44
4. Turn ON gas to and relight all other appliances turned off in step 1. Be certain that all appliances are functioning properly and
that all pilot burners are operating.
T
EMPERATURE
R
ISE
Temperature rise must be within the range specified on the unit rating plate. An incorrect temperature rise may result in
condensing in or overheating of the heat exchanger. An airflow and temperature rise table is provided in the Specification
Sheet applicable to your model. Determine and adjust temperature rise as follows:
1. Operate furnace with burners firing for approximately ten minutes. Ensure all registers are open and all duct dampers
are in their final (fully or partially open) position.
2. Place thermometers in the return and supply ducts as close to the furnace as possible. Thermometers must not be
influenced by radiant heat by being able to “see” the heat exchanger.
3. Subtract the return air temperature from the supply air temperature to determine the air temperature rise. Allow
adequate time for thermometer readings to stabilize.
4. Adjust temperature rise by adjusting the circulator blower
speed. Increase blower speed to reduce temperature rise.
Decrease blower speed to increase temperature rise. Refer
to
Startup Procedure and Adjustment -Circulator Blower
Speeds
for speed changing details.
C
IRCULATOR
B
LOWER
S
PEEDS
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 an ECM circulator blower. The heating blower speed is shipped set at “B”, and the cooling blower speed
setting is “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 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 display 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.
Model
HI / LO
*MVM970603BXAA
20-50/25-55
*MVM970803BXAA
30-60/25-55
*MVM970804CXAA
25-55/25-55
*MVM971005CXAA
35-65/25-55
*MVM971205DXAA
35-65/30-60
*CVM970603BXAA
35-65/30-60
*CVM970803BXAA
35-65/35-65
*CVM970804CXAA
35-65/35-65
*CVM971005CXAA
35-65/30-60
TEMPERATURE RISE
SUPPLY
AIR
RETURN
AIR
Temperature Rise Measurement
Figure 51
