Flue Discharge; Surface Temperatures; Flue System Location; Air Supply - Hamworthy Purewell Series Installation, Commissioning And Servicing Instruction

complete ensuring locating bolts are securely fitted.
See Section 13: SERVICING for further information.

6.6 Flue Discharge

The flue system must ensure safe and efficient
operation of the boiler to which it is attached, protect
the combustion process from wind effects and
disperse the products of combustion to the external
air.
The flue must terminate in a freely exposed position
and be so situated as to prevent the products of
combustion entering any opening in a building.
Where the flue diameter is less than 200mm (8") a
terminal must be fitted. Where the flue is of a larger
size consideration should be given to the fitting of a
flue discharge terminal or grill to stop ingress of
birds, etc.

6.7 Surface Temperatures

Combustible materials in the vicinity of the boiler and
flue shall not exceed 65°C during boiler operation.
The flue shall not be closer than 50mm to any
combustible material, except where it passes
through such material with a non-combustible sleeve
when the air gap may not be less than 25mm.

6.8 Flue System Location

The flue system must not be placed or fitted where
there is undue risk of accidental damage to the flue
pipe or undue danger to persons in the vicinity.
NOTE! The flue MUST be self-supporting. Check
that the flue and chimney are clear from any
obstruction.

7.0 AIR SUPPLY

Detailed recommendations for air supply are given in
BS 6644. The following notes are intended to give
general guidance. In all cases there must be
provision for an adequate supply of air for both
combustion and general ventilation, in addition to
that required for any other appliance.

7.1 Air Supply by Natural Ventilation

The boiler room must have, or be provided with,
permanent air vents directly to the outside air, at high
level and at low level. For an exposed boiler house,
air vents should be fitted preferably on all four sides,
but at least on two sides. Air vents should have
negligible resistance and must not be sited in any
position where they are likely to be easily blocked or
flooded or in any position adjacent to an extraction
system which is carrying flammable vapour. Grilles
or louvres must be so designed that high velocity air
streams do not occur within the space housing the
boiler.
The air supplied for boiler house ventilation shall be
such that the maximum temperatures within the
boiler house shall be as follows:
HAMWORTHY HEATING LTD.
1) At floor level (or 100mm above)
2) At mid-level (1.5m above floor level) = 32°C.
3) At ceiling level (or 100mm below)
Where both low and high level openings are used,
the grilles shall have a total minimum free area of: -
Low Level (inlet): 540cm² plus 4.5cm² per kiloWatt in
excess of 60kW total rated input.
High Level (outlet): 270cm² plus 2.25cm² per
kiloWatt in excess of 60kW total rated input.

7.2 Air Supply by Mechanical Ventilation

Air supplied to the boiler room by Mechanical means
should be as follows: -
1) Mechanical inlet and mechanical extract can be
utilised providing design extraction rate does not
exceed one third of the design inlet rate.
2) Mechanical extract ventilation with natural inlet
ventilation MUST NOT be used.
Figure No. 4 - Mechanical Ventilation Flow Rates
Atmospheric
Volume
NOTE: For Mechanical ventilation systems an
automatic control should be provided to cut off the
gas supply to the boiler, in the event of failure of air
flow in either inlet or extract fans.

8.0 WATER CIRCULATION SYSTEM

8.1 General

The Purewell Cast Iron Boiler has a low water
content and the requirements of minimum water flow
are given in Section 8.8:Minimum Water Flow
Rates and Figure No. 2. Recommendations for the
water circulation system are given in BS 6644 and
CP 342.
importance: -
1) In a combined central heating and hot water
system, the hot water storage vessel must be of the
indirect cylinder or calorifier type.
storage vessel should be insulated preferably with
not less than 75mm (3in) thick mineral fibre, or its
thermal equivalent.
2) Circulating pipework not forming part of the useful
heating surface should be insulated to help prevent
heat loss and possible freezing, particularly where
pipes are run through roof spaces and ventilated
cavities. Cisterns situated in areas, which may be
exposed to freezing conditions, should also be
6
PUREWELL PERMANENT IGNITION
Flow rate per 1000kW
total rated heat input
Boilers
Inlet air
(Combustion
ventilation)
m³/s.
1.10
The following notes are of particular
= 25°C.
= 40°C.
Extract air
(ventilation)
m³/s.
0.45
The hot water
500001090/B