Airflow - Rheem (-)802PA050314MSA Installation Instructions Manual

AIRFLOW

The importance of proper air flow over the heat exchanger cannot
be over emphasized.
C UTION
IT IS IMPORTANT THAT EACH DUCT SYSTEM BE SIZED
AND INSTALLED FOR THE SPECIFIC APPLICATION BY
PROPERLY APPLYING THE APPROPRIATE INDUSTRY AC-
CEPTED STANDARD. IF LESS THAN MINIMUM STAN-
DARDS 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.
One of the most common causes of heat exchanger failure is over-
heating due to low air flow. An air flow table is located inside the
blower door and on the following pages.
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 fur-
nace as possible yet out of a direct line from the heat ex-
changer. See Figure 31.
2. Insert a thermometer in the return air duct as close to the fur-
nace as possible.
3. Operate the furnace.
4. When the thermometer in the supply air duct stops rising (ap-
proximately five minutes), subtract the return air temperature
from the supply air temperature. The difference is the temper-
ature rise.
5. Compare the measured temperature rise to the approved tem-
perature rise range listed on the furnace name plate. See Fig-
ure 32.
If the measured temperature rise is above the approved range, ei-
ther the air flow is too low or the manifold pressure needs to be ad-
justed. More air must be moved 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 ap-
proved range, either the air flow is too much or the manifold pres-
sure needs to be adjusted. Use lower speed tap on the multi-speed
blower.
IMPORTANT: The measured temperature rise should be in the
middle of the range.
IMPORTANT: Some high-efficiency filters have a greater than nor-
mal resistance to airflow. This can adversely affect furnace opera-
tion. BE SURE TO CHECK AIRFLOW if using any filter other than
factory-provided filter.
THE MEASURED TEMPERATURE RISE SHOULD BE AS
CLOSE TO THE MIDDLE OF THE STATED RANGE AS POSSI-
BLE. 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 INSTALLER MUST AD-
JUST 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 EXCHANGER OR INTERMITTENT OPERATION.
THIS COULD CAUSE INJURY OR DEATH AND WILL VOID
THE MANUFACTURER'S WARRANTY FOR THIS PRODUCT.
46
FIGURE 31
TEMPERATURE RISE MEASUREMENT
FIGURE 32
TYPICAL FURNACE NAME PLATE
25 TO
AIR TEMPERATURE RISE
20 TO
HIGH FIRE
LOW FIRE FIRE
ASSEMBLED IN THE USA
ENERGY
PERFORMANCE
VERIFIED
802PA075417MSA
XXXXXX
55 °F (°C)
50 °F (°C)
91-22176-09