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Can the Dometic refrigerator operate on 120 vac modified sine wave?

Yahoo Message Number: 81422
Hi Folks,

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Has anyone operated their gas absorption refrigerator on their MSW inverter with success? Thanks,
Fred Kovol

Re: Can the Dometic refrigerator operate on 120 vac modified sine wa

Reply #1 –
Yahoo Message Number: 81427
Fred, I run my Norcold on 110v all the time when I am on the road. I haven't had a problem and don't have to worry about LP while driving.

Dave

aka Billy Byte (trusty hound)
2000 Allure #30443

Re: Can the Dometic refrigerator operate on 120 vac modified sine wa

Reply #2 –
Yahoo Message Number: 81441
Fred - Yes I have on a pure sine wave inverter. Mine is a Norcold 1200 LRIM. I wouldn't recommend running any appliance designed for utility power on anything but a pure sine wave. The frig's heaters draw between 16 and 40 amps as reported by the inverter. It works perfectly.

At 11:31 AM 8/6/2012, you wrote:

Re: Can the Dometic refrigerator operate on 120 vac modified sine wa

Reply #3 –
Yahoo Message Number: 81452
Should not be a problem, the only thing the AC runs (when on shore power) is the heating rod. The modified sine wane ='s the RMS value (heating power) of a pure sine wave.

Joe n Judy

98 Intrigue 10578.

Re: Can the Dometic refrigerator operate on 120 vac modified sine wa

Reply #4 –
Yahoo Message Number: 81453
Fred,

Just a word for the wise. If the loads provided are correct, 16 amps at 120 volts is 1,920 watts. 40 amps at 120 volts is 4,800 watts. Unless you have a very large inverter (or two of them in parallel) you will have problems with this. I know my 2,000 watt inverter wouldn't stand a chance. It will handle my new Samsung though. It pulls a whole 1 amp, 120 watts! Very happy with this upgrade.

Barney

07 Inspire 52059

Re: Can the Dometic refrigerator operate on 120 vac modified sine wa

Reply #5 –
Yahoo Message Number: 81455
According to the Dometic NDR 1292 Manual, there are two, 210 Watt, 120vac heaters connected in parallel for a total of 420 Watts. That's
3.5 amps at 120 volts, or approximately 40 Amps at 12 volts. I would
expect other models to be similar.

Dave

2000 Allure
#30444

Re: Can the Dometic refrigerator operate on 120 vac modified sine wa

Reply #6 –
Yahoo Message Number: 81458
That's 16 to 40 at the DC level. It's less than 5amps AC. AND, being an electric heater element, it does not care if it is modified, square or pure.

Dave

aka Billy Byte (trusty hound)
2000 Allure #30443

Re: Can the Dometic refrigerator operate on 120 vac modified sine wa

Reply #7 –
Yahoo Message Number: 81465
Dave,

That sounds more like it. Thanks for setting me straight.

Barney

07 Inspire 52059

Re: Can the Dometic refrigerator operate on 120 vac modified sine wa

Reply #9 –
Yahoo Message Number: 81481
Being a Newbie

Why aren't these coaches wired that way from the factory?

Elton Kossaeth
2K 40' Magna 5894

Re: Can the Dometic refrigerator operate on 120 vac modified sine wa

Reply #10 –
Yahoo Message Number: 81483
Maybe the people who designed them did not use them...................................

One needs to remember to turn the refer to gas if you dry camp over night or your batteries will be very sad by morning.

Dave

aka Billy Byte (trusty hound)
2000 Allure #30443

Re: Can the Dometic refrigerator operate on 120 vac modified sine wa

Reply #11 –
Yahoo Message Number: 81484
Elton,

I think Dave hit it on the head. If they were wired that way from the factory too many people would try to dry camp overnight instead of switching to gas and let the inverter run the batteries dead.

John

05 Inspire

Re: Can the Dometic refrigerator operate on 120 vac modified sine wa

Reply #12 –
Yahoo Message Number: 81491
Barney - Those amperages (16 and 40) are on the 12 VDC side. Even a smaller inverter will handle that load easily to include a 2000 watt unit. I caution folks on MSW units. There is a pulse width modulation circuit that controls power to the heaters that might not function properly on anything other than a sine wave for which it was designed. Running a gas absorption frig on an inverter is a viable option. I know only because I've done it. What is a problem is moving the refrigerator circuit to the inverter subpanel. In our bus the frig is on its own circuit. There are some special considerations that need to be addressed if you want to make this switchable. Documenting this is on my "to do" list of articles. At this point I just wanted to correct the misunderstanding on the amperages.

At 12:49 PM 8/7/2012, you wrote:

Re: Can the Dometic refrigerator operate on 120 vac modified sine wa

Reply #13 –
Yahoo Message Number: 81492
Dave - Your information is correct.

