Rheem RGPE series Installation Instructions Manual page 32

the zoning manufacturer), this limit must
be installed in the system to prevent the
furnace from overheating.
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 24.
2. Insert a thermometer in the return
air duct as close to the furnace as
possible.
3. Operate the furnace.
4. When the thermometer in the sup-
ply air duct stops rising (approxi-
mately five minutes), subtract the
return air temperature from the sup-
ply air temperature. The difference
is the temperature rise.
5. Compare the measured tempera-
ture rise to the approved tempera-
ture rise range listed on the furnace
name plate. See product specifica-
tion sheet and nameplate located
on furnace.
32
If the measured temperature rise is
above the approved range, either the air
flow is too low or the manifold pressure
needs to be adjusted. 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 approved 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 tempera-
ture rise should be in the middle of the
range. See product specification sheet
and name plate located on furnace.
IMPORTANT: Some high-efficiency fil-
ters have a greater than normal resis-
tance to airflow. This can adversely affect
furnace operation. BE SURE TO CHECK
AIRFLOW if using any filter other than
factory-provided filter.