11
7.0 Maintenance Procedures
The water heater should be inspected and serviced annually. As a minimum, check operation
of both pressure relief valve and T&P valve, check system for leaks, check expansion vessel
and check operation of thermostat.
7.1 Draining and Refilling the System
Draining
1. Switch off electrical power to immersion heater(s) and/or shut down the boiler.
2. Close the Stop Valve.
3. Open a hot water tap in order to reduce pressure in the water heater.
4. Drain from the drain cock at the base of the water heater.
Refilling
1. DO NOT switch on the immersion heaters or boiler until the system has been completely refilled.
2. Close the drain valve.
3. With hot tap open, turn on pumped cold water supply. When water flows from the hot tap allow to
flow for a short while to purge air and to flush through any disturbed particles.
4. Close hot tap and then open successive hot taps in system to purge any air.
The electrical supply can now be switched on.
7.2 Checking the expansion vessel
The charge pressure of the expansion vessel should be checked annually.
Method
Switch off power to immersion heater(s) and shut down boiler.
Close the Stop Valve.
Open a hot water tap in order to reduce pressure in the cylinder.
Remove the black cap on the end of the expansion vessel. Check the pressure with a good quality
tyre gauge.
The charge pressure can then be checked against the vessel nameplates by using a good tyre
gauge. If it is low then replenish it by using a nitrogen gas bottle with regulating valve, or a foot
pump. The pressure will normally be set to 3.5 bar.
Any fluid escaping from the expansion vessel valve indicates a leaking diaphragm and the vessel
should be replaced.
7.3 Checking the operation of safety valves
Manually operate the valve lever on the Temperature & Pressure Relief Valve for a few seconds.
Check that water is discharged and that it flows freely through the tundish and discharge pipework.
Check that the valve reseats correctly when released.
Repeat the procedure for the Expansion Relief Valve.
Note:
The water discharged may be very hot.
Important:
After servicing, preliminary electrical system checks must be carried out to ensure elec-
trical safety (i.e. polarity, earth continuity, resistance to earth and short circuit).
