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MAINTENANCE:
The following checks should be conducted annually:
Check the operation of the T & P valve and Expansion valve by rotating the heads of the valves in
turn until water is discharged. The discharge should stop immediately when the valve head is
released. Should this not be the case the valve should be replaced. Check that the discharged
water flows freely to waste and that there is no blockage.
Remove and clean the filter in the Pressure Reducing Valve.
The expansion vessel does not require any routine maintenance, however it is advisable to check
annually that the pre-charge pressure is 3.0 bar. However, if water is being discharged from the
expansion valve it may be indicative of pressure loss within the expansion vessel itself. To check
the pressure, isolate the unit from the cold supply and release any pressure by opening a hot tap until
water stops flowing. Then use a tyre pressure gauge to verify the pre-charge pressure. The vessel is
factory pre-charged to 3.0 bar. If the pressure is less than this it can be re-pressurised to 3.0 bar
using a suitable pump. If the unit is more than 5 years old when this problem is
experienced it may be advisable to replace the pressure vessel. If however, the pressure in the
expansion vessel is 3.0 bar, the discharge may be being caused by back pressure or cross-over
between the cold and hot water supplies - see below.
To replace the pressure vessel, unscrew from threaded connection. The new pressure vessel should
be checked to ensure it has a pre-charge of 3.0 bar, and then fitted to the cylinder, ensuring that the
threads are sealed appropriately.
Checking for back pressure
Back pressure from a faulty or uncontrolled mixer valve or appliance will cause the cylinder to over
pressurise and may result in water being discharged from the expansion valves. To check for back
pressure follow the steps below:
Turn off cold water supply to cylinder, whilst leaving cold supply to all mixer taps and
appliances connected.
Open a single hot tap, and run water for several minutes to dissipate any pressure in the cylinder,
the pressure on the gauge should be allowed to fall below 1 bar.
In turn open both the hot and cold taps on mixer valves and watch pressure on gauge. The pressure
will rise once the faulty mixer valve is opened as it will allow higher pressure cold water back into
the cylinder. The faulty mixer should then be replaced.
NB: A suitable gauge fitted to a hot tap will be needed for Tempest Stainless Models.
Use only genuine Telford replacement parts on all repairs.
NOTES ON WATER QUALITY AND SCALING:
Water hardness can vary considerably around the country. If furring of kettles normally occurs in
the area, then the unit should be fed with conditioned water only. This can be provided by a water
softener with a high capacity flow rate, or a suitable water conditioner (not supplied). It is
recommended that the temperature controls are set below 650C to prevent lime scale build up.
The performance of all water storage appliances and their associated components may
deteriorate if you do not protect adequately against hard water scaling. If more than 150ppm salts
are present in local water samples, an effective conditioner should always be used.
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