Dimplex SCx175sd Installation And Operation Manual page 9

Warning Notice – The discharge will consist of scalding water and steam. Asphalt, roofing felt and
non-metallic rainwater goods may be damaged by such discharges.
Typical discharge pipe arrangement.
Fig 7.2
Valve outlet size
Diameter Discharge pipe D1
½"
¾"
1"
Fig 7.3
Worked example
The example below is for a ½"diameter temperature relief valve with a discharge pipe (D2) having 4
elbows and a length of 7m from the tundish to the point of discharge.
From the table above the maximum resistance allowed for a straight length of 22mm copper
discharge pipe (D2) from a ½"diameter temperature relief valve is: 9.0m.
Subtract the resistance for 4 No 22mm elbows at 0.8m each = 3.2m.
Therefore, the maximum permitted length equates to: 5.8m.
5.8 m 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 ½"diameter temperature
relief valve equates to: 18m.
Subtract the resistance for 4 No 28mm elbows at 1.0 each = 4m.
Therefore the maximum permitted length equates to 14m.
As the actual length is 7m, a 28mm diameter copper pipe will be satisfactory.
Min. size of
Discharge pipe D2
from Tundish
15mm
22mm
28mm
Min. size of Max. length of
Straight pipe
22mm
Up to 9m
28mm
Up to 18m
35mm
Up to 27m
28mm Up to 9m
35mm Up to 18m
42mm Up to 27m
35mm
Up to 9m
42mm
Up to 18m
54mm
Up to 27m
Resistance created
by each elbow
Or bend
0.8m
1.0m
1.4m
-
-
1.7m
1.4m
1.7m
2.3m
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