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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 resistance test. Connect
test leads between an appliance earth point and the earth
wire of the appliance 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 connections at the appliance terminal
strip (fig.16). Repeat above test on the Live & Earth
connections 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 7.8.4.
●
●
●
●
●
Connect test leads between the Live & Ear th
connections at the appliance terminal strip (fig.16). The
meter should read approximately 230V ac. If so proceed
to next stage. If not, see 7.8.4.
●
●
●
●
●
Connect test leads between the Neutral & Earth
connections at the appliance terminal strip (fig.16). The
meter should read approximately 0 – 15Vac. If so polarity
is correct. If not, see 7.8.4.
Symptom
Possible cause
No display/ignition
Check wiring/check
electrical supply
No hot water
Check external controls
No heating
Check external controls
Fault code
Possible cause
10
Check gas supply, check
flue system, check polarity
COMPONENT
VALUE
Fan
230Vac
Pump
230Vac
Ignition transformer
230Vac
Gas valve
230Vac
Room thermostat connection
230Vac
NTC thermistor (dry contact)
10Kohm
NTC thermistor (wet contact)
10Kohm
FUNCTION
VALUE
Standard Heating Range (°C)
40 – 76
CH limited power at 75%
15 Min
Heating OFF hysterisis (
0
C)
SP + 2
Heating ON hysterisis (
0
C)
SP – 8
Anti-cycle delay
5-min
Pump over-run
5-min
Low output (min. %)
Min+25
CO function max temp. (
0
C)
87
CO re-light temp. (
0
C)
75
CO function time
15-min
Flow NTC max temp. (
0
C)
87
High limit thermostat (
0
C)
97
Burner thermostat (
0
C)
170
Maximum differential (
0
C)
35
IGNITION CONTROL
VALUE
Ignition attempts before L/O (lockout)
5
Re-ignition attempts after loss of flame signal 5
7.9 COMPONENT VALUES & CHARACTERISTICS
7.5 COMBUSTION ANALYSIS TEST
A combustion analysis check can easily be carried out on
the appliance via the test points located on the top of the
appliance (see 7.4).
•
Insert the flue gas analyser probe into the flue gas test
point (see fig. 35).
•
Operate the boiler in CO mode and compare the values
with those shown in section 2 (Nat. Gas) or section 10
(LPG). If different adjust the gas valve according to
7.4.1, 7.4.2 & 7.4.3.
7.6 EXTERNAL FAULTS
Before carrying out any faultfinding or component
replacement, ensure the fault is not attributable to any
aspect of the installation.
7.6.1 INSTALLATION FAULTS
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 between 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 resistance test. Connect
test leads between the Live & Earth connections at the
appliance terminal strip (fig. 16). If the meter reads other
than infinity there is a fault that must be isolated, carry
out a detailed continuity check to identify the location of
the fault.
These series of checks must be carried out before
attempting any faultfinding procedures on the appliance.
On completion of any task that required the disconnection
and re-connection of any electrical wiring or component,
these checks must be repeated.
7.8 FAULT FINDING
Before attempting any faultfinding, the electrical checks
as detailed in 7.8 must be carried out. Isolate the appliance
from the electrical supply.
Disconnect any external controls from terminal plug M5
(fig. 16), and insert a link-wire between the two wires at
the ‘TA’ connections (fig. 16).
NOTE
Restore the electrical supply to the boiler and turn the
selector switch to the on position. The boiler should now
function as described in section 7.2. Should the boiler fail
to respond, the internal fuses and connectors should be
checked to ensure integrity and continuity. If the boiler
still fails to respond, refer to the detailed faultfinding
flowcharts located at the end of this section.