We have a large Dometic RM1282 fridge with the the Dutch Aire aftermarket cooling unit installed which appears to draw 400-500+ watts. We have almost enough solar power to cover this but not quite (2900 watts on the roof and generate 12-16kw on a good day). Just wondering if there are things we can do to make it run more efficiently? I know we could run off propane, but as we're so close on our power I'd like to save the propane (it uses about $30/month in propane to run the fridge - we have to fill every 3 months and do almost no cooking with it) - We do run off propane when using the AC on hot days or need the power for other applications.
Also we are not currently interested in a residential fridge - maybe if this one goes out, but I like the option of propane and it does work well for us.
Any options/ideas I can try to get the most efficiency out of it possible?
Your coach would work well with a $400 Magic Chef. No propane required. Low power consumption. Twice the volume. That's the only way you could get more cooling.
4-500 watts is huge. Our 10 cu ft Samsung averages about 70 watts per hour. If 2900 watts of solar on the roof is just barely enough to run the refrig it is time to consider something else.
500 watts is about 1700 BTUs. New RV refrigerators in the 10 cu ft range use 1.5 lbs (0.37 gal) of propane per day or about 1400 BTUs. Your replacement may not be working right or very efficient.
Fans in the roof top vent space might improve cooling a bit. Make sure the flue stack is clean.
Agreed, that's A LOT of solar. We run our residential fridge with 1440 watts and maybe get down to 60% by morning and are usually topped back up by 11am.
I was hesitant to move away from a propane fridge when we moved into the FT but it's been a great change in 20/20 hindsight. Thanks to the solar we can just leave food and drinks in the fridge while it's parked between trips and not worry about it
The electric part of the propane fridge is very inefficient.
Our Norcold cools everything in the freezer compartment pretty quickly on shore power taking a bit longer to cool the reefer part. On propane, we have to raise the temp as the milk will freeze even with the sun on the side of the coach part of the day. If we have sun on the roof, I switch to power the fridge with the inverter. No aux fans or anything. The compartment is lined with backer board so that may help. I usually switch to propane around dinner time and for the rest of the night.
Pierce
If you are running your refrig on 120v from an original inverter it may be using 5-7 amps per hour just to be on and pulling 40 amps per hour (to get 500 watts) from your batteries to run the refrig. Your batteries can do that for about 8 hours.
At this time of the year 2900 watts should make about 5800 watts into the bateries. Are you sure you have 2900 watts of solar on a 36 ft coach?
My 9CFT draws 38ish watts. Runs about 30 hrs from the PSW 2000watt inverter.
14 panels all 210 watts sit nicely on the roof (we can run our AC for 6-8 hrs/day) - I know it's a very inefficient refrigerator, but as the Dutch Aire aftermarket parts are supposed to be more efficient I was hoping there was something I could do to bring it down a couple hundred watts. I know that eventually a residential fridge will be where we end up (but we can buy a lot of propane for the cost of a $1300 fridge) ... and yes, we run our Victron 5000 24/7 which has a good draw on it - but the fridge just seems to draw more than even an inefficient one should draw - with it turned off we recoup all our overnight losses by 10 am (sooner on long summer days) our break even point during summer is about 7 am (watts going in vs watts going out) ;-) without it we loose 10-20% each day.
We run ours on propane mostly but I noticed quite an improvement when I added the double fans on the lower intake vent. The kit came with two sets so I added the other double fan on the roof under the roof vent. And now it runs better on propane and electric.
Wow.... Now I really have solar envy. But where's your front ac and I'm seeing no satellite ?
If adding fans, they are quite a bit more efficient at the top of the condenser blowing UP.
That maintains laminar flow over the condenser fins.
Been there, done that.
We are very grateful I was able to install as much solar and battery bank (1600ah) as we have. We still have both AC's, but I did remove the satellite dish - I kept the housing for the moment, just in case a future mobile version of starlink fits in it ;-) if we want to watch something we stream it or watch it from our collection.
thanks for the info - I have an 8" radiator fan I was thinking about putting up there - tied into a thermostat so it shuts off when the temps are under 90 degrees (will have to experiment as I don't know what the ideal temperature for running a fridge is, but I know they require some heat) Wasn't sure if placement was best on the panel or roof vent - sounds like roof vent may be a better choice from your experience.
Two 4" computer muffin fans work much better than one 8" radiator fan and use a LOT less power.
2940 to be precise ;-) Flat mounted they generate 12-16kw during the summer and 8-12 during the spring (have not had them on over winter yet - remains to be seen) at peak they generate just over 2000 watts (3 strings, all in series, run to 3 70 amp charge controllers) So the one arced toward the sun always produces a little better per panel (one string has 4 panels, the others are both 5 panels)
Not on the original inverter any longer - PO replaced with a magnasine 2800 which I replaced with a Victron 5000. I wish we could run the fridge on 12v, but it's only a 2 way fridge :-(
We do have enough battery capacity (1648 ah) to run on diminishing returns for a few days so not too worried, but if there were a way to get more out of the fridge it would be nice.
