Help explaining power usage spikes

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Re: Help explaining power usage spikes

Postby Warpspeed » Sun Dec 24, 2017 11:16 am

I bought it (very cheaply) secondhand, but an internet search revealed 2.5 stars out of five, which is probably not great.

A couple of years ago I did an energy audit of every electrical item in the house.

Whirlpool WR1D41TW 410 Litres frost free fridge/freezer.
Monitored in mid winter, "on" duty cycle 19%.
Off power 0.5 watts
Running, 140 watts
Defrost unknown at that stage, but later chasing a fault the heating element had 350W tag on it.
Max peak start up surge measured as 1,081 watts
728 watt/hours total consumption measured over 24 hours.

Its hardly cutting edge, but it definitely craps all over what it replaced !
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Re: Help explaining power usage spikes

Postby Warpspeed » Sun Dec 24, 2017 11:49 am

jules wrote:Wow, that's interesting but rather scary. An hour of 350W per day is a significant amount of power.

Thinking about all this a bit more.
You need to melt solid ice quickly before all the goodies in the fridge, and particularly the freezer spoil.
So there is a certain logic in fitting a very powerful heater that only needs to run for a comparatively short time.

The above 19% duty cycle is very accurate, and 19% of 140 watts is 26.6 watts average.
It was measured by counting mains cycles coming from a current transformer fitted into a short mains extension cable.
When the load came on it counted up 50 counts/second.
Over 24 hours it counted up intermittently giving me the total compressor and heater run time.

Over 24 hours that works out to 638.4 watt/hours for the compressor.
The actual consumption of 728 watt hours might suggest one defrost cycle of around 90 additional watt hours for defrosting power.
If defrost lasted 0.257 Hours at 350 watts, which is probably about right, that could explain it.
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Re: Help explaining power usage spikes

Postby jules » Sun Dec 24, 2017 1:22 pm

one defrost cycle of around 90 additional watt hours for defrosting power.
If defrost lasted 0.257 Hours at 350 watts,


A bit more modest but still interesting ... nice sleuthing work :D !
Primary system: .8KW Trina panels; Plasmatronics PL40; 1,000Ah VRLA 12X2V battery bank; 1.7KW Selectronic inverter. Off grid for 30 years.

Spares; 5 x 12V, 1,000 Ah batteries plus a couple of regulators
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Re: Help explaining power usage spikes

Postby Warpspeed » Sun Dec 24, 2017 1:27 pm

I could probably buy a more efficient refrigerator.

But I could probably do much better (per dollar spent) by adding more second hand solar panels.
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Re: Help explaining power usage spikes

Postby Privatteer » Wed Dec 27, 2017 6:17 am

Thimsneb wrote: That would mean a timer is installed in the meter box?


Assuming you have space in the board that's an easy job. I have one on my solar HWS so its booster only comes on for a hour at night.

The warmer it is the more efficient the heat exchange will be.
Stage 1:
Fronius Primo 5 + 6.6kW Canadian Solar
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