Re: Measuring refrigeration power draw.

If the system is based on a Danfoss compressor with an electrical unit older
than about 12 months and doesn't have a "smart" controller like Fridoboat
SSC or Isotherm ASU it will run at a constant speed and use a constant
current so you only need total run time to calculate the relative power
usage. With the new Danfoss AEO electronics or a smart control the speed
varies and you do have to measure the current draw over time.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"GBM" <yachtingEXCLUDE@xxxxxxxxx> wrote in message
news:fHa8g.72806$fd.39308@xxxxxxxxxxxxxxxxxxxxx

"Terry K" <terry2@xxxxxxxxxxx> wrote

After noting a single cycle of start, run, stop, you then have the
onerous task of sitting beside the fridge all day with a beer or two,
counting, averaging the cycles per hour.

From a warm case of beer start, to keep score, or for all day, opening
the door for 20 seconds, closing it every hour, to work up a "typical"
duty cycle.

Alternatively, charge the battery check the specific gravity, let it
run for say 12 hours, then measure the sg of the battery, and
interpolate the number of amp hours from your battery specs.

How critical is all of this?

It's not too critical - Just want to decide whether or not additional
(difficult to add) insulation is warranted.

I don't really need a typical duty cycle - just let the unit run with box
closed for say 12-24 hours, then add temporary insulation and let it run
again. If the external temperature changes this could upset the results.
So
need to do test when weather is stable for a few days. I could measure
temperatures, acid SG and battery voltage at intervals.

I think this may give me an idea of whether or not to add the extra
insulation.

Thanks for suggestions!

GBM






Your time is say, 10 bucks an hour. The test equipment to do this
properly starts out ridiculously expensive, then proceeds toward the
incredulous, depending on the degree of accuracy desired.

A laptop data port, some software, an interface, or multimeter with
data output would do for centibucks what you could accomplish by rule
of thumb for a little effort.

Actually, I wonder if a digital audio recorder like windat might record
DC voltages across a current shunt in the DC supply. You would need to
test and calibrate the data.

Terry K





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