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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 us-
ing a suitable multimeter, carry out the following voltage tests:
•
connect test leads between the Live & Neutral connections
at the appliance terminal strip. The meter should read ap-
proximately 230V ac. If so proceed to next stage. If not, see
7.7.4.
•
connect test leads between the Live & Earth connections
at the appliance terminal strip. The meter should read ap-
proximately 230V ac. If so proceed to next stage. If not, see
7.7.4.
•
connect test leads between the Neutral & Earth connec-
tions at the appliance terminal strip. The meter should read
approximately 0 – 15Vac. If so polarity is correct. If not, see
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 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.
ISTANCE 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. 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 7.7 must be carried out. Isolate the appliance from
the electrical supply.
Disconnect any external controls from terminal plug (CN5 fig.
46), and insert a link-wire between the two wires at the ‘TA’
connections.
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. Should the boiler fail to respond, the
internal fuses and connectors should be checked to ensure
integrity and continuity.
COMPONENT
VALUE
Fan
230Vac
Pump
230Vac
Valve actuator
230Vac
Ignition transformer
230Vac
Gas valve
230Vac
Room thermostat connection
24Vdc
NTC thermistor (dry contact)
10Kohm
NTC thermistor (wet contact)
10Kohm
FUNCTION
VALUE
Standard Heating temperature
range (min – max °C)
40 - 80
DHW temperature
range (min – max °C)
37 - 60
75% maximum CH time
15 min
Heating OFF hysterisis (°C)
SP + 5
Heating ON hysterisis (°C)
SP – 5
DHW OFF hysterisis (°C)
SP + 5
DHW ON hysterisis (°C)
SP + 4
Anti-cycle delay
3-min
Pump over-run
30-sec
Low output (min. %)
Min+25
CO function max temp. (°C)
90
CO re-light temp. (°C)
78
CO function time
15-min
Flow NTC max temp. (°C)
90
High limit thermostat (°C)
105
Flue NTC max temp. (°C)
125
Maximum differential (°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 & CHARACTERIS-
TICS
APPLIANCE STATUS AND FAULT CODES
When the boiler detects a temporary fault condition, the ap-
propriate code is shown. If/when the fault is final, the pump
will perform a 60-second post circulation and fault code will be
displayed. See table on page. 5.
Summary of Contents for Vision 25C
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