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Want to be able to run a refrigerator and deep freezer...


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SkyMan

You're using 2 relays.  The ref would cycle several times before the freezer starts.

Once it did, it would have to finish before the ref could start.

You could even add a 3rd wheel to this with DPDT relays. 

Smart circuit.  A fused inverter might even protect it. 

Easy enough to test first on low voltage stuff.

Yes, this is the way I would do it. Rather than the ref having complete priority, I'd have it more of a first come first served basis thereby allowing either to have a complete cycle before allowing the other to cycle. I'd also separate the ref light from this allowing it to come on even if the freezer is cycling.
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Yes, this is the way I would do it. Rather than the ref having complete priority, I'd have it more of a first come first served basis thereby allowing either to have a complete cycle before allowing the other to cycle. I'd also separate the ref light from this allowing it to come on even if the freezer is cycling.

A battery operated LED motion activated wall light comes to mind.

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SkyMan

I think it would be easy to just rewire the light/door sensor to bypass the relay system.

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Ozepete

Our family company manufactures super efficient refrigeration systems for yachts, motor homes and other non-grid applications so this subject interests me. As said earlier the only advantage in the described control method would be to restrict the inverter load to one compressor at a time. There may be some power savings also as many inverters are poorly engineered and their co-efficiency can decrease with load.

Over decades we have continued to seek the most efficient conversion of electrical energy to heat pump output. Refrigeration is one of, if not the highest energy consumed for the average home so co-efficiency has become an important factor especially for those with limited power supply.

It is possible to operate a 180 liter chest fridge (+2c to +4c) while consuming less than 18 amperes per 24 hrs. (Independant test using our system)

 

The key issues for having a super low consumption fridge are:

 

Cabinet....

Insulation:  At least refrigeration grade urethane 32 to 60 Kg / M3 or better.   Must be thickest on the base (150mm) then walls (100mm) lid (50mm)

Cabinet: Top opening and with non conductive inner and outer linings (NO metal lining)

Lid seal: Should be very soft (easily compressed) an wide.

 

Refrigeration System......

Evaporator: Eutectic. This is a stainless steel tank that hold a liquid which freezes solid at about minus 6c. This allows refrigeration to happen and store 'cold'  when *convenient and not on demand like cyclic cold plate or forced air evaporator types. (* ie: When solar power is abundant)

Condensing unit:  DC hermetic compressor with combined air and water cooled condensor. (Or twin condenser fans in lieu of water cooling)  

 

Control System....

Eutectic plate: A digital contoller causes the system to run until it switches off when the eutectic mass is frozen. (Say minus 8c) This frozen eutectic mass maintains cabinet temperature untill the mass thaws and the unit runs again just like a renewable low temperature ice-block . (Phase change)

Condenser: The condensers water cooling is controlled between +35c and +40c regardless of the ambient. (Ideal condenser temperature)

 

Power economiser...

ECO2: This is a method we developed which compliments the eutectic operation. This device recognises that such power supplies fall into two groups.. limited (Battery only) and abundant (When DC voltage excedes 13.6 or mains power is detected) When 'abundant' power is detected it tricks the digital temperature controller into 'run mode' and also causes it to operate in the lower half of its parameters.

This means that power otherwise going no-where is used to refreeze the eutectic tank reducing the need to run later when on battery alone. (Some Yachties have repoerted that this 'abundant power alone has been sufficient to maintain their fridge without battery drain.

 

Cheers..

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