3.2.4 Program sequence
1. Pre-purge
At heat demand
1
the fan starts and dries to pre-purge speed
2
.
2. Ignition
The fan drives down to ignition speed
3
, ignition
4
switches on, the gas valves
5
open. The ignition spark ignites the fuel. A flame appears.
3. Safety time
Following the safety time (3.5 seconds)
6
ignition is switched off.
4. Stabilisation of the flame
If a flame signal
7
is transmitted, the flame stabilisation time
8
will follow.
5. Delayed heating operation
In the heating operation mode the delayed heating operation
9
is carried out first.
The heating capacity is restricted for the duration of the delayed time (the delayed
heating operation is omitted during DHW operation)
6. Modulating operation
The internal unit temperature regulator sets the speed setpoint for the fan
0
within
the programmed load limits.
7. Post-purge
Following every normal shut down, after faults and after the return of the power supply,
the fan is operated at the post-purge speed
q
.
Installation and operating instruction
Gas condensing boiler WTC-GB 90-A
3 Product description
83266502 • 1/2010-08 • La
14-95