"Will Dean" wrote in message
...
"Vortex" wrote in message
.. .

AFAIK the boiling point of ammonia (used in CFC free freezers is
about -30C) so I can imaging ambient temperatures in this order will
cause problems.

It's not really relevant to talk about the boiling point of refrigerants
without saying something about pressure - the way a fridge works is by
*changing* the boiling point of a liquid. Besides, I very much doubt your
freezer has ammonia in it - the CFC-free ones use hydrocarbon-based
refrigerants. Ammonia is used in industrial plant and absorption fridges.

I suspect that one reason for the caution about extreme temperatures is
that domestic fridges/freezers use a capiliary tube as an expansion
device, rather than the more sophisticated thermostatic devices used in
commercial plant. Because the capiliary is just a fixed flow restriction
rather than a proper temperature/pressure regulator, it's specified on the
basis of fairly narrowly constrained pressure/temperature conditions
throughout the plant.

A very cold condenser will give low high-side pressures which might be
outside those for which the capiliary was designed - it can also cause an
excessive proportion of the charge to hang around within the condenser.

All they're really saying in the instructions is that they designed the
freezer to perform to specification with a certain external temperature
range, and that outside that range it may not meet the spec.

Will




Thanks Will,

Given the minimal number of days/nights when temperature is sub-zero I think
I will prove empirically how things work.

Also I have a good excuse to research some kind of recording digital/usb
thermometer!

david