York 2000 Cooling System, Preliminary Operation Cooling, Cooling Sequence Of Operation

511.06-N5Y

OPERATION

COOLING SYSTEM

The unit has an air-cooled condenser and is factory-charged with Refrigerant-22.

The compressor is hermetically sealed, internally sprung, mounted on spring isolators and inherently (internally) protected. If there is an abnormal temperature rise in the compressor, the protector will open to shut down the compressor.

PRELIMINARY OPERATION COOLING

After the installation has been completed, the crankcase heater of the compressor must be energized for at least 4 hours before starting the unit. After this initial warm-up, the compressor should be given three false starts (energized just long enough to make a few revolutions) with a 5 minute delay between each start before being put into full time service.

NOTE: Prior to each cooling season, the crankcase heater must be energized at least 10 hours before the system is put into operation.

MINUTES	250
	200		T3 - 110 Minute Setting (Factory Set Point)
CYCLES,
	150				T2 - 80 Minute Setting
DEFROST
	100
BETWEEN	50
				T1 - 50 Minute Setting
TIME
	0
	-10	0	10	20	30	40	50	60
			OUTDOOR AMBIENT, DEG. F

FIG. 7 - DEFROST INITIATION TIMES

EXAMPLE: If the time is factory set on pin T-3 (110 minutes at 35° F outdoor) and the outdoor temperature climbs to 45° F, the time initiation cycle will decrease to every 100 minutes.

COOLING SEQUENCE OF OPERATION

When the thermostat calls for cooling, the compressor and the outdoor fan motor will be energized through terminal "Y1" and the supply air blower motor will be energized through terminal "G" (if the fan switch on the subbase is set in the "AUTO" position). The supply air blower motor will run continuously if the fan switch is set in the "ON" position.

The reversing valve is energized thru the "O" circuit when the subbase is in the cooling mode.

HEATING SEQUENCE OF OPERATION

The following sequence of operation is based on using a standard YORK heat pump thermostat with two heating stages.

FIRST STAGE HEAT

When the thermostat calls for heating, the compressor and the outdoor fan motor will be energized through terminal "Y1" and the supply air blower motor will be energized through terminal "G" (if the fan switch on the subbase is set in the "AUTO" position). The supply air blower motor will run continuously if the fan switch is set in the "ON" position.

SECOND STAGE HEAT

If compressor operation can not satisfy the heating requirements, second stage heat will energize supplemental electric heat (if supplied) thru the "W1" circuit.

DEFROST SEQUENCE OF OPERATION

The BCH has a unique “ambient modified” time-temperature defrost control that automatically adjusts to changes in the outdoor temperature. The defrost control will shorten the defrost initiation time periods above 35° F and will extend the defrost initiation time periods below 35° F. The control is factory set to defrost at 110 minutes (T3), but it can be field adjusted to defrost at 80 minutes (T2) or 50 minutes (T1) in areas with high humidity.

The curve in Figure 7 shows how defrost initiation times are automatically compensated for changes in outdoor temperature.

If the outdoor temperature drops to 10° F where ice is less likely to form, the 110 minute interval will extend to every 150 minutes.

Two requirements must be met before a defrost cycle can be initiated.

1.The defrost time cycle must be complete.

2.The liquid line temperature must be less than 28° F.

Defrost will terminate when the liquid line sensor reaches 55° F or after 10 minutes.

The defrost time cycle will restart 10 minutes after the start of the defrost cycle even though the liquid sensor terminated defrost after 3 minutes.

During troubleshooting, the defrost time can be reduced to 20 seconds by shorting out the SW1 test pegs on the module. The pegs are 1/2" long, 3/16" apart and are mounted on a white base. See Figure 8.

T2 - 80 MINUTE SETTING
T3 - 110 MINUTE SETTING
(Factory Set Point)	T1 - 50 MINUTE SETTING

SHORTING PEGS TO

OVERRIDE TIMER

FOR SERVICE

MOVABLE JUMPER

WIRE TO CHANGE

DEFROST TIMER

FIG. 8 - AMBIENT MODIFIED TIME/TEMPERATURE CONTROL

12 Unitary Products Group