Unvented Hot Water Cylinder
27
MAINTENANCE AND
SER
VICING (3)
Fault finding
The Fault Finding chart will enable operational faults to be identified and their possible causes rectified.
Any work carried out on the Megaflo
Commercial
unvented water heater and its associated controls
MUST be carried out by a competent installer for unvented water heating systems. In case of doubt
contact the Megaflo
Commercial
Service Department.
Table 17: 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 mo-
torised valve
Water discharges
from overflow visual
indicator (tundish)
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
detiorated
GRADUALLY
Check for scale build up in the DHW heat ex-
changer
Summary of Contents for Commercial 1000
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