Crown Boiler BSI172 Installation Instructions Manual page 38

Troubleshooting Chart for BSI Boilers Equipped with
McDonnell & Miller #67 Low Water Cut-offs and Vent Dampers
Caution: Read page 34 before attempting to use this chart
START
Thermostat
calls for heat
120 volts across
black and w hite
transformer
leads?
Y
N
*Pow er off
*Blow n fuse or
tripped
breaker
*Misw ired or
N
loose 120 volt
connection
Disconnect
* Defective
thermostat and
transformer
temporarily jump
See Note #6 on boiler thermostat
page 34 connections
together
* Bad connection in
thermostat w iring
* Defective thermostat
* Thermostat misw ired or
misapplied
Is there an audible
click as R8225 relay
pulls in w hen the
thermostat calls for
heat?
N
24 volts across
blue and yellow
w ires inside
junction box?
N
Y
Is 24 volts
present across
brow n and
yellow leads on
R8225 relay?
Y
* Defective
R8225
See Note #7
on page 34
Y
Does relay
pull in now ?
damper
open?
N
Y
24 volts
betw een terminal # 1
on 67 LWCO and
yellow tranformer
connection?
Y
24 volts present
betw een each
pressure limit
connection and
yellow transformer
connection?
Y
24 volts present
across blue lead on
R8225 and yellow
transformer leads?
* Loose
connection
betw een
N
transformer
and R8225
coil
38
37
Vent
Y
N
N
* Boiler off on low w ater
* Boiler off on pressure limit
* Defective pressure limit
Y
N
* Defective R8225