AC Freezer overheats with inverter?

[msponer]

Hi Everyone,

Our AC freezer runs well with our genset. However, on the inverter it's thermal cut off activates after about an hour.

It draws 4 amps at 220 volts, which our 150 amp/24 volt alternator keeps up with when we are motoring. We can run it and still charge the DC system 80 amps at 24 volts. The inverter is a 3000 watt Mastervolt.

What do you guys think, why would it overheat with the inverter, but not the genset?

Thank you.

Matt

[StuM]

Is it a pure sine wave or modified sine wave inverter?

Sounds like it may be modified sine wave. Motors such as AC compressors do run hotter and less efficiently on modified sine wave and can overheat. It is a result of the power characteristics of the square waveform.

[senormechanico]

Stu is exactly right.
Ditch the modified sine inverter.
Full sine inverter prices have dropped significantly in the last few years.

[msponer]

Very cool, thank you guys! I will look for a new inverter.

In the mean time, does it damage the compressor if the thermal cut off is tripping? We hope to be in Tahiti next week, and I don't know if a 3000 watt 24/220 sine wave inverter is something I can source there.

[msponer]

Oh, wait, I was wrong. It is a 'Victron Phoenix Sinewave Inverter' 24/220 3000 watt. Not a Mastervolt. When I get real Internet I will dig out the specs and confirm that it's a modified sine wave inverter, not a true sinewave.

Thanks again!

[sailorchic34]

Looks like the pheniox is a pure sine wave inverter....

Is the generator 50hz or 60hz??? and is the AC compressor motor 50hz or 60hz.

One fun fact is a 50hz motor will run fine on 60hz, though at a faster rpm. But a 60hz motor will tend to overheat if run at 50hz.

Also could be overcharged refrigerant or check connections in 24v power cables to inverter for corrosion.

[ColdEH]

Yes the Phoenix is a pure sine wave , I had one . It blew up , or just never really worked . Try another steady load on it , it may be your inverter is dying .

Thats a discontinued model as well and you can't get parts for them .

Regards

[StuM]

Just looked at the manual and it is pure sine. But it can be switched between 50 and 60Hz. So Sailorchic may well have the answer - mismatched frequencies between compressor and inverter.

(And SC, join the club I always have to have multiple attempts to type phoenix correctly )

There was one in our Belize when we bought her - but the charger wasn't working. We upgraded it straight away to a larger Mastervolt. (The marine electrician who did our post purchase upgrades took one look at it and said "Ah, the old Blue Death"

[sailorboy1]

while it sounds to be the inverter, the questions remains did this problem just start?

[pesarsten]

As to your question about damage to the compressor the answer is yes, each time the windings overheat and trip the thermal protector, the insulation on the windings suffers. How much damage can't be determined without looking at them, not possible in modern sealed units. An amp meter might give you a clue.

[msponer]

Thank you all for your help.

With your advice, I now think this is an issue with the hz. I just arrived in Papeete and, when the hardware store opens tomorrow, will go get a fancier electrical meter to see what is coming out of the inverter, and learn how to reconfigure it. The genset is 50hz. The fridge is running fantastic here on 50hz marina power.

[msponer]

I was wrong. I just got a better electrical meter, and shore power here in Tahiti is 60hz.

235v 52-55hz Genset, hz decreases with load -- Fridge happy
230v 60hz Shore power -- Fridge happy
220v 50hz Inverter -- Fridge overheats after an hour of runtime

The compressor has a smudged label that appears to indicate it will work off of 50 or 60hz, but it's hard to read. It's a "Rich Beer Condensor" with a Florida address on it.

I experimented with the compressor. It won't overheat if I hack a big bilge blower fan to blow right on it. Maybe that's the fix? What do you guys think?

Also, is it normal for the hz on the genset to be slightly off? Should I care or try to have it adjusted?

Thank you everyone.

[sailorboy1]

Originally Posted by msponer

What do you guys think?

I think that if you keep running you unit off the inverter with the frequency that it is going to burn out the windings!

Not only are you going to burn out your refrigerator, but any other AC load you run off the inverter is going to have problems if you get anywhere near the items rated power draw.

You have done a good job of tracing your problem to the inverter (you had that info in your initial post). Replace it and stop messing around.

[msponer]

Originally Posted by sailorboy1

You have done a good job of tracing your problem to the inverter (you had that info in your initial post). Replace it and stop messing around.

Ok, I will look for a new inverter here. But the numbers I have from it look right, right? So what do you think could be wrong -- is a normal failure mode for the sine wave to get weird in a way that's not seen in a cheap meters measurement of the voltage or hz?

[sailorboy1]

[QUOTE=msponer;2144256

235v 52-55hz Genset, hz decreases with load -- Fridge happy
230v 60hz Shore power -- Fridge happy
220v 50hz Inverter -- Fridge overheats after an hour of runtime
[/QUOTE]

You have lower voltage and low frequency off the inverter. By themselves each of those is going to cause more heating in windings. You put the two together and it isn't surprising the refrigerator overheats. The lower voltage by itself might be the problem as that increases the current load on the windings, but it doesn't matter. You know that problem is the power from the inverter.

It could have been this way for years and slowly has done a number on the windings to the point it overheats. So don't be over surprised if the refrigerator still fails down the road.