Central Heating System Pressure; To Shut Off Boiler; Frost Protection Mode - Baxi COMBI 105 HE User Operating Instructions Manual

Pressure Gauge
2
bar
Fig. 15
Normal Pressure (when cold)
2
bar
Fig. 16
Normal Pressure (operating)
2
bar
Fig. 17
Fault
2
bar
Fig. 18
Below Minimum
ON/OFF
Selector Switch
Reset
Fig. 19
OFF Position
© Baxi Heating UK Ltd 2007
3.0 Operating the Boiler
3.9

Central Heating System Pressure

1. The water pressure in the central heating system is
indicated by the pressure gauge.
2. With the system cold and the boiler not operating the
pressure should be between 0.5 and 1.0 bar. During
operation the pressure should not exceed 2.5 bar, and
will normally be between 1.0 and 2.0 (Figs. 15 & 16).
3. A pressure of 3 or greater indicates a fault. The safety
pressure relief valve will operate, at a pressure of 3 (Fig.
17). It is important that your Installer or Service
Engineer is contacted as soon as possible.
4. The MINIMUM pressure for correct operation is 0.5. If
the pressure falls below 0.5, this may indicate a leak on
the central heating system (Fig. 18).
3.10 To Shut Off the Boiler
1. For short periods: Turn the selector switch to the OFF
position (Fig. 19).
2. For long periods: Turn off the selector switch (Fig.19),
electricity and gas supplies.
If your home is to be left unoccupied for long
periods during cold weather the boiler and whole
system should be drained unless there is additional
frost protection.
3. Your installer will advise you about frost protection and
draining the system.
IMPORTANT: When the selector switch is in the '0'
(Off) position the electrical supply to the boiler is
isolated. The boiler will not operate and the integral
timer (if fitted) will require resetting once the
selector switch is set to either Position (i) or
Position (ii).
3.11

Frost Protection Mode

1. The frost protection feature will operate when the
selector switch is in the central heating and domestic hot
water mode.
The gas and electrical supplies to the boiler must be on
and the system pressure must be within the range
described in Section 3.9.
2. If the system temperature falls below 5°C, then the
boiler will fire until the water temperature has been
raised.
3. Further frost protection can be incorporated by using a
frost thermostat to protect the whole system.
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