RV to residential fridge compressor

[shootist]

Originally Posted by TRH299

So any guess on about how long the 120v ac unit would run on the inverter with (4) 6 volt house batteries assuming average conditions and no other non essential power being used?

I think 1 day 450ah÷2 225 ah @ 12v is 2800 watts available. Plugged in to shore, 3000 watt inverter on , refer on, this is the coach draw.

[shootist]

You will want to deal with the norcolds defrost method. Every 49 hours it shuts off until the fridg comes up to 41 f. That brings the freezers up to 10 to 20 degrees. I shut mine off every 45 hours so it doesn't defrost. As the frost builds I let it go through the cycle only until the fins are clear, then shut it off for 20 seconds and turn it back on. It can defrost very quickly and doesn't need to see such high temps before restarting. JR suggests at least setting the cycle for at night so it doesn't have to work as hard to recover.

[twinboat]

Originally Posted by TRH299

So any guess on about how long the 120v ac unit would run on the inverter with (4) 6 volt house batteries assuming average conditions and no other non essential power being used?

That will depend on the inverter. JC states that the 120 volt units draw 1 amp. That's about 10 amps at 12 volts thru an inverter. That makes inverter inefficiencies a determining factor.

Most inverters are about 85% to 90% effecent, so add a 15% loss, plus inverters varry in idle time amp draw.

Some will draw over 4 amps when not powering anything and others only draw 1/2 an amp.

If the fridge runs 1/2 the time, that's using a total of 120 AH in a 24 hour day, plus 15 AH in conversion losses, which equels 135 AH.

Add in the higher drawing inverter eating up 96 more AH, from your batteries for just being on and your up to 231 AH.

The 1/2 amp drawing one only eats 12 AH over the 24 hour period plus the 135 AH, for a total of 147 AH.

This is why some folks add a stand alone, small, more effecent inverter, just for the fridge. Leave the big one off unless needed.

In either case, the 4- 6 volt battery bank should give you more then 400 AH so with nothing else on, you should get 24 hours of refrigeration, drawing them down to 40% to 50% battery capacity.
Add some generator time every day and you won't get that low.

Its something that should be looked into.

[harleyjt]

Originally Posted by twinboat

That will depend on the inverter. JC states that the 120 volt units draw 1 amp. That's about 10 amps at 12 volts thru an inverter. That makes inverter inefficiencies a determining factor.

Most inverters are about 85% to 90% effecent, so add a 15% loss, plus inverters varry in idle time amp draw.

Some will draw over 4 amps when not powering anything and others only draw 1/2 an amp.

If the fridge runs 1/2 the time, that's using a total of 120 AH in a 24 hour day, plus 15 AH in conversion losses, which equels 135 AH.

Add in the higher drawing inverter eating up 96 more AH, from your batteries for just being on and your up to 231 AH.

The 1/2 amp drawing one only eats 12 AH over the 24 hour period plus the 135 AH, for a total of 147 AH.

This is why some folks add a stand alone, small, more effecent inverter, just for the fridge. Leave the big one off unless needed.

In either case, the 4- 6 volt battery bank should give you more then 400 AH so with nothing else on, you should get 24 hours of refrigeration, drawing them down to 40% to 50% battery capacity.
Add some generator time every day and you won't get that low.

Its something that should be looked into.

I'm considering swapping over to the 120v cooling unit too the next time I have an issue with my Nocold. I only have 2 - 6v batteries and currently no inverter. I'm thinking that I would add a dedicated inverter for the fridge to use when driving. When we are set up, I always have shore power as we don't do any boondocking. When driving, the engine alternator should keep the batteries charged up. And we would be fine for short stops along the way of several hours. Seems like that should work fine for us. Do you see any problem I'm overlooking with this plan?
jt

[Sbrownstein]

Originally Posted by harleyjt

I'm considering swapping over to the 120v cooling unit too the next time I have an issue with my Nocold. I only have 2 - 6v batteries and currently no inverter. I'm thinking that I would add a dedicated inverter for the fridge to use when driving. When we are set up, I always have shore power as we don't do any boondocking. When driving, the engine alternator should keep the batteries charged up. And we would be fine for short stops along the way of several hours. Seems like that should work fine for us. Do you see any problem I'm overlooking with this plan?
jt

You have a good plan. Add a reasonable sized pure sine wave inverter, something like a Xantrex ProWatt (they come in various sizes) and an automatic transfer switch ($50). Your usage should be fine as the engine alternator will keep up with little problem. Plugged into shore power and the inverter will automatically drop out. The Xantrex units have pretty much the lowest idle (non load) current that I have seen.

