CONNECTIONS PLUMBING
33
TEMPERATURE PRESSURE RELIEF VALVE
The temperature pressure relief valve is shipped behind the lower front cover of the water heater. The
temperature pressure relief valve must be fitted before the water heater is operated. Before fitting the relief
valve, make sure the probe has not been bent. Seal the thread with an approved thread sealant such as Teflon
tape - never hemp. Make sure the tape does not hang over the end of the thread.
Screw the valve into the correct opening (refer to the installation diagram on page 25) leaving the valve outlet
pointing downwards. Do not use a wrench on the valve body - use the spanner flats provided. A copper drain
line must be fitted to the temperature pressure relief valve (refer to "Relief Valve Drain" on page 33).
The valve must be insulated with a closed cell type insulation or equivalent (minimum thickness 9 mm) and
the insulation installed so as not to impede the operation of the valve. The insulation must be weatherproof
and UV resistant if exposed.
EXPANSION CONTROL VALVE
Local regulations may make it mandatory to install an expansion control valve (ECV) in the cold water line to
the water heater. In other areas, an ECV is required if the saturation index is greater than +0.4 (refer to “Water
Supplies” on page 11).
The expansion control valve must always be installed after the non-return valve and be the last valve installed
prior to the water heater (refer to diagrams on page 32). A copper drain line must be fitted to the expansion
control valve (refer to "Relief Valve Drain" on page 33).
The valve, if installed within 500 mm of the water heater, must be insulated with a closed cell type insulation
or equivalent (minimum thickness 9 mm) and the insulation installed so as not to impede the operation of the
valve. The insulation must be weatherproof and UV resistant if exposed.
RELIEF VALVE DRAIN
DN15 copper drain lines must be fitted to the temperature pressure relief valve, expansion control valve (if one
is installed) and solar circuit relief valve to carry the discharge clear of the water heater. Ensure the outlet of
the solar circuit relief valve is facing toward the rear of the water heater installation. Connect the drain lines to
the valves using disconnection unions. The drain line from the valve to the point of discharge should be as
short as possible, have a continuous fall all the way from the water heater to the discharge outlet and have no
tap, valves or other restrictions in the pipe work.
A drain line from a relief valve must comply with the requirements of AS/NZS 3500.4.
A drain line must be no longer than 9 metres with no more than three bends greater than 45° before discharging
at an outlet or air break. The maximum length of 9 metres for a drain line is reduced by 1 metre for each
additional bend required of greater than 45°, up to a maximum of three additional bends. Where the distance
to the point of final discharge exceeds this length, the drain line can discharge into a tundish.
Subject to local regulatory authority approval, the drain lines from the temperature pressure relief valve and
expansion control valve from an individual water heater may be interconnected.
The outlet of a drain line must be in such a position that flow out of the pipe can be easily seen, but arranged
so discharge will not cause injury, damage or nuisance. The termination point of a drain line must comply with
the requirements of AS/NZS 3500.4. Drain lines must not discharge into a safe tray.
In locations where water pipes are prone to freezing, drain lines must be insulated, must not exceed 300 mm
in length and are to discharge into a tundish through an air gap of between 75 mm and 150 mm.
If a drain line discharges into a tundish, the drain line from the tundish must be not less than DN20. The drain
line from a tundish must meet the same requirements as for a drain line from a relief valve.
Warning: As the function of the temperature pressure relief valve on this water heater is to discharge high
temperature water under certain conditions, it is strongly recommended the pipe work downstream of the relief
valve be capable of carrying water exceeding 93°C. Failure to observe this precaution may result in damage
to pipe work and property.
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