freezer ?reduce voltage

[thealoi]

I have read on an american website that one can reduce the power draw of a freezer by reducing the voltage to e.g. a Danfoss compressor as the latter is able to "drive" up to three cooling plates if needed. They recommend using an adjustable switching regulator (ref SWADJ3 by Dimension Engineering) see: http://www.dimensionengineering.com/DE-SWADJ3.htm

Has anyone done anything like this or have sufficient specialist knowledge to advise?

 

[Barry Jones]

No not heard this.

If you reduce the voltage a little, I think it will just draw more current when the compressor runs. Eventually, it won't start.

Do you have a link to the article ??

 

[sarabande]

this device

http://www.ukpowersaver.com/

and others like it, can save power - but at an initial capital cost.

 

[Barry Jones]

Oh okay - I know what is meant now.

A few years ago, they dreamt up a device called a SavaPlug device for compressor driven fridges.

It reduced the voltage supplied to a fridge once the compressor motor was running, so less power was needed overall. The problem was that most modern fridges have a thyristor control to do this already, so they clashed.

Seems to have vanished from the market.

Not sure if this power-saving device would have much bearing on a boat fridge which tends to be smaller and get switched off often.

 

[Talbot]

You will save more by making sure the freezer is full, as that seems to keep the compresor time to the minimum.

 

[tri39]

I have improved my top loading fridge/freezer by adding extra insulation internally with polystyrene panels, renewed yearly. The fridge is rarely full so reducing the internal volume helps. Then I find it can be switched off at night, especially if bottles and cans are acting as extra cold plates! A tray of beer at the bottom works wonders.

 

[owen-cox]

Reducing the voltage will not reduce the speed of the compressor as a danfoss compressor is run by a 3 phase inverter that changes frequency to control revolutions of the compressor motor. The voltage can be reduced slightly but this will draw more current as the compressor will use the same amount of power at a set speed. P=IV Power = current x voltage. There is a way of controlling speed of the compressor as the compressor can be set using resistors from 2000 rpm to 3500 rpm however the slower the compressor runs the longer it takes to cool. The Isotherm ASU does this intelligently so when a voltage supply is available ( 240V or engine running) it speeds the compressor to 3500 rpm. when the voltage is not available and it is running from batteries only it reduces the speed to 2000 rpm and changes the thermostat set point to a slightly warmer one to conserve battery energy. I have seen this done with a relay off the alternator that shorted out the thermostat when the engine was running to cool as much as possible when power is available.
Details on compressor speed control can be found here http://www.novakool.com/support/bd35f_compressor_data.pdf

 

[owen-cox]

I forgot to say that I agree with tri39 that the best way to conserve energy is to install more insulation. 250mm is recommended but more is better. I was also assuming you were looking at a DC fridge as the unit you have a link to is a DC unit. If it is mains voltage then the unit sarabande recommends would be suitable.