Variable Speed Freezer Compressor Test

Testing out the variable speed compressor feature and see how it affects energy consumption.

As shipped, the Sunstar freezer had a 510 ohm resistor in series with the thermostat contact. Using an audio spectrum app, this gave a 43Hz or 2580 RPM speed. At this speed, power was 66W, run time 40 minutes every 3 hours, energy consumption was 352WH/day. Removing that resistor gives a 2000 RPM speed, power dropped to 44W, run time increased to 94 minutes every 6 hours, resulting in 272WH/day consumption. This change reduced energy consumption by around 22%.

Secop information:
https://www.secop.com/about-us/history
https://www.secop.com/products/technical-literature/instructions-show/electronic-units-instructions

Blog post on variable speed operation:
https://coastalclimatecontrol.com/blog/variable-speed-refrigeration-and-air-conditioning-compressors

The DC freezer is proving it's benefits by staying powered off solar for over 2 weeks without the battery bank hitting 100% state of charge in early January. With the old upright freezer, I would have had to switch it back to grid power after a day or two of low power conditions. This is because I was able to switch off the AC output on the hybrid inverters most of the day to save on the power needed to operate that function.

In future videos, I'll be installing a 1500 ohm potentiometer in series with the thermostat to allow selecting any operating speed. Then I'll be installing an in-line watt meter to the freeze to be able to measure it's energy consumption. Then I'll be able to test energy consumption at the various speeds, both in a cool winter ambient temperature as well as in the hotter summer conditions.

Freezer is made in the USA by:
Solar Freeze, Llc
LaGrange Indiana

It seems that the compressor is made by Secop (formerly Danfoss) and is packaged by Keota for use in the Solar Freeze Sunstar freezers.

It is as "no frills" as you can get, manual defrost, no digital display, no WiFi, just a plain old thermostat dial and a power and fault LED indicator.

Ordered from:
https://www.thecabindepot.com/products/sunstar-solar-dc-chest-freezer-8cu
They seemed to have the best price including shipping. They are located in Canada, so you may get hit with a currency conversion fee when ordering, but there was no sales tax added.

Solar Freeze web site:
https://www.solarfreezellc.com/

Image credits:
BD35 cutaway:
debe @ https://forum.allaboutcircuits.com/threads/danfoss-compressor-speed-controller.118993/

Controller PCB:
obd.tech @ https://www.eevblog.com/forum/repair/repairing-electronic-control-unit-for-bd35-compressor/

More to come...
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