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OPERATING YOUR UNIT
The operation of your system is controlled by the indoor tempera-
ture control (for 674B, either a Thermidistat™ or dual fuel
thermostat is required). You simply adjust the thermostat and it
maintains the indoor temperature at the level you select. Most
thermostats of heating and cooling systems have 3 controls: a
temperature control selector, a FAN control, and a SYSTEM or
MODE control. Refer to your thermostat owner’s manual for more
information.
To better protect your investment and to eliminate unnecessary
service calls, familiarize yourself with the following facts:
1. During heat pump heating, increasing the thermostat setting
more than 2°F may cause the supplemental gas heat to be
turned on for a short period of time to satisfy the thermostat.
Needless use of the supplementary heat reduces potential
energy savings.
2. Ice or frost tends to form on the coil during winter heating
operation. Your heat pump is designed to automatically
melt the ice. When in this defrost cycle, it is normal for
steam or fog to rise from the outdoor unit. Do not be
alarmed!
I. COOLING MODE
With the SYSTEM or MODE control set to COOL, your unit will
run in cooling mode until the indoor temperature is lowered to the
level you have selected. On extremely hot days, your unit will run
for longer periods at a time and have shorter “off” periods than on
moderate days.
II. HEAT PUMP HEATING MODE
With the SYSTEM or MODE control of your indoor thermostat set
to HEAT, your unit will run in heat pump heating mode until room
temperature is raised to the level you have selected. Of course,
your system will run for longer periods to maintain a comfortable
environment on cooler days and nights than on moderate ones.
III. GAS HEAT MODE
Your heat pump is your primary heating source. Your system is
also be equipped with a supplemental gas heating source. On cold
days and nights, your system will automatically turn on the
supplemental heat in order to maintain the level of comfort you
have selected.
When your heat pump needs additional heat to keep you comfort-
able, your Bryant electronic thermostat will turn on the supple-
mental gas heat and display the “AUX HT” message.
IV. DEFROST MODE
When your heat pump is providing heat to your home or office and
the outdoor temperature drops below 45°F, moisture may begin to
freeze on the surface of the coil. If allowed to build up, this ice
would impede airflow across the coil and reduce the amount of
heat absorbed from the outside air. So, to maintain energy-efficient
operation, your heat pump has an automatic defrost mode.
The defrost mode starts at a preset time interval of 30 minutes,
although, it may be reset to 60, 90 or 120 minutes. Defrost will
start at the preset time only if the ice is sufficient to interfere with
normal heating operation.
After the ice is melted from the coil, or after a maximum of 10
minutes in defrost mode, the unit automatically switches back to
normal heating operation.
Do not be alarmed if steam or fog appears at the outdoor unit
during defrost mode. Water vapor from the melting ice may
condense into a mist in the cold outside air.
During certain weather conditions such as heavy snow and
freezing rain it is not uncommon for ice to build up on the unit
grille. This is normal for these weather conditions. Do not attempt
to remove the ice from the unit grille. This condition will not affect
the proper function of the unit and will clear within a few days.
V. EMERGENCY HEAT MODE
If you should have problems with the heat pump portion of your
system, this mode allows your supplemental gas heating source to
keep your home or office warm until your heat pump can be
serviced.
MAINTENANCE AND SERVICE
This section discusses maintenance that should be performed on
your system. Most maintenance should be performed by your
dealer. You, as the owner, may wish to handle some minor
maintenance for your new unit.
A. Routine Maintenance
All routine maintenance should be handled by skilled, experienced
personnel. Your dealer can help you establish a standard proce-
dure.
For your safety, keep the unit area clear and free of combustible
materials, gasoline, and other flammable liquids and vapors.
To assure proper functioning of the unit, flow of condenser air
must not be obstructed from reaching the unit. Clearance from the
top of the unit is 48 in. Clearance of at least 36 in. is required on
sides except the power entry side (42 in. clearance) and the duct
side (12 in. minimum clearance).
B. Maintenance and Care for the Equipment Owner
Before proceeding with those things you might want to maintain
yourself, please carefully consider the following:
WARNING: 1. TURN OFF ALL ELECTRICAL
POWER TO YOUR UNIT AND IN-
STALL LOCK-OUT TAG BEFORE
SERVICING OR PERFORMING
MAINTENANCE. ELECTRIC
SHOCK COULD CAUSE SERIOUS
INJURY OR DEATH.
2. When removing access panels or performing mainte-
nance functions inside your unit, be aware of sharp
sheet metal parts and screws. Although special care is
taken to keep sharp edges to a minimum, be extremely
careful when handling parts or reaching into the unit.
AIR FILTERS
The air filter(s) should be checked at least every 3 or 4 weeks and
changed or cleaned whenever it becomes dirty. Dirty filters
produce excessive stress on the blower motor and can cause the
motor to overheat and shut down.
This unit must have air filters in place before it can be operated.
These filters can be located in one of at least two places. In many
applications the installer will provide return air filter grilles
mounted on the wall or ceiling of the conditioned structure. In the
instance of filter grilles, the filters can simply be removed from the
grille and replaced.
The other typical application is an accessory filter rack installed
inside the unit itself. The following information is given to assist
in changing filters used in these internal filter racks.
Table 1 indicates the correct filter size for your unit. Refer to Fig.
2 to access filters installed in the accessory filter rack.
To replace or inspect filters in accessory filter rack (See Fig. 2):
TABLE 1—INDOOR-AIR FILTER DATA
UNIT SIZE FILTER SIZE
674B024-030 20x20x1
674B036 20x24x1
674B042-060 24x30x1
—2—