Instructions / Assembly

38
CIRCULATOR BLOWER SPEEDS
T O AVOID PERSONAL INJURY OR DEATH DUE TO ELECTRICAL SHOCK ,
TURN OFF POWER TO THE FURNACE BEFORE CHANGING SPEED TAPS .
WARNING
This furnace is equipped with a variable speed circulator blower.
This blower provides ease in adjusting blower speeds. The heat-
ing blower speed is shipped set at “B”, and the cooling blower
speed is set at “D”. These blower speeds should be adjusted by
the installer to match the installation requirements so as to pro-
vide the correct heating temperature rise and correct cooling
CFM.
Use the dual 7-segment LED display adjacent to the dip switches
to obtain the approximate airflow quantity. The airflow quantity
is displayed as a number on the display, rounded to the nearest
100 CFM. The display alternates airflow delivery indication and
the operating mode indication.
Example: The airflow being delivered is 1225 CFM. The dis-
play indicates 12. If the airflow being delivered is 1275, the
display indicates 13.
1. Determine the tonnage of the cooling system installed
with the furnace. If the cooling capacity is in BTU/hr divide
it by 12,000 to convert capacity to tons.
Example: Cooling Capacity of 30,000 BTU/hr.
30,000/12,000 = 2.5 Tons
2. Determine the proper air flow for the cooling system.
Most cooling systems are designed to work with air flows
between 350 and 450 CFM per ton. Most manufacturers
recommend an air flow of about 400 CFM per ton.
Example: 2.5 tons X 400 CFM per ton = 1000 CFM
The cooling system manufacturer’s instructions must be checked
for required air flow. Any electronic air cleaners or other devices
may require specific air flows, consult installation instructions of
those devices for requirements.
3. Knowing the furnace model, locate the high stage cooling
air flow charts in the Specification Sheet applicable to
your model. Look up the cooling air flow determined in
step 2 and find the required cooling speed and adjustment
setting.
Example: A *MVC960603B* furnace installed with a 2.5
ton air conditioning system. The air flow
needed is 1000 CFM. Looking at the cooling
speed chart for *MVC960603B*, find the air
flow closest to 1000 CFM. A cooling airflow of
1007 CFM can be attained by setting the
cooling speed to “C”.
4. Locate the blower speed selection DIP (S3) switches on
the integrated control module. Select the desired “cooling”
speed tap by positioning switches 1 and 2 appropriately.
Select the desired “adjust” tap by positioning switches 3
and 4 appropriately. To enable adjustments and select -5,
5, -10 or 10% trim, you must set dip switch S5-2 to
ON. If S5-2 is in the OFF position , you will receive 0%
trim. Refer to the following figure for switch positions
and their corresponding taps. Verify CFM by noting the
number displayed on the dual 7-segment LED display.
5. The multi-speed circulator blower also offers several custom
ON/OFF ramping profiles. These profiles may be used to
enhance cooling performance and increase comfort level.
The ramping profiles are selected using DIP switches S4-
1, 2. Refer to the following figure for switch positions
and their corresponding taps. Refer to the following bullet
points for a description of each ramping profile. Verify
CFM by noting the number displayed on the dual 7-segment
LED display.
12
A* OFF OFF
BONOFF
COFFON
DONON
Sw itch Bank: S4
DIP Sw itch No.
(*Indicates factory setting)
Ramping
Prof iles