Residential Refrigerator Power Requirements: UPDATE

[rorr1821]

I reported previously on this forum the installation of a Samsung Residential Refrigerator and stated at that time I would report back on power requirements after we dry camped. First I need to provide an overview of my system. I have a 2000 watt Magnum Energy pure sine wave inverter(MS2012-20B), Magnum Energy Smart Battery Combiner (ME-SBC), Remote Control (ME-RC), Magnum Energy Battery Monitor Kit (ME-BMK), original four Interstate 6 volt house batteries (U2200) with 232 A/H rating at 6 volts each (464 amp-hrs @ 12 volts total), two Interstate engine start batteries, and 8 KW diesel generator. I have no solar panels. We have a Monaco Diplomat 36PDQ with four slides. We are not fulltime.

The battery combiner insures that regardless of which battery bank is charged from any source both banks will receive a charge. So if I am traveling the engine alternator charges the engine batteries and after a preset charge point a maximum of 25 Amp's will flow to the house batteries. When using shore power or generator the opposite occurs after house batteries are charged the engine batteries are charged. Now one might ask why the OEM did not install a system to do this. According to my motorhome manual a system does exist, however my test could not confirm it was working, so I decided to install this work around which does work.

The Battery Monitor is great because it provides very accurate battery state of charge (SOC) and other very useful information. Talked to a large Solar installer in Oregon and they said this has proven to be a very accurate device.

The remote which is located in the motorhome is the central point from which everything is programmed and monitored. The setup is extremely important in that you must input information such as battery type (flooded or AGM), cut off points, charge point for AGS, etc. You can go to www.magnumenergy.com and read about these devices.

These are my energy power requirements based on some limited dry camping. First my parasite loads account for about 2.4 DC amps. This includes propane monitor, carbon monoxide detector, transmission and engine monitors, and probably some other things which I have not found. I put a cut off switch at the Microwave Convection oven and the TV entertainment center. These devices have a parasite draw even though they are turned off. The refrigerator draws about 11 Amps DC. This will change depending on outside temperatures. If the refrigerator runs 50% of the time, in theory I need about 55 Amps DC in a 10 hour period. My house battery bank is 464 A/H @ 12 volts. Also as batteries get older there is a degrading factor which must be considered and I am not sure how to apply that factor to my assessment.

On a typical day dry camping we will start the generator to use the microwave and if it is very hot run the AC in the evening for a few hours. But we have also watched TV at night with no generator and have not gone below 50% SOC of the batteries by the next morning. I find that rather amazing. To do this you have to keep lights off, turn main power off to the entertainment center before going to bed, watch the water pump usage, etc. You have to conserve, bottom line.

To insure maximum life of the batteries two things are necessary: Do not discharge below 50% and keep the correct water level in cells (distilled water only). On that point the water level should be about 1/8” below the fill tube as you look down into each cell. That tube has two slits on each side. There are battery fill device which can aid in this filling process so it is done correctly. The use of safety glasses and common sense must be used around batteries.

I was considering installing solar panels to aid in the charging of my battery bank. To install a 300 watt system at $300 per panel, panel brackets, MPPT controller, wiring, combiner, other miscellaneous parts. The total would be around $1500 if I do the install. This would produce according to the solar installers around 60 A/H charge per panel per day under optimum conditions. Theoretically this could provide 180 A/H into the batteries. Based on the short number of days we dry camp at any one time I am not convinced the payback justifies the solar panels. Running the generator at half power has a usage of less than ½ gallon diesel per hour which currently translated to around $2.00/hour. Granted you have the noise. However, solar under different circumstances may prove to be a good investment. As technology improves and prices go down this option will be more attractive for me.

Bottom line: Installing an energy star rated residential refrigerator was the best thing I could have done to this motorhome. Also I should note all refrigerators are not created equal. Another brand or size refrigerator could have much more power requirements. I had the freezer set to the maximum minus 8 degrees to see if it reality got that cold. I forgot I set it that cold and I took out a gallon of ice cream for a treat. I could not dip out the ice cream because it was like concrete. I was amazed to say the least.

Thanks for reading my article and hopefully it has provided some useful information for any future considerations.

Ray

[rossboyer]

I did a search for Samsung Refrigerator, and did not find your earlier post. Please restate the model number. Thank you.

[wolfe10]

I did a search for Samsung Refrigerator, and did not find your earlier post. Please restate the model number. Thank you.

Previous Post: http://community.fmca.com/topic/2363-residential-refrigerator-installation/page__p__11940__fromsearch__1#entry11940

Brett

[rossboyer]

Brett: Thanks--RWB

[WJS822]

This post was helpful, I am presently installing a Samsung 197 in my H.R. 40pdq Endeavor. Can't wait to have cold milk and frozen ice cream.

[cobrafang61]

Hi, fascinating post, I have issues with the 11 amps @ 12 volts DC for a residential refrigerator?

Amps X Volts = Watts, 11 Amps X 12 Volts = 132 watts, not much more than the 40 watt light bulb bulb inside it. Not to mention the defrost heater/s at minimum they are 1300 watts @ 120v, or over 10 amps @ 120 volts. Granted they run maybe 15-20 minutes every 8 hours, but that's substantial.

The compressor may draw 2-7 amps run load amps (RLA). But easily may have a 40 amp locked rotor amps draw (LRA).

This is why refrigerators require dedicated 20 amp appliance circuits.

If refrigerators used just a few hundred watts per hour, they could run 5 or more off a 20 amp circuit, but you are lucky if 2 will work in reality.

[RVerOnTheMove]

The math comes out to where a HH fridge uses very little electricitiy no matter the numbers. The average 20-21cf side-by-side HH fridge (current models, energy star) uses about 500kWh per year (about $60/year). If that means the fridge uses 500000 watts per year, that's 1370 watts per day or 57 watts per hour. If it runs half the time and is idle half the time that would means it uses about 120 watts while running or 1 amps AC.

[dickandlois]

I=P/V

I (Current in amps) equals P (Power in watts) divided by V (voltage) .

To start most refrigerator compressors requires somewhere between 3 to 5 amps for a medium sized unit. That is around 350 to 500 watts and one has to allow a surge current caused by the starting and run capacitor.

The run current / constant current would be around 2.5 to 3 amps for an energy star unit.

That equals 30 to 40 amps at 12 volts to run the units. The biggest issue comes down to the number of cycles per hr. and that is affected by the number of times the doors are opened and the temperature. Most of the coaches that are using the home stile refrigerators have gone to 6 - 6 volt deep cycle batteries.

Rich.