Service Manual
38
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 manu-
facturers 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 de-
vices may require specific air flows, consult installation instruc-
tions of those devices for requirements.
3. Knowing the furnace model, locate the high stage
cooling air flow charts in the Specification Sheet ap-
plicable to your model. Look up the cooling air flow
determined in step 2 and find the required cooling
speed and adjustment setting.
Example: A *MVM970603BN furnace installed with a
2.5 ton air conditioning system. The air flow needed
is 1000 CFM. Looking at the cooling speed chart for
*MVM970603BN, find the air flow closest to 1000
CFM. A cooling airflow of 1000 CFM can be attained
by selecting the cooling speed “C” and the adjust-
ment to “normal”.
4. Continuous fan speed is selectable at 25%, 50%, 75%
or 100% of the furnace’s maximum airflow capability.
Example: If the furnace’s maximum airflow capa-
bility is 2000 CFM, the continuous fan speed will be
0.25 x 2000 or 500 CFM.
5. Locate the blower speed selection DIP switches on the
integrated control module. Select the desired “cool-
ing” speed tap by positioning switches 1 and 2 appro-
priately. Select the desired “adjust” tap by
positioning switches 9 and 10 appropriately. Refer to
the DIP switch chart for switch positions and their
corresponding taps. Verify CFM by noting the number
displayed on the dual 7-segment LED display.
6. 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 us-
ing DIP switches 7 and 8. Refer to the following fig-
ure for switch positions and their corresponding taps.
Refer to the bullet points below for a description of
each ramping profile. Verify CFM by noting the num-
ber displayed on the dual 7-segment LED display.
• Profile A provides only an OFF delay of one (1) minute at
100% of the cooling demand airflow.
OFF
100% CFM 100% CFM
1 min
OFF
• 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 is pro-
vided.
50% CFM
1/2 min
100% CFM
100% CFM
1 min
OFF
OFF
• Profile C ramps up to 85% of the full cooling demand air-
flow and operates there for approximately 7 1/2 minutes.
The motor then steps up to the full demand airflow. Profile
C also has a one (1) minute 100% OFF delay.
100% CFM
OFF
OFF
• Profile D ramps up to 50% of the demand for 1/2 minute,
then ramps to 85% of the full cooling demand airflow and
operates there for approximately 7 1/2 minutes. The mo-
tor then steps up to the full demand airflow. Profile D has
a 1/2 minute at 50% airflow OFF delay.
OFF
OFF
7. Select the heating speed for your model from the heating
speed chart in the Specification Sheet. The “adjust” set-
ting (already established by the cooling speed selection)
determines which set of speeds are available. The selected
speed must provide a temperature rise within the rise range
listed with the particular model.
8. Select the desired “heating” speed tap by positioning
switches 3 and 4 appropriately. Refer to figure above.
Verify CFM by noting the number displayed on the dual 7-
segment LED display.
OPERATION