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Old 10-31-2015, 04:40 PM   #41
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A couple of years ago we replaced a wornout Norcold with a Summit FF 874 SS 8.1 cuft refrigerator freezer, 115 acv, 370 KWh/year, run amps 1.2, start amps 4.0. I thought a 900 watt inverter would run the unit but it doesn't, is there any way to calculate the size inverter I should use assuming that the 900 watt inverter can't start the unit because it was in a auto defrost mode ? Do I need a pure sine wave inverter ?

Sadly Summit discontinued this unit, it has proved to be quiet, and efficient and we love the convienience of the frost free feature.

Hate to hear that- I installed one a couple of years back- it's been a great unit.


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Old 10-31-2015, 05:15 PM   #42
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Originally Posted by HiDHo View Post
A couple of years ago we replaced a wornout Norcold with a Summit FF 874 SS 8.1 cuft refrigerator freezer, 115 acv, 370 KWh/year, run amps 1.2, start amps 4.0. I thought a 900 watt inverter would run the unit but it doesn't, is there any way to calculate the size inverter I should use assuming that the 900 watt inverter can't start the unit because it was in a auto defrost mode ? Do I need a pure sine wave inverter ?
Sadly Summit discontinued this unit, it has proved to be quiet, and efficient and we love the convienience of the frost free feature.
Get a plug in Killawatt meter to see what the unit draws. The one thing you won't see is the peak load, since that happens at startup for a second or so. You should size the inverter greater than the fridge requires, and build in some surge or short term peak loading on it for the startup current required to start the compressor.

All motors need a lot more power to start up than they need to run so if you're running motor loads on an inverter, add an extra bit for startup current surge requirements.
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Old 11-01-2015, 11:14 AM   #43
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Some inverters are better at starting fridges than others. I tried an older 1kW unit and it would not start my bar fridge. Went and bought another new 1kW unit and it works fine.
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