I cannot see why an ammeter should not be in the power line. You only need
to measure the current once.

To measure the time it is on, assuming a 12v fridge, the cheapest way is to
get an "old" 12v analog (mechanical movement) car clock and wire it after
the thermostat, this will then give you the time the fridge runs. A car
scrapyard is the place to visit.

Alec


"GBM" wrote in message
...
What is the best way of measuring the power drawn by a boat's
refrigeration
unit?

Is there a way to do this without any expensive instruments?

I was thinking of installing an ammeter in the line to the compressor to
determine the current draw, but manufacturer does not recommend this.
Even
with that, I would need an hour meter or some such device to know how
often
and for how long the compressor runs.

I would like to test existing installation, then add some "temporary"
insulation to the inside of the box and then test again to see what
improvement I might get if I added permanent insulation.

GBM