Technical information

20
It can accept up to 7l (1.5 gal) of expansion water. If the heating circuit
has an unusually high water content, calculate the total expansion and
add an additional sealed expansion vessel with adequate capacity.
D
omestic Water:
The domestic water must be in accordance with the relevant
recommendation of BS 5546:1990. Copper tubing to BS EN
1057:1996 is recommended for water carrying pipe work and must be
used for pipe work carrying drinking water. The domestic hot water
temperature should be be adjusted to trip at 60˚C. This temperature
will prevent the formation of limescale in hard water areas.
N
ote: This appliance is capable of producing domestic hot water of
u
p to 70˚C. For extra security against scalding a thermostatic
blending valve may be installed on the domestic hot water
outlet.
Secondary Return:
T
he secondary return connection can be used as an option. A Non
Return Valve (not supplied) must be fitted to prevent back flow and a
Bronze Pump will be needed in conjunction with a Pipe Thermostat to
circulate the hot water (neither of which are supplied).
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 pipe (i.e.
no elbow or bends)
Resistance created
by each elbow or
bend
G 1/2 15 mm 22 mm
28 mm
35 mm
Up to 9 m
Up to 18 m
Up to 27 m
0.8 m
1.0 m
1.4 m
G 3/4 22 mm 28 mm
35 mm
42 mm
Up to 9 m
Up to 18 m
Up to 27 m
1.0 m
1.4 m
1.7 m
G 1 28 mm 35 mm
42 mm
54 mm
Up to 9 m
Up to 18 m
Up to 27 m
1.4 m
1.7 m
2.3 m
Worked Example:
The example below is for a G 1/2 Temperature & Pressure 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 1
Maximum resistance allowed for a straight length of 22mm copper
discharge pipe (D2) from G 1/2 T & P valve is 9m.
Subtract the resistance for 4 no. 22mm elbows at 0.8m each = 3.2m.
Therefore the maximum permitted length equates to: 5.8m.
As 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
G 1/2 T & P valve equates to: 18m.
Subtract the resistance for 4 no. 28mm elbow at 1.0m each = 4m.
Therefore the maximum permitted length equates to: 14m
As the actual length is 7m, a 28mm (D2) copper pipe will be satisfactory.
Table 1. Sizing of copper discharge pipe “D2” for
common temperature valve outlet sizes.