24
Green T-T indicator LED is
on; there is a call for heat.
Verify the boiler control
board switch is on.
Verify 120vac is present at
the L-N terminals on the
printed circuit board labeled
“120vac Input.”
Replace control board.
No
UNITS WITh POWER
BLOCKS
Verify that the ceramic fuse
is good. If fuse is blown,
replace it with a new one.
UNITS WITh CIRCUIT
BREAKERS
Verify that the 15amp/
120vac circuit breaker is on.
If breaker is off, turn it on.
Verify that the thermostat
is operational and calling
for heat. Disconnect TT/TT
wires from boiler control
board and replace with a
jumper if necessary. The
T-T indicator LED should
come on with the jumper
installed.
OK
OK
Lights come on with jumper
and elements then energize
Replace circuit breaker or
power block, depending
on type of boiler.
Check service at main load
center.
Verify that 240vac is
present across L1 and L2.
LED light/boiler off
with jumper installed
120vac not present
120vac
present
240vac not present
240vac present
Yes
Is audible alarm sounding
and red fault LED flashing?
Yes (see Flowchart #3)
No (See Flowchart#2)
Potentially bad thermostat.
Consult thermostat
manufacturer’s manual or
replace thermostat.
TrouBLEsHooTing - fLoWcHArT#1
!
WARNING
Due to exposure to potentially dangerous volt-
ages, troubleshooting should be performed
by a qualified installer or service agency only.
Failure to do so could result in property dam-
age, personal injury, or loss of life.