19
Mynute 24m
7.5
CHECKING THE EXPANSION VESSEL
Carry out the component removal procedure as
described in section 6.4. You must ensure that the
boiler is completely drained of water. Using a
suitable pressure gauge, remove dust cap on
expansion vessel and check the charge pressure.
The correct charge pressure should be 0.8 bar - 0.1
bar. If the charge pressure is less, use a suitable
pump to increase the charge.
NOTE
You must ensure the safety valve is in the open
position whilst re-charging takes place. Replace
the dust cap and carry out the relevant commis-
sioning procedure (section 5).
7.6
EXTERNAL FAULTS
Before carrying out any fault finding or component
replacement, ensure the fault is not attributable to
any aspect of the installation.
7.6.1
INSTALLATION FAULTS
7.7
ELECTRICAL CHECKS
Any electrical checks must be carried out by a
suitably qualified person.
7.7.1
EARTH CONTINUITY TEST
Isolate the appliance from the electrical supply
and using a suitable multi-meter carry out a resist-
ance test. Connect test leads between an appli-
ance earth point and the earth wire of the appli-
ance supply cable. The resistance should be less
than 1 ohm. If the resistance is greater than 1 ohm
check all earth wires and connectors for continuity
and integrity.
7.7.2
SHORT CIRCUIT CHECK
Isolate the appliance from the electrical supply
and using a suitable multi-meter, carry out a short
circuit test between the Live & Neutral connec-
tions at the appliance terminal strip (fig. 16).
Repeat above test on the Live & Earth connec-
tions at the appliance terminal strip (fig. 16).
NOTE
Should it be found that the fuse has failed but no
fault is indicated, a detailed continuity check will
be required to trace the fault. A visual inspection
of components may also assist in locating the
fault.
7.7.3
POLARITY CHECK
With the appliance connected to the electrical
supply and using a suitable multimeter, carry out
the following voltage tests:
•••••
connect test leads between the Live & Neutral
connections at the appliance terminal strip (fig.16);
the meter should read approximately 230V ac. If
so proceed to next stage. If not, see section 7.7.4.
Symptom
No ignition
No hot water
No central heating
Possible causes
Check external wiring
Check external controls
Check external controls
Check external controls
•••••
connect test leads between the Live & Earth
connections at the appliance terminal strip (fig.16);
the meter should read approximately 230V ac. If
so proceed to next stage. If not, see section 7.7.4
•••••
connect test leads between the Neutral & Earth
connections at the appliance terminal strip (fig.16);
the meter should read approximately 0-15V ac.
If so polaruty is correct. If not, see section 7.7.4.
7.7.4
REVERSED POLARITY OR SUPPLY FAULT
Repeat the above tests at the appliance isolator,
if testing reveals correct polarity and/or supply at
the isolator, re-check wiring and connections be-
tween the isolator and the appliance.
If tests on the isolator also reveal reversed polarity
or a supply fault, consult the local electricity
supplier for advice.
7.7.5
RESISTANCE TO EARTH CHECK
Isolate the appliance from the electrical supply
and using a suitable multi-meter carry out a resist-
ance test. Connect test leads between the Live &
Earth connections at the appliance terminal strip
(fig.9a). If the meter reads other than infinity there
is a fault which must be isolated, carry out a
detailed continuity check to identify the location of
the fault.
IMPORTANT
These series of checks must be carried out before
attempting any fault-finding procedures on the
appliance. On completion of any task which re-
quired the disconnection and re-connection of any
electrical wiring or component, these checks must
be repeated.
