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 74 ).
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 74: ETC Flash Codes
Red LED Green LED
1. Power Failure Off Off
2. Control Failure On Off
3. Blackout Condition 7 pulses Off
4. Brownout Condition 6 pulses Off
5. Limit Switch Fault 8 pulses Off
6. Dual HPS Faults 3 pulses 3 pulses
7. HPS1 Fault Off 3 pulses
8. HPS2 Fault 3 pulses Off
9. Dual LPS Faults 4 pulses 4 pulses
10. LPS1 Fault Off 4 pulses
11. LPS2 Fault 4 pulses Off
12. Dual FS Fault 5 pulses 5 pulses
13. FS1 Fault Off 5 pulses
14. FS2 Fault 5 pulses Off
15. GV False Proof 9 pulses Off
16. GV Lost Proof 10 pulses Off
17. 2nd Stage in ASCD (Heat/Cool) Rapid Flash On
18. 2nd Stage On (Heat/Cool) On On
19. 1st Stage in ASCD (Heat/Cool) Off Rapid Flash
20. 1st Stage On (Heat/Cool) Off On
21. Fan Only (no Heat/Cool) Off Fast Heartbeat
22. No Alarms in Memory 2 pulses 2 pulses
23. Normal Idle Off Slow Heartbeat
24. Factory Test Mode Rapid Flash Rapid Flash
INSTALLATION MANUAL ZY SERIES 3-10ton 60 Hertz R-410A114
Johnson Controls Ducted Systems
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