Question about powering a compressor fridge

skagitstan · 07-30-2015, 12:36 AM

I'm going to be installing a Norcold DE0061 in my conversion. It can run on 120VAC and 12VDC.
My question is if anyone can think of a good reason to supply 120V to the fridge?

I will certainly be running from 12V. If 120V shore is available, it will be charging my batteries via the MS2012's converter. If it isn't available, I would want the fridge running from 12V, not 120V from the MS2012 inverter section. So what circumstances would dictate supplying 120V to the fridge?

Stan

booster · 07-30-2015, 12:45 AM

Quote:

Originally Posted by skagitstan

I'm going to be installing a Norcold DE0061 in my conversion. It can run on 120VAC and 12VDC.
My question is if anyone can think of a good reason to supply 120V to the fridge?

I will certainly be running from 12V. If 120V shore is available, it will be charging my batteries via the MS2012's converter. If it isn't available, I would want the fridge running from 12V, not 120V from the MS2012 inverter section. So what circumstances would dictate supplying 120V to the fridge?

Stan

We went through the same questions when we went shopping for our compressor frig. We wound up with Isotherm, but I think all the Danfoss compressor frigs are the same.

What I was told by Isotherm is that the frig is basically a DC input over a fairly wide range, and then that is converted to to run the compressor at the set speed(s). If you plug into 110v it goes through an inverter to get to DC, so it is really not all that needed, as long as you have enough shore charger to cover the 5ish amps of DC that the frig takes.

We bought a DC only and have not had any issues running DC all the time.

gerrym51 · 07-30-2015, 12:59 AM

i have a norcold dc only fridge in my zion and no issues i can think of.

since it's dc i never worry about issues when i turn on the inverter,

it is 5.5 cubic feet it is dc558xx

Davydd · 07-30-2015, 03:03 AM

Our 2-door 6.8 cf NovaKool compressor refrigerator/freezer runs only 12V all the time. I guess I don't understand why they make them dual 120V/12V unless they sell them in other situations where 120VAC is the norm and only source.

BobB · 07-30-2015, 03:54 AM

Has anyone asked Norcold or NovaKool why? I mean they make them, so maybe they have a reason to have the option?

Maybe it is as simple as (1) most choose to run them one way or another + (2) less expensive to just make one model that does both.

Davydd · 07-30-2015, 04:48 AM

The Novakool model in my B runs only on 12VDC. There is no 120VAC option.

avanti · 07-30-2015, 04:59 AM

Quote:

Originally Posted by Davydd

The Novakool model in my B runs only on 12VDC. There is no 120VAC option.

I bet if you look behind your unit, you will find an unconnected 120VAC connection. Most of their units seem to ship that way. (It's only a power brick). But, I agree with everybody else. In an RV, running on 120V makes little sense.

Davydd · 07-30-2015, 05:43 AM

Maybe, but their own literature says only 24VDC for this model and that is the way it is set up to run in my B. Could be they can run 120VAC but there is no reason to in an RV. Maybe in a tiny home on the electrical grid. Those kind of homes borrow a lot from the RV world. But here, you can look for yourself. This is the back of my refrigerator.

rockymtnb · 07-30-2015, 03:50 PM

Quote:

Originally Posted by skagitstan

I'm going to be installing a Norcold DE0061 in my conversion. It can run on 120VAC and 12VDC.
My question is if anyone can think of a good reason to supply 120V to the fridge?

We have the DE0041 in our Sprinter which is smaller but shares the same electrical components as the DE0061. We were told the reason it's wired into 120VAC shore power before the inverter was to isolate the fridge load from the battery charger section of the inverter. That allows the multi-stage charger to properly detect battery charge state and correctly shift from bulk charge to absorption phase, and then finally to float charge.

However you would definitely NOT want to power the DE0061 from inverter supplied 120VAC. That would entail double conversion loss, first from 12VDC to 120VAC in the inverter and then back again to 12VDC in the DE0061 (yep, the Norcold is 12V native and uses an onboard AC/DC converter when AC powered).

