830841-BIM-D-0512
26
Johnson Controls Unitary Products
Defrost Termination –
Same as when Outdoor Ambient Temperature is above
Balance Point as previously discussed.
Third Stage Heat Call –
“Y1”, “Y2”, “W2” and “G” from the
thermostat:
Depending on the model of the thermostat, the dead band, and/
or time delay settings programmed into the thermostat, there
can be additional delays between 2
nd
and 3
rd
stage heating
operation.
Mechanical heating will operate for 30 seconds after receiving a
“W2” call from the thermostat when control voltage from “Y1”
and “Y2” are present. After 30 seconds, mechanical heat is de-
energized and the unit operates using gas heat only for the
remainder of the heating call.
The unit will continue to operate at full capacity (Gas Heat) until
the thermostat is satisfied.
Outdoor Ambient Temperature is Below the Low Temperature
Cutout
When the Outdoor Ambient Temperature is below the Low
Temperature Cutout setting on the YorkGuard VI Defrost
Control Board, mechanical heat is not allowed. The Residential
Dual Fuel Package Units will operate using gas heat only.
First Stage Heat Call
On a first stage heating call, the thermostat sends 24 Volts AC
out of the “Y1” terminal to the CFM Selector Board (CFMCB)
and to the “Y1” terminal of the YorkGuard VI Defrost Control
Board (DCB).
If the outdoor ambient temperature sensor connected to the
DCB indicates that the temperature is below the Low
Temperature Cutout (LTCO) set point, the DCB will provide 24
Volts AC out of the “W1OUT” terminal.
24 Volts AC from passes through the CFM Selector Board
(CFMCB) and is provided to the “W1” terminal on the Spark
Ignition Control Board (EMCB).
The EMCB will send 120 Volts AC out of the “H-IND” terminals
energizing the DM in high speed for pre-purge of the heat
exchanger. The control board continues the pre-purge cycle for
approximately 15 seconds and then initiates an ignition trial
period.
The control board energizes the pilot terminal “P” on the gas
valve and spark ignition for up to an 85 seconds. When the
Flame Sensor senses pilot flame (minimum of 0.2
microamperes), the pilot valve remains energized and spark
ignition is de-energized.
The EMCB control board provides a 2 second flame
stabilization period prior to energizing the main gas valve. The
EMCB provides 24 Volts AC to the “M” and “HI” terminals of the
gas valve, operating the gas heat section at full fire for
approximately 60 seconds.
The EMCB then de-energizes “H-IND” at the DM and provides
120 Volts AC out of the “IND” terminal reducing the DM to low
speed. Control voltage is also removed from “HI” at the gas
valve reducing gas heat operation to low fire operation.
Second Stage Heat Call
If the thermostat initiates a second stage heating call at the “Y2”
terminal when the outdoor ambient temperature is below the
LTCO, 24 Volts AC is immediately sent to the “Y2” terminal on
the DCB. This provides control voltage to the “W2” terminal on
the EMCB energizing the gas valve at high fire. The EMCB will
also send 120 Volts AC out of the “H-IND” terminal and remove
120 Volts AC from the “IND” terminal energizing the DM at high
speed.
The unit will continue to operate at full capacity (Gas Heat) until
the thermostat is satisfied or the call is reduced to “Y1” first
stage heating only.
If the call is reduced to a first stage call, the gas heat section will
reduce to low fire.
If the heating call is satisfied, the gas heat section is de-
energized and the DM will operate for a 30 second post purge
cycle. At the same time the blower will operate until the on-
board Blower Off Delay selection of 60, 90, 120, or 180
seconds expires.
Emergency Heat Call
When the thermostat is set to emergency heat on the
Residential Dual Fuel Package Units, 24 Volts AC is provided to
the “W1” terminal on the Spark Ignition Control Board (EMCB).
The EMCB will send 120 Volts AC out of the “H-IND” terminals
energizing the DM in high speed for pre-purge of the heat
exchanger. The control board continues the pre-purge cycle for
approximately 15 seconds and then initiates an ignition trial
period.
The control board energizes the pilot terminal “P” on the gas
valve and spark ignition for up to an 85 seconds. When the
Flame Sensor senses pilot flame (minimum of 0.2
microamperes), the pilot valve remains energized and spark
ignition is de-energized.
The EMCB control board provides a 2 second flame
stabilization period prior to energizing the main gas valve. The
EMCB provides 24 Volts AC to the “M” and “HI” terminals of the
gas valve, operating the gas heat section at full fire for
approximately 60 seconds.
The EMCB then de-energizes “H-IND” at the DM and provides
120 Volts AC out of the “IND” terminal reducing the DM to low
speed. Control voltage is also removed from “HI” at the gas
valve reducing gas heat operation to low fire operation.
After operating at low gas heat for 15 minutes, the DCB will
provide 24 Volts AC to the “W2” terminal on the EMCB
energizing the gas valve at high fire. The EMCB will also send
120 Volts AC out of the “H-IND” terminal and remove 120 Volts
AC from the “IND” terminal energizing the DM at high speed.
