515.28-N3Y
12 Unitary Products Group
YORKGUARD V continuously monitors temperature sensors
which measure outdoor ambient temperature and the tem-
perature of the refrigerant liquid at the outdoor coil. When the
relationship between these temperatures reaches a value
which has been determined by the electronic control to be
indicative of need for defrost, the defrost cycle is initiated pro-
vided the liquid temperature is colder than 40
o
F.
YORKGUARD V energizes the fan relay which stops the out-
door fan and energizes the reversing valve relay to switch the
refrigerant circuit to cooling. YORKGUARD also energizes
the first step of supplemental heat (either electric heat or fos-
sil fuel) to prevent cold drafts in the conditioned space.
The defrost cycle is terminated when:
1. The liquid line temperature exceeds 70
o
F, or,
2. 14 1/2 minutes from the initiation of the defrost cycle, or,
3. the liquid line reaches 45
o
F and holds above 45
o
F for a
continuous 3 minutes.
YORKGUARD V de-energizes the fan relay and reversing
valve relay to return unit to normal heating cycle.
INDICATIONS OF PROPER OPERATION
COOLING
Cooling operation is the same as any conventional air condi-
tioning unit.
1. The outdoor fan should be running, with warm air being
discharged from the top of the unit.
2. The indoor blower (furnace or air handler) will be operat-
ing, discharging cool air from the ducts. coils or other
parts in the air circuit. Clean as often as necessary to
keep the unit clean. Use a brush, vacuum cleaner
attachment, or other suitable means.
3. The vapor line at the outdoor unit will feel cool to the
touch.
4. The liquid line at the outdoor unit will feel warm to the
touch.
HEATING
Indications of proper Heating operation is as follows:
1. The outdoor fan should be running, with cool air being
discharged from the top of the unit.
2. The indoor blower (furnace or air handler) will be opera
ing, discharging warm air from the ducts.
3. The vapor line at the outdoor unit will feel warm to the
touch.
4. The liquid line at the outdoor unit will feel cool to the
touch.
FIGURE 9 : YORKGUARD "V" MODULE
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