Davydd · 07-30-2015, 04:48 PM

Quote:

Originally Posted by Davydd

Maybe, but their own literature says only 24VDC for this model and that is the way it is set up to run in my B. Could be they can run 120VAC but there is no reason to in an RV. Maybe in a tiny home on the electrical grid. Those kind of homes borrow a lot from the RV world. But here, you can look for yourself. This is the back of my refrigerator.

Edit: 12VDC, not 24VDC.

skagitstan · 07-30-2015, 05:09 PM

Quote:

Originally Posted by rockymtnb

... We were told the reason it's wired into 120VAC shore power before the inverter was to isolate the fridge load from the battery charger section of the inverter. That allows the multi-stage charger to properly detect battery charge state and correctly shift from bulk charge to absorption phase, and then finally to float charge. ...

I don't understand this. If true, wouldn't it make it unwise to solar charge your batteries with a modern MPPT controller? I have never heard someone claiming that you should not have active loads on a solar installation, mobile or fixed.

Also, the MS2012 manual does not warn about this. About all they say is in the toubleshooting section:
"Low charging rate when using a generator: Generator output is too low to power both load and charger."
The recommended solution is to "Reduce the load, increase the generator’s RPMs."

Stan

Davydd · 07-30-2015, 05:22 PM

Quote:

Originally Posted by skagitstan

Also, the MS2012 manual does not warn about this. About all they say is in the toubleshooting section:
"Low charging rate when using a generator: Generator output is too low to power both load and charger."
The recommended solution is to "Reduce the load, increase the generator’s RPMs."

Stan

What is considered a low charging rate using a generator according to the manual? Is it defined?

skagitstan · 07-30-2015, 06:19 PM

Nope, it's undefined. I guess it depends on the number of anti-anxiety pills the user took that day.

rockymtnb · 07-30-2015, 06:33 PM

Quote:

Originally Posted by skagitstan

I don't understand this. If true, wouldn't it make it unwise to solar charge your batteries with a modern MPPT controller? I have never heard someone claiming that you should not have active loads on a solar installation, mobile or fixed.

I don't know that it would be "unwise" to run loads while charging from solar. It might result in a less than fully optimal SOC charge profile. But the alternative would require switching off loads during charging and then presumably switching the load back in later, which would also result in less than 100% SOC.

Some Morningstar solar controllers do have separate outputs for load (constant voltage) and battery charging. Perhaps that's to optimize the charging profile?

skagitstan · 07-30-2015, 06:43 PM

True about the controller, but doesn't that hookup become a problem when you want to use a device when the sun's not out?

booster · 07-30-2015, 07:50 PM

I think folks are talking about two different issues here, and it can get very confusing that way

I think the MS2012 Magnum is a 100 amp charger/inverter that also has a separate output breaker for branch circuits.

From playing with our new MS2000, I can tell you that there about a billion different ways to configure things, and examples you have been told are some of them.

The comments about the charger not transitioning to float properly have to do with how they are sensing and controlling that transition. It can be an issue based an a couple of things that are configured. It will only be an issue if:

You are using "return amps", or "SOC" settings to trigger the transition

You have the Magnum ARC remote to get all the options, so you can make those settings.

You DO NOT have the BMK battery monitor installed.

In return amps or SOC, the charger looks at the amps going (allegedly) to the battery. If there is no monitor kit installed, it does a very rough calculation of the amps to the battery based on the AC amps into the charger section. First off, it is a rough estimate to be sure. Secondarily, and what is being talked about, is that if you have the frig running, the charger will not know the power is going to a load instead of the batteries and will stay in absorption to long, or forever, whichever comes first.

If you have the battery monitor kit, it runs on a shunt and measures the actual amps to the battery, so it does not matter what is running or how long it runs. It will still get the correct reading and transition properly.

The other issue concerning the generator, it think is referring to much bigger loads than a 12v frig will take. I don't think 60 watts to a frig is going to overload any generator and short the power to the batteries. It surely isn't going overtax a 100 amp charger.

The solar should take care of itself. If there is not enough solar to run the van and charge batteries, it won't do it, and if you are shore power, the solar (if it setup correctly) is just along for the ride.

I may be missing something, but I think it can all be taken care of pretty easily.

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