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Old 10-14-2021, 02:42 PM   #1
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Dometic RM2351 Fridge Cooling Problem

Hello forum folks. Iíll try to be as brief and organized as I can. Thanks for your help in advance.

I have a Dometic RM2351 refrigerator made in 2013 in my Gulfstream Kingsport travel trailer, which I purchased used (the trailer). The fridge has had intermittent cooling problems since I bought it.

Initially, a couple seasons ago, I noted the venting was very poor, so I installed baffles to improve efficiency. I also noted a moderate kink in the copper gas line, just before the burner/jet assembly, so I replaced the line with gentler bends. This seemed to improve the efficiency. On my last camping trip, however, it seemed to cool well in the days prior to the trip, then fail to cool during the trip. We were operating on gas during this latest trip, as we had no hookups. I am pretty obsessive about leveling whenever we run the fridge, so I donít suspect that. I did the Ďpre-cool' before the trip on 120v at my house. All the food that went into it before the trip was pre-cooled in our home fridge. The two previous trips this year, we had hookups, so ran the fridge on 120v, with no cooling issues. I have never had a cooling issue while running on 120v, so Iím assuming itís a gas issue, unless someone believes otherwise.

The propane tank was lower, but all other gas appliances (stove, heater, water heater) worked properly during the entire weekend trip. The burner flame ignites quickly and stays lit either when 120v power is lost in auto mode, or when gas is selected manually with the button. The flame is blue and is centered below the flue. I cleaned the burner and flue in place with compressed air, about 25-30 psi, when I got home from the trip. It did not really appear to be very dirty. I have checked for propane leaks with soapy water between the tanks and the fridge, but given that the other appliances are working and the fridge flame appears right (does it?) I donít suspect a leak to be the cause. There is no evidence of a cooling system leak (no yellow residue).

The frustrating part is that it has been running on propane now for about 48 hours, and the temps are fantastic (the only things in the fridge now are thermometers and a rock hard bottle of water in the freezer. Fridge is in the mid 30s, freezer at about 0. Iím wondering about the propane regulator and the rubber pigtail between the tank and regulator. Also the rubber line between the regulator and the rigid pipe that is plumbed under the trailer. Is the regulator going bad? Has one of the rubber lines delaminated inside causing an intermittent constriction? I have not done a pressure test on the propane, as I donít have the equipment to do so, and I wonder if there might be other troubleshooting steps I can take before I invest in a test kit. Could the gas pressure have been low enough, given the tank was getting a bit lower, that the fridge wasnít working but the other appliances were? Are fridges that sensitive to the gas pressure? What else am I missing? Where should I be looking that I havenít looked? Am I barking up the wrong tree while focusing on the gas?

I tried brevity...clearly Iím not very good at it, but I wanted to make sure I covered all the troubleshooting Iíve done. Iím going to try to include a photo of the flame if the forum allows.

Thanks for any help,

Jason


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Old 10-14-2021, 11:15 PM   #2
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Cools well on 120VAC so cooling unit is NOT the issue

Propane appliances run OK.....tank being a bit lower is NOT the issue
*Propane tank pressure varies but even if down to 20# in the tank the LP Main Reg controls at 0.39PSI (11"WC with at minimum of 50% appliances in service)

**Stove has it's own Reg under the stove top that controls stove/oven to 10"WC (0.36psi)...so even if Main LP System was down to 10"WC the stove would still operate OK

Furnace is GAS Hog but can heat with low LP Pressure
Water Heater can also...just increases heating time

Fridge....
Your Flame LOOKS great
BUT flame at 10"WC will LOOK great also
Flame temp would be 'cooler' at less then 11"WC .....cooler flame does not generate enough heat to boil ammonia into vapor in sufficient amounts to properly cool fridge down
*Hot ammonia vapor condenses into warm Liquid Ammonia...the more vapor produced/the more it can be condensed into Liquid ammonia/the more heat can be absorbed when the liquid comes into contact with the Hydrogen Gas.....Flashes into VERY COLD Liquid that absorbs the heat from freeze/food compartments

Fridge on propane is NOW cooling properly
But are any other appliances being used??
Or just fridge only?


