HAMWORTHY HEATING LTD
6
WESSEX 100 M
500001080/F
losses. The control system and valves, where fitted,
should be regulated to avoid lower flows occurring.
The flow corresponding to 15°C temperature rise
across the boiler is the minimum recommended at
any time.
3.4
Time Clock Control
In order to avoid local overheating and progressive
calcium deposition at zero flow conditions where
boilers are operated from time clocks, provision
should be made for a 5 minute circulating pump
over-run after the last boiler has ceased firing.
NOTE!
Time clocks should not interrupt live, neutral
or earth connections, see
Section 9.0:
ELECTRICAL SUPPLY
(p11) for details. See
Figures 8.12 (p12) and 9.1 (p13) for wiring details.
3.5
Minimum System Pressure
To comply with guidance note
PM5 (Health and
Safety Executive)
, the minimum pressure
requirements at the boiler are given below as
examples: -
1) Single installed boiler running at 82°C flow
temperature. Minimum head required is not less
than 2 metres or 0.2 bar.
2) Single installed boiler running at 95°C flow
temperature. Minimum head required = 5.1 metres
or 0.5 bar.
See Section 8.10.1
(p10).
3) Modular boiler installation running at 82°C flow
temperature and 11°C rise across system.
Minimum head required = 4.3 metres or 0.42 bar.
4) Modular boiler installation running at 82°C flow
temperature and 15°C rise across system.
Minimum head required = 9.4 metres or 0.92 bar.
See
Section 8.11
(p10) for Pressurised Water
Systems.
4.0
LOCATION
4.1
(See Figures 2.1 (p3) & 2.2 (p4) for dimensions /
clearances and weights.) The location chosen for
the boiler
MUST
permit the provision of a
satisfactory flue system and an adequate air supply.
The location must also provide adequate space for
servicing and air circulation around each unit. This
includes any electrical trunking laid along the floor
and to the appliance.
Allow adequate space, this must not be less than
500mm at the rear, for flue and flow / return
connections. Allow 650mm (minimum) in front of the
boiler for servicing.
The boiler must be installed on a level non-
combustible surface that is capable of adequately
supporting its weight (when filled with water) and
any ancillary equipment.
Any combustible material adjacent to the boiler and
the flue system must be so placed or shielded to
ensure that its temperature does not exceed 65°C.
Further details regarding boiler location are given in
BS 6644
.
5.0
GAS SUPPLY
5.1
Service Pipes
The local gas region must be consulted at the
installation planning stage in order to establish the
availability of an adequate supply of gas. An existing
service pipe must not be used without prior
consultation with the local gas region.
5.2
Meters
A new gas meter will be connected to the service
pipe by the local gas region, or a local gas region
contractor. An existing meter should be checked,
preferably by the gas region, to ensure that it is
adequate to deal with the rate of gas supply
required.
5.3
Gas Supply Pipes
Supply pipes must be fitted in accordance with
BS
6891
or
IGE/UP/2
as appropriate. Pipework from the
meter to the boiler must be of adequate size. Do not
use pipes of a smaller size than the boiler gas
connection. The complete installation must be
purged and tested for soundness as described in
BS
6891
or
IGE/UP/1
and
IGE/UP/1A
as appropriate.
5.4
Boosted Supplies
Where it is necessary to employ a gas pressure
booster, the controls must include a low-pressure
cut-off switch at the booster inlet. The local gas
region must be consulted before a gas pressure
booster is fitted.
5.5
Boiler House Control Valve
A manual valve for boiler house isolation shall be
fitted in the gas supply line. It shall be clearly
identified and readily accessible for operation,
preferably by an exit.
5.6 Boiler Gas System Leak Check
The Wessex 100 M boiler is supplied with a single gas
pipe which exits the base tray at the rear left hand
side, see Figure 2.1 (p3) for position. The incoming
mains gas supply must be capable of supplying gas to
the boiler at the required pressure and volume, under
all firing conditions. An approved isolating valve and
union should be installed for each boiler in a
convenient and safe position and be clearly marked.
Ensure that the manual gas service valve is in the
OFF position.
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