Bryant UNIT 379H - Manual (Page 4)

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NOTE; If aluminum conductors are used, the connec­
tions 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 “Pentrox A.” When
it is suspected that the connection will be exposed to
moisture, it is very important to cover the entire con­
nection completely to prevent an electro-chemical ac­
tion 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 connectors should be used.
SECTION VII. START-UP AND ADJUSTMENTS
Before starting the unit, make sure that the gas pipe is
purged and free from air. Do not purge into the com­
bustion chambers. All gas piping connections should
be leak-tested.
WARNING; Do not use an open flame to leak-test.
Use a soap-and-water solution.
Start-Up
COOLING
Refer to appropriate Bryant Model 566 installation
instructions for cooling section starting procedure.
HEATING
Follow the lighting instructions attached to the unit.
The sequence of control operation is as follows;
1. Turn on electrical power and gas supply to unit.
2. When pilot gas cock is opened, gas flows to pilot
and to pilot pressure switch. Pilot pressure switch
then closes to complete 24-Volt circuit. Pilot then
lights automatically. The circuit is then completed
through switching of first pilot to second-pilot igniter
coil automatically lighting second pilot. After the
pilots have been automatically lighted, electrical po­
tential is available to first stage gas valve. When
thermostat calls for heating, a circuit is completed be­
tween Wl and 4. This allows current to flow through
first-stage gas valve and fan switch. If room tempera­
ture continues to drop, second stage of thermostat will
complete a circuit between 4 and W2, energizing
second-stage gas valve, bringing unit to full power. On
setting room thermostat below room temperature,
both stages of firing will shut off.
Safety Pilot Test
1. If any one pilot should be extinguished, switch ac­
tion of pilot will interrupt electrical circuit of first-
stage gas valve consequently, unit will shut off.
2. To check this operation, turn pilot gas valve off
manually. The pilots should re-ignite automatically
when pilot gas valve is turned on.
NOTE; There will be a time interval or delay before
the pilot coils will ignite the pilot again.
Limit Control
1. Bryant Model 379 is equipped with lower and up­
per limit controls.
2. If lower limit opens, first stage of automatic gas
valve is de-energized, shutting off gas.
3. If upper limit opens, first stage of the automatic gas
valve is de-energized, and the SPDT switching action
of upper limit bypasses gas valves circuit and ener­
gizes fan delay relay and blower motor starts.
4. Upper limit control has a dual function; its primary
action is to shut off the gas valve, but it also energizes
the blower motor if the furnace becomes overheated.
The recommended method of checking the limit con­
trols is to gradually block off the return air after the
furnace has been operating for a period of at least 5
minutes. As soon as the limit is proved safe, the return
air opening should be unblocked to permit normal air
circulation. By using this method to check the limit, it
can be established that (providing the limit is func­
tioning properly) it will fail-safe if there is motor
failure or overheating of the heating section of the
unit.
Fan Relay
The unit utilizes a fan delay relay located in the con­
trol box. Upward movement of the adjustment lever
causes a lengthening in the “off’ cycle, this results
automatically in shortening the “on” cycle. Down­
ward movement of the adjustment lever has the oppo­
site effect, the “off” cycle is shortened, the “on” cycle
is lengthened.
Adjusting Gas Input (Natural Gas Unit)
The gas input should agree with that shown on the
unit rating plate (450,000 Btuh). The burners are
equipped with fixed orifices. The burners on the
natural gas units are equipped with No. 38 drill size
orifices.
The following method may be used to adjust the input
on natural gas units.
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