29
AIR FLOW
The importance of proper air flow over
the heat exchanger cannot be over
emphasized.
IT IS IMPORTANT THAT EACH
DUCT SYSTEM BE SIZED AND
INSTALLED FOR THE SPECIFIC
APPLICATION BY PROPERLY
APPLYING THE APPROPRIATE
INDUSTRY ACCEPTED STANDARD.
IF LESS THAN MINIMUM
STANDARDS ARE APPLIED, THE
EQUIPMENT USER COULD EXPECT
TO EXPERIENCE HIGHER UTILITY
BILLS, MAJOR COMPONENT
FAILURE, VARYING DEGREES OF
AIR NOISE OR OTHER
UNSATISFACTORY ISSUES, OVER
WHICH THE MANUFACTURER HAS
NO CONTROL.
TEMPERATURE RISE CHECK
To determine if the air flow is correct,
make a temperature rise check.
1. Insert a thermometer in the supply
air duct as close to the furnace as
possible yet out of a direct line
from the heat exchanger. See
Figure 21.
2. Insert a thermometer in the return
air duct as close to the furnace as
possible.
FIGURE 21
TEMPERATURE RISE MEASUREMENT
GAS FURNACE (DIRECT
DRIVE) INSTRUCTIONS FOR
CHANGING BLOWER SPEED
DISCONNECT THE ELECTRICAL
SUPPLY TO THE FURNACE BEFORE
ATTEMPTING TO CHANGE THE
BLOWER SPEED. FAILURE TO DO
SO CAN CAUSE ELECTRICAL
SHOCK RESULTING IN SEVERE
PERSONAL INJURY OR DEATH.
The blower motor is wired for blower
speeds required for normal operation
as shown.
If additional blower speed taps are
available (leads connected to “M1” and
“M2” on the electronic control), speeds
may be changed if necessary to fit
requirements of the particular
installation. Reconnect the unused
motor leads to “M1” or “M2.” Check
motor lead color for speed designation.
Heating speeds should not be reduced
where it could cause the furnace air
temperature to rise to exceed the
maximum outlet air temperature
specified for the unit.
IMPORTANT:
Always check air
temperature rise after changing the
heating speed for any reason.
WARNING
!
!
CAUTION
FIGURE 22
TYPICAL FURNACE NAME PLATE