Hi guys,hoping the experienced gurus here might take a moment to give a newb a little time and expertise.just got used 2000 phoenix pop-up a few weeks ago (my 1st rv and 1st experience with DC) i do HVAC repairs for living so OK with AC.there is no info with the camper that tells me what size fuses it should have. not sure if the right sizes are in there now.problem i'm having is with the dometic Model RM2354 3 way, single door fridge. works great with 120 VAC and propane but if turned to 12v it blows a 5 amp fuse in the little breaker/fuse panel inside the camper (not outside). the furnace quits working also when that 5 amp fuse blows. lights are oki downloaded the manual and it lists a 3 amp control system fuse and 5 amp AC heater fuse in the power module. the 12 VDC heater is listed as 30 amp (in line blade fuse).VDC is all new to me, but it seems like a 5 amp is a little low.do i need to take to the local RV dealer and have them figure out what size fuses are supposed to be in the 5 fuse slots or is there an easy way to check amp draw (like i would with my amprobe on VAC.thanks for your consideration.Bob

"12 Volts DC ConnectionThis refrigerator model requires a continuous 12 volt DC supply to maintain the automatic energy system. The connection is made to the positive and negative terminals of the terminal block on back of the refrigerator."That doesn't sound like it's a 3-way..but, you did indicate it was. Most fridges are around 300w.

This presumably would be for the controls of the fridge, and there's a separate fuse or circuit breaker for the 12V heater power?10A might be reasonable for the fridge and furnace controls if they're the only things on the circuit. 5A is rather small and probably would blow if both were used simultaneously. Often the RV maker will put a little key to the fuses and their proper sizes in with the fuse panel or in other literature, at least if they're nice about things. Sometimes these lists/charts are a bit hard to decipher, though...particularly in regard to what circuit has what stuff on it.

I would try removing each fuse and use my meter probes, on the amp setting, to touch each side of the fuse holder. This should complete the circuit, allowing the appliance to run, and also tell you how much current each appliance is drawing.Of course, my Fluke only goes up to 10 amps, so if I had reason to believe it was more than that, I guess I would just keep putting progressively higher fuses - 10 amp, 15 amp, 20 amp, etc. until I found the first one that didn't blow.

12 volt fuse size in the refrigertor's fuses is 25 amps so the "House" fuese feeding it would need to be bigger (if you run that thing on 12 volts. SUGGESTION do not use 12 volt mode. Use only gas and electric in a PUP you do not have enough battery to run the fridge on 12 volts.(Fuse is from a Dometic owner's manual the heater is between300 and 400 watts and that means a 25 amp flash bulb. er fuse.

Your RM2354 fridge IS a 3-way ....120V AC element, Propane & 12V DC elementThe DC Power Supply to the terminal block in outside fridge compartment should be fed from the battery with a 30A in-line fuse close to battery . NOT from a Fuse in the DC Dist panel.The DC from terminal block also feds DC to circuit board and the 3A fuse on circuit board is protection for the DC controls, propane etcThe DC element is powered directly from the terminal block in outside compartment with a 30A in-line fuse before the DC power goes to the DC Element Relay---hence the reason the DC Power should come directly from battery,DC Dist Panel fuses are not set up for 30A fed.Normal amp draw for your DC element---150W/12.5AA 2-way fridge WOULD be powered from the DC Dist Panel via a 5a, 7.5A even 15A fuse....but not 3-ways.

what size fuses? | Good Sam Community

Old-Biscuit
Explorer III
Oct 10, 2018
scarletfire wrote:
Hi guys,

hoping the experienced gurus here might take a moment to give a newb a little time and expertise.

thanks for your consideration.

Bob

Hi Bob,

Hoping the newb would respond back to info provided and followup questions asked
ItsyRV
Explorer
Oct 10, 2018
scarletfire wrote:
problem i'm having is with the dometic Model RM2354 3 way, single door fridge.
works great with 120 VAC and propane but if turned to 12v it blows a 5 amp fuse in the little breaker/fuse panel inside the camper (not outside). the furnace quits working also when that 5 amp fuse blows. lights are ok

In a nutshell, that model pulls 12.5 amps just for the DC heating element alone. So a 5 amp fuse is going to blow all the time. (see page 11 of the service manual for the DC requirements). In addition, the DC element was not designed for continuous use but rather to maintain cooling while "traveling".

Just to add, the 5 amp fuse probably is for the DC control portion while on A/C or Propane; not the D/C heating element. You need a separate dedicated line and fuse if using the D/C full operation for the heating element if your RV wasn't wired for it.
wa8yxm
Explorer III
Oct 10, 2018
I will say this again. On a Pop UP you likely have one small 12 volt battery. I would disable the 12 volt heater element (pull the big fuse on the refrigerator fuse board if needed) I would not use the 12 volt option EVER. 12.5 amps the other person (Who clearly did the research.. thanks) said. 100/12 is 8 and change. but with Peukert's law, you get about 1 hour of operation if you are lucky before your battery is damaged.
Old-Biscuit
Explorer III
Oct 11, 2018
3-way fridges DC Heating element is for maintaining fridge temps during transit NOT for cooling fridge down, not for use w/o means of battery charging/maintaining battery voltage

DC option to be use when trailer is connected to tow vehicle and tow vehicle charge line active.....

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