Fault Finding
19
10 Fault
Finding
DANGER OF ELECTRIC SHOCK
— Disconnect the electrical supply before removing any electrical equipment cover.
Table 2:
Faults, Causes and Remedies
Fault
Possible Cause
Remedy
Cylinder cools down overnight
One pipe circulation in the case of short pipe
networks with low pressure loss
Install a non-return valve as close as possible
to the cylinder
Primary heating is not
working. Boiler runs for a short
period, goes off, then comes
on again. This is repeated until
the cylinder reaches its target
temperature
Air trapped in heat exchanger
Vent air from heat exchanger circuit
Heat exchanger surface too small
Check data for boiler and cylinder. The
problem may be solved by increasing the
flow from boiler
Intermittent water discharge
through tundish on warm up
Expansion vessel has lost its charge pressure
(vessels with external expansion only)
Follow steps listed in Service & maintenance
section
Internal air gap needs replenishing
Follow steps listed in Servicing &
maintenance section
Only cold or lukewarm water
comes out of taps
Programmer set to heating only or not
switched on for hot water
Set programmer to call for hot water on
demand
Central heating boiler malfunction
Check boiler operation. If faulty consult
manufacturers instruction manual
High limit thermostat has tripped
Check and re-set. The cause will need to be
identified
Pump malfunction
Check wiring and/or plumbing connections to
pump
If only cold water comes out of taps, hot and
cold pipes may have been connected up
incorrectly
Check connections and have them changed if
necessary
Continuous water discharge
Pressure reducing valve (PRV) not functioning
properly
Check pressure from PRV. Replace cartridge if
necessary.
Expansion relief valve not seating correctly
Manually lift the valve once or twice to clear
debris from the seat. If this does not cure the
problem, replace the valve.
Temperature and pressure relief valve not
seating correctly
Manually lift the valve once or twice to clear
debris from the seat. If this does not cure the
problem, replace the valve.
