16
NOTE: BTU content of the gas should be
obtained from the gas supplier. This measured
input must not be greater than shown on the
unit rating plate.
4.
Relight all other appliances turned off in step 1. Be
sure all pilot burners are operating.
Temperature Rise Check
Check the temperature rise through the unit by placing
thermometers in supply and return air registers as close
to the unit as possible. Thermometers must not be able to
sample temperature directly from the unit heat exchangers,
or false readings could be obtained.
1.
All registers must be open; all duct dampers must be
in their final (fully or partially open) position and the
unit operated for 15 minutes before taking readings.
2. The temperature rise must be within the range
specified on the rating plate.
Checking Temperature Rise
NOTE: Air temperature rise is the temperature
difference between supply and return air.
With a properly designed system, the proper amount of
temperature rise will normally be obtained when the unit
is operated at rated input with the recommended blower
speed.
If the correct amount of temperature rise is not obtained,
it may be necessary to change the blower speed. A higher
blower speed will lower the temperature rise. A slower
blower speed will increase the temperature rise.
NOTE: Blower speed MUST be set to give the
correct air temperature rise through the unit as
marked on the rating plate.
External Static Pressure Check
The total external static pressure must be checked on this
unit to determine if the airflow is proper.
1. Using a digital manometer measure the static pressure
of the return duct at the inlet of the unit (Negative
Pressure).
Total External Static
2. Measure the static pressure of the supply duct (Positive
Pressure).
3. Add the two readings together.
NOTE: Both readings may be taken simultaneously
and read directly on the manometer is so desired.
4. Consult proper table for quantity of air.
If the external static pressure exceeds the minimum or
maximum allowable statics, check for closed dampers, dirty
filters, undersized or poorly laid out ductwork.
Blower Speed Adjustments
WARNING
To avoid personal injury or death due to electric shock,
remove electrical power from the unit before changing
speed taps on the blower motors.
EEM Motors
NOTE: Refer to the wiring diagram in the appendix
to verify speed tap settings.
A/GPU14 models are equipped with EEM motors. EEM
motors are constant torque motors with very low power
consumption. This motor is energized by 24V. Adjust the
CFM for the unit by changing the 24V low voltage leads to
the speed terminal block on the motor.
SPEED
TAP
DEFINITION
LEAD
COLOR
SPEED
TAP
DEFINITION
LEAD
COLOR
SPEED
TAP
DEFINITION
LEAD
COLOR
T1
Fan Only
Green
T2
High Speed
T4
Low Speed Yellow
T3
Low Speed
White
T5
High Speed
FAN ONLY
HEATING
COOLING
Single Stage Models
