THM FC19 Intermittent - reset using Spectrolink controller

THM / THM5 / THM6 FC19 HX-OT2 open at start resetting using a Spectrolink controller 



Click link to view YouTube Video resetting FC19 using Spectrolink controller 



FC 19: HX OT2 open at start
The BSC has detected that heat exchanger over temperature switch 2 (HX OT2, 130 C) is  open at start-up and heat exchanger over-temperature switch 1 (HX OT1, 80, 90 or 110 C) is closed - the system goes to 'lockout 2' and can only be reset using a Braemar SCC from  service mode. This switch is connected in the 24V supply line to the gas valve on/off coil - if 
it is open the heater cannot operate. This indicates that either or both HX OT1 or HX OT2 is
faulty - both switches should be replaced.


Potential causes
• Wiring disconnected from HX OT2.

. Power outages whilst heater was running in heat mode and power came back on before OT switches had time to cool and reset

• Faulty HX OT1 (switch does not open when hot),  and/or faulty HX OT2 (switch open when cool)
Poor airflow due to restrictive ductwork - check ductwork guidelines have been followed 

Poor airflow due to low fan speed selected by users


Potential remedies
• Check wiring - reconnect if required.
• REPLACE BOTH HX OT1 and HX OT2:
.  After replacing both switches check system for normal  operation and normal air flow rates.
 

. If intermittent FC19 continues to be observed and it is apparent there are no airflow issues with heater (see potential causes above) there is potential the MCB (modulating board) is required to be replaced

Pt# 640365 PCB Modulating Control Board (MCB) NG

Pt# 643410 PCB Modulating Control Board (MCB) LPG 

For heaters pre-serial number T12071732 (2012 manufacture and earlier) - replace MCB (Pt# above NG or LPG) and Loom BSC to MCB Pt# 641096


Resetting using Spectrolink controller:
After the fault has been rectified, reset from service mode as follows:
• Press the ON/off button to turn the SCC off.
• Open door on SCC.
• To enter service mode press and hold 'zone 3' button for 5 seconds.
• Wait 5 seconds - latest recorded diagnostic code will display with 'F01', 'RESET' will flash.
• Press and hold the small recessed 'door button' and press the 'RESET' button.
• To clear recorded codes press and hold the 'FAN' button for 5 seconds.
• To exit service mode close the door on the SCC and press the ON/OFF button.