Originally Posted by a64pilot
I believe the frost free part is done literally by resistance heating
, and if that's true I can see how that part uses more energy than the compressor
, but I believe there are units that have an energy saving setting that turns off the frost free part.
I think even the seals
may be heated?
The frost-free system is indeed basically a resistance heater around the evaporator, a timer that turns it on, and a sensor on the evaporator that turns the heater off if it gets too hot.
Yes, it takes quite a bit of juice. But only once a day for 15-30 min or so. Never seen one with a switch, but you _could_ bypass it by removing a wire to the heater. You'd get a block of ice completely covering the evaporator within days though.
are commonly heated to reduce condensation
. (It's called the stile heater) On big U.S. style domestic units that is commonly a resistance heater and it's what is turned off in 'energy efficient' mode. On cheaper units around 10cf or so, the stile heat is just part of the condenser. i.e. a condensor tube run between the fridge and freezer
On my boat, I've got a Norcold icebox
conversion fridge. Aircooled. Pulls 6A or so when running. Duty cycle is around 60% or so. (Yes, I need better insulation) With 200W of solar
I can run it for 2-3 days before the batts are pulled down too much for my comfort. Manually turning it off at night, then letting it get waaaaay cold when it's sunny. All lights on the boat are now LED, no significant other draw when on a cruise
. 220AH battery
Semi-Related Long RV story to prove domestic fridges work:
My RV had the standard Dometic propane thing. It was awful. Had to be perfectly level. Didn't get very cold - couldn't have ice cream. Took 24 hours to cool down. Used lots of propane. Pulled 12v of about .5A not running, 2-3A when running. Was a major fire hazard. When it died I was very happy (wasn't all the way dead, but don't tell my wife that)
I replaced it with Vissani 9.9 cu. ft. Top Freezer Refrigerator in Black-HVDR1040B - The Home Depot
For basically the price
of a new propane unit (which would still suck) I got:
1. The new residential fridge
2. 480 watts of solar
3. 2000W PSW inverter
4. 30A MPPT
controller (Midnite solar kid)
RV only has 220AH battery
bank, I've got room for 2 more GC6s but I haven't added them yet 'cause we haven't needed them.
In so cal
, I can pretty much run that fridge and the rest of the RV forever. We don't plug
in if we've got hookups unless we want to run the AC. Overnight drop is around 30ah running the fridge off the batteries. Batteries fully charged (float) by 1-2 pm or so the next day - even with a pretty good overcast.
Fridge pulls ~8A (12v) once it's running. Defrost pulls more, but it's rare. Inverter
overhead is worse than the defrost overall ('bout .5-1A). Duty cycle is less than 30%. It'll keep ice cream hard as a rock. It cools down in an hour or so. It's 4cf bigger so I no longer need a cooler for beer
. If it breaks, it's a $300 unit to replace. Better all around.
If I had to put something in a boat now
For a cat, if there was somewhere to put a domestic fridge I wouldn't hesitate to use one and plaster the bimini
Drop-in top-load Engel would be the shizznat IMHO on a mono or a cat. (I've used em a lot jeeping) 3-5A draw, around 30% duty. And very reliable. Would be much less power than a domestic fridge. You can drop in a new one or work on it out of the boat if it breaks.
I don't think I'd go to any watercooled solution. I'd be worried about corrosion
on a keel cooler
, and a pump type system seems like overkill. Dedicated marine
style units are also pretty expensive, making the Engel look better to me.