Thermo Pride MODEL OPA - Manual (Page 27)

All installations and services must be performed by qualified service personnel.
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3. All wiring sizes must comply with local codes or the National Electrical Code.
To minimize voltage drop to the appliance, the next larger size wire should be
used when long wiring runs, in excess of 100 ft., are employed. Refer to the
wiring diagrams when wiring or servicing.
NOTICE: Proper operation of the heating section of this unit depends upon
correctly connecting the electrical power source. The hot leg, L1, of the
supply circuit must be connected to the black line lead and the neutral leg,
N, to the white line lead in the burner compartment junction box. All
ungrounded circuit conductors must be broken by the disconnecting
switch to prevent the hazard of electrical shock when servicing this
appliance.
In the event a circuit breaker trips or a fuse blows as a result of the operation of
this appliance, investigate the appliance electrical system to determine the
cause. Correct any electrical faults and abnormal conditions before putting the
unit back into operation. Do not put in a larger fuse and do not exceed
maximum fuse size listed on the rating label in order to temporarily “fix”
the problem. The rating label is located on the inside of the burner compartment
cover.
The appliance control system contains a 15 amp. time-delay type fuse to
protect the heating system control circuitry. The control fuse is located within
the junction box, which is located in the burner compartment. In the event the
fuse blows, replace the fuse with one of equivalent type and rating.
1. Electronic Air Cleaner (EAC) and Humidifier Installation
The standard control system for the appliance does not have the ability to
directly control the operation of an electronic air cleaner or a humidifier. If
these devices are used, a means to initiate and discontinue their operation
must be provided external to the accessory if such means is not provided
internally. Typically, an airflow sensing control is installed in the duct system
to determine operation of the furnace and automatically activate (and also
deactivate) the EAC or humidifier.
If the control system contains the Honeywell brand model ST7997 electronic
fan timer, this unit has designated terminals to control the operation of an
electronic air cleaner and/or humidifier. These terminals provide line voltage
for the control of these accessories, refer to Figure 4.