11
Unvented
To install an A.O.Smith water heater on an unvented cold
water supply system a kit of valves and fittings listed by
the water research centre and complying with part G3 of
the current building regulations and BS 7206 should be
used. Installation should be carried out generally as
shown on diagram 5.
Diagram 5 – Connection diagram (unvented system)
1
Gas cock
2
Stop valve
3
Expansion vessel
4
T&P valve
5
Non-return valve
6
Circulation pump
7
Drain valve
8
Pressure limiting
valve
9
Expansion valve
A Gas Supply
B Hot Water
C Cold Water
D Hot Water Supply
E Return Circulation
A.O.Smith water heaters are tested to a maximum
pressure of 12 bar and a maximum working pressure of
8 bar.
Dead legs on a hot water installation are undesirable.
Where possible they should be avoided. Where the
inclusion on the system of a dead leg is unavoidable the
following restrictions should be applied:
-
for pipes not exceeding 19 mm. Inside diameter;
maximum length of dead leg permitted 12.0 metres;
-
for pipes exceeding 19 mm. But not exceeding 25
mm. Inside diameter; maximum length of dead leg
7.5 metres;
-
for pipes with an inside diameter exceeding 25 mm.
maximum dead leg 3.0. metres.
Depending on the length and insulation of the water
piping and the water demand frequency, it may be
necessary to install a circulation system on the drain
cock. The return pipe of the circulation piping can be
fitted on the top of the drain cock after the sealing plug
has been removed (see diagram 6).
Diagram 6 – Connection point for the return piping.