[maint1]

I stopped by JC Refrigeration last month and they told me that the 120v ac compressor was the way to go. Would prefer to go 12v dc but I don't want to make a $1000 dollar mistake. Let us know how your conversion works for you. We rarely dry camp but I like to have the option. Will probably drive out next spring to have them do the work.

[Piros1]

Originally Posted by TRH299

So any guess on about how long the 120v ac unit would run on the inverter with (4) 6 volt house batteries assuming average conditions and no other non essential power being used?

I can’t speak for the conversion since I gave a residential unit in my coach from the factory but your question on batteries I have some feedback on. If you notice most coaches that came with the residential refrigerator option usually have two to four extra batteries as part of that option along with either a larger or second inverter. This has been my observation when looking at different RV’s. As for as how long your existing batteries will last depends on how many amps the conversion uses and what is drawing from the batteries at that time. So kind of a loaded question.

[Sbrownstein]

From experience, my 335DS came with a residential reefer, 4 deep cycle batteries and a 2000 watt Xantrex ProWatt, feeding only the reefer. I can go 24 hours without charging when boondocking. In your case, since you never boondock, 2 batteries should be fine and there is never an issue when running down the road since the alternator will keep everything charged anyway, regardless of reefer cycles.

When boondocking I run the generator for a few hours morning and evening and all seems to be fine. I have an SOC meter and I never go below 75% charge using this philosophy. I did add the charge wizard to my PD9260 so that those few hours are always run with the converter in boost mode. Solar makes up the rest to get back to 100%. Frankly, there is coffee and such to make anyway and, of course, if I am running A/C, everything stays totally charged. If I run the generator for 5 or 6 hours a day total, that means the batteries only provide about 8 amps of DC for the reefer in the remaining 18 or 18 hours.

I also have another Xantrex, a 1000 watt to run everything else (TVs, satellite receivers, chargers and my CPAP at night.) Still never had a problem.

[Timaz]

Originally Posted by hardy1000

X2 on JC 12v unit I had mine installed last year and have been very happy with it.

I just called JC because my fridge is only down to 44 after more than 12 hrs of running after waiting more then 24 hrs to start it. He told me to remove the thermister from the fins to see if the compressor has shut off because of it. Mine was on the far right fin. Can you tell me which fin your thermister is attached to?

[palehorse89]

Mine is on the second fin in from the right side looking at it.........

[shootist]

I put mine sixth from the left, out of the way of the fans. Freezers are at 0 and the fridge at 32, set on 4. It runs a lot in warm weather for sure but the norcold unit never kept the freezers real cold and froze the refer too.

[Timaz]

Update! After completely disconnecting the the thermistor the fridge will only come down to 46F. The installer who does a lot of these says the unit is done. He will contact JC to ship a new one asap. Half of the fins in the fridge are 50+ degrees and the right half are 32 . So I'm hoping to have a new one installed next weekend. The freezer is only 22F.
Stuff happens in manufacturing...I was just hopping it wasn't going to happen to me. I will update next week.

[hardy1000]

Originally Posted by Timaz

I just called JC because my fridge is only down to 44 after more than 12 hrs of running after waiting more then 24 hrs to start it. He told me to remove the thermister from the fins to see if the compressor has shut off because of it. Mine was on the far right fin. Can you tell me which fin your thermister is attached to?

Here is a photo of my 12v install there is no theremister I can see. The Norcold had a theremister on the 5th fin from the right (see mark on fin where thermeister was located, about 1/2 way down the fin). The only wire I see is to power the fan. See photo.

Mine works very well. Freezer is 0 and keep the fridge at 32.

[jmck1737]

We had JC put in a 120 volt unit in our dometic on July 1st. So far it is great. Had several very hot days this summer and the temp stayed in the mid 30/s which is a huge improvement over the old 2 way fridge. We went with the JC due to reputation and not having to have any of the wood work redone.

Another big advantage is the quick cool down to start a trip. We came home for 2 weeks as wife had some family issues to take care of. When it was time to head back out I did what I have done for years and started the fridge 3 days before we were scheduled to leave forgetting we had a compressor now. I was shocked when I walked in the MH later that evening and the fridge was already 34 and the freezer in the teens.

We had the install completed at JC in Shipshewanna and it was quick and professional. Highly recommend them. Plus they have an optional 3 year extended warranty for a very reasonable price so a total of 6 years warranty which you will not get with a residential I don't think.