Dometic fridge power consumption observations

[buzzmonster]

Ok so now have the trimetric 2025 installed, as an engineer very interesting. I observe that the dometic fridge draws about 0.8 amps constantly it does not appear to matter if it is cooling or not, which I can tell from if gas is being used or not. This makes it a power hog, sprung to my mind that the power only needs to be supplied to the fridge when the thermostats demands it and potentailly not all the time. However I know that herk posted the manuals and a diagram of the internal workings but we are camping in the mountains and can only use the app so no search function that I can find.
Anyway thinking out loud about creating a circuit to monitor internal temps and trip a relay to power up fridge on demand rather than constantly, but would like to see if the fridge circulates coolant all the time irrespective of if it is cooling ?
Seems like a very large power draw just for a control board.

Isnt it funny how one mod leads to thoughts of more and more ?

Sorry for any typo small iPhone big fingers plus stupid autocorrect !!!!!

[OldCoot]

Originally Posted by buzzmonster

Ok so now have the trimetric 2025 installed, as an engineer very interesting. I observe that the dometic fridge draws about 0.8 amps constantly it does not appear to matter if it is cooling or not, which I can tell from if gas is being used or not. This makes it a power hog, sprung to my mind that the power only needs to be supplied to the fridge when the thermostats demands it and potentailly not all the time. However I know that herk posted the manuals and a diagram of the internal workings but we are camping in the mountains and can only use the app so no search function that I can find.
Anyway thinking out loud about creating a circuit to monitor internal temps and trip a relay to power up fridge on demand rather than constantly, but would like to see if the fridge circulates coolant all the time irrespective of if it is cooling ?
Seems like a very large power draw just for a control board.

Isnt it funny how one mod leads to thoughts of more and more ?

Sorry for any typo small iPhone big fingers plus stupid autocorrect !!!!!

Think you meant Herk, not jerk.
Also, these refrigerators do not circulate coolant like a home refrigerator. The amonia is boiled by external source (elec. element or propane flame) and absorbs heat from the inside of the box, condenses and the process repeats. This is controled by the interior thermostat.

[buzzmonster]

Yes I meant Herk, sorry. Fixed original post

[gerrym51]

Originally Posted by buzzmonster

Ok so now have the trimetric 2025 installed, as an engineer very interesting. I observe that the dometic fridge draws about 0.8 amps constantly it does not appear to matter if it is cooling or not, which I can tell from if gas is being used or not. This makes it a power hog, sprung to my mind that the power only needs to be supplied to the fridge when the thermostats demands it and potentailly not all the time. However I know that herk posted the manuals and a diagram of the internal workings but we are camping in the mountains and can only use the app so no search function that I can find.
Anyway thinking out loud about creating a circuit to monitor internal temps and trip a relay to power up fridge on demand rather than constantly, but would like to see if the fridge circulates coolant all the time irrespective of if it is cooling ?
Seems like a very large power draw just for a control board.

Isnt it funny how one mod leads to thoughts of more and more ?

Sorry for any typo small iPhone big fingers plus stupid autocorrect !!!!!

i think you'll find this power is going to the circuit board that controls the fridge not the fridge itself

[Herk7769]

Than you for fixing that

1 amp DC is 12 watts, certainly no "power hog" in the big scheme of things as you will learn with your Trimetric.

You will find that a single filament bulb draws 1.1 amps.

The fridge draws that to power the control board and hold the solenoid valve open when calling for "cold." If you shut it off manually, the fridge/freezer can take minutes to warm up and hours to cool back down.

If you don't have enough amps available; get a bigger battery bank.

[buzzmonster]

Thanks Herk,
Sorry about the typo, I am loving the monitor, we only have LED bulbs through out and we have two young kids so most of the time we are outside enjoying the fire so they are not used. Our average power consumption over 36 hours is just over an amp, with the fridge being the lions share.
We never camp with Hook ups so power is important to us as currently it is the limiting factor.
We have two 12v batteries, just rebuilt the battery box to accept two Trojans when these batteries die.
If the solenoid valve on the fridge is normally closed which I would expect on propane service then there should not be a huge current draw just to monitor the temperature. I am wondering if we have a problem with the fridge as the fins do ice heavily, but the gas does appear to shut off which suggests that the thermostat is at least working. It is on the warmest setting.

I used to use a thermostat module that gave a digital read out from a remote probe and could be set with a set point that demanded heat or cold with programmable hysterisis to prevent overly cycling the heating source. This could be run from a single AA battery for months, but I had it on a mains power supply. Used it to precisely monitor my fish tank temperature.
I was toying with the concept of using the same system to be able to accurately monitor both fridge and freeze temps and turn on the fridge board only when needed. I might do some experiments to see how quickly the fridge cools and heats up, I am assign that the propane valve is either on or off and doesn't modulate ? If it dies modulate then that might explain the power use, but I doubt it does.

Or perhaps I just want more readouts now that I have the trimetric, always been a sucker for data !!!!!

[Herk7769]

Solenoid valves are "normally" powered "ON" and de-powered "OFF."

Your propane solenoid is on of these. If the fridge is running too often, and it is not cooling properly, additional air flow through the back of the fridge will certainly help you. Get the solar powered on that goes on the roof for boondockers.

Amazon.com: Camco 42165 RV Refrigerator Solar Vent System: Automotive

Another mod of mine waiting on funding.

Another thing to make sure of is the defroster switch in the frame of the freezer door. It uses a 12VDC heater to "Climate Control" the freezer. Left on when boondocking it will kill your battery pretty quickly.

[orangeminnie]

Buzz: Did you try your experiment? I suspect that this is a very old design, and could draw MUCH less with an updated board.

[DavidBo]

Originally Posted by orangeminnie

Buzz: Did you try your experiment? I suspect that this is a very old design, and could draw MUCH less with an updated board.

Considering that this thread is almost 8 years old, I wouldn't hold your breath for a response!

[bikendan]

Holy Thread Resurrection, Batman! [emoji1786]

[NXR]

And here I was thinking that he's lucky he doesn't have a Norcold Polar 18 four-door. My buddy has one and the control board pulls almost three amps when not calling for cooling.

Ray

[DavidBo]

Originally Posted by NXR

And here I was thinking that he's lucky he doesn't have a Norcold Polar 18 four-door. My buddy has one and the control board pulls almost three amps when not calling for cooling.

Ray

It's not just the board. The door seal heaters probably draw the most power, that's why I installed a switch to turn mine off when boondocking.