Benchmark ZWB 7-29 CC1 Installation And Servicing page 94

Failure identification procedure
Loose or broken contact on heat store NTC sensor
Check
1. Heat store NTC sensor lead is not
fitted as described in the installation
instructions (i.e. the cable does not
pass through the cable grip in the
switchbox).
Boiler indicates P1, P2, P3 at start-up and then restarts with P1..
Check
1. Fuse T 1,6 A (312) defective.
2. The PCB control board is damaged.
46
Action
B Record condition of appliance as found in cus-
tomer service record.
B Route cable as specified in installation instruc-
tions.
Action
B Turn ON the appliance.
yes:
B Change the fuse.
B Power OFF the appliance.
Start sequence not completed? ↓2.
↓2.
no:
B Make a note of the altered service settings (see
table 1, "First Service Level; Values that can be
modified" at page 8 and table 5, "Secondary
Service Level; Values that can be modified" at
page 11).
B Power OFF the appliance.
B Disconnect the boiler electrical connection.
B Change PCB control board.
B Reconnect the boiler electrical connection.
B Turn ON the appliance.
B Restore service settings previously noted down.
7 181 465 346 GB (03.02)