Patent ID: 6334321
Filing Date: 2002-01-01
Classification: F25B

Abstract:
A method for controlling a coil defrosting cycle in a reversible heat pump system using a refrigerant cycle, comprising the steps of:monitoring a plurality of performance variables of said heat pump system; determining a final frost factor from said plurality of performance variables; and defrosting said coil after said frost factor reaches a predetermined value and certain conditions of said system are met; wherein said step of monitoring includes beginning a first timer; periodically monitoring an outside temperature (OAT) near said coil; and periodically monitoring a saturated suction temperature (SST) of said heat pump system; and wherein said step of determining include determining a first temperature delta as a reference; determining a second temperature delta as the OAT minus the SST; determining a change in said second temperature delta by comparing said second temperature to said first temperature delta; determining a first frost factor as said change times a gain factor if said change is not greater than a specified amount, and determining said first frost factor as said change times said gain factor plus an integrator factor if said change is greater than said specified amount; for each subsequent period, determining a second frost factor as said change times said gain factor if said change is not greater than said specified amount, and determining said second frost factor as said change times said gain factor plus said integrator factor if said change is greater than said specified amount; and selecting said final frost factor as a greater of said first frost factor and said second frost factor.