Fridge power consumption and operation

[Limoges_Camper]

Hi there,

I am in the process of installing an inverter and making some automatic circuitry to make the transition between shore power and battery power fully automatic. In this process, I am going to turn off certain circuits that have a high drain on power.

What puzzles me a bit, is the fridge: there is a switch that has 3 positions: auto, off, and gas. So far, I figure the way to go is if you are on shore power, stick it to "auto". If you aren't, then stick it to gas. What I don't is what happens if the shore power goes out while it's in the "auto" position. I'm concerned that it will draw too much current from the 12 VDC side of things, and will quickly drain the battery.

Does anyone have any figures on what the fridge should be drawing from the 12VDC side? I understand that in the gas position, the fridge still required 12 VDC to operate the ignition and possibly gas valve. I assume that when it is in the "auto" position, that it uses an electric element to replace the heat from the propane flame.

Here is a wiring diagram of what I am proposing. As you can see, it will automatically switch to inverter power if the power drops off on the shore power side (and if the inverter's on/off switch is in the "on" position).

[MrWizard]

moved from technology

[MrWizard]

when i had an RV fridge
it was NEVER in AUTO mode..never on elec...unless i ran out of LP and Temporarily switched to elec

leaving it on LP all the time is .. IMO the best way to operate an RV fridge
save the 120v mode for emg use, it use so little propane in can run months on some RV LP tanks

running on 120v all the time is the best way to have it NOT work on LP when you need it to

[pianotuna]

Hi,

Mine draws 34 amps on the DC setting, and 325 watts on the AC setting. Duty cycle is 2:3 so daily consumption is around 4.8 kwh per day.

[dan-nickie]

Here is another simple diagram.
This assumes an ATS is built into the Inverter.

[dan-nickie]

As stated, that is a pretty complicated solution that already has some simpler methods to accomplish what you want to do.

You want to research using a 'sub panel' with your inverter and an ATS (automatic transfer switch).

Here is one example document I quickly googled about it.
BlueSea Inverter Sub Panel

And no worries about leaving the fridge on 'auto' and let it switch to propane as it does not pull a battery down quickly.

[sch911]

Jeez that's allot of work. Why not just get an inverter that has a ATS integrated into it. There are many....

[Limoges_Camper]

A question about converter cooling fans: does anyone know of one that has a 2 speed model? I'd rather have a low speed, and continuous sound of a fan than the on and off operation that mine is now.

[Limoges_Camper]

korbe wrote:
My frig has those same 3 settings. Auto allows it to switch to gas if the 110 power is interupted, and when on gas it stays on gas. No 12-volt except a little while on gas and not connected to shore power.

RLS7201 wrote:

Limoges_Camper wrote:
What I don't is what happens if the shore power goes out while it's in the "auto" position.

As the word "auto" implies, the refrigerator automatically switches to gas if you loose shore power. And will return to AC when shore power resumes.


Richard

thanks guys!

I just need to figure out where to place an 8th relay that will disable the 120VAC supply to the fridge when in inverter mode. I'll need to look into the Dometic user manual to figure this part out.

I don't care if the water heater looses heat, but I do care if the batteries are run dry because of the fridge, and then food spoils.

[Limoges_Camper]

AnEv942 wrote:
DC heater element is refrigerator model dependant with varied wattages. Just look up replacement element for your unit. Our dometic draws 17amps on DC element.
If your controls doesnt allow selecting AC verses auto. simply manually unplug (or add switch) the DC element from board (could incorporate that output as a warning light that power is off or DC element off/unplugged).

Some units will cycle into DC in auto mode. Mine isnt supposed to but it has, twice. I cannot manually repeat but went from gas to DC when it emptied the tank, then drained the batteries while away.

So there is a 120VAC as well as a 12 VDC heating element in yours?

[korbe]

My frig has those same 3 settings. Auto allows it to switch to gas if the 110 power is interupted, and when on gas it stays on gas. No 12-volt except a little while on gas and not connected to shore power.

[RLS7201]

Limoges_Camper wrote:
What I don't is what happens if the shore power goes out while it's in the "auto" position.

As the word "auto" implies, the refrigerator automatically switches to gas if you loose shore power. And will return to AC when shore power resumes.


Richard

[AnEv942]

DC heater element is refrigerator model dependant with varied wattages. Just look up replacement element for your unit. Our dometic draws 17amps on DC element.
If your controls doesnt allow selecting AC verses auto. simply manually unplug (or add switch) the DC element from board (could incorporate that output as a warning light that power is off or DC element off/unplugged).

Some units will cycle into DC in auto mode. Mine isnt supposed to but it has, twice. I cannot manually repeat but went from gas to DC when it emptied the tank, then drained the batteries while away.