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Using a square-wave inverter for refrigerators

11 posts in this topic

Many electronics require sine-wave power for stability and to prevent damage to sensitive components. Until recently, this hasn't been a problem for kitchen appliances powered by square-wave inverters. My query is this: Is it safe to power a Vissani HMDR 1030we with a square-wave power source, and if so, is it safe to use a timer on it to turn the power off during the night? The problem we encountered was that the unit wouldn't turn itself back on when the power returned, at least not until we turned the unit off (to zero) with the thermo switch and then turned it to 9. This is a warm climate and the ambient temp was above 70 F all night. 

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I would say it depends on the specs of the inverter as well as those of the fridge. I suggest obtaining specs of the inverter you have and asking the fridge manufacturer this question. Reponsible technicians probably would not delve into safety concerns when you are doing something outside of those suggested or recommended by the manufacturer.

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Can anyone post a wiring diagram for this refrig. It looks like it has a simple cold control and timer so I don't know why it wouldn't power back up. If you are unplugging it at night it might make sense to take the defrost timer out since being off for 6-8 hours should defrost it enough plus you save the electrical load of the heater. If it still won't come back on without resetting the cold control then there might be a problem with the cold control.

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The following is found at the top of page 6 of the user manual:

 

 

NOTE

If the unit is unplugged or loses power; you must wait 3 to 5 minutes

before restarting the unit. If you attempt to restart before this time delay, the

refrigerator may not start.

 

 

source


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The manual also says "Do not use with inverter" yet the solar guy said that it would be OK. This begs the question: What area of the fridge would be sensitive to a square-wave power source? Would JJ Surfer's idea of disconnecting the defrost timer address the issue?

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The manual also says "Do not use with inverter" yet the solar guy said that it would be OK. This begs the question: What area of the fridge would be sensitive to a square-wave power source? Would JJ Surfer's idea of disconnecting the defrost timer address the issue?

I am not so sure the "do not use with inverter" issue is analogous. If your issue is the fridge will not restart after a loss of power, doesn't that note indicate a possible reason why? Before informing you of compatibility, was the solar guy aware that after a power loss you have to wait 3-5 minutes before turning on this fridge otherwise it will not start?

Having to turn off and then turn back on the fridge after a power loss is apparently an intentional design. So i guess my question is do you consider this "problem" a defect or are you trying to circumvent the design?

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If you turn off any refrigerator then turn it right back on the compressor usually won't start because of the high head pressure.

 

The 3-5 minutes before it will start is for the pressures to equalize.

 

If it is just a standard mechanical cold control/t-stat and no electronics then that is all that note should be referring to.

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if that is the case, re: it has a mechanical cold control, then if your fridge will not turn on until turning it to 9, then as JJ Surfer stated, there must be a problem with the cold control.

I have not been able to find a diagram, is there not one located behind the toe grille?

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In clarifying the issue with the owner, it seems as though the fridge was never unplugged or turned off intentionally. What she did was turn the thermo down to the "1" position at night to save the batteries. In the morning, she turned it back up to 4 and the unit never powered up. Frozen items were melting. She finally got the fridge back to life by turning the thermo down to "0" and then up to Max, which worked. Has anyone ever seen a thermostatic control with a built-in reset? It doesn't make sense to me because if there is a power failure, the owner is not expected to go through a reset sequence after the power returns. Don't forget that this unit was built (or designed) in Italy. But the question still remains: Is it safe (to the unit) to turn the power off every night? JJ Surfer thinks it would be if the defrost switch is disconnected. But he can't be sure until the wiring diagram is examined. The owner reports that she could not find a diagram. 

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Next time when the control is turned up to 4 from 1 and the unit isn't running, give the control dial a good hand slap.  If it starts up you have a bad cold control/t-stat.  Even if the compressor isn't running and cooling the evaporator/freezer fan should be blowing air if the cold control contacts are closed and calling for cooling.

 

Turning it down to zero manually opens the contacts all the way then when turned back on the contacts snap together good making good contact again until the t-stat opens and cycles on it's own, (this is what you will find on any refrigerator that has failing contact points in the t-stat that sometimes fails to start back up after an off cycle - this sounds like what is happening in this case).

 

Do you know how old this refrigerator is?

Edited by Budget Appliance Repair

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The fridge was purchased one month ago, new.

 

DurhamAppliance quoted the owner's manual which states:

 

 NOTE

If the unit is unplugged or loses power; you must wait 3 to 5 minutes
before restarting the unit. If you attempt to restart before this time delay, the
refrigerator may not start.

This would present a problem for anyone living in this area who is on the grid, where it is common to have several power outages every week; some of which are less than 3 to 5 minutes. This is not a problem for our new fridge owner, who is totally off the grid. I think our local Home Depot needs to post a warning on their display unit. 

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