CenCon
56
SPEED SENSOR – DJ
With a digital AC voltmeter, measure the AC volts present on terminals “YS to GS”. When the combustion
blower is running there should be 4 to 6 Vac present. If the AC voltage
is not present, check the tachometer
sensor to magnet gap. It should be 1/16 to 1/8 inch. If the gap is satisfactory, attempt to repair by flipping the
magnet over, then flipping the tachometer sensor over, before replacing the tachometer sensor to correct the
problem. Note: No part of the speed sensor’s sensing element should be located over the end of blower motor
shaft.
TOP LOADING
Ensure the top loading tube from the modulating valve is located is not pointed directly UP. Ideally it enters
from the bottom and is located at either side of the burner box and bent to a 90° angle pointed towards the
heat exchanger. This location was chosen to obtain reasonably constant pressure readings not affected by air
velocity.
AIR BALANCING
Installation and air balancing is often done during warmer weather than that experienced in the cold of winter.
If the air balance did not account for ambient temperature, the appliance could be having lower than expected
temperature rise in cold weather conditions. As the fan is a constant volume device and as it is located before
the heat exchanger, air will expand as it is heated. The amount of change could be up to a 20% increase in air
volume from -30°F to +70°F.
Blower
1/8”
Magnet
Magnet
Retainer
Hall
Effect
Sensor
