Heat Pump Installation Guide
61
Connect the tundish and route the discharge pipe which must be routed in accordance with Building
Regulations - Part G3 of schedule 1.
When operating normally water will not be discharged. Water discharge from the temperature and
pressure valve will only occur under fault conditions. The tundish is pre-fitted as shown below.
The discharge pipe (D2) coming from the tundish should terminate in a safe place where there is no
risk to persons near the discharge, be of metal and:
•
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 diagram 1, Table 1
and the worked example. An alternative approach for sizing discharge pipes would be to follow
BS6700 Specification for design, installation, testing and maintenance of services supplying wa-
ter for domestic use within buildings and their curtilages.
•
Be installed with a continuous fall. The discharge must be visible at the final point of discharge.
G1/2
G3/4
G1
Min. size of discharge
pipe D1
15mm
22mm
28mm
Min. size of discharge
pipeword D2 from tundish
22mm 28mm 35mm 28mm 35mm 42mm 35mm 42mm 54mm
Max. length of straight
pipe (no bends or elbows)
Up to
9mm
Up to
18mm
Up to
27mm
Up to
9mm
Up to
18mm
Up to
27mm
Up to
9mm
Up to
18mm
Up to
27mm
Deducts the gure below
from the maximum length
for each bend or elbow in
the discahrge pipe
0.8m
1m
1.4m
1.0m
1.4m
1.7m
1.4m
1.7m
2.3m
Sizing of copper discharge pipe (D2) for a temp, relief valve with a G1/2 outlet size (as supplied)
Temperature & Pressure Relief Valve
Smart Plumb Compact Installation
