A method comprises the steps of (a) providing a refrigeration unit having a refrigerated
or heated space and at least one measured operating parameter, (b) providing heat
to the refrigerated space when the at least one measured operating parameter exceeds
a first threshold, (c) terminating provision of heat when the at least one measured
operating parameter exceeds a second threshold, and repeating steps b-c when the
at least one operating parameter falls below the first threshold. In using this
method, the unit can be operated continuously, with substantially higher refrigerant
mass flow and evaporator pressure then in the prior art. Higher refrigerant mass
flow rate and higher evaporator pressure improve oil return to the compressor,
thus reducing the like hood of compressor damage due to oil pump out.