York BP120 Motor Sheave Datum, Sequence of Operations Overview, Cooling Sequence of Operation

66307-YIM-B-0606

TABLE 32: MOTOR SHEAVE DATUM

	1VM50x7/8		1VP56x1-1/8
(1-1/2 & 2 HP Motor)			(4 HP Motor)
Turns Open		Datum Dia.	Turns Open	Datum Dia.
		in. (mm)		in. (mm)
0		4.4 (111.7)	1	5.3 (134.6)
1/2		4.3 (109.2)	1-1/2	5.2 (132)
1		4.2 (106.6)	2	5.1 (129.5)
1-1/2		4.1 (104.1)	2-1/2	5.0 (127)
2		4.0 (101.6)	3	4.9 (124.4)
2-1/2		3.9 (99)	3-1/2	4.8 (121.9)
3		3.8 (96.5)	4	4.7 (119.3)
3-1/2		3.7 (94)	4-1/2	4.6 (116.8)
4		3.6 (91.4)	5	4.5 (114.3)
4-1/2		3.5 (88.9)	5-1/2	4.4 (111.7)
5		3.4 (86.3)	6	4.3 (109.2)

OPERATION

SEQUENCE OF OPERATIONS OVERVIEW

For the Predator® series of units, the thermostat makes a cir- cuit between "R" and "Y1" for the first stage of cooling.

The call is passed to the Unit Control Board (UCB), which then determines whether the requested operation is available and, if so, which components to energize.

For heating, the thermostat makes a circuit between “R” and “W1” for the first stage heating. The UCB energizes the com- pressors #1 and #2 and their condenser fans. The “W1” call also energizes a separate relay (RY1), de-energizing the reversing valve allowing the unit to run in the heating mode. A time/temperature control operates the defrost cycle.

The thermostat makes a circuit between “R” and “W2” for the second stage of heating. The UCB passes the “W2” signal on to the electric heaters if available. In both cases, when the “W1” call is sensed, the indoor blower is energized.

If at any time a call for both heating and cooling are present, the heating operation will be performed. If operating, the cool- ing system is halted as with a completion of a call for cooling. Heating always takes priority.

COOLING SEQUENCE OF OPERATION

CONTINUOUS BLOWER

By setting the room thermostat fan switch to "ON," the supply air blower will operate continuously.

INTERMITTENT BLOWER

With the room thermostat fan switch set to "AUTO" and the system switch set to either the "AUTO" or "HEAT" settings, the blower is energized whenever a cooling or heating opera- tion is requested. The blower is energized after any specified delay associated with the operation.

When energized, the indoor blower has a minimum run time of 30 seconds. Additionally, the indoor blower has a delay of 10 seconds between operations.

NO OUTDOOR AIR OPTIONS

When the thermostat calls for the first stage of cooling, the low-voltage control circuit from “R” to “Y1” and “G” is com- pleted. The UCB energizes the economizer (if installed and

free cooling is available) or the first available compressor* and the condenser fans. For first stage cooling, compressor #1 is energized. If compressor #1 is unavailable, compressor #2 is energized. After completing the specified fan on delay for cooling, the UCB will energize the blower motor.

When the thermostat calls for the second stage of cooling, the low-voltage control circuit from “R” to “Y2” is completed. The control board energizes the first available compressor. If free cooling is being used for the first stage of cooling, com- pressor #1 is energized. If compressor #1 is active for first stage cooling or the first compressor is locked-out, compres- sor #2 is energized. In free-cooling mode, if the call for the second stage of cooling continues for 20 minutes, compres- sor #2 is energized, provided it has not been locked-out.

If there is an initial call for both stages of cooling, the UCB will delay energizing compressor #2 by 30 seconds in order to avoid a power rush.

Once the thermostat has been satisfied, it will de-energize Y1 and Y2. If the compressors have satisfied their minimum run times, the compressors and condenser fans are de-ener- gized. Otherwise, the unit operates each cooling system until the minimum run times for the compressors have been com- pleted. Upon the final compressor de-energizing, the blower is stopped following the elapse of the fan off delay for cooling.

*To be available, a compressor must not be locked-out due to a high or low-pressure switch or freezestat trip and the anti-short cycle delay (ASCD) must have elapsed.

ECONOMIZER WITH SINGLE ENTHALPY SENSOR -

When the room thermostat calls for "first-stage" cooling, the low voltage control circuit from "R" to "G" and "Y1" is com- pleted. The UCB energizes the blower motor (if the fan switch on the room thermostat is set in the "AUTO" position) and drives the economizer dampers from fully closed to their min- imum position. If the enthalpy of the outdoor air is below the set point of the enthalpy controller (previously determined),

Unitary Products Group 33