HAMWORTHY HEATING LTD
WESSEX-HE 200 BOILER
500001008/K
7
8.0 WATER CIRCULATION SYSTEM
8.1 General
The boiler has a low water content and the
requirements of minimum water flow are given in
Section 8.8 and Figure No. 3. Recommendations for
the water circulating system are given in
BS 6644
and
CP 342
.
The following notes are of particular importance.
In a combined central heating and hot water system,
the hot water storage vessel must be of the indirect
cylinder or calorifier type. The hot water storage
vessel should be insulated preferably with not less
than 75mm thick mineral fibre, or its thermal
equivalent.
Circulating pipework not forming part of the useful
heating surface should be insulated to help prevent
heat loss and possible freezing, particularly where
pipes run through roof spaces and ventilated cavities.
Cisterns situated in areas that may be exposed to
freezing conditions should also be insulated.
Insulation exposed to the weather should be rendered
waterproof.
Drain valves must be located in accessible positions,
which permit the draining of the whole system,
including the boiler and hot water storage vessel.
8.2 Pressure Relief Valve (Safety Valve)
The most important single safety device fitted to a
boiler is its safety valve and each boiler, or in the
case of modular installations, each bank of boilers,
must be fitted with a pressure relief valve to
BS 6759
Part 1 (ISO 4126)
and sized as in
BS 6644
(see
below).
BS 6644
provides comprehensive information for the
selection and location of safety valves and attention is
drawn to the higher capacity requirements of safety
valves for unvented hot water systems.
8.3 Open Vent Pipe and Cold Feed Pipe
(See
BS 6644
).
Refer to Figure No. 2 for the open vent connection
A vent pipe and cold feed pipe must be fitted to the
water system between the boiler and the first isolating
valve in the water system. The sizes of these pipes
are shown below. The vent pipe must rise
continually, must not be valved except by a design
which when closed for maintenance, the boiler is
open to atmosphere. The pipe shall be protected
against freezing where this might occur.
8.4 Altitude Gauge (Water Pressure Gauge)
See Figure No. 2 for position of tapping.
Every boiler or group of boilers should be provided
with a gauge complete with isolating valve.
8.5 Thermometer (Temperature Gauge)
See Figure No. 2 for position of tapping.
A thermometer complete with pocket should be fitted
in the pipework to indicate water flow temperature.
8.6 Drain Valves
See Figure No. 2 for position of tapping.
Each boiler must have a suitably sized drain valve
fitted.
8.7 Circulating Pump
One or more circulating pumps will be required to
circulate water around the boilers and heating
system. Figure No. 3 shows the hydraulic resistance
of the module. The pump should be sited to facilitate
servicing. It is important to note that when Wessex
boilers are used to replace boilers on an existing
system, the pumps should be checked for
performance against the new boiler waterside
pressure drop to ensure that the minimum flow rate
can be obtained. It is also important that the existing
system be flushed through to remove any loose
matter, which may have accumulated. If in any doubt
regarding the cleanliness of the system, a coarse
filter should be fitted in the return pipework to the
boilers.
8.8 Minimum Water Flow Rates
The minimum water flow rate per module is shown in
Figure No. 3 and should be maintained through each
PRESSURE RELIEF VALVE
(Open Vented Systems Only)
OPEN VENT AND COLD FEED PIPE
Open Vent Size
Cold Feed Size
Wessex-HE 200
19mm clear bore
38mm
32mm
Wessex-HE County
32mm clear bore
50mm
38mm
BOILER
