Residential Refrigerator Power Usage 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, 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 928 A/H at 6 volts which must be converted back to 12 volts for an available total of 464 A/H. 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. 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 draw 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

[fansill]

Ray,

Great information...Thanks for sharing and keep telling us all about your tips for power savings. I love it.

Faith

[TurtleKent]

Yes, great information. I'm thinking of a refrig conversion also, very challenging to find something to fit the hole left by a Norcold 1201. In our case are limited by having the refrig located in a slide, and most refrig are too tall to fit. What model Samsung did you install, and do you have available the energy guide numbers from the yellow tag? That might give me(and others) a reference point as we shop for replacement refrig. Thanks, and enjoy.

[Brigadoon]

Thanks for the update. It gives me things to think about should I decide eventually do some dry camping.

[BryanL]

re: " 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 928 A/H at 6 volts which must be converted back to 12 volts for an available total of 464 A/H."

to put this into easier to understand units ... 11 amps at 12v for 12 hours is about 1.6 kWh per day energy use for the refrigerator. 55 amps at 12v for 10 hours is 6.6 kWh. These seem high. Most energystar rated refrigerators seem to run at about 1 kWh/day and some even less.

You've got 4 batteries at about 70# each for a 280# battery bank. At 12 watt hours per pound usable energy capacity, you have about 3.4 kWh usable energy capacity. 464 AH at 12v would be 5.6 kWh. close enough for battery estimations.

Note that the AH rating for batteries is for a draw of about 60 watts each. That's 240 watts for a 4 battery bank. If you pull more power than this, you'll get less battery capacity available and less than 240 watts, more available capacity.

kWh is kilowatt hour. A kWh costs about ten to twenty cents on most people's electrical bills and is about the amount of energy stored by a typical RV battery.

[rorr1821]

Quote:

Originally Posted by TurtleKent Yes, great information. I'm thinking of a refrig conversion also, very challenging to find something to fit the hole left by a Norcold 1201. In our case are limited by having the refrig located in a slide, and most refrig are too tall to fit. What model Samsung did you install, and do you have available the energy guide numbers from the yellow tag? That might give me(and others) a reference point as we shop for replacement refrig. Thanks, and enjoy.

The model number is RF197ACBP for the black finish. However, it comes in three other finishes. I do not have the yellow energy tag with me but you should be able to get that from Samsung direct. This model fits the width and depth of the Norcold but the height must be expanded about 6" as I recall.

Ray

[rorr1821]

Quote:

Originally Posted by BryanL re: " 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 928 A/H at 6 volts which must be converted back to 12 volts for an available total of 464 A/H." to put this into easier to understand units ... 11 amps at 12v for 12 hours is about 1.6 kWh per day energy use for the refrigerator. 55 amps at 12v for 10 hours is 6.6 kWh. These seem high. Most energystar rated refrigerators seem to run at about 1 kWh/day and some even less. You've got 4 batteries at about 70# each for a 280# battery bank. At 12 watt hours per pound usable energy capacity, you have about 3.4 kWh usable energy capacity. 464 AH at 12v would be 5.6 kWh. close enough for battery estimations. Note that the AH rating for batteries is for a draw of about 60 watts each. That's 240 watts for a 4 battery bank. If you pull more power than this, you'll get less battery capacity available and less than 240 watts, more available capacity. kWh is kilowatt hour. A kWh costs about ten to twenty cents on most people's electrical bills and is about the amount of energy stored by a typical RV battery.

I confused about what point you are trying to make. When dealing with DC I believe that A/H is a better way to reference usage requirements. The meters that I have measure DC A/H's and my battery bank has rating of around 460 A/H's. Please clarify.

Ray

[BryanL]

re: "When dealing with DC I believe that A/H is a better way to reference usage"

The problem is the one shown in this discussion where there is need to be careful about the voltage of the battery being used. If the proper units for power and energy are used, then that source of potential error goes away. It also makes it easier to compare usage to household usage (and to understanding the label on Energy Star rated products).

Amp hours should always be accompanied by the voltage involved in order to avoid ambiguity when it comes to an energy measure. Use watt hours and you'll be clear regardless of whether your rig house voltage is 12v or 24v or the batteries in your bank are 6v, 12v, or 2v or 8v or whatever.