Hk j l – Baxi Potterton BBU 15 HE User Manual

Page 37

12.0 Fault Finding

Check and correct if necessary
1. The mechanical set of the gas valve
(CO2 values - see instruction)
2. Flame sensing electrode and lead connections
3. Flame sensing electrode position

Flame current should be more than 0.5 μA

Replace PCB

YES

Replace flame sensing electrode

Check the gas supply pressure:

For Natural Gas greater than

10 - 11 mbar

Replace Safety Thermostat

YES

Overheat Thermostat or

Condensate Safety Float Switch

operated or faulty

Allow to cool. Continuity

across thermostat terminals

more than 1.5 ohm

Press the Service Reset switch

for 5 seconds

Fan connections correct at fan.
PCB - X401 connector terminals 5,6,7 & 8

YES

Replace fan

Temperature sensors faulty.
Cold resistance approximately
10kΩ @ 25° C (CH sensor)
(resistance reduces with increase in temp.)

Replace sensor

YES

If pump is running the heat exchanger could be
obstructed

Replace heat exchanger

Restore Boiler Control defaults

Continuity across plug

terminals at 3 & 4 of connector

X401 more than1.5 ohm

Replace PCB

YES

Condensate drain system fault

Check condensate system

and Pump

Replace Safety Float Switch

or wiring

IMPORTANT:There is no limit to the number of repeated ‘Service Reset’

operations but the Boiler Control must be refreshed by ‘Restoring Boiler

Control Default’ as described on p.34 following the final ‘Service Reset’ and

before the Boiler Control reset is re-used.

YES