Evaporator wiring diagrams normally will have a drawing number that starts with a three-letter designation, “GPX”
or “GPU”. An example of a typical diagram is GPX-S-908.
Plug Fan “No Airflow Alarm” Current Sensing Switch (Plug Fan Unit Only)
The current sensing switch is pre-wired and set at the factory and does not normally require adjustment in the field.
But if the plug fans speed operating mode is changed in the field, the current sensing switch may require adjustment
of the no airflow alarm.
Unit with backward curve plenum fans with electronically commutated (EC) motor (i.e., plug fan) use a current
sensing switch (CT) as a safety to alarm when the air flow is unusually low or no air flow. Figure 14 - Current Sensing
Switch shows the CT used to detect a “No Airflow Alarm”. Before starting the adjustment, make sure you have a
small flat blade screwdriver that can fit in the potentiometer slot of the relay.
Figure 14 - Current Sensing Switch
5.19.1 "No Airflow" Switch Adjustment
The following steps show how to use the controller to adjust the plug fan speed to run at a desired low current draw
setpoint.
1. With the unit running, enter the Factory Level password. To gain access to the menus, press the Menu
button then use the UP or Down keys and the Enter key to enter the Factory Password 0002. Next,
proceed to Menu I: Manual Control and press Enter.
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