DC refrigeration question

[Wdeertz]

I have a Vitrifugro AC/DC refrigerator on my boat. I leave both AC and DC circuits on and I understand it defaults to AC if power is present. I’ve been at anchorage for several days and system was cooling really well but when I recently pulled into a marina and connected to shore power the temperatures rose over the next several days. I assume AC power is getting to the unit as the light bulb is operating. I suspected the AC converter may be bad so I switched off the AC circuit and sure enough 12 hours later I was back to normal temperatures.

Am I correct in that a AC/DC refrigerator has a DC compressor and when on AC power it just converts this to 12v DC?

If this is the case I see no benefit of the AC mode as I can always run on DC power and while on shore power my battery charger keeps me fully charged. I mistakenly assumed the AC mode would cool better but this wouldn’t be the case if it’s simply converting to DC.

 

[Comodave]

I don’t know but I also have a Vitrifugo so I am interested in the answer. I added a 12 volt fan and a top and bottom vent to the refer cabinet and had a huge increase in the performance of mine.

 

[O C Diver]

I am not familiar with your specific refrigerator, but would say your assumptions are correct. There is probably no measurable efficiency difference between the two power sources when connected to shore power. In 12 volt operation it is probably more efficient as it is a 12 volt compressor, but that efficiency is offset by the loss of your battery charger making 12 volts. I wouldn't worry about it and just run it on 12 volts till it dies.

Ted

 

[Wdeertz]

I don’t know but I also have a Vitrifugo so I am interested in the answer. I added a 12 volt fan and a top and bottom vent to the refer cabinet and had a huge increase in the performance of mine.

Thanks for the reply, I also added a 12v fan to improve performance. I generally only need to use the fan on very hot days. Vents are also a good idea but in my installation I have no room to add.

 

[Wdeertz]

I am not familiar with your specific refrigerator, but would say your assumptions are correct. There is probably no measurable efficiency difference between the two power sources when connected to shore power. In 12 volt operation it is probably more efficient as it is a 12 volt compressor, but that efficiency is offset by the loss of your battery charger making 12 volts. I wouldn't worry about it and just run it on 12 volts till it dies.

Ted

Ok thanks for confirming my thought process makes sense. Hopefully I can get a couple more years out of it before it goes dead.

 

[Ski in NC]

Don't leave frozen bait in the thing and go away for a week!!

Ask me how I know. And I don't want to talk about it!!

 

[High Wire]

If it cools better on DC then keep it on DC.
Now if the cooling was equal then I would use the source that consumes the lowest overall amphours.

 

[obthomas]

I have a 10 year old Norcold and it is AC/DC. The AC converter burned up a couple of years ago and I was left running on 12 volts. Sensing a need to repair my refrigerator I called Norcold. They told me they had made a change and all of the power modes are now on one circuit board and long story short it would be more economical for me to buy a new refrigerator.

I said I would rather repair my refrigerator and all I needed to know is what DC voltage the burned up AC converter produced. Norcold were jerks and told me they didn't have that information anymore. So I used a variable power supply and tried 12 volts, 24 volts and finally at 36 volts the unit started working properly. Some time later I learned that 40 VDC was the original voltage. I bought a fan cooled 120AC/40VDC converter on Ebay for about $30 and it has been working perfectly on my refrigerator for about 2 years now.

In summary my refrigerator takes 120VAC and provides 40VC to a second circuit board that has the smarts to run a 24 VDC fan and a 12 volt compressor. When the 40VDC is not available the second board takes 12 VDC and runs the refrigerator including the 24VDC fan.

 

[rslifkin]

The old swing compressor Norcolds were odd beasts, as you noticed. The Danfoss units are actually a 3 phase AC compressor IIRC, driven by the controller board using either single phase AC or 12/24v DC input.

Personally, I run the AC/DC versions on AC when on shore power or generator, as that leaves a few extra battery charger amps available for charging.

 

[Comodave]

Thanks for the reply, I also added a 12v fan to improve performance. I generally only need to use the fan on very hot days. Vents are also a good idea but in my installation I have no room to add.

