Technical information

Installation and servicing instructions strictly reserved
for qualified gas installers
17
3.5 Terminal Guard
A terminal guard is required if persons could come
into contact with the terminal or the terminal could
be subject to damage.
If a terminal guard is required, it must be positioned
to provide minimum of 50mm clearance from
any part of the terminal and be central over the
terminal.
The guard should be similar to that shown in
diagram 3.6.
A suitable guard is manufactured by:
Tower Flue Components
Morley Rd.
Tonbridge
Kent
TN9 1RA
Size: 280mm x 280mm x 270mm.
4 WATER SYSTEM
4.1 Draining Tap
A draining tap must be provided at the lowest point
of the system, which will allow the entire system
and hot water system to be drained.
Draining taps shall be to the current issue of BS
2879.
4.2 Safety Valve
A safety valve need not be fitted to an open-
vented system.
4.3 Pump
The pump should be fitted on the flow pipe from
the boiler and have isolating valves each side.
A variable duty pump should be set to give a
temperature difference of no greater than 20°C
between the flow and return, with the thermostat
set at “MAX”, which is about 80°C, to give a flow
rate as shown in table 3.
See chart for pressure loss of the boiler, diagram
4.1.
High resistance microbore systems may require
a higher duty pump.
4.4 Flow Rate
If it is necessary to alter the flow rate, the system
can be fitted with a lockable balancing valve in
the main flow or return pipes shown as valve “A”
in diagram 4.3. The flow rate through the boiler
must not be allowed to fall below that given in
Table 3.
Diagram 3.6
12571
Terminal Guard
TABLE 3 FLOW RATE
MODEL MINIMUM FLOW RATE
18 HE 777.8 LITRES/HR
30 HE 1220 LITRES/HR
This is equal to 20ºC differential at
maximum heat input