Moffat Turbofan G32MS Service Manual Download Page 26

Page: 26 / 70

-26-

Revision 6/F3590

Moffat Ltd, February 2005

Gas valve faulty

The gas valve performs two functions:
- Providing regulation of gas pressure for

the burner,

- Opening and closing gas supply to the

main burner.

In all cases it must first be established that the
gas supply is on, that the manual isolating
valve in line with the gas valve on the
appliance is open, and that the supply

pressure is equal to or greater than the
required burner operating pressure (refer
specification section).
To determine if valve solenoids are operating
correctly, attach a pressure gauge to the
burner pressure test point after the gas valve,
and turn thermostat on. Check gas pressure.
If pressure is not correct for the appliance
specifications, remove the regulator cap on
the gas valve, and adjust the regulator spring
to increase or decrease the pressure. If the

NOTE:

Ensure all wiring and connections to

ignition box are correct before replacing.

Ensure unit has Earth/Ground connection
on unit and at supply.

If ignition box generates a spark, but burner
doesn’t ignite, or if burner ignites but doesn’t
stay alight, firstly check correct electrode
assembly operation. Refer fault diagnosis
6.1.2 - Burner Ignition Spark Not Working.
If all checks are correct, but burner fails to
stay alight then burner box is faulty - replace.

NOTE:

Correct flame sensing current can be

between flame rectification rod lead and

ignition box terminal. Turn on power and
thermostat. With burner running a current of
no less than that specified below should be
read.
Fenwal Models

0.7 micro Amps

If no current reading, or less than specified,
re-check electrode settings, gas pressure, gas
type etc, and if still not correct, ignition box
requires replacement.

Ignition box faulty - 220-240 Volt models
only

The direct spark ignition control boxes used
on 220-240 volt model G32’s are operated
from direct voltage supply from the

thermostat / hold thermostat circuit.
Correct ignition box operation should result in
ignition box commencing spark at ignition
electrodes and opening gas valve to ignite
burner, then maintain burner on after

successful ignition.

IMPORTANT:

These models have a

pre-purge period of 5 seconds before the
spark and gas valve opening commences.
For all 220-240 volt models after using SIT
ignition boxes, check correct supply voltage
across terminal T10 (red phase wire), and
terminal T12 (black neutral wire) on ignition
box.
The measured voltage should equal the

supply voltage, ie 220-240 volts. If not check
wiring.
If voltage is ok, but no spark is generated,

check that all wiring at ignition box has good
connections.
Ensure that the ignition box has earth/ground
connection, and that appliance has earth/
ground at supply, and supply is earthed.
If all connections are ok, and no ignition
sequence operating, then ignition box is faulty
- replace.
If ignition box generates spark, but burner
doesn’t ignite, or if burner ignites but doesn’t
stay alight, firstly check correct electrode
assembly operation. Refer fault diagnosis
6.1.2 - Burner Ignition Spark Not Working.
If all checks are correct, but burner fails to
stay alight then ignition box is faulty - replace.

NOTE:

Correct flame sensing current can be

checked by inserting a multi-meter capable of
measuring micro-amps in series with flame
rectification rod connection to ignition box.
With power off, disconnect flame rectification
rod connection to ignition box and connect
multimeter between flame rectification rod
lead and ignition box terminal. Turn on power
and thermostat. With burner running a current
of no less than that specified below should be
read.
All Models

1.0 micro Amps

If no current reading, or less than specified,
re-check electrode settings, gas pressure, gas
type etc, and if still not correct, ignition box
requires replacement.