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27
AST 14 C 255/00
ELECTRICAL CONNECTIONS
SOLENOID VALVES SV1 and SV2
3.5 GAS VALVE
The boiler is approved for operating with gas valve, model SIT 845:
Gas valve characteristics
EV1 and EV2 safety coil operating power supply
230 VAC 50 Hz
EV1 operating current
40 mA
EV2 operating current
12 mA
EV1 supply pin
4 - 5
EV2 supply pin
4 - 1
Modulation coil operating power supply
17 Vdc
Max. operating pressure
60 mbar
Working temperature
-15 / 60°C
Modulation parameters
Current of gas modulation coil at maximum output
120 (natural gas) / 170 (LPG)
mADC
Current of gas modulation coil at minimum output
20 (natural gas) / 30 (LPG) mADC
Current of gas modulation coil at the end of the
ignition ramp for CTFS boilers
80% of maximum current
Current of gas modulation coil at the end of the
heating rising ramp
At maximum CH output (P7)
Coils
Safety coil interchangeability
Yes
EV1 resistance value
~ 1600 Ohm
EV2 resistance value
~ 6.77 KOhm
Modulating coil resistance value
~ 78 Ohm
The valve features a compensation pressure point connected to the combustion
chamber through a silicone pipe.
Valve thus knows the pressure on nozzles and can supply the correct quantity of gas even
in case of overpressure or vacuum inside the chamber.
For example, upon ignition when fan is activated, a vacuum develops inside the
combustion chamber. Thanks to this pressure point, valve decreases nozzle pressure so
as to balance any exceeding gas supply due to vacuum.
GAS OUT
GAS IN
Gas inlet
pressure
measurement
point
E
Gas outlet
pressure
measurement
point
D