Glow-worm Xtramax - Manual (Page 31)

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18 Fault Finding
WARNING. Always isolate the boiler from the electrical supply
before carrying out any electrical replacement work.
On completion of a fault finding task that has required the
disconnection and making of electrical connections, the check
for earth continuity, polarity and resistance to earth must be
carried out.
If any gas-carrying components are disturbed, removed or
replaced it will be necessary on completion to check for gas
soundness with leak detection fluid.
Before trying to operate the boiler make sure that :
• All gas supply cocks are open and that the gas supply has
been purged of air.
• The heating system pressure is at least 1 bar.
• There is a permanent mains supply to the boiler.
• The fuse on the PCB is intact.
Preliminary electrical system checks, as outlined in a multimeter
instruction book, are the first checks to be carried out during a
fault finding procedure.
Should there be any doubt about the voltage supply to any of the
components, it is possible to carry out a simple electrical test to
ensure all is operational in that area.
To carry out the electrical test, gain access to the main Printed
Circuit Board (PCB), as described previously, and measure the
voltages according to table 2.
Table 2
Voltage Measured value Measuring point
230 Volt 230 V AC Between terminals H8.1 and H8.2
24 Volt maximum 33V DC Between terminals B2.4 and B2.7
15 Volt 15V + 0.5V Between terminals B2.4 and B2.2
Display 5V + 0.5V Between terminals B2.4 and B4.2
09 FF
Sec 052
A fault code is displayed on the left hand side of the LCD display, whilst at the same time, the letters appear with a
telephone symbol.
Thermistor values
The following table applies to the central heating, domestic hot
water and storage vessel thermistors:
Temperature ( ° C) Resistance ( Ω )
0 32565
5 25345
10 19875
15 15700
20 12500
25 10000
30 8060
35 6535
40 5330
45 4370
50 3605
55 2989
60 2490
65 2085
70 1755
75 1480
80 1260
85 1070
90 920
95 785
100 680
System pressure sensor
The resistance of the sensor at various pressures is as follows:
0 bar between 280 Ω and 320 Ω
1 bar between 195 Ω and 220 Ω
3 bar between 93 Ω and 143 Ω
The XTRAMAX has an on-board fault diagnostic
system. Should a fault occur on the boiler, the warning
LED at the top of the user display will illuminate
and the LCD display will indicate the precise area
where the fault has occurred.