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Old 08-25-2019, 03:28 PM   #1
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Running on LP and shore power at the same time

Hello there folks, for the past 2 years I've been fighting to get my old Dometic compact fridge to cool down sufficiently on LP with no luck. It works great on 110 but only cools to 44 degrees F overnight when its 54 F. And 60*when it gets to 75 on LP. My question is can I run the fridge on both LP and 110 via my inverter at the same time?



I only consider this because I have a decent solar setup but I'm not comfortable running it solely off my batteries.



Thanks for your replies in advance.



Mike J
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Old 08-25-2019, 06:55 PM   #2
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It sounds like you have a problem with your LP burner . It should cool to the same temperature on either AC or LP. On most fridges , you can only run one mode at a time ( AC, LP, DC). The newer models will have an "Auto" mode which will select the mode depending on the availability of the fuel. If both LP and AC are used at the same time , there is a possibility of overheating.
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Old 08-25-2019, 10:48 PM   #3
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Thanks for the reply!

I tested this today and the AC cut out when the AC setting temp was reached. I assume the overheating condition could only occur if the ACs thermostat malfunctioned.

Mike
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Old 08-25-2019, 10:56 PM   #4
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Can NOT use BOTH heat sources at same time.....fridge controls do not allow dual heat use


Cools on AC but NOT on LP
Then issue is with the LP side
Either LP System Pressure is LOW (S/B 11"WC---0.4 psi)
Burner is dirty.....orifice is dirty
Flue is dirty

Or gas control is faulty




Model of this Dometic compact would be helpful.........!!!
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Old 08-26-2019, 04:40 PM   #5
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Quote:
Originally Posted by Old-Biscuit View Post
Can NOT use BOTH heat sources at same time.....fridge controls do not allow dual heat use


Cools on AC but NOT on LP
Then issue is with the LP side
Either LP System Pressure is LOW (S/B 11"WC---0.4 psi)
Burner is dirty.....orifice is dirty
Flue is dirty

Or gas control is faulty




Model of this Dometic compact would be helpful.........!!!
My unit allows for dual control. I know this because it's running on both since yesterday. My question really was" knowing that the LP only does so much cooling and the 120V has a thermostat that kick's out once set temp is reached then is there any issue that could cause a problem. The way I see it the 120 v thermostat is a safety net. But I could be wrong.

The unit is a Dometic RM2190.

The problem is likely a pressure issue as I've already cleaned the flue, burner and orifice.

Mike
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Old 08-26-2019, 05:18 PM   #6
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RM2190????


That is an LP/12VDC ONLY fridge (same as the RM2150)


A RM2201 is the 3 way (AC/LP/DC)
AC has it's own thermostat
LP has a thermostat that allows gas flow to go to 'bypass' ....so flame stays on all the time



DC element and LP should NOT be used at same time







Not cooling on LP.....
Burner, orifice, flue cleaned.
LP System Pressure
Gas Valve FILTER saturated restricting flow
Gas Valve Thermostat faulty
fardo.net/gallery/d/16725-3/Dometic+RM2190+Diagnostic+Service+Manual.pdf
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Old 08-26-2019, 05:31 PM   #7
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Your fridge does allow both modes of operation at the same time , but from the manual it states

"DO NOT ATTEMPT TO OPERATE THE REFRIGERATOR BY BOTH GAS AND ELECTRICITY AT THE SAME TIME. ALWAYS ENSURE THAT ONE METHOD OF OPERATION IS TURNED OFF BEFORE USING THE ALTERNATIVE"
The concern would be overheating of the refrigerant and causing the cooling unit to fail.
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Old 08-26-2019, 11:59 PM   #8
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Quote:
Originally Posted by Old-Biscuit View Post
RM2190????


That is an LP/12VDC ONLY fridge (same as the RM2150)


A RM2201 is the 3 way (AC/LP/DC)
AC has it's own thermostat
LP has a thermostat that allows gas flow to go to 'bypass' ....so flame stays on all the time



DC element and LP should NOT be used at same time







Not cooling on LP.....
Burner, orifice, flue cleaned.
LP System Pressure
Gas Valve FILTER saturated restricting flow
Gas Valve Thermostat faulty
fardo.net/gallery/d/16725-3/Dometic+RM2190+Diagnostic+Service+Manual.pdf
Unless the unit was changed out then it is 2190 as my pop up states on the sticker inside of the trailer and I can assure you it does have 120 and 12 volt.
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Old 08-27-2019, 12:13 AM   #9
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Originally Posted by Soppy View Post
Your fridge does allow both modes of operation at the same time , but from the manual it states

"DO NOT ATTEMPT TO OPERATE THE REFRIGERATOR BY BOTH GAS AND ELECTRICITY AT THE SAME TIME. ALWAYS ENSURE THAT ONE METHOD OF OPERATION IS TURNED OFF BEFORE USING THE ALTERNATIVE"
The concern would be overheating of the refrigerant and causing the cooling unit to fail.
I do appreciate how that would be the case if LP was capable of producing an adequate amount of heat to bring the ammonia to boil. I've been running it with the electric thermostat turned to 5 out of 7 to keep the temp in the fridge above freezing thus eliminating overheating the unit.

Understand that this is a 22 year old unit and if burning it out is the worst that can happen then I am willing to risk that as I never have shore power on the road. So, unless I'm able to keep the unit properly cool without 120 v then it's useless anyhow.

So far so good. Solar is keeping up and temp hasn't dipped below 1 degree.
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Old 08-27-2019, 09:49 AM   #10
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Quote:
Originally Posted by adrenelin500 View Post
Unless the unit was changed out then it is 2190 as my pop up states on the sticker inside of the trailer and I can assure you it does have 120 and 12 volt.

Then the sticker was mislabeled....
The 2150/2190/2201 are all in same 'model series'
Except the 2201 was the 3 way model


Yes on the 2201 you can run the 120VAC & LP at same time
Each has it's own thermostat to control each heat source
LP stays on/not hot enough to boil the ammonia......stuck in bypass mode (small flame) because thermostat is BAD
Parts unavailable........waste of LP to just let it burn
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