Refrigeration – Automatic control – Preventing – removing or handling atmospheric condensate
Patent
1985-05-22
1986-05-27
Tanner, Harry B.
Refrigeration
Automatic control
Preventing, removing or handling atmospheric condensate
62155, F25D 2106
Patent
active
045907714
ABSTRACT:
By sensing the outdoor ambient temperature and the outdoor coil temperature in a heat pump when the outdoor coil is frost-free, a control system determines the split or difference that will later exist between those temperatures (the coil temperature drops as frost accumulates) when sufficient frost has built up on the outdoor coil to necessitate defrosting. When that defrost temperature split, called the Normal Defrost Value or NDV, is exceeded, defrost is initiated and the coil will be defrosted. Since the amount of frost that may have already accumulated on the coil is unknown when the control system is initially powered up (such as when power is restored after an outage), the control system calculates, from the current outdoor ambient temperature, an assumed value for the coil temperature which is likely to exist if the coil were frost-free. The first NDV determined after power up is based on the assumed coil temperature. As a safety feature to prevent damage to the heat pump, a Default Defrost Value (DDV), which is the maximum temperature split that will be allowed between the outdoor ambient temperature and the coil temperature, is calculated based on the current outdoor temperature. If the coil temperature ever drops below the outdoor temperature to an extent greater than the DDV, the outdoor coil is defrosted. If two successive default defrosts are requested within one hour, the heat pump's compressor is turned off and locked out.
REFERENCES:
patent: 4302947 (1981-12-01), Mueller et al.
patent: 4328680 (1982-05-01), Stamp et al.
patent: 4338790 (1982-07-01), Saunders et al.
patent: 4373349 (1983-02-01), Mueller
patent: 4417452 (1983-11-01), Ruminsky et al.
patent: 4474024 (1984-10-01), Eplett et al.
Dellinger Wayne D.
Harnish James R.
Shaffer Jacob E.
Borg-Warner Corporation
Tanner Harry B.
Tracy James E.
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