HAMWORTHY HEATING LTD
10
WESSEX 100 M
500001080/F
thermostat) is also fitted to the boiler and must be
set at 100°C.
8.10.1.2
High Temperature Option
If a higher water temperature is required (and the
system head and components are suitable) the
boiler can be supplied with a higher range
temperature limiter which must not be set higher
than 120°C. The control thermostat must not be set
higher than 106°C and this will allow a maximum
flow temperature of 120°C. It should be noted that at
these flow temperatures, the approximate flue gas
temperature will increase to 145°C.
NOTE!
The minimum difference between control
thermostat and temperature limiter
must never
be
less than 10°C.
8.10.2
Water Flow Controls
Any external mixing valve/shunt pump or similar
controls should
ALWAYS ENSURE
that the
minimum water flow rate as shown in Figure 2.2 (p4).
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.
8.10.3
Frost Protection
Consideration should be given to fitting a frost
thermostat set at approximately 4°C
8.11
Unvented Pressurised Systems
See Figure 1.1 (p2) for typical layout of a
pressurised (Un-vented) Hot Water System.
In order to correctly size a pressurisation unit for any
heating system certain parameters are required.
These are: -
1)
Static height of highest component in system.
2)
System volume - if not known a general rule of
thumb of 10 litres/kW installed boiler power can be
used.
3)
Maximum flow temperature, i.e. most systems run
at 82°C.
4)
Maximum system hot working pressure, generally
given in barg.
From the above information Hamworthy Heating can
size the pressure unit and 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.
8.5
Thermometer
See Figure 1.1 (p2) for typical position. A
thermometer complete with pocket should be fitted
in the pipework to indicate water flow temperature.
8.6
Drain Valves
Each boiler should have a 15mm NB drain valve
(not H.H.L. supply) fitted to drain the boiler only.
The heating system in total should have drain valves
as recommended by
BS 6644
. See Figure 1.1 (p2)
for recommended positions.
8.7
Circulating Pump
One or more circulating pumps will be required to
circulate water around the boilers and heating
system. Figure 2.2 (p4) shows the hydraulic
resistance of the boiler. The pump should be sited to
facilitate servicing. It is important to note that when
Wessex boilers are used to replace boilers on an
existing system, the pumps should be checked for
performance against the new boiler waterside
pressure drop 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.
NOTE:
If boilers are run off time clock control, a
pump overrun (not HHL supply) should be fitted
which must run for a minimum of 5 minutes on shut-
down of the last boiler.
8.8
Minimum Water Flow Rates
Minimum water flow rates are shown in Figure 2.2
(p4). 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.
8.9
Water Pressure Drop
The waterside hydraulic resistance (Pressure drop)
is shown in Figure 2.2.
8.10
Control Schemes
8.10.1
Temperature Controls
Adjustable High and Low fire control thermostats are
supplied with each boiler and should be set to
operate within the range 50-90°C for standard
applications. The setting of the Low fire thermostat
is generally 3-5°C below the control (High fire)
thermostat. A temperature limiter, (hand reset limit
Содержание Wessex 100 M100
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