Operating Principle - Baxi Heat 616 Installation And Service Manual

4.2

Operating Principle

Mains On.
(CH or DHW demand)
Self test cycle for 20s
(output setting displayed)
Flow
NO
temperature less
than set point ?
YES
10 second pre-purge
5 second ignition
Flame detected ?
YES
Burner on
Modulate output
Flow temp or
rate of rise too
high ?
YES
Burner Off
(Demand satisfied)
NO
Over Temp
Fault ?
YES
Lockout
7726858-01 (1/19)
NO
5th ignition attempt ?
YES
Ignition Lockout
NO
Mains Off
1. Switched Live On: When the boiler switched live turns on
the boiler, a 20 second check cycle takes place. If the flow
temperature is less than the boiler set-point temperature the
ignition cycle will start. Pre-purge, Ignition and Burner on.
2. Fan Pre-Purge: The boiler has a 10 second pre-purge (Fan
On, Spark Generator and Gas Valve off) before the start of the
ignition sequence.
3. ignition: The boiler has a 5 second ignition period (Fan,
Spark Generator and Gas Valve on) and burner on occurs when
a flame is detected. If a flame is not detected within the 5
second ignition period then 4 more ignition attempts are made.
If a flame is not detected after the 5 ignition attempts the boiler
goes to an ignition lock-out and an error code is displayed.
4. Burner on: After a successful ignition, Burner on occurs (Fan
and Gas Valve on, Spark Generator off). The boiler flow
temperature is controlled by varying the fan speed (and thereby
the gas rate) to achieve the optimum boiler operation. If the
boiler flow temperature exceeds the boiler set-point, the burner
will turn off (Fan and Gas Valve off).
5. Overtemperature: If a boiler overtemperature event occurs
(triggering the safety thermostat) the burner shuts down (Fan off
and Gas Valve off). A locking signal is generated and an error
code is displayed.
6. Lockout: If a lock-out error is displayed (Fan, Spark
Generator and Gas Valve off) the boiler can only be reset by
manually pressing the reset button. If 5 lock-outs are reset
within a 1 hour period then boiler becomes inoperable. It is
necessary to switch off the power supply to the boiler, and when
reinstated the reset button pressed again to operate the
appliance.
Any lock-out errors that occur regularly will require further
investigation and rectification.
Baxi Customer Support: 0344 871 1545.
Description of the Product
600 Heat
4
19