12
9. Maintenance
9.1 General
Maintenance requirements
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 is periodically inspected and manually
opened to ensure no blockage has occurred in the
valves or discharge pipework. Maintenance of this
appliance should only be carried out by a suitably
qualified person. Failure to do so could invalidate the
warranty.
WARNING
Disconnect from all electrical supplies
before beginning any work on the product.
Water contained within the product may
be very hot!
Maintenance should be carried out by a
competent person and any replacement
parts should be authorised Heatrae Sadia
spare parts.
It is recommended that maintenance is
carried out annually and should include
the checks detailed in the sections below.
Little maintenance is required, however in
hard water areas the product will require
periodic descaling to ensure efficient
operation.
9.2 Standard inspection & maintenance
operations
To descale:
`
Switch off and disconnect the electrical supply.
Turn off the water supply to the product.
`
Open a hot tap to relieve any system pressure.
Disconnect the plumbing connections to the
product and remove from the wall bracket (note
full weights of product). Empty the product
through the outlet connection.
`
Remove the terminal cover by using a large flat
bladed screwdriver to depress the 3 snap lugs
located in the top 3 rectangular depressions.
`
Remove the insulating pad from the terminal
housing. Disconnect the electrical terminations
to the thermostat. Disconnect earth links to the
earthing stud.
`
Remove the element plate assembly by
unscrewing the five securing screws, a tapped
jacking point is provided. Remove any loose
scale from the container. Carefully clean off any
scale from the element and thermostat pocket.
DO NOT clean scale from interior container
walls.
`
Re-assemble the element plate assembly
fitting a new sealing gasket. Note the correct
orientation of the element plate by reference
to Figure 07 below. Rewire the product with
reference to the Wiring Diagrams. Refit the
insulating pad to ensure the correct operation of
the thermostat.
Outlet
Cable
clamp
Inlet
Inlet
Earth
post
Earth
post
Thermostat
securing
post
Front
Front
Cable
clamp
Combined
thermostat
and thermal
cut-out
Temperature /
pressure
relief valve
Temperature /
pressure
relief valve
Combined
thermostat
and thermal
cut-out
Outlet
`
Re-commission the product following the
Installation and Commissioning instructions.
`
The Temperature/Pressure Relief Valve and,
if fitted, the Pressure (expansion) Relief Valve
should be regularly checked. This is to remove
limescale deposits and to verify that it is not
blocked. To check the valves:
Manually operate the valves by either twisting
the cap or lifting the lever. Ensure water
flows freely from the valve(s) and through the
discharge pipes. Ensure the valve(s) reseat
correctly when released.
`
The Expansion Vessel, if fitted, should have a
pre-charge pressure of 0.41 MPa (4.1 bar). This
can reduce over time and eventually require re-
charging. To do this:
`
Turn off water supply to the product; open a hot
tap to relieve system pressure.
`
Remove dust cap from top of Expansion Vessel
`
Check pre-charge pressure using a tyre
pressure gauge. If the pressure is lower than
0.41 Mpa (4.1 bar) it should be recharged using
a tyre pump (Schraeder Valve type). DO NOT
OVER CHARGE.
`
Re-check pressure and when correct replace
dust cap.
`
Turn on mains water supply and close hot tap.
Figure 7 – 3kW model
Figure 7 – 4.5kW model
