AC/DC Refrigerators

[rbryan4]

Started a new thread on this topic rather than continue to hijack the baffle discussion. I found a company in Vancouver that makes marine/rv ac/dc fridges, and they have surprisingly low amperage draw:

Nova Kool, refrigerators, freezers, Marine, RV, Truck

[rbryan4]

Another interesting discussion about replacing absorption fridge with ac/dc. The two limiting factors seem to be power (although the compressor fridges use far less power than the absorption ones do) and the COST. The compressor fridges are pricey.

northern-lite.org • View topic - Nova kool refrigerators

[Ron in BC]

Originally Posted by rbryan4

S

I found a company in Vancouver that makes marine/rv ac/dc fridges, and they have surprisingly low amperage draw:

[]

I had one of their units in a previous boat I built. I used the "F" plate and built a very well insulated fridge/freezer compartment. It worked really well but since I also had a generator monitoring electrical demand wasn't all that important. Now, having had a holding plate system and seeing how well it works I'd go with a holding plate and one of their compressors. The nice thing is that they come pre-charged with quick connectors so they lend themselves to DIY use.

Ron

[rbryan4]

Originally Posted by Ron in BC

I had one of their units in a previous boat I built. I used the "F" plate and built a very well insulated fridge/freezer compartment. It worked really well but since I also had a generator monitoring electrical demand wasn't all that important. Now, having had a holding plate system and seeing how well it works I'd go with a holding plate and one of their compressors. The nice thing is that they come pre-charged with quick connectors so they lend themselves to DIY use.

Ron

Interesting. I did see on their website the DIY kits for converting a simple Icebox. I assume that would be way cheaper than the full fridge.

[hotfishtacos]

I read through the Nova Cool literature and although the electrical power required for their units is lower than the evaporative units, the highly efficient home type refrigerators are much lower still. I did some research this evening on inverters and learned the the low end of the commercial units have stand-by modes where they draw almost no power when not under load. If that info is considered with the data I saw on the really efficient Whirlpool units, you can install and run a home unit in your RV + the current draw for the inverter for around 10 amps per day. That is less than my Dometic uses per hour on DC and is pretty amazing. A comparable Nova Cool unit would use 5+ amps per hour. Just do the math. It would take my 2 solar panels slightly more than 1 hour to recharge that current draw.

[Cypherian]

Did you perchance find a price on one? Just a quick look seems no one wants to post a price.
Cypher

[wayne_m]

The Nova Kool literature also shows a very low draw at 24 volts. is there a way to provide dual 12 volt batteries in the trailer supplying both 24 volts to the fridge and 12 volts for the other circuits? My very rudimentary understanding of electrical circuits would mean that the batteries would need to be in series to supply the necessary voltage to the fridge and parallel for the other circuits. Can this be done? Are there switches or relays of some sort that could accomplish this? Would that change how the batteries are recharged or capacity/ voltage/ wattage of any solar panels? If wired in series can the electrical circuits be configured so that 12 volt circuits are supplied by only one of the batteries?

[rbryan4]

Originally Posted by Cypherian

Did you perchance find a price on one? Just a quick look seems no one wants to post a price.
Cypher

They appear to be sold via distributors, mainly boat and marine supply dealers. Some solar panel suppliers also sell them. I even found some for sale on eBay. Here is the distributor list on their website.

Nova Kool, refrigerators, freezers, Marine, RV, Truck

I also found their 4.3 cf model for about $911 USD (ouch) on a google search.

[Ron in BC]

Originally Posted by rbryan4

Interesting. I did see on their website the DIY kits for converting a simple Icebox. I assume that would be way cheaper than the full fridge.

The other aspect of a DIY installation is that you can design your own compartment. In my case, I used 4" of 1" slabs of foam with foil between the layers. Space wasn't the concern that it would be with a trailer installation. If I was going to make my own system I would convert the space under the dinette seat into a top loading fridge/freezer.

I did also previously have an Engel 12v/220v (Europe) fridge. On 12v it was an energy hog and I hated feeling all the cold "fall out" every time the door was opened. With the holding plate system it didn't get used much, except when in port.

Ron

[rbryan4]

Originally Posted by Ron in BC

The other aspect of a DIY installation is that you can design your own compartment. In my case, I used 4" of 1" slabs of foam with foil between the layers. Space wasn't the concern that it would be with a trailer installation. If I was going to make my own system I would convert the space under the dinette seat into a top loading fridge/freezer.

I did also previously have an Engel 12v/220v (Europe) fridge. On 12v it was an energy hog and I hated feeling all the cold "fall out" every time the door was opened. With the holding plate system it didn't get used much, except when in port.

Ron

Even more interesting! Top loading would make a lot of sense. Cold air sinks, warm air rises. Theoretically you could open and close a top loader way more often without any significant drop in temperature. But where to put it? Maybe your dinette idea, but we'd miss the dining space.