On mine I wired the fan to the circuit board. Vitrifugo has a 500 mAmp designed into the circuit board to run the fan whenever the compressor is running. The fan I added draws 50 mAmps. Even a few small holes top and bottom will really help with cooling efficiency.

 

[Wdeertz]

I have a 10 year old Norcold and it is AC/DC. The AC converter burned up a couple of years ago and I was left running on 12 volts. Sensing a need to repair my refrigerator I called Norcold. They told me they had made a change and all of the power modes are now on one circuit board and long story short it would be more economical for me to buy a new refrigerator.

I said I would rather repair my refrigerator and all I needed to know is what DC voltage the burned up AC converter produced. Norcold were jerks and told me they didn't have that information anymore. So I used a variable power supply and tried 12 volts, 24 volts and finally at 36 volts the unit started working properly. Some time later I learned that 40 VDC was the original voltage. I bought a fan cooled 120AC/40VDC converter on Ebay for about $30 and it has been working perfectly on my refrigerator for about 2 years now.

In summary my refrigerator takes 120VAC and provides 40VC to a second circuit board that has the smarts to run a 24 VDC fan and a 12 volt compressor. When the 40VDC is not available the second board takes 12 VDC and runs the refrigerator including the 24VDC fan.

Companies that don’t provide after sale support aren’t worth supporting. I’ve been looking for a Vitrifugro manual online that has a wiring schematic but haven’t been able to locate. The Vitrifugro website was of no use.

So on 12v power it runs a 24v fan so it must have a step up converter. Seems it would be more efficient to just go with a 12v fan.

 

[Wdeertz]

On mine I wired the fan to the circuit board. Vitrifugo has a 500 mAmp designed into the circuit board to run the fan whenever the compressor is running. The fan I added draws 50 mAmps. Even a few small holes top and bottom will really help with cooling efficiency.

I’ve wired my fan directly to 12v power and have a manual switch to turn on and off as needed. Your method is probably a better option, may consider this change. Thanks

 

[Comodave]

Well you don’t have to do anything it just comes on automatically but you need to find a low draw fan. I got mine on Amazon, it was for a computer but works fine in this application. It is so quiet you can’t even hear it. I put it on the lower vent blowing air into the cabinet and then put a vent high so the hot air can get out of the cabinet.

 

[Boat]

Here's some info:


https://www.vitrifrigofridges.co.uk/installation.htm

 

[EngNate]

All modern AC/DC fridges run on DC and have an AC-DC power supply and a relay that switches over when AC is present. A failed power supply will in many cases cause it to switch over to AC but not get power. As long as charger capacity isn't an issue there's no reason to use the AC input at all, and for sure don't put a fridge AC on the inverter buss if it has a DC input, that does double the conversion loss. These DC refrigeration compressors have three phase AC motors electronically driven by an inverter module and these are now found in most higher end domestic refrigerators as well.

 

[catalinajack]

All modern AC/DC fridges run on DC and have an AC-DC power supply and a relay that switches over when AC is present. A failed power supply will in many cases cause it to switch over to AC but not get power. As long as charger capacity isn't an issue there's no reason to use the AC input at all, and for sure don't put a fridge AC on the inverter buss if it has a DC input, that does double the conversion loss. These DC refrigeration compressors have three phase AC motors electronically driven by an inverter module and these are now found in most higher end domestic refrigerators as well.

Which is exactly why purchasing an AC/DC model makes no sense. Eliminate the middleman and power directly from DC. Plus, an expensive subject-to-failure inverter module is not present.

 

[EngNate]

Which is exactly why purchasing an AC/DC model makes no sense. Eliminate the middleman and power directly from DC. Plus, an expensive subject-to-failure inverter module is not present.

The inverter module is always there, it is key to high efficiency operation, along with the compressor design that it works with. It's the additional stage of the 120AC-DC converter that's eliminated with a DC only unit. As shown earlier in the thread, new ones have it all in one box, which means you're not likely to find a current model that is DC only.

