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Page 133
C14-1 DIAGRAM WITH D5 DIAGRAM
Honeywell W973 Control System and T7067 Thermostat with Modulating Economizer and Warm-up
7-C14-1 Section with D5 Section
The Honeywell W973 control, when added to the GCS16 system, allows the use of electronic
ramping thermostat, discharge temperature sensors, return air temperature sensors and/or
remote thermostats and transmitters. The W973 control system is designed for use with
Honeywell T7067 electronic ramping thermostat and Honeywell Q667 subbase. An intercon
necting W973 relay kit must be used to adapt the W973 to the GCS16.
NOTE - Use of the Honeywell W973 controller with the GCS16 requires use of the W973
relay kit and CMC3-1 time clock. This arrangement is designed for use with Honeywell T7067
electronic ramping thermostat and Honeywell Q667 subbase or equivalents. A remote set
point transmitter with either a return air temperature sensor or a room temperature sen
sor may be used in place of the room thermostat. None of the thermostat/sensor combina
tions affect the following operation sequence.
NOTE - In order to understand how these optional controls affect the operation of the GCS16,
you must first understand howall GCS16 components work. Refer to the operation sequence
for basic unit operation.
The W973 plugs in to the GCS16 inside the control makeup area of the GCS16 blower
compartment (see figure 98). Jack J17 connects to unit plug P16. Then plug P17 connects to
jack J16. Jumper plug J19 supplied with the W973 must be connected to plug P19 on the
W973. Jumper plug J12 also supplied with the W973 is not used with GCS16 series units and
may be discarded.
The W973 relay kit mounts inside the control makeup area of the GCS16 blower compartment
next to the W973. No wiring is required. GCS16 jumper plug P3 is removed and discarded.
Warmup kit harness plug P6 connects directly into GCS16 jack J3 in the blower compartment.
The warmup kit mounts next to the W973 relay kit as shown in figure 99. Wiring pigtails must
be connected as shown in the wiring diagram on the adjacent page. Otherwise, all other con
nections are made using jackplugs. Warmup kit harness plug P8 connects directly into jack J6
of the W973 relay kit. Economizer plug P4 plugs in to jack J8 of the warmup kit.
WARNING - CONNECT ONLY RELAY KITS DESIGNED FOR THIS CONTROL SYSTEM.
RELAY KITS DESIGNED FOR OTHER CONTROL SYSTEMS ARE NOT COMPATIBLE
AND CONTROL DAMAGE OR FAILURE WILL RESULT. FOR EXAMPLE, A W7400
RELAY KIT MUST NEVER BE CONNECTED TO A W973 CONTROL SYSTEM.
WARNING - RELAY KITS MUST BE CONNECTED IN THE ORDER THEY APPEAR ON
THE UNIT CONTROL WIRING DIAGRAM ON THE ADJACENT PAGE.
Operation Sequence:
1- Room temperature is controlled by a thermistor located in A2 (T7067A) thermostat or remote
A2 (T7067B) transmitter (RT2). As room temperature changes, thermistor resistance also
changes. If room temperature goes up, thermistor resistance goes down. If room tempera
ture goes down, thermistor resistance goes up. The thermistor allows 2.5V/F
(1.4V/C
).
When the cooling setpoint is crossed, the T7067 begins transmitting a cooling ramp from ter
minal 4 through TB1-4 to terminal 4 of A1. As room temperature increases, the cooling ramp
increases from 1 to 16 VDC.
When the heating setpoint is crossed, the T7067 begins transmitting a heating ramp from ter
minal 5 through TB1-5 to terminal 5 of A1. As room temperature increases, the cooling ramp
increases from 1 to 16 VDC.
2- Generally, A1 cooling contacts C1 close when voltage input to A1 terminal 4 reaches 4VDC.
C2 cooling contacts close when voltage input to A1 terminal 4 increases to 5 VDC.
A1 heating contacts H1 close when voltage input to A1 terminal 5 reaches 4 VDC and H2 con
tacts close when the voltage ramp increases to 5 VDC.
3- To provide anticipation, discharge sensor RT1 modifies the voltage that A1 receives at termi
nals 4 & 5. If discharge temperature goes up, RT1 resistance goes down. For every 25
F
change in discharge temperature, A1 will offset the setpoint 1
F. As a result, RT1 may require
a higher or lower voltage input to A1 terminals 4 or 5 before closing C1, C2, H1 or H2.
Day Operation (Occupied Period):
4- Time clock CMC3-1 contacts open. Relay K38 in relay kit de-energizes.
5- Contacts K38-1 open, removing setback resistor R4 from the circuit.
Contacts K38-2 open, removing setup resistor R5 from the circuit.
Contacts K38-3 close, control of blower B3 is shifted to A2 terminal 10. During day operation
when contacts K38-3 are closed, blower B3 is controlled by A2 terminal 10 and can operate in
ON or AUTO modes.
6- Power is supplied to the economizer continuously through blower relay K3-2. Contacts K7-1
and K41-3 control economizer operation.
7- Initial heat demand (voltage ramp from A2 terminal 5) closes H1. First stage heat and relay
K40 energize.
8- Contacts K40-1 open to lock out the economizer for the first heating demand.
9- Increased heating demand (increased voltage from A2 terminal 5) closes H2 (not used in this
application).
10- When the first heating demand is satisfied, the heating section of the GCS16 and relay K40 are
deenergized.
11- Contacts K40-1 close and power reaches time delay DL7. DL7 begins a 30 second count be
fore closing.
12- If a second heat demand reaches relay K40 within 30 seconds, K40-1 opens, time delay DL7
resets and the economizer locks out (warmup continues) during the second call for heat.
13- If a second demand does not reach relay K40 within 30 seconds, K40-1 remains closed and
time delay DL7 closes at the end of 30 seconds.
14- When time delay DL7 closes, relay K41 is energized.
15- Contacts K41-1 close to lock-in economizer. The economizer remains locked-in until contacts
K42-1 open (at night or during unoccupied periods).
Contacts K41-2 open (not used in this application).
Contacts K41-3 close to supply power to the economizer.
Contacts K41-4 open (not used in this application).