Gas Manifold Pressure Measurement And Adjustment; Gas Input Rate Measurement (Natural Gas Only) - Intertek MES80 Installation Instructions Manual

Gas Line
Gas
Shutoff
Valve
Drip Leg Cap
With Fitting
Measuring Inlet Gas Pressure (Alt. Method)
Gas Manifold Pressure Measurement and
Adjustment
T
O PREVENT UNRELIABLE OPERATION OR EQUIPMENT DAMAGE
GAS MANIFOLD PRESSURE MUST BE AS SPECIFIED ON THE UNIT RATING
. O
PLATE NLY MINOR ADJUSTMENTS SHOULD BE MADE BY ADJUSTING
THE GAS VALVE PRESSURE REGULATOR
Only small variations in gas pressure should be made by
adjusting the gas valve pressure regulator. The manifold
pressure must be measured with the burners operating. To
measure and adjust the manifold pressure, use the following
procedure.
1. Turn OFF gas to furnace at the manual gas shutoff
valve external to the furnace.
2. Turn OFF all electrical power to the system.
3. Outlet pressure tap connections:
a. White-Rodgers valve:
Back outlet pressure test screw (outlet pressure Tap)
out one turn (counterclockwise, not more than one
turn).
4. Connect calibrated U tube manometer (or appropriate
pressure gauge) at the gas valve outlet pressure tap.
See White-Rodgers 36J22Y-204 gas valve Figure 13
for location of outlet pressure tap.
5. Turn ON the gas supply.
6. Turn ON power and close thermostat "R" and "W"
contacts to provide a call for heat.
7. Using a leak detection solution or soap suds, check
for leaks at outlet pressure Tap screw (White-Rodgers
valve). Bubbles forming indicate a leak. SHUT OFF
GAS AND REPAIR ALL LEAKS IMMEDIATELY!
Gas Line
To Furnace
Manometer Hose
Figure 14
CAUTION
.
8. Measure the gas manifold pressure with burners firing.
Adjust manifold pressure using the following Manifold
Gas Pressure table.
Natural Gas
9. Remove regulator cover screw from the outlet pressure
regulator and turn screw clockwise to increase pressure
or counterclockwise to decrease pressure. Replace
regulator cover screw.
10. Turn OFF all electrical power and gas supply to the
system.
11. Remove the manometer hose from the hose barb fitting
or outlet pressure Tap.
12. Replace outlet pressure tap:
a. White-Rodgers valve: Turn outlet pressure test screw
in to seal pressure port (clockwise, 7 in-lb minimum).
13. Turn ON electrical power and gas supply to the system.
14. Close thermostat contacts to provide a call for heat.
15. Retest for leaks. If bubbles form, SHUT OFF GAS AND
REPAIR ALL LEAKS IMMEDIATELY!

Gas Input Rate Measurement (Natural Gas Only)

,
THE
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 at high fire rate, time
and record one complete revolution of the gas meter
dial, measuring the smallest quantity, usually the dial
that indicates 1/2 cu. ft. per revolution. You will use this
number to calculate the quantity of gas in cubic ft. if the
furnace would consume if it ran steadily for one hour
(3600 seconds).
3. If the 1/2 cu. ft. dial was used, multiply your number
X 2. EXAMPLE: If it took 23 seconds to complete one
revolution of the 1/2 ft. dial (23 x 2 = 46).
This tells us that at this rate, it would take 46 seconds to
consume one cu. ft. of gas. This tells us that in one hour,
the furnace would consume 78 cu. ft. of gas. (3600/46 =
78) The typical value range for 1 cu. ft. of natural gas is
around 1025 BTU. Check with your gas utility, if possible.
In this example, the furnace is consuming 80,000 BTUH.
NOTE: The final manifold pressure cannot vary by more
than ± 0.2" w.c. for Natural from the specified setting.
Consult your local gas supplier if additional input rate
adjustment is required.
4. Turn ON gas and relight appliances turned off in step
1. Ensure all the appliances are functioning properly
and that all pilot burners (if applicable) are operating.
23
Manifold Gas Pressure
2.8" - 3.2" w.c.
Table 10