Publication No. 5106226
15
Typical Discharge Pipe Arrangement
Condensate Trap
500 mm
Flexible Tube
supplied
Metal discharge pipe from
Tundish with continuous fall
Fixed
Grate
Discharge
above
Fixed
Grate
Trapped Gulley
Internal
S.V.P.
21.5 mm
PVC
Overflow
Pipework
Tundish
T.P.R. Valve
300mm min.
450mm min.
MAX0011A
Fig. 7
Installation Requirements
Valve
Minimum
Minimum
Maximum
Resistance
outlet
dischage
discharge
resistance
created by
size
pipe D1
pipe D2
allowed,
each elbow
from
expressed
or bend
tundish
as a length
of straight
pipe (i.e. no
elbows or
bends)
22 mm
up to 9 m
0.8 m
G1/2
15 mm
28 mm
up to 18 m
1.0 m
35 mm
up to 27 m
1.4 m
28 mm
up to 9 m
1.0 m
G3/4
22 mm
35 mm
up to 18 m
1.4 m
42 mm
up to 27 m
1.7 m
35 mm
up to 9 m
1.4 m
G1
28 mm
42 mm
up to 18 m
1.7 m
54 mm
up to 27 m
2.4 m
Table 1. Sizing of copper discharge pipe (D2) for common temperature
relief valve outlet sizes.
Note:
shaded area is reproduced for completeness
but does not apply to this boiler.
dwellings occupied by blind, infirm or
disabled people, consideration should be
given to the installation of an electronically
operated device to warn when discharge
takes place.
Note:
The discharge will consist of scalding
water and steam. Asphalt, roofing felt and
non-metallic rainwater goods may be
damaged by such discharges.
Worked example of discharge pipe sizing
The example below is for a G1/2 temperature
relief valve with a discharge pipe (D2) having 4
No. elbows and length of 7 m from the tundish to
the point of discharge.
From Table 1:
Maximum resistance allowed for a straight length
of 22mm copper discharge pipe (D2) from a G1/2
temperature relief valve is 9.0 m.
Subtract the resistance for 4 No. 22 mm elbows at
0.8m each = 3.2 m.
Therefore the permitted length equates to: 5.8 m.
5.8 m is less than the actual length of 7 m
therefore calculate the next largest size.
Maximum resistance allowed for a straight length
of 28 mm pipe (D2) from a G1/2 temperature
relief valves equates to 18 m.
Subtract the resistance of 4 No. 28 mm elbows at
1.0 m each - 4.0 m.
Therefore the maximum permitted length equates
to: 14 m.
As the actual length is 7 m, a 28 mm min. (D2)
copper pipe will be satisfactory.
Warnings
• Under No circumstances should the factory
fitted Temperature/Pressure Relief Valve be
removed other than by Authorised Potterton
personnel. To do so will invalidate any
warranty or claim.
• The cold water Inlet Control Group must be
fitted to the mains water supply to the
Powermax HE when it is operated as an
unvented system.
• Control and safety valves MUST NOT be
tampered with.
• The discharge pipe MUST NOT be blocked
or used for any other purpose.
• The tundish must not be removed but can be
sited outside the RH panel using the opening
provided.
• Electrical components must not be sited near
the tundish.
