14.0 Fault Finding
43
Flow overheat
thermostat will not
reset until flow
temperature < 60° C.
Is
flow temperature
> 60° C ?
Fan protection
thermostat will not
reset until casing
temperature < 90° C.
Is
fan ambient
temperature > 90° C ?
Dry-fire lockout cannot
be reset until there is
water in the system
and the pump is on.
Is
water in system and
pump on ?
Replace interface PCB.
Control
knob switch short
circuit when on and
open circuit when
off ?
(K)
Wiring from control PCB
to interface PCB faulty.
Control
PCB control knob
switch pins short circuit
when on and open
circuit when
off ?
(J)
Replace control PCB.
YES
YES
YES
NO
NO
NO
NO
No Lockout Reset
No Fan
YES
YES
NO
NO
Is
flow temperature
thermistor between 0.5k
and 20k ? (measured at
flow temperature
thermistor)
Replace flow
temperature
thermistor (red)
Is
control PCB
sensor connections
0.5k
to 20k
?
(I)
Wiring from control
PCB to sensor faulty.
Replace control PCB.
Spark
Electrode
Ignition
PCB
Control
PCB
Condensate
Trap
Detection Electrode
Gas
Valve
Mains
Input
Optional
Pump Feed
Transformer
Overheat
Stat
Casing
Stat
Thermistor
Dry Fire
Flow Switch
DC
Fan
User PCB
br
br
w
g/y
g/y
br
b
b
b
b bk
br
bk
bk
bk
bk
bk
r
r
r
br
g
w
N P/F
bk
S/L
Pump
L
N
br
b
o o o o o o o o
g/y
br
r
b
bk
Earth
Electrode
I
J
K