per minute, divide 60 by 19 = 3.16. To
calculate rotations per hour, multiply 3.16
• 60 = 189.6. Multiply 189.6 • 1 (0.5 if using
a 1/2 cubic foot dial) = 189.6. Multiply
189.6 • (the Btu rating of the gas). For this
example, assume the gas has a Btu rating
of 1050 Btu/ft.
3
. The result of 199,000 Btuh
is within 2% of the 200,000 Btuh rating of
the furnace.
Manifold Gas Pressure
Adjustment
Two Stage
About this task:
This gas furnace has two heat stages. Therefore, the
gas valve has two adjustment screws located under
two cover screws. The second stage adjustment
screw is adjacent to the "HI" marking on the valve
and the first stage adjustment screw is located
adjacent to the "LO" marking on the valve (See
Figure and Figure ).
Manifold pressure adjustment procedure.
Adjust second stage pressure first (refer to for input
value), then adjust first stage pressure (refer to
Table for input value).
1. Turn off all power to the unit.
2. Using the outlet pressure port on the gas
valve, connect a manometer to monitor the
manifold pressure.
3. Remove cover screws covering HI and LO
pressure adjustment screws.
4. Turn on power to the unit.
5. Set thermostat to call for second stage heat
and start furnace.
6. If necessary, using a screwdriver, turn
thesecond stage adjustment screw
(adjacent to the “HI” marking on the valve)
clockwise to increase manifold pressure
or counterclockwise to decrease manifold
pressure.
7. After the high manifold pressure has been
checked, adjust the thermostat to call for first
stage heat.
8. If necessary, using a screwdriver, turn the first
stage adjustment screw (adjacent to the “LO”
marking on the valve) clockwise to increase
manifold pressure or counterclockwise to
decrease manifold pressure.
9. Once pressure has been checked, replace the
cover screws covering the HI and LO pressure
adjustment screws.
Table 59: Gas Heat Stages
Model
(Size)
Gas Heat
Description Opt.
# of Burner
Tubes
1st Stage
Input
(Mbh)
2nd Stage
Input
(Mbh)
Total
Input
(Mbh)
Low
D
2
-
70
70
Med
E
3
-
114
114
ZXA7
(6)
High
F
3
100
145
145
Low
D
3
90
125
125
Med
E
4
125
180
180
ZX08
(7.5)
High
F
5
176
220
220
Low
D
3
90
125
125
Med
E
4
125
180
180
ZX09
(8.5)
High
F
5
176
220
220
Low
D
4
125
180
180
Med
E
5
176
220
220
ZX12
(10)
High
F
5
200
250
250
Low
D
4
125
180
180
Med
E
5
176
220
220
ZX14
(12.5)
High
F
5
200
250
250
INSTALLATION MANUAL ZX SERIES 6 - 12.5 Ton 60 Hertz R-410A
92
Johnson Controls Ducted Systems
Содержание ZX Series
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