Power use for a glass lid fridge?

[Maury Markowitz]

Hi everyone, I'm very new to this field, so forgive me this noob question…

A customer has asked us to provide a battery backup for his pair of True TFM-51 glass lid freezers. In order to estimate what sort of batteries we needed, we need to know the daily consumption. True doesn't list this anywhere in their specs.

I wrote to them, and after a rather circuitous route, they said it burns 4 kW per 24 hours at 75 degrees. This is a bit odd - the peak power of the compressor is listed, and it's 2.5 Amps. At 115, that means it would draw 6.9 kW per 24 hours. So their estimate suggests the compressor is running about 60% of the time?

But then someone suggested we could do a lot better by simply buying a DC freezer. So I looked up the Sundanzer DCF225. It's only 8 cubic feet, instead of 13, so we'd need two of them and get some extra space. And how much would two of them draw a day?

1000 Wh.

So True says their 13.3 cf freezer is going to burn 4 kW a day, and the equivalent DCF225's would burn 1 kW.

Can anyone shed a little light one this? Is the True estimate wrong?

[Maury Markowitz]

Oh, I should also note that the motor on the compressor is only 1/3 hp. That's about 250 Watts. So according to that, the maximum possible draw should be only 6 kW.

I'd love to know if anyone's ever hooked one of these to a Kill-A-Watt

[Brian_UK]

The compressors do not run continually, when the unit is at temperature the compressor switches off. That is why the difference between 4 and 6 kW.

[Magoo]

Get hold of an old battery out of an electric fork hoist that has a couple of dead cells, fork hoist people sell them off for scrap recycle value, then get an inverter from DC to AC, you could add trickle charging from solar cells or wind mills. It will go for ever.

[Maury Markowitz]

The compressors do not run continually, when the unit is at temperature the compressor switches off. That is why the difference between 4 and 6 kW.

Well obviously, but that would require two things:

1) The compressor has to be running at about 75% duty cycle. Seriously, it's on 75% of the time? My fridge is on maybe 10% of the time, and it's front opening.

2) This freezer has to be TEN TIMES less efficient than this other model. Two times, sure, 10 times?!

Hasn't anyone out there hooked one of these up to a meter some time?