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9. Maintenance
9.1 General
Maintenance requirements
Only competent persons having received adequate
training are permitted to work on the appliance and
the installation. Unvented hot water systems have
a continuing maintenance requirement in order to
ensure safe working and optimum performance. It
is essential that the relief valve(s) are periodically
inspected and manually opened to ensure no
blockage has occurred in the valves or discharge
pipework.
Similarly cleaning of the strainer element and
replacement of the air in the internal expansion
volume will help to prevent possible operational faults.
The maintenance checks described below should be
performed by a competent person on a regular basis,
e.g. annually to coincide with boiler maintenance.
After any maintenance, please complete the relevant
Service Record section of the Benchmark Checklist
on page 35 of this document.
9.2 Standard inspection & maintenance
operations
Inspection
The immersion heater boss can be used as an access
for inspecting the cylinder internally.
Safety valve operation
CAUTION
Water discharged may be very hot!
Manually operate the Temperature/Pressure Relief
`
Valve for a few seconds (Fig. 3, page 9).
Check water is discharged and that it flows freely
`
through the tundish and discharge pipework.
Check valve reseats correctly when released.
`
Repeat the above procedure for the Expansion
`
Relief Valve. (Fig. 3, page 9).
Strainer
Turn off the isolating valve prior to the Pressure
`
Reducing Valve or the main stop cock to the
system.
Open the lowest hot tap in the system to relieve the
`
system pressure.
Using a spanner unscrew the Pressure Reducing
`
Valve cartridge and remove the housing. The
strainer will be removed with the cartridge. (see
Fig. 16, page 30).
Wash any particulate matter from the strainer
`
under clean running water.
Replace the strainer and screw the Pressure
`
Reducing Valve cartridge into the moulded housing.
Close hot tap, turn on isolating valve or main stop
`
cock to the system. Check for leaks.
Descaling immersion heater(s)
CAUTION
DO NOT use a sharp implement as damage
to the element surface could be caused.
Turn off the mains water supply, isolate the electrical
supply and turn off boiler.
Attach a hosepipe to the drain cock having sufficient
`
length to take water to a suitable discharge point
below the level of the unit.
Open a hot tap close to the unit and open drain
`
cock to drain the cylinder.
Open the cover(s) to the immersion heater
`
housing(s) and disconnect wiring from immersion
heater(s) thermostat(s).
Unscrew the immersion heater backnut using the tool
`
supplied and withdraw the immersion heater from the
cylinder. Take care when removing the immersion
heater from the cylinder and work within safe working
practices.
Carefully remove any scale from the surface of the
`
element(s).
Ensure sealing surfaces are clean. Fit a new gasket
`
(spare part no. 7035165).
Replace immersion heater(s), making sure the
`
gasket is correctly fitted and does not become
displaced as the immersion heater is replaced.
Rewire, check, close and secure immersion heater
`
housing cover(s).
Re-commissioning
Check all electrical and plumbing connections are
`
secure. Close the drain cock.
With a hot tap open, turn on the cold water supply
`
and allow appliance to refill.
DO NOT switch on the immersion heater(s) or
`
boiler until the appliance is full.
When water flows from the hot tap allow to flow
`
for a short while to purge air and flush through any
disturbed particles.
Close hot tap and then open successive hot taps in
`
system to purge any air.
When completely full and purged check system for
`
leaks.
The heating source (immersion heater(s) or boiler)
`
can then be switched on.
25
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