Ariston GENUS HE 35 Plus Installation And Servicing Instrucnion page 20

Table 1. Sizing of copper discharge pipe "D2" for
common temperature valve outlet sizes.
Valve outlet size
G 1/2
G 3/4
G 1
20
Minimum size of
discharge pipe D1* discharge pipe D2*
15 mm
22 mm
28 mm
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.
Domestic 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.
Note: This appliance is capable of producing domestic hot water of
up to 70˚C. For extra security against scalding a thermostatic
blending valve may be installed on the domestic hot water
outlet.
Secondary Return :
The 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).
Minimum size of
resistance allowed,
from tundish expressed as a
length of pipe (i.e.
no elbow or bends)
22 mm
28 mm
35 mm
28 mm
35 mm
42 mm
35 mm
42 mm
54 mm
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 7 m from the
Tundish to the point of discharge.From Table 1
Maximum resistance allowed for a straight length of 22 mm copper
discharge pipe (D2) from G 1/2 T & P valve is 9m.
Subtract the resistance for 4 no. 22 mm elbows at 0.8m each = 3.2 m.
Therefore the maximum permitted length equates to: 5.8 m.
As 5.8m 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
G 1/2 T & P valve equates to: 18 m.
Subtract the resistance for 4 no. 28 mm elbow at 1.0m each = 4 m.
Therefore the maximum permitted length equates to: 14 m
As the actual length is 7 m, a 28 mm (D2) copper pipe will be satisfactory.
Maximum Resistance created
by each elbow or
Up to 9 m
Up to 18 m
Up to 27 m
Up to 9 m
Up to 18 m
Up to 27 m
Up to 9 m
Up to 18 m
Up to 27 m
bend
0.8 m
1.0 m
1.4 m
1.0 m
1.4 m
1.7 m
1.4 m
1.7 m
2.3 m