Heatrae Sadia Multipoint ECO 30L V 3kW Installation, Operation And Maintenance Manual page 14

Minimum Size Of
Valve
Discharge Pipe
Outlet Size
G1/2
G3/4
G1
Table 6: Sizing of copper discharge pipe (D2) for common temperature relief valve outlet sizes
Safety device
(e.g. Temperature
relief valve)
Discharge pipe (D2) from tundish,
with continuous fall. See Building
Regulation G3 section 3.56,
Table 1 and worked example
Figure 7: Typical discharge pipe arrangement (extract from Building Regulation G3 Guidance Section 3.50)
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Minimum Size Of
Discharge Pipe D2
D1 From Tundish
22mm
15mm 28mm
35mm
28mm
22mm 35mm
42mm
35mm
28mm 42mm
54mm
Metal discharge pipe (D1) from
Temperature relief valve to tundish
600mm maximum
300mm
minimum
Maximum Resistance
Allowed, Expressed As A
Length Of Straight Pipe
(I.E. No Elbows Or Bends)
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
Tundish
Resistance
Created By Each
Elbow Or Bend
0.8m
1.0m
1.4m
1.0m
1.4m
1.7m
1.4m
1.7m
2.3m
Discharge below
fixed grating
(Building Regulation
G3 section 3.61 gives
alternative points
of discharge)
Fixed grating
Trapped
gully