REMEHA 1000 Indirect, Installation Manual

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3.63 The discharge would consist of high temperature water and steam. Asphalt, roofing felt and non-metallic rainwater goods may be damaged
by such discharges.
Worked example of discharge pipe sizing
Fig 11: shows a G1/2 temperature relief valve with a discharge pipe (D2) having 4 No. elbows and length of 7m from the tundish to the point of
discharge.
From Table 5:
Maximum resistance allowed for a straight length of 22mm copper discharge pipe (D2) from a G1/2 temperature relief valve is 9.0m.
Subtract the resistance for 4 No. 22mm elbows at 0.8m each = 3.2m
Therefore the permitted length equates to: 5.8m
5.8m is less than the actual length of 7m therefore calculate the next largest size.
Maximum resistance allowed for a straight length of 28mm pipe (D2) from a G1/2 temperature relief valves equates to 18m.
Subtract the resistance of 4 No. 28mm elbows at 1.0m each = 4.0m
Therefore the maximum permitted length equates to: 14m
As the actual length is 7m, a 28mm (D2) copper pipe will be satisfactory.
page 15
Valve
Outlet Size
Minimum Size Of
Discharge Pipe D1
Minimum Size Of
Discharge Pipe D2
From Tundish
Maximum Resistance
Allowed, Expressed As A
Length Of Straight Pipe
(I.E. No Elbows Or Bends)
Resistance
Created By Each
Elbow Or Bend
G1/2 15mm
22mm
28mm
35mm up to 9m
up to 18m
up to 27m
0.8m
1.0m
1.4m
G3/4 22mm
28mm
35mm
42mm up to 9m
up to 18m
up to 27m
1.0m
1.4m
1.7m
G1 28mm
35mm
42mm
54mm up to 9m
up to 18m
up to 27m
1.4m
1.7m
2.3m
Table 5: Sizing of copper discharge pipe (D2) for common temperature relief valve outlet sizes