Fault Finding And Diagnosis; Fault Finding - Worcester 41-311-67 Installation, Commissioning And Servicing Instructions

7

FAULT FINDING AND DIAGNOSIS

7.1

FAULT FINDING

This fault finding information is for guidance
only. Worcester cannot be held responsible
for costs incurred by persons not deemed to
be competent.
The electronic control system for this boiler
incorporates a blue central indicator. This normally
confirms the permanent mains supply but, by flashing at
different rates during a fault, provides a guide to the
cause as listed.
Blue light Lockout
indication reset button
Off Off
On Off
Tab. 26
6 720 644 743a (2010/10)
Fault Possible solution/check
No power at Permanent mains supply to boiler.
control board
Fuse F1 - 2.5A or Fuse F3 - 0.5A.
Transformer (primary coil below 60 Ω, both secondary coil
below 10 Ω).
Otherwise replace control board.
Boiler not Live demand at ST10-L
operating during
Fascia mounted timer (if fitted)
central heating
CH knob in winter position
demand (HW ok)
Diverter valve
Control board
Boiler operating Some older thermostats (containing capacitors) may give a low
without live voltage return at ST10-L
demand at ST10- open.
L (from external
Check that there is no permanent live at ST10-L
R
room thermostat
source.
timer)
Boiler not Ensure cold inlet DHW outlet are correctly piped i.e. are not
operating during crossed piped.
hot water
Flow Turbine test:
demand (CH ok)
B Check for 5 volts d.c. across red and black wires
B Check for 2.5 volts d.c. across the yellow and red wires with
the water flowing.
Check diverter and motor and control board.
Boiler not Fan
operating during
Control board
any demand.
FAULT FINDING AND DIAGNOSIS
This fault finding system assumes that the appliance has
been operating normally until the time of failure (i.e. not
a first installation error).
PRELIMINARY CHECKS : Preliminary electrical system
checks are the first electrical checks to be carried out
during a fault-finding procedure. On completion of the
Service/Fault-Finding task which has required the
breaking and remaking of electrical connections, check:
(a) EARTH CONTINUITY,
(b) SHORT CIRCUIT CHECK,
(c) POLARITY and
(d) RESISTANCE TO EARTH.
(from external room thermostat/timer)
R
when the thermostat contacts are
R
from another
R
65