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( g
)
counterclockwise to reduce manifold pressure. Manifold pressure should be set to pressure specifi ed
on the appliance rating plate. Always adjust regulator according to original equipment manufacturer's
specifi cations listed on the appliance rating plate.
IOM
IOM
When the correct pressure has been established, securely replace the regulator cover screw.
6. Turn off the gas and electrical supply to the furnace.
7. Remove the manometer hose from the outlet pressure tap boss, and tighten the outlet pressure tap screw
using the 3/32" Allen wrench. (Clockwise, 7 in-lb minimum).
ALL REGULATOR ADJUSTMENTS MUST BE DONE BY A TRAINED, QUALIFIED TECHNICIAN.
IMPROPER MODIFICATIONS OR ADJUSTMENTS CAN RESULT IN FIRE OR EXPLOSION
CAUSING PROPERTY DAMAGE, SEVERE PERSONAL INJURY OR LOSS OF LIFE.
8. Turn on the gas supply and electrical power to the furnace.
9. Turn on system power and energize valve.
10. Using a leak detection solution or soap suds, check for leaks at pressure boss screw. Bubbles forming
indicate a leak. SHUT OFF GAS AND FIX ALL LEAKS IMMEDIATELY!
13.6
CHECKING FURNACE INPUT
The natural gas supply pressure should be a maximum of 10.5" w.c. and minimum of 5" w.c (recommended 7"
w.c.). The LP gas inlet supply pressure should be 11" to 13" w.c.. The input rating of the furnace is based on
1000 Btu/ft.³ gas with a specifi c gravity of 0.6.
Since heating values for the gas vary geographically, the actual furnace input and output will vary accordingly.
For example, natural gas with a 900 Btu/ft.³ heating value will reduce the input to 90% of the rated input.
Natural gas with a 1100 Btu/ft.³ heating value will increase the input to approximately 110% of the rated input.
This is not usually a problem; however, adjustments to compensate for this can be made by minor adjustments
to the burner manifold pressure or by changing the burner orifi ce size. Contact the fuel supplier for specifi c
heating content values.
Any adjustments to the burner manifold pressure should be carried out with the use of a manometer or
calibrated Magnehelic® gauge. Do not adjust the gas valve pressure regulator more than ±0.3" w.c. from that
specifi ed on the rating label. Refer to Figure 27.
IMPORTANT:
NEVER ADJUST THE INPUT
OF
THE
EXCEED THE INPUT SHOWN
ON THE RATING PLATE.
Heating Value of Gas x 3600
Input =
Time in Sec. for 1 cu. ft.
where:
•
input is expressed in Btu/hr
•
heating value of the gas is expressed in Btu/ft
•
and time is the number of seconds required for
the test dial to indicate 1 cubic foot.
If using a gas meter with SI (metric) units:
•
1 cubic foot = 0.0283 cubic meters
•
1 cubic meter = 35.315 cubic feet
•
0.01 cubic meter = 0.3531 cubic feet
•
0.5 cubic meter = 1.766 cubic feet
W415-2306 / C / 09.22.20
g
!
FURNACE
TO
3
H18.6.4A
j
WARNING
!
30.
FIGURE 30 - MANOMETER MEASURING GAS MANIFOLD PRESSURE
H3.21
H18.5.5B
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