281 Issue 1 - Service Manual - BX3
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6.2 Combustion Fan Servicing
General Service
1.
Check that the motor’s shaft spins freely.
2.
While in operation during a prepurge, check for any unusual noise, such as bearing or
scraping noise.
If there is any suspicion of an underperforming combustion fan or that the entire system is
resulting in low vacuum pressure, the following should be performed:
1. Isolate the heater’s power supply.
2. Check the motor’s winding resistance with the wire looms removed.
3. Re-insert the motor’s wiring loom.
4. Connect a manometer into the combustion fan vacuum pressure hose to measure the
vacuum pressure just prior to the combustion fan.
5. Re-apply power to the heater and force it into an overheat mode to power up the
combustion fan. (
Warning:
Remember the motor operates with 240 Vac.)
6. Measure the combustion fan vacuum pressure, and ensure that it reaches the value as
specified in the table below.
Combustion Fan Motor
Resistance Reading
Fime
Winding Resistance @20
o
C
24.3 Ohms
If the vacuum pressure is below the specified values:
1.
Check that the flueing is within the allowable specifications.
2.
Look for any physical causes of underperformance such as the buildup of soot or silicon in
the combustion fan housing or flue pipe. Clean if necessary.
Servicing while removed
It may be required to remove the combustion fan to inspect it totally.(Refer to section 7.2 C for
removal procedure of the combustion fan).
For air pressure signals please refer to technical information sheet.