At 01:15 PM 8/7/2012, you wrote:

Re: Can the Dometic refrigerator operate on 120 vac modified sine wa

Reply #14 –
Yahoo Message Number: 81495
As Dave indicated, anything that is a pure resistive load will run fine on a modified sine wave inverter. Where the problem comes is when there is an electronic control board between the supply and load. Some electronic control boards use 12vdc and others use 120vac which are designed to run on pure sine wave ac power source. Otherwise the life of the control could be shortened. Most refrigerators such as my Dometic use 12vdc for the controls and the ambient temp/climate control heaters. The Dometic has two 210w 120vac used for the ac mode.
I had a friend of mine that insisted that he could use his microwave on his modified sine wave inverter when we dry camped together. After a few months of such use, he fried the control board in it and ended up replacing the microwave.
My coach originally had a Heart Freedom 20 inverter. That was fine for watching a little tv (old crt type). When I started to install some of my ham radio equipment that ran on 12vdc it was real obvious the source of all the RF noise in the equipment. Then when my charger decided to go south and I started to plan a TV upgrade, it was obvious the potential problems that could be avoided using a pure sine wave inverter. That is when I upgraded the inverter/charger to a pure sine wave Magnum. Although I could now operate my Dometic refrigerator on the inverter, I do not.

Jim Hughes

2000 Allure #30511

Re: Can the Dometic refrigerator operate on 120 vac modified sine wa

Reply #15 –
Yahoo Message Number: 81498
To end this back and forth about this issue, I plugged my NDR1492 into the Ice maker socket. I'm assuming that it will handle at least 500 watts. Turned on my inverter and the elements drew about 40 amps DC according to the Heart Interface. I measured the A/C Watts and it was 430. So it's not a big deal to connect, the wiring is already there. I checked and no chattering relays.
I believe that the control circuit board switches the A/C and everything is controlled by DC.
I suppose I should wait till it cools down from ambient 90 degrees F but don't want to crash the batteries.

Jon Baum

Magna 2K 5923

Re: Can the Dometic refrigerator operate on 120 vac modified sine wa

Reply #16 –
Yahoo Message Number: 81501
I've hooked many RV refrigerators up to the inverter (both modified & pure and always making sure it's big enough to handle the load) and the only problem is remembering to turn the refer off of AUTO once you turn off the ignition.

From:Jon Sent: Thursday, August 09, 2012 11:13 AM To:Country-Coach-Owners@yahoogroups.com Subject: [Country-Coach-Owners] Re: Can the Dometic refrigerator operate on 120 vac modified sine wave?

To end this back and forth about this issue, I plugged my NDR1492 into the Ice maker socket. I'm assuming that it will handle at least 500 watts. Turned on my inverter and the elements drew about 40 amps DC according to the Heart Interface. I measured the A/C Watts and it was 430. So it's not a big deal to connect, the wiring is already there. I checked and no chattering relays.
I believe that the control circuit board switches the A/C and everything is controlled by DC.
I suppose I should wait till it cools down from ambient 90 degrees F but don't want to crash the batteries.

Jon Baum
Magna 2K 5923

Quote from: "kc4fws"
As Dave indicated, anything
that is a pure resistive load will run fine on a modified sine wave inverter. Where the problem comes is when there is an electronic control board between the supply and load. Some electronic control boards use 12vdc and others use 120vac which are designed to run on pure sine wave ac power source. Otherwise the life of the control could be shortened. Most refrigerators such as my Dometic use 12vdc for the controls and the ambient temp/climate control heaters. The Dometic has two 210w 120vac used for the ac mode.

Quote
>

I had a friend of
mine that insisted that he could use his microwave on his modified sine wave inverter when we dry camped together. After a few months of such use, he fried the control board in it and ended up replacing the microwave.



My coach originally had a Heart Freedom 20 inverter. That was fine for watching a little tv (old crt type). When I started to install some of my ham radio equipment that ran on 12vdc it was real obvious the source of all the RF noise in the equipment. Then when my charger decided to go south and I started to plan a TV upgrade, it was obvious the potential problems that could be avoided using a pure sine wave inverter. That is when I upgraded the inverter/charger to a pure sine wave Magnum. Although I could now operate my Dometic refrigerator on the inverter, I do not.

Quote
Jim Hughes

2000 Allure

#30511

Quote
>

--- In
href="mailto:Country-Coach-Owners%40yahoogroups.com">mailto:Country-Coach-Owners%40yahoogroups.com, David Tuttle wrote:

Quote

> That's 16 to
40 at the DC level. It's less than 5amps AC. AND, being an electric heater element, it does not care if it is modified, square or pure.

Quote

>

> Dave

> aka Billy Byte (trusty
hound)

Quote
2000 Allure #30443
>
>

>

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Can the Dometic refrigerator operate on 120 vac modified sine wa

Reply #17 –
Yahoo Message Number: 81504
Why not connect the frig through a relay (like the front TV) when the ignition is on the frig is connected to the inverter, when the ignition is off the frig is connected to the AC bus. Setup like that when you shut off the ignition and you are not connected to AC the frig will automatically shift to propane.

Earl Densten

03 Intrigue 11554