Bryant Outdoor Heating Unit 379A User Manual download pdf (Page 5)

local code governing such wiring. Field low voltage

connections are to be made in accordance with the

wiring diagram shown in Figure 8.

A separate electrical line should be run for this in

stallation and should contain a fused switch in a con

venient location. Refer to Electrical Connections

(Table III) on page 2 for maximum fuse size and

minimum wire size. Field wiring connections are

made in the control box located in the blower com

partment. See Figure 5.

NOTE: If aluminum conductors are used, the con

nections must be made in accordance with the

National Electric Code. Aluminum wire connections

must be made with special connectors. In preparing

the wire just before installing the connector, all

aluminum wire must be “brush-scratched” and the

wire coated with a corrosion inhibitor, such as “Pen-

trox A.” When it is suspected that the connection will

be exposed to moisture, it is very important to cover

the entire connection completely to prevent an electro

chemical action that will cause the connection to fail

very quickly. Reducing the effective size of the wire,

such as cutting off strands so that the wire will fit a

connector, is very poor practice. Proper size con

nectors should be used.

Wiring entrances are provided in the left side of the

unit. Wiring entrances to the unit are shown in the

dimensional drawing on page 2.

NOTE: The wiring entrances to the unit must be

weathertight.

Use thermostat and subbase assembly P/N

34427D031. Set thermostat heat anticipator at 0.8

amps.

VII. STARTUP AND ADJUSTMENTS

Before starting the unit, make sure the gas pipe is

purged and free from air. Do not purge into the com

bustion chamber. All gas piping should be leak tested.

CAUTION: Remove shipping bolt from blower as

described on label attached to blower access panel.

WARNING: Never use a match or other open flame

to check for gas leakage.

Refer to chiller installation instructions for a circuit

description of the cooling section.

The sequence of control operation for the furnace is as

follows:

1. Turn on electrical power and gas supply to unit.

2. Refer to Figure 7. Note that the 24V control circuit

voltage is applied across unit terminals 4 and X when

power is turned on to the furnace.

When the pilot gas cock is opened, the pilot pressure

switch closes and completes the circuit to the glow coil

of pilot assembly (6B) which ignites the pilot Ap

proximately one minute after the pilot is ignited, heat

from the pilot causes the pilot assembly’s normally

closed contacts to open and the normally open con

tacts to close. This action breaks the ignition circuit

and makes the control circuit to the gas valve.

When the thermostat calls for heating, terminal 4 is

connected to terminal W through the thermostat. This

completes the circuit to the gas valve (5B) and to the

heating blower relay (2G). The energized gas valve

opens and supplies gas to the burners. The contacts of

the energized heating blower relay close and make the

line voltage circuit to the blower motor (3A) and,

starts the blower fan.

Pilot Safety Test

If the pilot should go “out”, the pilot assembly’s nor

mally open contacts (which were closed by pilot

ignition) will reopen and break the circuit to the gas

valve. The de-energized gas valve will close and

shutoff the gas supply to the burners.

This safety feature can be checked by closing the pilot

gas cock. The -burners should shutoff within 90

seconds.

NOTE: The pilot will reignite automatically by

means of glow coil ignition when the pilot gas cock is

opened again. There will be a short time delay before

pilot reignition occurs.

Limit Control

The function of the hi-temp limit control (7K) is to

shutoff the gas supply to the burners and maintain an

electrical circuit to the blower motor if the furnace

becomes overheated. The limit control can be checked

by gradually blocking off the return air after the fur

nace has been operating for at least five minutes. As

soon as the limit has functioned to shutoff the gas

valve, unblock the return air opening to permit nor

mal air circulation.

Blower Fan Relay (Heating)

The heating blower fan relay (2G) is located in the

control box and is adjustable to permit lengthening or

shorting the “OFF” cycle. The “ON” cycle is

automatically adjusted as the “OFF” cycle is changed.

The fan control adjusting lever is factory-set at the

center position and should give optimum performance

in most installations. However, on unusual in

stallations or where the line voltage is considerably

above or below the rated output, it may be necessary

to increase or decrease the length of time the blower

remains on. For longer blower operation, move the

adjusting lever toward the “MAX OFF” position. In

this position the control line switch makes contact

sooner and takes the maximum time to break contact.

For shorter blower operation, move the lever in the

opposite direction.

Blower Fan Relay (Codling)

The unit is also equipped with a cooling blower fan

relay (2A). When a chiller is used in conjunction with

the furnace to form a combination heating and

cooling system, this relay is energized by the chiller

transformer when there is a demand for cooling.

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Bryant Outdoor Heating Unit 379A User Manual Page 5

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