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Cold Water Inlet
A ½" connection is provided for connection to 15mm pipe. An integral isolating valve provides control of the
incoming water supply. An internal non-return valve prevents possible back-flow should the water main fail.
CAUTION: If the incoming water pressure exceeds 5 bar it is necessary to install a Pressure Reducing
Valve set at 2.5 bar on the water main into the dwelling. This will protect the boiler and prevent constant opening of
the 7 bar relief valve.
Hot Water Outlet
A ½" connection is provided for connection to 15mm pipe. To ensure economic operation the pipe run between
the boiler and taps should be in not more than15 mm dia. pipe and the distance as short as possible. The pipe-work
should be insulated to reduce heat loss.
Safety Valve Connections
The 7 bar pressure relief valve on the domestic hot water store may discharge boiling water and should be piped to
a safe but visible drain point e.g. a gulley where any discharge will not cause damage or injury.
CAUTION :A tundish should be incorporated close to the appliance where any discharge will be visible but
not hazardous. The pipe-work should have a continuous fall to the drain and should be of minimum 22mm dia. if
more than one discharge is connected to it.
The 3 bar pressure relief on the sealed heating system may discharge boiling water and should be piped with a
continuous fall to a safe yet visible point where any discharge cannot cause damage or injury.
4.8 DHW DISCHARGE PIPE-WORK
The CMX electric combi boiler range incorporates a 50 L unvented hot water storage vessel and an internal,
temperature and pressure relief valve.
CAUTION: The discharge pipe-work from the T&P relief valve must be installed by a competent person
and in accordance with Part G3 of The Building Regulations.
The position of the tundishshall be visible to the occupants and shall be positioned away from any
•
electrical device.
The pipe size and distance from the T&P valve to the tundish and from the tundish to termination point
•
must comply with the requirements of Part G3 of the Building Regulations
The discharge pipe must fall continuously from the valve outlets and be un-obstructed
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The discharge pipe material must be capable of conveying water / steam at 100ºC
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The final discharge point must be in a safe and visible position
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Table 1 – Sizing of copper discharge pipe "D2" for common temperature relief valve outlet sizes
*Refer to paragraphs 3.5, 3.9, and 3.9(a) of Approved Document G
ValveOutletSize
Minimum size if
discharge pipe
D1*
G1/2
15mm
G3/4
22mm
G1
28mm
Minimum size of
Maximum resistance allowed,
discharge pipe
expressed as length of straight
D2* from tundish
pipe (i.e. no elbows or bends)
22mm
28mm
35mm
28mm
35mm
42mm
35mm
42mm
54mm
8
Resistance created by
Up to 9m
Up to 18m
Up to 27m
Up to 9m
Up to 18m
Up to 27m
Up to 9m
Up to 18m
Up to 27m
each elbow or bend
0.8m
1.0m
1.4m
1.0m
1.4m
1.7m
1.4m
1.7m
2.3m
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