Installer’s Information Manual
Page 23
CHECKING GAS SUPPLY PRESSURE
1. Turn off gas at equipment shut-off valve in gas supply
line just ahead of furnace.
2. Remove inlet pressure plug from gas control.
3. Install 1/8" NPT manual shut-off valve in hole vacated
by plug. Make sure valve is in off position.
4. Attach manometer to 1/8" NPT manual shut-off valve
just installed.
5. Slowly open equipment shut-off valve in gas supply line
just ahead of furnace.
6. Slowly open 1/8" NPT manual shut-off valve leading to
manometer.
7. Turn on all gas appliances attached to gas supply line.
8. With furnace operating, read gas supply pressure on
manometer.
•
Natural gas supply pressure must be between 5
and 7 inches W.C.
•
Propane gas (LP) supply pressure must be
between 11 and 13 inches W.C.
9. If gas supply pressure is not within these limits, call gas
supplier.
10. Turn off all gas appliances attached to gas supply line.
SECTION 16. MANIFOLD
PRESSURE ADJUSTMENT
You will need a 0 to 15 inch water manometer with 0.1 inch
resolution and a 1/8" NPT manual shut-off valve to measure
actual manifold pressure.
WARNING
: Correct manifold pressure is
necessary for proper ignition and burner operation. Failure
to accurately adjust pressure could cause heat exchanger
failure.
Check gas supply pressure first. Follow instructions in
Section 15.
1. Turn off gas at equipment shut-off valve in gas supply
line just ahead of furnace.
2. Remove plug from outlet pressure tap in gas control.
3. Install 1/8" NPT manual shut-off valve in hole vacated
by plug. Make sure shut-off valve is in off position.
4. Attach manometer to 1/8" NPT manual shut-off valve
just installed.
5. Slowly open equipment shut-off valve in gas supply line
just ahead of furnace. Start furnace following
"Operating Instructions" on front door.
6. Slowly open 1/8" NPT manual shut-off valve leading to
manometer.
7. Read manifold pressure on manometer.
8. Adjust manifold pressure by turning gas control
regulator adjusting screw clockwise to increase
pressure or turning counter-clockwise to decrease
pressure. Manifold pressure must be within allowable
range below:
•
Natural gas manifold pressure must be between
3.2 and 3.8 inches W.C.
•
Propane gas (LP) manifold pressure must be
between 9.7 and 10.3 inches W.C.
NOTE: For natural gas, if gas flow rate can't be properly
set within these pressure ranges then you must change
main burner orifices to obtain proper gas flow rate.
9. Shut off furnace. Turn off gas at equipment shut-off
valve in gas supply line just ahead of furnace. Install
outlet pressure tap plug in gas control. Turn on gas.
10. Check regulator adjustment cover screw and gas
control plug for gas leaks. Use a commercial soap
solution made for leak detection.
SECTION 17. CHECKING GAS
INPUT RATE
It is the installer's responsibility to see that the Btu input
rate of the furnace is properly adjusted. Under-firing could
cause inadequate heat, excessive condensation or ignition
problems. Over-firing could cause sooting, flame
impingement or overheating of heat exchanger.
WARNING
: Failure to adjust furnace to the proper
firing rate could cause heat exchanger failure.
Depending on your local gas heating value and elevation,
you may need to adjust manifold pressure or change
orifices to get proper gas input rate. Check with your local
gas supplier to determine heating value (Btu/cu.ft.) of
natural gas in your area.
NOTE: If furnace is being installed at an altitude of more
than 2000 feet above sea level, you must derate the
furnace. See Section 18, "Derating For High Altitude."
NATURAL GAS INPUT RATE
Natural gas heating value (Btu/cu.ft.) can vary significantly.
Before starting natural gas input check, obtain gas heating
value at your location from local supplier. You will need a
stopwatch to measure actual gas input.
1. Gas supply pressure must be between 5 and 7 inches
W.C. for natural gas. See Section 15, "Gas Supply
Pressure Adjustment."
2. Turn off all other gas appliances.
3. Start furnace following "Operating Instructions" on front
door.