2013 Vintage......8-9 yr old Main LP Reg.


***Never test LP System with pressures greater then 0.5 psi. (1/2#)
Gas valves on fridge, water heater, furnace WILL be damaged
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Old 10-15-2021, 09:46 AM   #3
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Thanks for your thoughts, Old-Biscuit. First, to answer your questions: Only the fridge is being used now, as it sits in front of my house. On the trip, all the other appliances were used...water heater, stove top at dinner time and furnace to warm up at bed time and early in the morning, but not all night. Would that sporadic use of the other appliances, coupled with the possibility of a faulty main LP regulator be enough to cause that much loss of cooling?

Based on your troubleshooting, would you suggest buying or building a manometer like in the link posted below, or simply replacing the main LP regulator? Other troubleshooting steps? Recommendations for a replacement regulator? I currently have a dual output regulator with two tanks. There is a manual valve to switch between the two tanks, but to be honest, I don't know if it also has an auto switch feature. Would be nice to have that if they're considered reliable.

Measuring Gas Pressure with Manometer

Thank you,

Jason
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Old 10-15-2021, 10:56 AM   #4
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Homemade manometer is easy to build and will tell you exactly what the Main LP Reg is able to maintain with appliances in service
S/B able to provide full flow/control pressure with ALL...but only need 50% in service to measure

2013 vintage
That would be an Auto Change-over Reg
Lever is for 'Indication' (Green/Red Indicator)
1st cylinder OPD Valve opened is then Primary and lever s/b pointed towards that cylinder.
Then other cylinder OPD Vlave can be opened placing it in stand-by/Secondary
When 1st cylinder goes empty...reg swaps to Secondary/Indicator goes RED
Then turn lever towards 2nd cylinder and valve out 1st cylinder
Indicator goes back to Green
1st cylinder can then be removed/refilled/installed/vlved in as back-up


2013...new reg and NEW pigtail hoses from each cylinder to regulator

Cavagna 924N is a good LP Reg




*YES...only having fridge in service the reg seems to have been able to keep up
But when you were out on your trip and fridge water heater, occasional furnace it couldn't maintain hence the fridge temps getting warm
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Old 10-15-2021, 11:42 AM   #5
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Old Biscuit,

Thanks for the review on the auto change over...it is indeed that type...looks like a Flame King brand, despite no markings I can see.

I believe I will build a manometer and measure the pressure, and likely replace the reg and pig tails.

Where is the best place to measure the gas pressure? Test port on the fridge jet assembly? Somewhere else? This will probably determine what fittings I need to get for the manometer.

Thank you,

Jason
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Old 10-15-2021, 02:01 PM   #6
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Fridge gas valve test port...it is on the downstream side of gas valve

IIRC 1/8" nipple....

After hooking manometer up...start ALL stove top burners on HIGH to place demand on LP System
Then start fridge.....
**If AC is available start on AC then when ready to test gas just unplug fridge power cord and let it swap to gas automatically then you can watch flame ignite and measure pressure
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Old 10-15-2021, 02:06 PM   #7
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Old Biscuit,

All understood. Thanks for the details. Off to get the manometer supplies.

Jason
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Old 10-15-2021, 02:32 PM   #8
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I attempted to take the test port plug out to take with me to compare threads and diameter at the hardware store, and the plug would not come out, even with significant torque. I hesitate to try harder, for fear of stripping out the plug. Is there another place I can easily test the LP pressure? The plug isn't reverse threaded, is it? From the few threads I can see on it, it does not appear to be. The flare connections to the furnace or water heater? Neither are terribly accessible, but might have to do? The stove top line is the most accessible, where it connects to the stove regulator underneath the cooktop. But then I wouldn't be able to use the burners to add load.

Thoughts?

Jason
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Old 10-15-2021, 09:49 PM   #9
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Hook up using the propane supply line to stove...under the stove top
Use furnace, water heater and fridge to supply demand

Fridge test port should not be that tight....so best to use stove for testing
*Right hand threads

Here is a write up on building manomter and testing LP System----Pressure, Leak down, Lockup etc
RV U Tube Manometer
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Old 10-16-2021, 05:03 PM   #10
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Old Biscuit,

All makes sense. Thanks for the link on the manometer...I had seen others but this one is better. I'm on shift both days this weekend so I'll have to begin again on Monday. It seems likely I'll be replacing the main LP regulator...its so helpful that they're all out of stock.

