System Design: This
System Design: This boiler is suitable only for sealed systems. Drain Cocks: These must be located in accessible positions to permit the draining of the whole system. The taps must be at least 15 mm nominal size an manufactured in accordance with BS 2870:1980. Safety Valve Discharge (Primary Water): The discharge should terminate facing downwards on the exterior of the building in a position where discharging (possibly boiling water & steam) will not create danger or nuisance, but in an easily visible position, and not cause damage to electrical components and wiring. The discharge must not be over an entrance or a window or any other type of public access. Mains Water Feed - Central Heating: There must be no direct connection to the mains water supply even through a non-return valve, without the approval of the Local Water Authority, and must be in accordance with water supply regulations. Your attention is drawn to, for GB: Guidance G24.2 and recommendation R24.2 of the water regulations guide and for IE: the current edition of I.S.813. Filling: A temporary method for initially filling the system and replacing lost water during servicing and initial filling (complying to current water regulations and byelaws) is provided. The flexible hose must be removed once the system has been filled. Domestic Hot Water Storage Discharge Pipe Work 1) The tundish must be installed directly below the discharge outlet connection of the boiler. 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 outside 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 are joined together within the appliance. 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 18 m and 27 m at least 3 sizes larger, and so on. Bends must be taken into account in calculating the flow resistance. See fig. 10.4 (page 19) and Table 1 (page 20). 4) The discharge pipe must have a vertical section of pipe at least 300 m in length, below the tundish before any elbows or bends in the pipework. 5) The discharge pipe must be installed with a continuous fall. 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 100 mm 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. 18
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 3 m from any plastic guttering systems that would take 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. Temperature & pressure relief valve Metal discharge pipe (D1) from temperature & pressure relief valve. to tundish. 500 mm Max. Tundish 300 mm Min. Metal discharge pipe (D2) from tundish with continuous fall. See Table 2 and worked example. Discharge below fixed grating. (see page 6 for alternative points of discharge). Fixed grating Fig.10.4 Trapped gulley The single common discharge pipe should be at least one pipe size large than the largest individual discharge pipe to be connected. If unvented hot water storage systems are installed where discharges from safety devices may not be apparent I.e. in dwellings occupied by the blind, infirm or disabled people, consideration should be given to the installation of an electronically operated device to warn when discharge takes place. Note: The discharge will consist of scalding water and steam. Asphalt, roofing felt and non-metallic rainwater goods may be damaged by such discharges. Warning The outlet from the temperature & pressure relief valve must not be used for any other purpose. The temperature & pressure relief valve must not be removed in any circumstances. Any of the above will totally invalidate the warranty. Note The discharge from the central heating and domestic hot water systems may be joined together after the tundish. Air Release Points: These must be fitted at all high points where air naturally collects and must be sited to facilitate complete filling of the system. The appliance has an integral sealed expansion vessel to accommodate the increase of water value when the system is heated. 19
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