38
37
Troubleshooting Chart for BSI Boilers Equipped withMcDonnell & Miller #67 Low Water Cut-offs and Vent DampersCaution: Read page 34 before attempting to use this chart
Is there an audible
click as R8225 relay
pulls in wh en the
thermostat calls f or
heat?
Does rel ay
pull in now?
Vent
damper
open?
START
Thermo st at
calls f or heat
24 volts across
blue and yellow
wires inside
junction box?
120 volts ac ross
black and w hite
transformer
leads?
*Pow e r o ff
*Blown f use or
tripped
breaker
*Misw i red or
loose 120 volt
connection
N
Y
* Def ec tiv e
transf ormer
See Note #6 on
page 34
N
Y
* Bad connectio n in
thermostat w iring
* Defectiv e thermostat
* Thermostat misw ired or
misapplied
N
N
24 volts
between terminal #1
on 67 LWCO and
yellow tranformer
connection?
24 volts present
between each
pressure limit
connection and
yellow t ransfor mer
connection?
* Boiler off o n pressur e limit
* Defective pressure limit
Is 24 volts
present acr oss
brow n and
yellow lead s on
R8225 relay?
Disconnect
thermostat and
temporarily jump
boiler thermostat
connections
together
* Loose
connection
between
transformer
and R8225
coil
* Defe cti ve
R8225
See Note #7
on page 34
* Boiler off on low water
24 volts present
across blue lead on
R8225 and yellow
transf ormer leads?
* Def ect ive R8225
Y
Y
N
N
Y
Y
Y
N
N
Y
Y
N