Airflow - Rheem *96V series Installation Instructions Manual

The importance of proper air flow over the heat exchanger
cannot be over emphasized.
NOTE: Where the maximum airflow is expected
to be over 1800 CFM, BOTH sides or the bottom
must be used for the return air.
IT IS IMPORTANT THAT EACH DUCT SYSTEM BE
SIZED AND INSTALLED FOR THE SPECIFIC APPLICA-
TION BY PROPERLY APPLYING THE APPROPRIATE
INDUSTRY ACCEPTED STANDARD. IF LESS THAN
MINIMUM STANDARDS ARE APPLIED, THE EQUIP-
MENT USER COULD EXPECT TO EXPERIENCE
HIGHER UTILITY BILLS, MAJOR COMPONENT FAIL-
URE, VARYING DEGREES OF AIR NOISE OR OTHER
UNSATISFACTORY ISSUES, OVER WHICH THE MANU-
FACTURER 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 57.
2. Insert a thermometer in the return air duct as close to
the furnace as possible.
3. Operate the furnace for a minimum of 15 minutes in
gas heat mode.
4. When the thermometer in the supply air duct stops ris-
ing (approximately five minutes), subtract the return
air temperature from the supply air temperature. The
difference is the temperature rise.
5. Compare the measured temperature rise to the ap-
proved temperature rise range listed on the furnace
name plate. See Figure 58.
FIGURE 57
TEMPERATURE RISE MEASUREMENT
If the measured temperature rise is above the approved
range, the air flow is too low. Airflow must be increased by
speeding up the blower, by removing restrictions in the
duct system, or by adding more supply or return air duct. If
the measured temperature rise is below the approved
range, the air flow is too much. Use lower speed tap on
the multi-speed blower.
THE MEASURED TEMPERATURE RISE SHOULD BE AS
CLOSE TO THE MIDDLE OF THE STATED RANGE AS
POSSIBLE. FOR EXAMPLE, IF THE RISE RANGE IS 40
TO 70°F (4.5°-21°C), THE MIDDLE OF THE RISE RANGE
IS 55°F (12.8°C). IN ALL APPLICATIONS, THE IN-
STALLER MUST ADJUST THE TEMPERATURE RISE TO
THIS "MIDDLE" POINT AS CLOSELY AS POSSIBLE.
ALSO, THE TEMPERATURE RISE SHOULD NEVER BE
ABOVE OR FALL BELOW THE STATED RANGE. DOING
SO COULD CAUSE DAMAGE TO THE HEAT EX-
CHANGER OR INTERMITTENT OPERATION. THIS
COULD CAUSE INJURY OR DEATH AND WILL VOID THE
MANUFACTURER'S WARRANTY FOR THIS PRODUCT.
FIGURE 58
TYPICAL FURNACE NAME PLATE
105