Steffes HPB22 Troubleshooting Guide - Manual (Page 8)

DISCHARGE AIR
Check-Out Procedure
Models: HPB11B, HPB15B and HPB22B
Page 6
CHECK OUT PROCEDURE:
The failure of the melt link is often the result of another problem that exists within the booster. Typically, the failure is a
direct result of the inability of the booster to regulate its output temperature. If the primary problem is not rectified, melt
link failure could occur again. Thus, after the failed melt link has been replaced, the booster MUST be tested to ensure
that failure will not reoccur.
1. Check for proper connection of the remote mounted duct sensor, “IF USED”.
CAUTION: Shorting of the duct sensor to the ductwork WILL cause a malfunction in the booster and result
in the melt link failing. An inspection of the duct sensor mounting and clearance must be
performed.
2. Remove the electrical panel cover on the front of the booster.
3. Disconnect blowers to test damper operation by removing the purple wire from the blower relay. Energize the
booster’s control circuit to observe the damper motor.
4. With no heat call to the booster, the damper motor should go to a fully closed
(CW) position. (See Figure 1)
5. Now, initiate a Stage 2 heat call from the booster’s room thermostat. The
damper motor should go to a fully open (CCW) position. (See Figure 2)
6. If the damper does not move to an opened and closed position as shown in
Figures 1 and 2, check the damper system for mechanical binding and/or for
damper motor malfunction.
7. De-energize the control circuit and remove the “RED” damper motor wire from
the CCW terminal.
8. Energize the control circuit again and initiate another heat call from the booster’s
room thermostat.
9. Check voltage from the COM terminal and the now disconnected “RED” wire
on the damper motor. 24 VAC should be present. Also, check the voltage
between the COM and CW terminal. No voltage should be present.
10. Remove the air discharge sensor. Inspect the temperature sensing bulbs for
separations or breaks in the mercury columns at the center of the bulbs. It may
be necessary to warm the bulbs to fully view the mercury columns. In many
cases, if a separation exists, it can be removed by the heating of the sensor
causing the mercury to move to the top of the bulb.
CAUTION: Overheating the bulb can cause it to burst. SAFETY GLASSES MUST BE WORN WHEN
HEATING THE BULBS.
NOTE: Early booster models incorporated an air discharge sensor that signaled the booster’s control system
directly. Newer models use triac controls. If the booster that is being serviced does not have the triac
switches on the air discharge sensor, it is recommended that the sensor be replaced.
11. De-energize the control circuit. Jumper between the upper and lower copper bulb mounting brackets of the 145
degree mercury bulb (inner bulb) on the air discharge sensor which is located in the base of the booster.
12. Energize the control circuit and check the status of the #4 LED Red light on the booster’s interface board. This
light must be energized (indicates the damper is satisfied).
13. Retest the voltage at the damper motor. (Refer to steps 7, 8 and 9.) If the booster does not respond correctly to the
voltage check, replace the air discharge sensor. Voltage should be zero between the COM terminal and “RED”
damper motor wire. It should also be zero between the COM terminal and the CW terminal.
14. De-energize the control circuit again. With the 145 degree sensing bulb jumper still in place on the air discharge
sensor, jumper between the upper and lower copper bulb mounting brackets of the 160 degree sensing bulb (outer
bulb).
CCW CW 
CLOSED
Figure 1
CCW CW 
OPEN
Figure 2