Bryant Legacy 674D Installation Instructions Manual Download Page 14

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4. Verify the following conditions:

a. Make sure gas line is free of air. Before lighting the unit

for the first time, perform the following with the gas
valve in the “OFF” position:

NOTE

: If the gas supply pipe was not purged before connecting

the unit, it will be full of air. It is recommended that the ground
joint union be loosened, and the supply line be allowed to purge
until the odor of gas is detected. Never purge gas lines into a
combustion chamber. Immediately upon detection of gas odor,
retighten the union. Allow 5 minutes to elapse, then light unit.

b. Make sure that condenser--fan blade is correctly

positioned in fan orifice. Leading edge of condenser--fan
blade should be 1/2 in. (12 mm) maximum from fan

orifice.

c. Make sure that air filter(s) is in place.

d. Make sure that condensate drain trap is filled with water

to ensure proper drainage.

e. Make sure that all tools and miscellaneous loose parts

have been removed.

START--UP

Step 1 — Check for Refrigerant Leaks

Proceed as follows to locate and repair a refrigerant leak and to

charge the unit:

1. Locate leak and make sure that refrigerant system pressure

has been relieved and reclaimed from both high-- and
low--pressure ports.

2. Repair leak following Refrigerant Service procedures.

NOTE

: Install a bi--flow filter drier whenever the system has been

opened for repair.

3. Add a small charge of R--410A refrigerant vapor to system

and leak--test unit.

4. Recover refrigerant from refrigerant system and evacuate to

500 microns if no additional leaks are not found.

5. Charge unit with Puron (R--410A) refrigerant, using an

electronic scale. Refer to unit rating plate for required
charge.

Step 2 — Unit Sequence of Operation

674D----A Sequence of Operation

a. CONTINUOUS FAN

(1.) Thermostat closes circuit R to G energizing the

blower motor for continuous fan.

b. COOLING MODE

(1.) If indoor temperature is above temperature set

point thermostat closes circuits R to G, R to Y and
R to O--The unit delivers cooling airflow.

c. HEAT PUMP HEATING MODE

Outdoor temperature above balance point setpoint of
thermostat.

(1.) On a call for heating, terminals “Y” and “G“ of the

Hybrid thermostat are energized. The “Y“ signal is

sent to the Defrost Board (DB) terminal “Y”. The
DB has a built in five minute anti--short cycle timer
which will not allow the compressor to restart

before the time delay has expired.

(2.) “T2” energizes the compressor contactor via the

High Pressure Switch (HPS) and Low Pressure
Switch (LPS). The compressor and outdoor fan
start. Thermostat “G” energizes the Interface Fan

Board terminal “G”. The blower motor is energized
through contacts of the IFB.

(3.) When the thermostat removes the “Y” and “G”

calls, the compressor contactor and outdoor fan are

de--energized. The evaporator motor is de--ener-
gized after a 90 sec. delay.

d. GAS HEATING MODE

Outdoor temperature below balance point setpoint of
thermostat.

Heating Sequence of Operation

(See Fig. 14 and 15 and unit wiring label.)
On a call for heating, terminal W of the thermostat is energized,
starting the induced--draft motor. When the pressure switch senses

that the induced--draft motor is moving sufficient combustion air,
the burner sequence begins. This function is performed by the

integrated gas unit controller (IGC). The indoor (evaporator)--fan

motor is energized 45 sec after flame is established. When the
thermostat is satisfied and W is de--energized, the burners stop

firing and the indoor (evaporator) fan motor shuts off after a
45--sec time--off delay. Please note that the IGC has the capability

to automatically reduce the indoor fan motor on delay and increase
the indoor fan motor off delay in the event of high duct static

and/or partially--clogged filter.

NOTE

: An LED (light--emitting diode) indicator is provided on

the control board to monitor operation. The control board is
located by removing the burner access panel (see Fig. 18). During
normal operation, the LED is continuously on.

Step 3 — Start--up Heating and Make Adjust-

ments

UNIT COMPONENT DAMAGE HAZARD

Failure to follow this caution may result in damage to the unit

being installed.

Complete the required procedures given in the Pre--Start--Up

section before starting the unit. Do not jumper any safety

devices when operating the unit.

CAUTION

Complete the required procedures given in the Pre--Start--Up
section before starting the unit. Do not jumper any safety devices

when operating the unit. Make sure that burner orifices are

properly aligned. Unstable operation my occur when the burner
orifices in the manifold are misaligned.
Follow the lighting instructions on the heating section operation
label (located on the inside of the control access panel) to start the

heating section.

NOTE

: Make sure that gas supply has been purged, and that all

gas piping has been checked for leaks.

Pipe Plug

Manifold

A07679

Fig. 10 -- Burner Assembly

674D