Thermo Pride MODEL OPA - Manual (Page 28)

All installations and services must be performed by qualified service personnel.
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Figure 4: The Fan Control Module
NOTICE: It is important to confirm that the operating voltage of the
humidifier or EAC being installed matches the output of this control. If
not, a field supplied relay or transformer may be necessary to provide
the proper control and supply voltage for the accessory being installed.
Refer to the manufacturer’s instructions for the humidifier or EAC for
additional information.