burner flame height and size pre and post and I can confirm improvement, however, I have not conducted the test and cannot confirm 11 WC.

I have now purchased a new control board (upper and lower) and a new thermistor.  Most recently the refer was getting and staying below 32 on electric (during a trip to Illinois with slightly lower temps).  No such luck on gas.  I have also added the Rockwool mineral wool (although thanks for the baking pan suggestion PDX David).   Also thanks to GrampaKilt for the information from arprv.com.  I will check it out.

So, I guess I will replace the control boards next.  It never has worked on DC mode.  I am also hopeful that this will help.  Any further comments and suggestions are appreciated!
« Last Edit: September 25, 2020, 01:32:29 PM by happyhiker »