Can This Inverter Handle Multiple Refrigerators?

November 09, 2017

Can This Inverter Handle Multiple Refrigerators?

An off-grid farm recently asked us whether their 4-building site could handle 4 refrigerators, at atmospheric water generator, and some lights. Power to the site is provide with 7kW PV array with a 6kW Outback Flexpower Two inverter which is basically two 3kW inverters. Our gut feel was that the site could handle the refrigerators but we wanted to gather data to back this up. So we hooked up a 24 cubic ft Frigidaire refrigerator (larger than the one to be installed on site) to an Onset HOBO current data logger to see how much power it draws when the compressor kicks on. (NOTE: This particular refrigerator uses about 3.5 kWh of energy per day so it would not be a good choice for the site since they'll need four units. But this is the refrigerator we had for testing. The actual refrigerator for the site would be smaller and more energy efficient to reduce it's drain on the batteries overnight.)

power measurements of a refrigerator when compressor kicks on

The data collected by the HOBO showed that while the refrigerator spent most of its time drawing about 160W of power with the compressor on and somewhere between 0-10W with the compressor off, it drew over 1100W for about a second when the compressor kicked on. And since our HOBO only recorded current every second, it's possible that the instantaneous draw could be even higher. 

Each 3kW inverter in the FlexPower Two would be set up to power two refrigerators. So in the unlikely event that the compressors from both refrigerators kicked on at exactly the same time, the instantaneous draw would be 2200W or higher. The inverter is capable of sustaining 3000W in continuous output and 6000W for a few seconds. So we concluded that the inverter could handle both refrigerators without a problem. We recommended, however, that they get slightly smaller and more energy efficient refrigerator to reduce the energy used overnight from the batteries. 

 





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