 

[EngNate]

Repairing the compressor controller

If you are, or know, an electronics hobbyist with soldering skills many of these refrigerator inverter modules that have failed can be repaired. Though other things can happen, the single most frequent cause of failure is cracks developing in the soldering where the larger component terminals connect with the PC board. Newer ones may be encapsulated but the rest come apart without difficulty and it takes just minutes with some magnification to spot these points and fix them. If you have a failed one it is definitely worthwhile to look at this before shelling out for a replacement. This is what to look for:

 

[catalinajack]

The inverter module is always there, it is key to high efficiency operation, along with the compressor design that it works with. It's the additional stage of the 120AC-DC converter that's eliminated with a DC only unit. As shown earlier in the thread, new ones have it all in one box, which means you're not likely to find a current model that is DC only.

You are correct, of course. My memory is faulty. I pulled out the manual for my three-year-old Vitrifrigos. Indeed, they can run on AC and DC. However, only the DC side is required. There is no need to plug into AC also. If one does wire the AC side, this fridge will default to AC which will then be inverted to 12VDC. That was my point. Why bother going thru an AC middle man to get to the same place. Plus, when not on shorepower, there will be a loss going from battery bank to AC and, then, more loss going from AC to DC at the fridge. It only makes sense to do this if the fridge has access to only AC power.

As an aside, we have two 4.4 cf fridge-only units. They have performed flawlessly for three years keeping food plenty cold even in hot climes. In fact, at times, in more temperate climes, we have had some items, mainly delicate veggies, freeze in the bottom drawer where the coldest air resides.

 

[Comodave]

You are correct, of course. My memory is faulty. I pulled out the manual for my three-year-old Vitrifrigos. Indeed, they can run on AC and DC. However, only the DC side is required. There is no need to plug into AC also. If one does wire the AC side, this fridge will default to AC which will then be inverted to 12VDC. That was my point. Why bother going thru an AC middle man to get to the same place. Plus, when not on shorepower, there will be a loss going from battery bank to AC and, then, more loss going from AC to DC at the fridge. It only makes sense to do this if the fridge has access to only AC power.

As an aside, we have two 4.4 cf fridge-only units. They have performed flawlessly for three years keeping food plenty cold even in hot climes. In fact, at times, in more temperate climes, we have had some items, mainly delicate veggies, freeze in the bottom drawer where the coldest air resides.

If you get freezing in the bottom of the fridge, try one of the small standalone fans to circulate the air in the fridge better. We have one in ours and it really helps keep the temperature more even throughout the fridge. It runs on 1 or 2 D cells, can’t remember which.

 

[Wdeertz]

Thanks to all for the replies, it was very helpful. The unit is working really well on DC power so will just keep operating in this mode until it dies.

 

[Greatlaker221]

Question, is it typical for a new AC/DC fridge compressor to shut off if power drops below a certain voltage? I can’t hear the compressor when underway due to engine noise and when I shut down, running just on battery, the compressor shuts off . Voltage on battery is normally 12.5v

 

[FF]

Yes most will shut down , but measure the Voltage At the compressor , not at the battery.

 

[eman]

ac/dc norcold refrigerator

I just went through this issue with to ACDC de00601 norcold. I guess is the AC inverter Burns Out and the unit runs on DC only. It does not make sense to buy an AC DC refrigerator if it will not run on AC correctly. I understand that my charger we'll keep the batteries charged however I don't need that running constantly with a load on it because of the refrigerator. I I'm never going to buy an AC DC refrigerator again especially norcold. There can be thousands of these units out there that are not running on AC and just on DC and you would never know unless the battery is allowed to drain to the point where it AC should take over and it does not

 

[Flyguy1967]

Similar problem with my Norcold DE0061but sightly different. Running on shorepower/AC freezer will freeze and regret will cool but give it a day or 2 and come back to the boat, green light on, fan running but not cold. Think the os the same issue but just at the beginning stage? I'll try running on just DC and see what happens.