HAMWORTHY HEATING LTD. PUREWELL AUTOMATIC IGNITION 500001035/G
4
The flow corresponding to 22
°
C temperature rise across
the boiler is the minimum recommended flow at any time.
For boiler pressure drop see Figure No. 2.
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
for details. See Figure No. 12 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.
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 22
°
C rise across system. Minimum
head required = 10.5 metres or 1.03 bar.
See
Section 8.11
for Pressurised Water Systems.
4.0
LOCATION
4.1
(See Figure No. 9 for dimensions/weights and
clearances.) 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.
Allow adequate space, this should not normally be less
than 460 mm. at the rear, for flow and return connections.
Also allow at least 460 mm. on one side, the other side
must be no less than 150 mm. Allow 610mm (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
IM/16
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
IM/2
and
IM/5
as appropriate.
See Figure No. 11 for recommended gas flows in pipes.
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
Although the boiler receives a gas leak check and gas
train component integrity check prior to leaving the
factory, transport and installation may cause
disturbance to unions, fittings and gas valve assemblies’
etc. During commissioning a further test for soundness
should be carried out on the boiler gas pipework and
components. A procedure guide is given below. Care
must be taken not to allow leak detection fluid on or
near any electrical parts or connections (If used). See
Figure No. 3 - Gas valve/pipework leak check test
procedure.
