York B3CH 048 and 060 Cooling System, Preliminary Operation Cooling, Defrost Initiation Times

035-12984-001-A-0204

OPERATION

screw fully clockwise and then energize and de-energize terminals “R” to “G”. With terminals “R” to “G” energized, turn the minimum position screw counterclockwise until the desired minimum position has been attained.

11. Replace the filter section access panel.

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 opens to shut down the compressor.

PRELIMINARY OPERATION COOLING

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

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.

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 2°C (35°F) and will extend the defrost initiation time periods below 2°C (35°F). The control is factory set to defrost at 110 minutes (T3), but it can be field

FIG. 7 - DEFROST INITIATION TIMES

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.

EXAMPLE: If the time is factory set on pin T-3 (110 minutes at 2°C (35°F) outdoor) and the outdoor temperature climbs to 7°C (45°F), the time initiation cycle decreases to 100 minutes.

If the outdoor temperature drops to -12°C (10°F) where ice is less likely to form, the 110 minute interval increases to 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 -2°C (28°F).

Defrost terminates when the liquid line sensor reaches 13°C (55°F) or after 10 minutes.

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

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