York International ZQ Series Installation Manual page 67

Gas Valve
The UCB monitors the gas valve (GV). Any time the
UCB senses voltage at the GV without a call for heat
for a continuous five-minute period, the UCB will
lock on the indoor blower and flash a code on the
ETC, or will send error message to the LCD Display
on the Smart Equipment™ board. When the UCB
no longer senses voltage at the GV the UCB will de-
energize the indoor blower after the expiration of
the indoor blower heating off delay.
If the voltage has been sensed at the GV for at least
15 seconds during the fan on delay for heating and
the UCB no longer senses voltage at the GV (W1
call for heat removed or an ICB fault exists), then
the UCB forces the indoor blower on for the indoor
blower heating off delay.
The gas valve is of the redundant type. If for any
reason the main gas valve fails in the open position,
then the redundant valve ahead of the main gas
valve will shut off the flow of gas to both the pilot
and main gas valves.
Centrifugal Switch
The centrifugal switch is mounted on the end of
the draft motor and it is an integral part of the
motor assembly. On a call for heat, the ICB checks
the centrifugal switch (CS) for open state before it
energizes the draft motor. If it is closed, then the
ICB will lock out the furnace and flash a code. If
open, then the ICB will energize the draft motor
and verify that the switch closes before initiating
the purging and ignition sequence. If at any time
during furnace operation the centrifugal switch
opens, then the ICB will de-energize the pilot and
main gas valves and monitor the centrifugal switch.
If the centrifugal switch closes and the call for heat
still exists, then the ICB will retry the purging and
ignition sequence.
Roll-out Switch
This temperature sensitive switch is located in the
burner vestibule just above the right hand side
of the burner assembly. In the event of the flame
spilling out into the burner manifold area the roll-
out switch will open, the ICB will close both the main
and pilot gas valves and flash a code (see Table 57 ).
The ICB will not retry the ignition sequence during
the same call for heat.
Flame Sense Circuit
The flame sensor is mounted on the left hand side
of the burner assembly and is positioned such that
the pilot flame surrounds the tip of the sensor. On
a call for heat the ICB checks for the flame sense
circuit to be open. If open, then the ICB initiates the
purging and ignition sequence. Once the pilot flame
is present, the ICB monitors the flame sense circuit
for pilot flame stability. If the pilot flame is unstable
or lost completely, then the ICB will immediately
close both the pilot and main gas valves. The ICB
will retry the purging and ignition sequence. If the
flame is unstable or lost more than 16 times during
the same call for heat, then the ICB will lock out
furnace operation for 5 minutes.
Flash Codes or Error Messages
The UCB will initiate a flash code on the ETC, or
send an error message to the LCD Display on Smart
Equipment™ associated with errors within the
system.
Table 57: ETC Flash Codes
1. Power Failure
2. Control Failure
3. Blackout Condition
4. Brownout Condition
5. Limit Switch Fault
6. Dual HPS Faults
7. HPS1 Fault
8. HPS2 Fault
9. Dual LPS Faults
10. LPS1 Fault
11. LPS2 Fault
12. Dual FS Fault
13. FS1 Fault
14. FS2 Fault
15. GV False Proof
16. GV Lost Proof
17. 2nd Stage in ASCD (Heat/Cool)
18. 2nd Stage On (Heat/Cool)
19. 1st Stage in ASCD (Heat/Cool)
20. 1st Stage On (Heat/Cool)
21. Fan Only (no Heat/Cool)
22. No Alarms in Memory
23. Normal Idle
24. Factory Test Mode
INSTALLATION MANUAL ZQ SERIES 3 - 5 ton 60 Hertz R-410A
Johnson Controls Ducted Systems
Red LED Green LED
Off Off
On Off
7 pulses Off
6 pulses Off
8 pulses Off
3 pulses 3 pulses
Off 3 pulses
3 pulses Off
4 pulses 4 pulses
Off 4 pulses
4 pulses Off
5 pulses 5 pulses
Off 5 pulses
5 pulses Off
9 pulses Off
10 pulses Off
Rapid Flash On
On On
Off Rapid Flash
Off On
Off Fast Heartbeat
2 pulses 2 pulses
Off Slow Heartbeat
Rapid Flash Rapid Flash
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