Potterton Gold Installation And Servicing Instructions page 8

tundish;
(b) be a separate branch pipe with no sanitary appli-
ances connected to it;
(c) if plastic pipes are used as branch pipes carrying
discharge from a safety device they should be either polyb-
utalene (PB) to Class S of BS 7291-2:2006 or cross linked
polyethylene (PE-X) to Class S of BS 7291-3:2006; and
(d) be continuously marked with a warning that no
sanitary appliances should be connected to the pipe.
Note:
1. Plastic pipes should be joined and assembled with
fittings appropriate to the circumstances in which they are
used as set out in BS EN ISO 1043-1.
2. Where pipes cannot be connected to the stack it may
be possible to route a dedicated pipe alongside or in close
proximity to the discharge stack.
Termination of discharge pipe
3.61 The discharge pipe (D2) from the tundish should
terminate in a safe place where there is no risk to persons
in the vicinity of the discharge.
3.62 Examples of acceptable discharge arrangements are:
(a) to a trapped gully with the end of the pipe below a
fixed grating and above the water seal;
(b) downward discharges at low level; i.e. up to 100mm
above external surfaces such as car parks, hard standings,
grassed areas etc. are acceptable providing that a wire
cage or similar guard is positioned to prevent contact,
whilst maintaining visibility; and
(c) discharges at high level: e.g. into a metal hopper
and metal downpipe with the end of the discharge pipe
clearly visible or onto a roof capable of withstanding high
temperature discharges of water and 3m from any plastic
guttering system that would collect such discharges.
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.
VALVE OUTLET
SIZE
G 1/2
G 3/4
G 1
Table 3: Sizing of copper discharge pipe (D2) for common temperature relief valve outlet sizes
NOTE: The above table is based on copper tube. Plastic pipes may be of different bore and resistance. Sizes and
maximum lengths of plastic should be calculated using data prepared for the type of pipe being used.
8
MINIMUM SIZE OF MINIMUM SIZE OF
DISCHARGE PIPE D1 DISCHARGE PIPE D2
FROM TUNDISH
15MM 22mm
28mm
35mm
22MM 28mm
35mm
42mm
28MM 35mm
42mm
54mm
Worked example of discharge pipe sizing
Fig. 5: 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 3:
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.
WARNINGS:
•
Under no circumstances should the factory
fitted temperature/pressure relief valve be
removed other than by a competent
person. To do so will invalidate any
guarantee or claim.
• The cold water combination valve assembly
must be fitted on the mains water supply to
the POTTERTON GOLD cylinder.
• No control or safety valves should be tampered
with or used for any other purpose.
• The discharge pipe should not be blocked or
used for any other purpose.
• The tundish should not be located adjacent
to any electrical components.
RESISTANCE CREATED BY
MAXIMUM RESISTANCE
EACH ELBOW OR BEND
ALLOWED, EXPRESSED
AS A LENGTH OF
STRAIGHT PIPE (I.E. NO
ELBOWS OR BENDS
UP TO 9M 0.8M
UP TO 18M 1.0M
UP TO 27M 1.4M
UP TO 9M 1.0M
UP TO 18M 1.4M
UP TO 27M 1.7M
UP TO 9M 1.4M
UP TO 18M 1.7M
UP TO 27M 2.3M