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C
B
S
IRCULATOR
LOWER
PEEDS
T
O AVOID PERSONAL INJURY OR DEATH DUE TO ELECTRICAL SHOCK, TURN
OFF POWER TO THE FURNACE BEFORE CHANGING SPEED TAPS.
This furnace is equipped with a multi-speed circulator blower. This
blower provides ease in adjusting blower speeds. The Product Data
Book applicable to your model* provides an airflow table, showing
the relationship between airflow (CFM) and external static pressure
(E.S.P.), for the proper selection of heating and cooling speeds. The
heating 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 provide the
correct heating temperature rise and correct cooling CFM.
Use the CFM LED (green), adjacent to the integrated control
module fuse to verify airflow quantity. The green CFM LED
blinks once for each 100 CFM of airflow.
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 Product Data Book 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 *MV90704BXA furnace installed with a 2.5
ton air conditioning system. The air flow needed
is 1000 CFM. Looking at the cooling speed chart
for *MV90704BXA, find the air flow closest to
1000 CFM. A cooling airflow of 990 CFM can
be attained by setting the cooling speed to "C"
and the adjustment to "-" (minus).
NOTE: Continuous Fan Speed will be 56% of
high stage cooling.
4. Locate the blower speed selection DIP 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. Refer to the following figure for switch positions
and their corresponding taps. Turn off power to furnace for a
minimum of 10 seconds, allowing motor to reset and recognize
new speed selection. Turn on power to furnace. Verify CFM
by counting the number of times the green CFM LED blinks.
WARNING
8 7
6 5
4 3 2 1
Cooling
Speed
Tap A
8 7
6 5
4 3 2 1
Cooling
Speed
Tap B
8 7
6 5
4 3 2 1
Cooling
Speed
Tap C
8 7
6 5
4 3 2 1
*
Cooling
Speed
Tap D
Cooling Speed Taps
*
(
indicates factory setting)
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
5 and 6. Refer to the following figure for switch positions
and their corresponding taps. Refer to the bullet points
below for a description of each ramping profile. Turn OFF
power to the furnace for a minimum of 10 seconds, allowing
motor to reset and recognize the new profile selection. Turn
ON power to the furnace. Verify profile selection by counting
the green CFM LED blinks and timing each step of the
ramping profile.
•
Profile A provides only an OFF delay of one (1) minute at
100% of the cooling demand airflow.
100% CFM
OFF
Cooling
Demand
•
Profile B ramps up to full cooling demand airflow by first
stepping up to 50% of the full demand for 30 seconds. The
motor then ramps to 100% of the required airflow. A one (1)
minute OFF delay at 100% of the cooling airflow.
30
8 7
6 5
*
Normal
O
O
F
F
F
F
8 7
6 5
+ (Plus)
Adjust
O
O
F
N
F
8 7
6 5
- (Minus)
Adjust
O
O
N
F
F
Adjust Taps
*
(
indicates factory setting)
O
O
N
N
8 7
6 5
Heating
Speed
Tap A
O
O
F
F
F
F
8 7
6 5
*
Heating
Speed
Tap B
O
O
F
N
F
8 7
6 5
Heating
Speed
Tap C
O
O
N
F
F
8 7
6 5
Heating
Speed
Tap D
O
O
N
N
Heating Speed Taps
*
(
indicates factory setting)
100% CFM
1 min
4 3 2 1
O
O
F
F
F
F
4 3 2 1
O
O
F
N
F
4 3 2 1
O
O
N
F
F
4 3 2 1
4 3 2 1
4 3 2 1
4 3 2 1
OFF
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Table of Contents
Troubleshooting
