Flues - Hamworthy Sherborne Series Installation, Commissioning And Servicing Instructions

5.4 Flues

Flue termination, routing and construction must comply with the requirements of the Clean Air
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Act 1993—Chimney Memorandum, BS 6644 BS 5440 and IGE/UP/10.
Any flue must be self supporting and separable from the boiler for servicing requirements.
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The maximum number of modules firing into a common chimney is 9. For larger installations
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refer to HHL Technical.
Due to the low flue gas temperature, 60°C - 130°C, condensation will occur in the flue, flue
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materials must be non-corrosive and utilise fully sealing joints.
Flue construction is recommended of a twin wall, insulated type to maintain buoyancy within
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the flue.
Adequate facilities must be provided for draining the flue condensation. The flue system MUST
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NOT drain through the boiler. See section 5.2.
Horizontal flue runs must be kept as short as possible and be inclined at minimum 2° towards
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the termination.
The flue system must be designed acknowledging that there may be a positive pressure gen-
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erated by the boiler combustion fan. Refer to Appendix C.
The flue system must be designed to limit the max. suction (cold) to 30Pa negative, measured
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at the connection to the boiler. If the suction is greater than 30Pa, refer to HHL Technical.
This condition must then be checked hot and with all boilers firing, the max. pressure at
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the connection to the boiler should be 100Pa positive.
In the event that the flue system when hot does generate a suction, the max. suction is
100Pa.
Any stabiliser fitted must be in or close to the vertical chimney.
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Fan dilution - the design must provide for the use of balancing and trim dampers, and
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their location and operation must be such that the constraints detailed above can be met.
Care must be taken to ensure that the fan performance is matched to deliver the appro-
priate dilution, whilst ensuring that the excessive suction is not applied to the boilers. If in
doubt, refer to HHL Technical.
Fan assist - the use of fan assist must only be a last resort, as the boilers have sufficient
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fan performance to drive the system. If in doubt, refer to HHL Technical.
Connecting flue systems may be smaller in internal diameter than the boiler connection
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and must be designed to deliver the necessary condition at the connection to the boiler.
Refer to Hamworthy Heating Technical dept. for assistance.
Note: Due to high thermal efficiency of the Sherborne boiler & the resultant low flue gas tem-
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peratures there will be visible pluming of the flue gases at the flue termination. This is likely
even when the boiler is not operating at condensing temperatures.
HAMWORTHY HEATING LTD
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SHERBORNE 500001167/E