5862
9
BURNER STARTING DIFFICULTIES AND THEIR CAUSES
OPERATING FAULTS
Lock-out may occur, because of:
- flame failure;
- ionization probe earthed;
- air pressure switch open.
Shut-off may depend on the gas pressure switch opening.
DIFFICULTIES
CAUSES
The burner goes through
the purge period normally,
the flame ignites, but the
burner goes to lock-out,
within two seconds after
the ignition if:
The ionization probe is earthed or not in contact with the flame, or
its wiring to the control box is broken, or there is a fault on its insu-
lation to earth.
The ionization current is weak (lower than 3 ±A).
The burner goes to lock-
out, after the purge period,
because the flame does not
ignite; the causes may be:
The valve is passing too little gas (low pressure in the gas pipe-
work)
.
The valve is defective
.
The pipe has not been purged from the air
.
The ignition arc is irregular or has failed
.
The burner does not pass
through the pre-purge peri-
od and the control box
goes to lock-out:
The air pressure switch does not change over: it has failed or the air
pressure is too low (combustion head bad set)
.
Flame simulation exists (or the flame really lights).
The burner does not start at
the thermostat closing, be-
cause of:
Gas is not supplied.
The gas pressure switch does not close: incorrectly adjusted.
The air pressure switch is changed over to the operational position.
The fuse of the control box is broken.
The burner repeats the
start-up cycle without oc-
curring the lock-out:
This particular trouble is caused by the gas pipework pressure that
is very close to the value of the gas pressure switch setting, owing
to the sudden pressure decrease the valve opens and actuates -
only temporaneously - the opening of the pressure switch, thereafter
the valve closes, the motor stops and the pressure increases again;
the pressure switch closes and the start-up cycle is repeated and so
forth.
To prevent this trouble, setting the gas pressure switch at a lower
value.
