281 Issue 1 - Service Manual - BX3
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3.8 Pressure Switch
PRESSURE SWITCH:
The pressure switch is a Cleveland NS2 series diaphragm pressure differential activated switch.
The BX3 models have one pressure switch. Please refer to the technical data sheets for the
operating range.
The pressure switch for proving sufficient combustion airflow is located in the vicinity of the
combustion fan and measures the vacuum pressure in the heat exchanger outlet box. If there is
insufficient vacuum pressure to ensure safe and reliable ignition, or combustion quality, the
switch will go open circuit and the 24 volt supply to the gas valve cut.
3.9 Main Fan Assembly Operation
ROOM AIR FAN
A centrifugal fan and Permanent Split Capacitor (PSC) motor, housed in a metal scroll are used
for room air circulation, and this is contained within the fan cabinet.
The room fan has 3 speed settings and can be adjusted to obtain the required air flow. The three
settings are low, medium and high and can be changed by shifting the position of the fan spade
terminal.
Note:
Refer to data sheets for fan and capacitor specifications.
