On floor-standing models a secondary return may be fitted (consult the label on the face of the unit for the correct location). A non-return valve (not supplied) must be fitted to prevent back flow and a bronze pump will be needed in conjunction with a pipe thermostat to circulate the hot water (both not supplied).
NOTE: an extra expansion vessel may be required where the additional volume of the secondary return exceeds the capacity of the expansion vessel supplied.
NOTE!
THE SAFETY RELIEF VALVES MUST NOT BE USED FOR ANY OTHER PURPOSE
1) The tundish must be vertical and fitted within 500mm of the temperature & pressure relief valve and must be located with the cylinder. The tundish must also be in a position visible to the occupants, and positioned away from any electrical devices. The discharge pipe from the tundish should terminate in a safe place where there is no risk to persons in the vicinity of the discharge and to be of metal.
2) Discharge pipes from the temperature & pressure relief and expansion relief valve may be joined together.
3) The pipe diameter must be at least one pipe size larger than the nominal outlet size of the safety device unless it's total equivalent hydraulic resistance exceeds that of a straight pipe 9m long.
I.e. Discharge pipes between 9m and 18m equivalent resistance length should be at least 2 sizes larger than the nominal outlet size of the safety device. Between 18m and 27m at least 3 larger, and so on.
Bends must be taken into account in calculating the flow resistance. See FIG. 2.9 and TABLE 2.
4) The discharge pipe must have a vertical section of pipe at least 300mm in length, below the tundish before any elbows or bends in the pipework.
5) The discharge pipe must be installed with a continuous fall.
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2.9 CONNECTION TO SERVICES It is recommended that a 22mm pipe run should supply the outlets throughout the building, especially to baths and showers. Short runs of 15mm pipe may be used to connect basins and sinks.
2.10 SECONDARY RETURN
2.11 DISCHARGE PIPEWORK
6) The discharge must be visible at both the tundish and the final point of discharge, but where this is not possible or practically difficult; there should be clear visibility at one or other of these locations. Examples of acceptance are:
i) Ideally below a fixed grating and above the water seal in a trapped gully.
ii) Downward discharges at a low level; i.e. up to 100mm above external surfaces such as car parks, hard standings, grassed areas etc. These are acceptable providing that where children may play or otherwise come into contact with discharges, a wire cage or similar guard is positioned to prevent contact, whilst maintaining visibility.
iii) Discharges at high level; I.e. into a metal hopper and metal down pipe with the end of the discharge pipe clearly visible (tundish visible or not). Or onto a roof capable of withstanding high temperature discharges of water 3m from any plastic guttering systems that would collect such a discharge (tundish visible).
iv) Where a single pipe serves a number of discharges, such as in blocks of flats, the number served should be limited to not more than 6 systems so that any installation can be traced reasonably
easily. The single common discharge pipe should be at least one www.tradeplumbing.co.ukpipeCallsize largeSalesthan theOnlargest08708034288individual discharge pipe to be
