With the usual wiring, the compressor and fan come on at the same time. This
also happens in window units; compressor and condensor fan are wired on the
same switch. However, in too cold outdoor weather, this results in too cold
refrigerant feeding into the evaporator. Could easily be sub freezing temp
refrigerant, which would cause evaporator icing. Can also result in poor
liquid to vapor conversion in the evaporator. Leading to liquid return to
the compressor. The restaurant units I've serviced used a pressure control
to turn on the condensor fan. A thermal control could be used, but I've not
seen one.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"Old and Grunpy" t. wrote in message
...


I do a lot of commercial HVAC and refrigeration
work and when I have to run a piece of equipment
under low ambient conditions like the AC at a
restaurant which often has to run in the winter,
I install whats called a "head pressure" or "low
ambient" control. For the large AC unit that you
would find at a restaurant, it's a simple matter
of controlling the condenser fan. When the fan
is turned off by the electric controller, the head
pressure rises until reaching a preset limit then
the condenser fan comes back on. This keeps things
from freezing up and protects the compressor from
flooding with liquid freon.

Sorry Uncle that does not stop refrigerant from floading compressor
but actually does the oposit however it helps for compressor from
cutting out on low pressure switch and saving compressor from
pumping oil out of crankcase. However for the health of compressor
if unit is going to be use all year round additional items need to be
install
(depend) on system size, Crankcase heater, suction accumulator,
large Recivers also need rap around heater.