1.6.4
Gas (see figs. 5 and 6)
1.6.5
When the main gas tap (33) is turned to the on posi-
tion gas is admitted to the gas section (7). Pressing
the ignitor button (9) operates a microswitch causing
the commencement of a firing cycle. The fan chan-
ges from low to high speed and after a purge period
of approx 14 seconds a continuous stream of sparks
are delivered lighting the pilot gas (3). Simultaneously,
the thermoelectric valve (14) is opened and after a
further 5 seconds, sufficient energy is being produ-
ced by the thermocouple (5) for the thermoelectric
valve to be retained in the open position.
When the ignitor button is slowly released gas is ad-
mitted to the underside of the solenoid valves (IO, 11
and 12).
There are 3 solenoid valves (I) the centre (blue) valve
(11) fixed at l/3 of max rated output, (2) the right
hand hot water (black) valve (12) fixed at 213 of maxi-
mum rated output, (3) the left hand central heating
(orange) valve (IO) which is variable up top 2/3 maxi-
mum rated output.
The gas admitted by the orange valve is varied by ad-
juster (6).
FUNCTIONAL FLOW DIAGRAM
1
1 Switch 1 1
S$Toff
1 \siq
S!!h 1
Pressure
over
Switch on
Valve
,r
11°C
- Frost
Thermostat
Limit
Boiler 82°C
Control
Thermostat
113 C Blue
Solenoid
Fig. 7
1.6.6 Safety Controls
In addition to the normal safety controls the CELTIC
FF incorporates the following features.
Should the central heating water flow reduce to be-
low 300 L/h (1.1 gal/min) the gas supply to the burner
is turned off, see figs 3 & 4 (36).
Built in boiler protection is provided by turning the
burner and pump on if there is any risk of frost da-
mage.
7
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