Gas Input Rate Measurement; Temperature Rise - Goodman MVC8 Installation Instructions Manual

4. Attach a hose and manometer to the outlet pressure
barb fitting (Honeywell valve) or outlet pressure boss
(White-Rodgers valve).
5. Turn ON the gas supply.
6. Turn on power and close thermostat "R" and "W1"
contacts to provide a call for low stage heat.
7. Measure the gas manifold pressure with burners firing.
Adjust manifold pressure using the Manifold Gas
Pressure table shown below.
8. Remove regulator cover screw from the low (LO) outlet
pressure regulator adjust tower and turn screw clockwise
to increase pressure or counterclockwise to decrease
pressure. Replace regulator cover screw.
9. Close thermostat "R" and "W2" contacts to provide a
call for high stage heat.
10. Remove regulator cover screw from the high (HI) outlet
pressure regulator adjust tower and turn screw clockwise
to increase pressure or counterclockwise to decrease
pressure. Replace regulator cover screw.
11. Turn off all electrical power and gas supply to the system.
12. Remove the manometer hose from the hose barb fitting
or outlet pressure boss.
13. Replace outlet pressure tap:
a. Honeywell VR9205 valve: Remove the 1/8" NPT hose
barb fitting from the outlet pressure tap. Replace the
outlet pressure boss plug and seal with a high quality
thread sealer.
b. White-Rodgers 36G54 valve: Turn outlet pressure test
screw in to seal pressure port (clockwise, 7 in-lb
minimum).
14. Turn on electrical power and gas supply to the system.
15. Close thermostat contacts "R" and "W1/W2" to energize
the valve.
Using a leak detection solution or soap suds, check for leaks
at outlet pressure boss plug (Honeywell valve) or screw (White-
Rodgers valve). Bubbles forming indicate a leak. SHUT OFF
GAS AND REPAIR ALL LEAKS IMMEDIATELY!
NOTE: For gas to gas conversion, consult your dealer for
appropriate conversion.
M anifold Gas Pressure
Gas
Natural Low Stage
High Stage
Propane Low Stage
High Stage
G I R M
AS NPUT ATE EASUREMENT
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.
Range Nom inal
1.6 - 2.2" w .c. 1.9" w .c.
3.2 - 3.8" w .c. 3.5" w .c.
5.7 - 6.3" w .c. 6.0" w .c.
9.7 - 10.3" w .c. 10.0" w .c.
(N G O
ATURAL AS NLY
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
of gas being delivered to the furnace. If the dial is a one
cubic foot dial, divide the number of seconds recorded in
step 2 by one. 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 sum of the installation's gas heating
value and 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.
EXAMPLE:
Installation's gas heating (HTG) value: 1,000 BTU/ft
(Obtained from gas supplier)
Installation's seconds per cubic foot: 34 sec/ ft
Conversion Factor (hours to seconds): 3600 sec/hr
Input = (Htg. value x 3600) ÷ seconds per cubic foot
Input = (1,000 BTU/ft
Input = 106,000 BTU/hr
Minor changes to the input rate may be accomplished through
manifold pressure adjustments at the gas valve. Refer to Sec-
tion XIV, Startup Procedure and Adjustment - Gas Manifold
Pressure Measurement and Adjustment for details. NOTE:
The final manifold pressure cannot vary by more than ± 0.3"
w.c. from the specified setting. Consult your local gas supplier
if additional input rate adjustment is required.
5. Repeat steps 2 through 4 on high stage.
6. Turn ON gas to and relight all other appliances turned off
in step 1. Be certain that all appliances are functioning
properly and that all pilot burners are operating.
T R
EMPERATURE ISE
Temperature rise must be within the range specified on the unit
rating plate. An incorrect temperature rise may result in con-
densing in or overheating of the heat exchanger. An airflow and
temperature rise table is provided in the Specification Sheet
applicable to your model. Determine and adjust temperature
rise as follows:
1. Operate furnace with burners firing for approximately ten
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 Startup Procedure and Adjustment -Circulator
Blower Speeds for speed changing details.
27
3
x 3600 sec/hr) ÷ 34 sec/ ft
3
)
3
3
3