Thanks again for your invaluable help. I'll post with results.

Jason
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Old 10-17-2021, 10:58 AM   #11
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I noticed your white condensation drain line goes straight down from the fridge, apparently below the access panel area. I recently noticed mine had fallen apart, and my fridge was running hot, apparently because warm air was getting in through the half inch hole where the condensation line enters the refrigerator section.

I replaced it with a similar-size hose that is black, but I put a low bend in the line so I have a water-filled P-trap. Out camping last week my fridge was running 31 to 34 degrees, whereas before it was running 39 to 45. I think having that P-trap closing off any chance of warm air invading the refrigerator makes a huge difference. The end of my line goes to an insect cap on the access panel frame.

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Old 10-17-2021, 11:12 AM   #12
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Quote:
Originally Posted by tap4154 View Post
I noticed your white condensation drain line goes straight down from the fridge, apparently below the access panel area. I recently noticed mine had fallen apart, and my fridge was running hot, apparently because warm air was getting in through the half inch hole where the condensation line enters the refrigerator section.

I replaced it with a similar-size hose that is black, but I put a low bend in the line so I have a water-filled P-trap. Out camping last week my fridge was running 31 to 34 degrees, whereas before it was running 39 to 45. I think having that P-trap closing off any chance of warm air invading the refrigerator makes a huge difference. The end of my line goes to an insect cap on the access panel frame.

Attachment 346328

OP stated Freezer/Food Compartment cool/maintain cold on 120VAC
Temps warm up on Propane.....

Drip Tray drain line would affect 120VAC and GAS cooling abilities

Always a good idea to check that drain line due to the cheap material used but that is not OPs issue ---YET LOL
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Old 10-17-2021, 11:40 AM   #13
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Quote:
Originally Posted by Old-Biscuit View Post
OP stated Freezer/Food Compartment cool/maintain cold on 120VAC
Temps warm up on Propane.....

Drip Tray drain line would affect 120VAC and GAS cooling abilities

Always a good idea to check that drain line due to the cheap material used but that is not OPs issue ---YET LOL
To be fair, he's not absolutely sure it's a gas problem. We don't know the other variables, like perhaps where he lives it's a cooler climate, and where he recently travelled it was much warmer. In fact several trips before when my fridge was getting very warm, I tried running it on 110, then propane (even though I had a 110 hookup) and I really wasn't sure what the issue was. Sometimes it seemed okay on propane, sometimes it seemed okay on 110.

However once I noticed the condensation line was falling apart, and as I said, replaced it and put the water filled P-trap in, I went camping last week and the fridge is now cooler than it's ever been. Even when brand new, it never got down to 31 degrees. It was usually up around 38 to 42, on gas or electric.

I'm not sure why you're so dismissive of putting a P-trap in the condensation line, but many people think otherwise, and in my experience, it definitely is helping.

So before the OP spends a whole lot of money and time on diagnosing this issue, it would be very simple to test and see if it helps. In fact he could just temporarily cap off that line and see what happens.
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Old 10-17-2021, 02:31 PM   #14
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Tap4154, Thanks for your point about the drain line. I had noted the addition of the low point 'trap' in previous research and have it on the to do list. It currently runs straight down through the floor to a bug cap on the end of the line. To fill in some of the variables, I live in the Colorado Front Range and was camping not far away at Rocky Mountain National Park. The temp differences were not much, maybe 10-15 degrees cooler in the Park, on average. It certainly couldn't hurt to check the condition of the drain line closely, and plug the end temporarily to see if that affects performance. It's just that it was running so well on 120v, and then also some of the time it was working well on gas (Freezer below zero and fridge low 30s). After I was back from the trip and emptied the fridge, which was about 75% full for the trip, I ran the fridge on gas for almost a week with fantastic performance. Granted, the other gas appliances were not in use.

Thanks again for all the input.

Jason
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