E-News Issue #50
230 AC FridgesAs you know we still recommend 12/24V fridges for solar systems as being considerably more efficient than the 230V ones.
Despite their higher cost, we still think it is a cheaper option for residents outside of Queensland.
The situation in Queensland might be more 'line ball' in that most qualify for a 75% subsidy on the batteries as well!
However, in several years time, this larger battery bank will need replacing.
An extra several hundred-amp hours of battery storage to be purchased every several years is not cheap these days!
We have come across problems with two 230V fridge installations (which we did not recommend).
Both have to do with the autostart function on some inverters.
One customer had a fridge that tripped an internal switch when the inverter went into standby mode. This is apparently a 'brown out' protection device for the grid.
Another one of our customers has a fridge that won't start up when the inverter is in standby mode (with nothing else connected).
It would seem that this fridge has some sort of soft start relay that the inverter does not see as a load.
So this customer now needs to keep their inverter on run mode all the time which further adds to the inefficiency of the system.
Peter McCloy encountered a problem with a customer who bought a fridge with automatic defrost. It would not restart after the defrost cycle, despite the fact that the light still went on, and if you left it off for a while it would start again.
These refrigerators use a small heater to defrost, but after the defrost cycle do nothing for a while, except for a timer which controls the cycle.
This timer does not pull enough current to start the inverter, and so the cycle never finishes.
However, if you open and close the door enough, each time the door is opened the light trips the inverter and the cycle will eventually finish.
Similarly if you leave it switched off, temperature rises and the machine will start when you turn it back on.
Remedy: Have someone disconnect the auto defrost cycle, or leave the inverter on, but preferably don't buy an auto-defrost model.
While I appreciate that some 230V fridges are getting more efficient, we suggest you still think twice before going down this track.
Neil McIntosh pointed that all chest type fridges use less power than an upright. In the Queensland summer his 160 litre Fischer & Paykel 230V
chest freezer (run as a fridge) used 768Wh. The same unit uses 389Wh on 12/24 Volts.
I'd also suggest that if you are using a unit designed as a freezer, you may, in some cases, need to change the thermostat.
Consult your refrigeration mechanic about this.
The other point you may wish to consider is that any modifications (like disconnecting the auto defrost etc) may void the manufacturer's warranty.
This is particularly true if a qualified person does not carry it out.
Cheers from Dave and all the RPC crew.
Dave Lambert (Director)
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