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Pressure & Temperature/expansion Relief Valve Pipework
The tundish should be vertical, located in the same space as the unvented hot water storage system and be fitted as close as
possible and within 600mm of the safety device e.g. the temperature relief valve. The tundish must be positioned away from
any electrical devices.
The discharge pipe (D2) from the tundish should terminate in a safe place where there is no risk to persons in the vicinity of
the discharge, be of metal (or a material capable of conveying water/steam at 100ºC) and:
a) Be at least one pipe size larger than the nominal outlet size of the safety device unless its 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 two sizes larger than the nominal outlet size of the safety device, between 18 and 27m at least 3 sizes
larger, and so on. Bends must be taken into account in calculating the flow resistance. Refer to the table and the worked
example.
An alternative approach for sizing discharge pipes would be to follow BS EN 806-2:2005 Specification for design installation,
testing and maintenance of services supplying water for domestic use within buildings and their curtilages.
b) Have a vertical section of pipe at least 300mm long, below the tundish before any elbows or bends in the pipework.
c) Be installed with a continuous fall.
d) It is preferable for the discharge to 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 acceptable
discharge arrangements are:
1. Ideally below the fixed grating and above the water seal in a trapped gulley.
2. Downward discharges at a low level; i.e. up to 100mm above external surfaces such as car parks, hard standings,
grassed areas etc. are acceptable providing that where children play or otherwise come into contact with discharges, a
wire cage or similar guard is positioned to prevent contact whilst maintaining visibility.
3. Discharges at a high level; e.g. into 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 and 3m
from any plastic guttering systems that would collect such discharges.
4. 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 pipe size larger 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
blind, infirm or disabled people, consideration should be given to the installation of an electronically operated device
to warn when discharge takes place.
Safety
The safety devices supplied or fitted on an Gabarrón Mattira combi boiler are selected for their suitability for the
temperatures and pressures involved. They must not be changed, removed or by-passed and it is essential that only genuine
replacement parts supplied or approved by Elnur UK Limited are used. This includes the immersion heaters, which must
incorporate an energy cut-out. All parts are available to approved installers from Elnur UK Ltd.
Combination Inlet Group Combines elements 1, 2 and 3 below.
1. Pressure Reducing Valve - This must be fixed near the cylinder. The cold water supply to any mixer taps/showers must be
taken from the cold water tapping of this valve to ensure balanced hot and cold pressures. This valve is factory set to
ensure the correct operating pressure for the Gabarrón Mattira combi boiler.
2. Non Return Valve - This is integral with the pressure reducing valve to prevent backflow of hot water towards cold water
draw off points.
3. Cold Water Expansion Relief Valve - This safety device is preset at the factory and will relieve excess cold water pressure
resulting from a fault condition.
Immersion Heaters
These are 3x3kW plus 3x2kW 240V~ heaters and incorporate a thermostat and a manually reset energy cut-out which
operates at 80°C. They have incoloy elements to prolong their life expectancy in aggressive water conditions.
The control thermostat of the immersion heaters for direct heating of our cylinders can be set up to 60°C. During
commissioning the actual temperature that the cylinder reaches when the thermostat(s) operate should be tested and
adjusted so that it achieves a minimum of 60°C. This temperature needs to be achieved on a regular basis.
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