RV Residential Refrigerators

justme wrote:

John & Angela wrote:

justme wrote:
It is said the sine wave inverters are better the modified inverters. However, I have been powering my cabin's refer, lights, computers and furnace for 5 years with a modified sine wave inverter (Xantrex 3kw) and have no problems. I guess because theory is better than real life to some. Also, some refrigerators require 8-10 amps at 120vac(100+amp @ 12v) and I wonder how the life of the vehicle alternator is affected by this intermittent power draw from the batteries while driving.

Good afternoon "justme". Yes in many cases modified sine wave inverters do a fine job, however with a 120 volt AC motor on many residential fridges (not all) a sine wave inverter will do a better job.

Also you may have slipped a decimal point on the power usage of a modern compressor type fridge. Although there was a time when they did indeed draw that much power, a modern residential fridge will draw around 1 amp of power when running and actually only runs about 20 minutes out of the hour.

Cheers.

J and A

I don't think I slipped a decimal point because I was reading the label on many units at the RV show. The current drain ranged from 2-10 amps at 120vac. Where did you get your information from? Also 4 door absorption units draw 5.5 amps at 120vac and 2.2 amps at 12vdc on propane. Also, every residential unit will operate properly with modified sine inverters-- albeit slightly less efficiently, but not worth noting. Also, if your can identify what residential units will draw around 1 amp, I would be greatly interested.

Good morning. All good questions. The tags on the appliance indicate a worst case sceenario for the appliance, for example, during a compressor startup my fridge draws about 9 amps for just under 1/3 of a second. You can see why this number is irrelevant in calculating daily power usage. The most accurate way to measure current draw is with a clamp on ammeter however a "kill-a-watt meter" is a 19 dollar alternative. You can also look at the energuide rating which for most will be around 400 kilowatts plus or minus annually. Using 365KW as a guide (for simplicity of math) means it uses about 1kw per day. Doing a little backwards math, .9 amps (that's point 9 amps) at 115 volts comes out around 100 watts. Multiply that by 24 hours and if the fridge ran all day it would use 2.4 kilowatts per day. But of course fridges don't run all day and usually only cycle on about 30 to 40 percent of the time. So let's say for easy math 1kw per day, times 365 days gets you to an energuide sticker of 365. These numbers are a little off from mine but you get the idea.

Hope that helps.

Happy trails.

J and A