GMS8 Installation Manual

29
Range Nominal
Natural Low Stage 1.6 - 2.2" w .c. 1.9" w .c.
High Stage 3.2 - 3.8" w .c. 3.5" w .c.
Propane Low Stage 5.7 - 6.3" w .c. 6.0" w .c.
High Stage 9.7 - 10.3" w .c
.
10.0" w .c.
Manifold Gas Pressure
Gas
GAS INPUT RATE M EASUREM ENT (NATURAL GAS ONLY)
The gas input rate to the furnace must never be greater than that
specified on the unit rating plate. To measure natural gas input
using the gas meter, use the following procedure.
1. Turn OFF the gas supply to all other gas-burning appliances
except the furnace.
2. While the furnace is operating, time and record one
complete revolution of the smallest gas meter dial.
3. Calculate the number of seconds per cubic foot (sec/ ft
3
) of
gas being delivered to the furnace. If the dial is a two cubic
foot dial, divide the number of seconds recorded in step 2
by two.
4. Calculate the furnace input in BTUs per hour (BTU/ hr). Input
equals the installation’s gas heating value multiplied by a
conversion factor (hours to seconds), divided by the number
of seconds per cubic foot. The measured input must not be
greater than the input indicated on the unit rating plate.
EXAM PLE:
Installation’s gas heating (HTG) value: 1,000 BTU/ ft
3
(Obtained from gas supplier)
Installation’s seconds per cubic foot: 34 sec/ ft
3
Conversion Factor (hours to seconds): 3600 sec/ hr
Input = (Htg. value x 3600) ÷ seconds per cubic foot
Input = (1,000 BTU/ ft
3
x 3600 sec/ hr) ÷ 34 sec/ ft
3
Input = 106,000 BTU/ hr
This measured input must not be greater than the input
indicated on the unit rating plate.
5. Turn ON gas and relight appliances turned off in step 1.
Ensure all the appliances are functioning properly and that
all pilot burners are operating.
TEM PERATURE RISE
Air temperature rise is the temperature difference between supply
and return air. The proper amount of temperature rise is usually
obtained when the unit is operated at the rated input with the “as
shipped” blower speed. If the correct amount of temperature
rise is not obtained, it may be necessary to change the blower
speed.
An incorrect temperature rise can cause condensing in or over-
heating of the heat exchanger. Determine and adjust the tempera-
ture rise as follows. The temperature rise must be within the range
specified on the rating plate or Specification Sheet applicable to
your model. (Please contact your dist ribut or or our website for the
applicable Specification Sheet referred to in this manual.)
SUPPLY
AIR
RETURN
AIR
Temperature Rise Measurement
1. Operate furnace with burners firing approximately 15
minutes. Ensure all registers are open and all duct dampers
are in their final (fully or partially open) position.
2. Place thermometers in the return and supply ducts as close
to the furnace as possible. Thermometers must not be
influenced by radiant heat by being able to “see” the heat
exchanger.
3. Subtract the return air temperature from the supply air
temperature to determine the air temperature rise. Allow
adequate time for thermometer readings to stabilize.
4. Adjust temperature rise by adjusting the circulator blower
speed. Increase blower speed to reduce temperature rise.
Decrease blower speed to increase temperature rise. Refer
to the following section for speed changing details.
CIRCULATOR BLOW ER SPEED ADJUSTM ENT
T O AVOID PERSONAL INJURY OR DEATH DUE TO ELECTRICAL SHOCK ,
TURN OFF POW ER TO THE FURNACE BEFORE CHANGING SPEED TAPS .
WARNING
Furnaces are equipped with either a PSC or EEM circulator blower
motor. Either blower provides ease in adjusting blower speeds.
Refer to the Blower Performance Data in the back of the manual for
proper selection of heating and cooling speeds. The cooling blower
speed is shipped set on HIGH. The heat blower speed for
* (M ,H,D)H8 / ADSS8 models is shipped on M EDIUM. For * (M ,D)H8
/ ADSH8 models high heat ships on M EDIUM and low heat is
shipped on MEDIUM -LO. For GM E8 / AMEH8 models high heat
ships on M EDIUM-HI (T4) and low heat is shipped on M EDIUM
(T3). These blower speeds should be adjusted by the installer to
match the installation requirements so as to provide the correct
heating temperature rise and the correct cooling CFM .
To adjust the circulator blower speed, proceed as follows:
1. Turn OFF power to the furnace.
2. Select the heating and cooling blower speeds that match
the installation requirements from the airflow table in the
Specification Sheet applicable to your model. (Please
contact your dist ribut or or our website for the applicable
Specification Sheet referred to in this manual.)