Hamworthy Sherborne Series, Installation, Commissioning And Servicing Instructions

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HAMWORTHY HEATING LTD
48
SHERBORNE 500001167/E
E1.6 Thermometer
A thermometer complete with pocket should be fitted in the pipework to indicate water flow temperature.
E1.7 Drain Valves
Each boiler should have a 15mm NB drain valve (not Hamworthy Heating Ltd supply) fitted in the boiler return to
drain the boiler only. The heating system in total should have drain valves as recommended by BS 6644.
E1.8 Circulating Pump
One or more circulating pumps will be required to circulate water around the boilers & heating system. The pump
should be sited to facilitate servicing. It is important that when Sherborne boilers are used to replace boilers on an
existing system, the pumps should be checked for performance against the new boiler waterside pressure loss to
ensure that the minimum flow rate can be obtained. It is also important that the existing system be flushed through
twice 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.
If boiler / system pumps are not controlled by the boiler, a pump overrun (not Hamworthy Heating Ltd supply)
should be fitted, which must run for a minimum of 5 minutes on shutdown of the last boiler.
E1.9 Minimum Water Flow Rates
Minimum water flow rates are shown in table at beginning of Appendix E. These flow rates should be maintained
through the boiler at all times whilst the boiler is firing. If the water flow rate is allowed to fall below the minimum
the boiler heat exchanger could fail due to the resultant scale formation. Particular attention should be paid to the
restriction of external flow circuits during periods of low heat demand.
E1.10 Waterside Pressure Drop
The waterside hydraulic resistance (Pressure drop) is given in table at beginning of Appendix E.
E1.11 Water Flow Controls
Any external mixing valve / shunt pump or similar controls MUST always ensure that the minimum water flow rate
as given in table at beginning of Appendix E is maintained. If there is any doubt relating to site flow conditions it is
suggested that a flow switch is fitted. The flow switch should be connected such that the boiler will shut down if
insufficient flow occurs.
E1.12 Frost Protection
The boiler is equipped with it’s own two stage frost protection capability, assuming that the circulating pump is
controlled by the boiler. If this is not the case, consideration should be given to fitting a frost thermostat set at
approximately 4°C
E1.13 Unvented Systems
For system design refer to BS 7074 Part 2. In order to correctly size a pressurisation unit for any heating system
the following parameters are required.
•
Static height of highest component in system (metres)
•
System volume. If this is not known, a general rule of thumb of 10litres/kW of installed boiler power
can be used.
•
Maximum flow temperature (°C)
•
Maximum system hot working pressure, generally given in bar gauge.
From the parameters given, Hamworthy Heating can size the pressurisation unit & also the expansion vessel
required.
Care must be taken in sizing expansion vessels to ensure maximum acceptance factors are not exceeded.
Normally manufacturers of vessels impose a limit of 0.5. This value must not be exceeded at any time during the
operation of the boiler, this includes the over pressure condition should a safety valve lift.
Consideration should also be given to sizing of the safety valve(s) in the system. Refer to BS 6759: Part 1 for
further information & to BS 6880: Part 1 for design considerations.