If I tilted a row of panels I'd probably have enough solar input too - but after having two of them shake lose I prefer not loosening them again, especially on a regular basis ;-)
figured I'd just run the big fan on a very low speed - I do have a 4" left from a project venting cabin air into the inverter bay (old battery/fuel bay) to keep the inverter cooler (it was overheating when our temps were reaching 118 earlier this summer in central WA) so I may try it first to see how it performs.
but now what project can I find to use that 8" fan on ... and I have 2 10" radiator fans too that need a project - lol
That is a LOT of watts on the roof for a 36'. Plus, that's only a potential with the actual wattage being quite a bit lower than that. Our panels are about 13 years old now but even with new 350 watt panels, there is still only room for about 4 large panels so our total would be about a 13-1400 watt potential. Unless the panels are tilted and can track the sun, almost impossible on an RV, the output is going to be much less, and when the panel temperature goes above 77 degrees, the output is less. In summer, panel temps may reach 150 degrees.
Running the fridge on propane at night does not seem to drop the tank level that I can tell.
Pierce
all your observations are quite true - and this isn't a big deal, just trying to find a way to run off AC if possible - looks like we will just continue on propane, at least part time :-) ($30/month really isn't that bad when you spend a lot more on repairs, etc..)
Put a sheet of Reflectix on the outside of motorhome behind fridge to keep that side cooler. Some have added a ZipDee awning on this site even though there is no window.
Yup, 2 heating elements, are like a dead short in layman's terms. That is how I explain it to people so they can understand. Same with an electric coffee pot, running water heater on AC,hot plates, electric heaters and curling irons.
Just sayin'
Chris
Where ever possible I park with the fridge on the south side or at least facing east to avoid the afternoon sun, every little helps.
propane fridges tend to lose efficiency when overloading does not allow
proper air circulation. also one minute with the door open takes about
one hour to recover.
Do the "dollar bill test" all around the door gaskets. Should be able to pull it through, but with resistance that is equal all around.
Make sure the condensate drain hose either has a restrictor in it OR a drip loop. If not, warm air will continually rise into the refrigerator section/cold air will exit the drain hose.
Battery powered interior fans help also. Been using them for years,
Amazon.com: Beech Lane RV Fridge Fan, High Power 3,000 RPM Motor, Easy On... (https://www.amazon.com/gp/product/B094SDPGF3/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1)
Chris
I have the two door Norcold. Added two fans on interior fins and one fan at top outside just under roof top vent. Amazing difference. Would never try to power on electric with my solar.
Since this is an AC fridge discussion, thought I'd add my opine on ventilation for residential fridge installs. I'm no physicist, but every cooling system actually removes heat from whatever it is cooling. I don't believe that you can get the most efficiency and/or longevity out of your residential fridge if you hermetically seal it into the wall opening. That heat has to go somewhere. Unless you have a Sub-Zero or other $10K frig that is.
When I had my residential Samsung installed at MOT, the only complaint I had on the install was that the tech professionally sealed up both the back access panel and roof vent. When I asked him where the heat was going to go, he looked at me like a deer in headlights. I persuaded him to hole-saw a few 3" holes in the beautiful, black painted top plywood panel he had installed inside the roof vent opening. I leave the kitchen window cracked a bit for an air inlet source. At least I am happy anyway and confident my frig is "breathing" freely. Woody.
Pyolet, I was concerned as you were about ventilation for my Samsung.
After researching with several professional installers, and looking at the Samsung install instructions attached, I found you do not need to ventilate, as it ventilates itself, out from under the refrigerator, and to the front.
The Samsung installation manual gives you the required clearances on the top, sides, and rear. The requirements on the top and sides is 3/8 inch clearance for ventilation and 1-2 inches on the rear for ventilation and water/electrical connections. The hot air is expelled out the front from underneath.
The installer blocked off totally the rear and roof vent. The refrigerator works flawlessly and uses about 1.75 KW of electricity, on the average, per day. On days we open and close the refrigerator less, we use less kwh, as low as 1.12 and 1.44 kwh as in the screenshot below. The shared album below will show the interior space of the RF20HFENBSR we have in our FT.
Shared album - John Lewis - Google Photos (https://photos.app.goo.gl/E8QX9NQnWwUQJpqB8)
Recheck the JC Refrigeration site and look at their ALL electric upgrades,they come in 120 volt or 12 volt,they list the watt draw
at 96,either yours is not all electric or you have other draws to come up with this 400 to 500.
I use a built for friges, battery powered fan. Takes 2 d cell batteries. Works to circulate the air better
Our 12v fridge fans to move air behind our electric fridge: