Electric Heating Sequence Of Operations - York SUNLINE MagnaDRY WR300 Installation Manual

284813-YIM-C-1008
Air Flow
Evaporator
Coil
FS
Sol 1
Sol 2
FIGURE 24 - SYSTEM PIPING SCHEMATIC

ELECTRIC HEATING SEQUENCE OF OPERATIONS

The following sequence describes the operation of the
electric heat section.
For units with VFD and electric heat, the speed
of the indoor blower motor continues to be con-
trolled by duct static pressure via the VAV con-
trol board.
If there are VAV boxes present in the duct sys-
tem, the boxes must be driven to the full-open
position using a customer-supplied power
source to assure adequate airflow across the
heating elements.
58
Piping T
TXV
Check
Valve
Air Flow
Hot Gas
Coil
Open in
Bleed Line to clear
Suction line
Cooling
the Hot Gas Coil
bleed
when it is not in use
Open in
Reheat
Check
Valve
HPS
Indoor Blower
Refrigerant flow in cooling mode
Refrigerant flow in reheat mode
LPS
Piping T
Accumulator
Compressor
Single-stage heating (applies only to 18 KW heater, all
other heaters MUST use a two-stage thermostat):
a. Upon a call for heat by the thermostat, the heater
contactor (6M) will be energized. After completing
the specified fan on delay for heating, the UCB will
energize the blower motor.
b. The thermostat will cycle the electric heat to satisfy
the heating requirements of the conditioned space.
Two-stage heating (applies to all heaters except 18
KW):
a. Upon a call for first-stage heat by the thermostat, the
heater contactor (6M) (6M & 7M on 72 KW, 240V)
will be energized. After completing the specified fan
on delay for heating, the UCB will energize the
blower motor.
Condenser
Fan
Condenser
Coil
HPS
C1
Hot Gas Re-Heat
Solenoid Valve
(Sol 3)
Johnson Controls Unitary Products