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Fault finding
The fault finding chart will enable operational faults to be identified and their possible causes rectified. Any work carried
out on the Andrews water heaters and its associated controls MUST be carried out by a competent installer for
unvented water heating systems. In case of doubt contact the Andrews Water Heaters service department.
Table 12: Fault Finding guide
Fault
Possible Cause
Remedy
No hot water flow
Mains water supply off
Check and open stop cock/isolating valve
Strainer blocked
Turn off water supply, remove strainer and
clean
Cold water combination valve incorrectly
fitted
Check and refit as required
Water from hot tap
is cold
Indirect programmer set to central
heating only
Check, set to domestic hot water programme
Indirect boiler not working
Check boiler operation. If fault is suspected
consult boiler manufacturer’s instructions
Indirect thermal cut-out has operated
Check, reset by pushing button on thermal cut-
out
Check operation of indirect thermostat
Indirect motorised valve not connected
correctly
Check wiring and/or plumbing connections to
motorised valve
Water discharges
from overflow visual
indicator
INTERMITTENTLY
Incorrect pre-charge pressure for expansion
vessel
CONTINUALLY
Check pressure from pressure reducing valve
Remove expansion relief cartridge from pressure
relief valve and check seating. If necessary fit
new cartridge
Water discharges
from the T&P relief
valve intermittently
Expansion relief valve faulty
Check valve and replace if necessary
Water discharges
from the T&P relief
valve continually
Thermal control failure
NOTE: Water will be very hot
Switch off power to immersion heater(s) and
shut down boiler. DO NOT turn off water
supply. When discharge stops check all thermal
controls, replace if faulty
Performance has
deteriorated
GRADUALLY
Check for scale build up in the DHW heat
exchanger
SUDDENLY
Check the operation of the blending valve.
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