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4x4FF's avatar
4x4FF
Explorer
May 05, 2015

Inverter size

Hi all,

I just got my new residential fridge installed in my 5er. It is a whirlpool WRT111 and it is 10.7 cu ft. I love it so far. With the unit being at ambient temperature (and never having been ran I might add) I plugged it into a kill a watt meter for start up. After watching it for some time the absolute highest wattage I observed was 120 and that was briefly. Normally it ran between 80 and 90 watts while running. I know that the kill a watt isn't sensitive enough to show the peak wattage at compressor startup so that number may be a bit higher.

My question is what size inverter would you guys recommend?

Before we begin, I just want to say I would love to get a 5000 watt inverter and run with 8 6v batteries....but.....That can't happen right now. I have NO intention of boondocking. I only want the inverter to power the fridge while traveling and maybe during campground power outages. I will be running off of 2 6v interstate batteries. What size inverter can I get by with? I am looking at a Xantrex ProWatt in either the 600 or 1000 watt output. Money matters so if I can save $100 by going with the 600 that is fine with me. If you guys can recommend a good inverter other than the Xantrex in the $100 to $250 price range I am all ears. I just want a PSW inverter. I just want to make sure I have enough to power the fridge while I am on the road. I also purchased the Xantrex Transfer relay. What do you think or what other information can I provide?

Thanks,

Steve

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  • Golden_HVAC's avatar
    Golden_HVAC
    Explorer
    May 05, 2015
    Hi,

    The 600 watt probably will handle the job just fine. The 1000 watt will consume more power to run the same load that running a smaller inverter near it's full rated load.

    I found that out running my TV and satellite dish. When using my built in 1500 watt inverter, my total draw might be 8 amps, but changing to the 300 watt inverter will use a total of about 5.8 - 6 amps. It has much smaller transformer, and smaller capacitors, ect, so not nearly as much parasitic draw.

    A pair of 6 volt batteries are the minimum with that load. Anything smaller, and the voltage will 'dip' to far when starting the compressor, and you might never recover, unless the engine is on, or you have a huge solar system that is putting out more than say 20 amps!

    80 watt load - figure about 8 amps from the battery into the inverter into the load.

    Your propane CO leak detectors team up to use about 1 amp per hour, or about 20 AH daily. No matter how much you conserve, you can not drop below about 35 AH on a typical RV battery draw. With your electric refrigerator, add about 80 amp hours daily, and you will be good. So yes you 'could' go boondocking, with about 3 solar panels - this place has 140 watt on sale for $229 recently.

    SunElec.comp

    Have fun camping!

    Fred.

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