[rbryan4]

Ron, you're only about 20 miles away from their factory if my google maps aren't lying. Just saying it might be nice if a forum member mozied on by there sometime.....lol

[Ron in BC]

Originally Posted by rbryan4

Maybe your dinette idea, but we'd miss the dining space.

It wouldn't affect the dining space. I meant under the dinette seat on the curb side. In our case all we keep in that space is a bunch of shoes which could find another home.

On the boat that I built and used the Nova Kool components I had exactly the same setup. I just learned to sit on the other side so the cook could access items without me having to move

One things for sure, the climate is heating up and long term I can see a switch to a compressor based system given that solar power is so much cheaper and viable now.

Ron

[wayne_m]

The Nova Kool fridge is also very compact so it doesn't appear that it could be direct replacement in a 5.0 or a 21...

[rbryan4]

Originally Posted by wayne_m

The Nova Kool fridge is also very compact so it doesn't appear that it could be direct replacement in a 5.0 or a 21...

Au Contraire, Wayne. They make much larger models as well. None of them have a draw over 5.2 amps:

Nova Kool, refrigerators, freezers, Marine, RV, Truck

[BCnomad]

Drooling over the larger units for sure.



Good reads::


Fridge doesn't seem to be cold enough ...


Not sure why foil over the heat element would help?




How to determine how many amps my residential fridge takes?


Technical thoughts.

[Brian B-P]

Originally Posted by hotfishtacos

If that info is considered with the data I saw on the really efficient Whirlpool units, you can install and run a home unit in your RV + the current draw for the inverter for around 10 amps per day.

What does this mean? "amps per day" doesn't make sense, so did you mean

• 10 amp-hours per day (and if so, is that at 12V or 120V?)
• 10 amps current, averaged over the day (and again if so, is that at 12V or 120V?)

I don't think 10 amp-hours at 12V to run a home refrigerator is amazing, it's implausible... that's 0.12 kWh/day.

10 amp-hours per day at 120V would be 1.2 kWh/day; for comparison, a mobile unit which takes 5A at 12V and runs half the time would use 720 Wh or 0.72 kWh/day. The smaller mobile unit still wins, in this more plausible scenario.

This is what Whirlpool calls "Industry's Most Energy-Efficient Top Freezer Refrigerator Available":
Whirlpool® 19 cu. ft. ENERGY STAR® qualified Top-freezer Refrigerator
The Energy Guide for this appliance says that it uses 345 kWh/year, or 0.947 kwh/day... meaning that the "10 amp" value must be 10amp-hours per day at 120 volts, which would be about 100 Ah at 12V, while an RV-sized NovaKool will likely run about half that.

I still think it's impressive that such a large refrigerator (18.9 cubic foot) can run on that little power.

[Brian B-P]

Originally Posted by wayne_m

The Nova Kool literature also shows a very low draw at 24 volts.

Is it less than half of the current draw at 12V? If not, there's no advantage.

Originally Posted by wayne_m

is there a way to provide dual 12 volt batteries in the trailer supplying both 24 volts to the fridge and 12 volts for the other circuits? My very rudimentary understanding of electrical circuits would mean that the batteries would need to be in series to supply the necessary voltage to the fridge and parallel for the other circuits. Can this be done?

You can do this, but the two batteries will end up unequally discharged, so it will work very poorly. You could run a 24-volt battery bank entirely separate from a 12-volt battery, but now you need two separate charging systems. I can't see how this could ever be worthwhile, since fundamentally there's no significant advantage to 24 volt operation.

[wayne_m]

Originally Posted by rbryan4

Au Contraire, Wayne. They make much larger models as well. None of them have a draw over 5.2 amps:

Nova Kool, refrigerators, freezers, Marine, RV, Truck

I stand corrected...

[wayne_m]

Originally Posted by Brian B-P

Is it less than half of the current draw at 12V? If not, there's no advantage.


You can do this, but the two batteries will end up unequally discharged, so it will work very poorly. You could run a 24-volt battery bank entirely separate from a 12-volt battery, but now you need two separate charging systems. I can't see how this could ever be worthwhile, since fundamentally there's no significant advantage to 24 volt operation.

Amperage draw is half that of 12v operation. Their 6.3 cubic foot model draws 2.6 amps on 24vdc. If the Nova Kool technology is better than the amonia based system in the Dometic fridge, can a simple method be devised to make the dual voltages work?

[wayne_m]

Can you use a voltage divider? If the system 24 VDC from the outset, can a charging system be configured to provide the 24 VDC necessary for the batteries and use a voltage divider to provide power to the 12 volt circuits? If the only 12 volt draw are the lights and some electronic devices the 'watts' would minimal. Are there 24 volt solar panels? If under tow what effect would there be on TV charging system? Can you Ohm's law types figure this out?