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Zymurgest · 10-03-2020, 01:45 PM

After searching literally hundreds of sites, I couldn't find an answer to a very simple question: are there any 12 volt heaters available to heat the ammonia absorption portion of a Dometic RV style fridge? I know that they can run on either 120 AC, or on propane, but no mention of 12 volt DC operation. The function of the heater is to boil the Ammonia so it can cool the fridge, so why can't a 12 volt heater be used either along with or instead of the 120 VAC heater? Is there something fundamentally wrong with my assertion, or is there something else going on I've yet to consider? TIA!

jcussen · 10-03-2020, 02:00 PM

Quote:

Originally Posted by Zymurgest

After searching literally hundreds of sites, I couldn't find an answer to a very simple question: are there any 12 volt heaters available to heat the ammonia absorption portion of a Dometic RV style fridge? I know that they can run on either 120 AC, or on propane, but no mention of 12 volt DC operation. The function of the heater is to boil the Ammonia so it can cool the fridge, so why can't a 12 volt heater be used either along with or instead of the 120 VAC heater? Is there something fundamentally wrong with my assertion, or is there something else going on I've yet to consider? TIA!

Some can run on 12 volts, should have a indication on your eyebrow or control panel. Just bought a sprinter van with the 12 volt option, but manufacturer did not install 12 volt element so must run on 120 or gas, if I do not install the 12 volt element.

twinboat · 10-03-2020, 02:21 PM

Many of the 120 volt elements are upwards of 350 to 400 watts in the 7 to 8 cubic foot fridges.

350 watts is 3 amps at 120 volts, at 12 volts that's 30 amps.

6 hours of 30 amps is 180 AH. You would need a lot of batteries to make it thru the night.

Small fridges will use less energy but market demands larger ones.

Gas is so much more effecent then 12 volt fridges that they fell out of favor.

Brad Wilf · 10-03-2020, 09:43 PM

Quote:

Originally Posted by twinboat

Many of the 120 volt elements are upwards of 350 to 400 watts in the 7 to 8 cubic foot fridges.

350 watts is 3 amps at 120 volts, at 12 volts that's 30 amps.

6 hours of 30 amps is 180 AH. You would need a lot of batteries to make it thru the night.

Small fridges will use less energy but market demands larger ones.

Gas is so much more effecent then 12 volt fridges that they fell out of favor.

Yup, years back “almost” all rv fridges were 3 way, not so much anymore.. 12 v side sucked for efficiency, the newer dedicated 12v compressor fridges seem to be better for efficiency.

Old-Biscuit · 10-03-2020, 09:59 PM

YES some Dometic and Norcold fridges are 3-way -- AC, LP and DC

DC Heater Elements require a circuit board that has circuit/fusing for the DC Element PLUS an element holder on boiler next to the AC Element
And an upper display for the 3-way operation

DC is OK when traveling...vehicle alternator can keep up with DC Demand on batteries
DC is NOT meant to be used to COOL Fridge down...fridge needs to be already COOL before using the DC
DC is NOT meant to be used when 'boonsocking' ...high demand on batteries

seaeagle2 · 10-09-2020, 06:43 PM

My Uncle Bill who has owned every type of RV, and has forgotten more than most us will ever know about RV's always told me don't bother with the 12V setting on a 3 way fridge, they just don't work very well....not enough heat to make it work correctly.