Johnson Controls ZY Series User Manual

Checking gas heat input
Two Stage Gas Heat
About this task:
This unit has two stages of gas heat. First stage
input is considered the minimum input for the
furnace. The intended input for each furnace
is shown in Table 77. The table applies to units
operating on 60 Hz power only.
To determine the rate of gas flow (Second Stage).
1. Turn off all other gas appliances connected to
the gas meter.
2. Turn on the furnace and make sure the
thermostat is calling for Second stage (100%
input) heat.
3. Measure the time needed for one revolution
of the hand on the lowest increment dial on
the meter. A typical gas meter has a 1/2 or a 1
cubic foot test dial.
4. Using the number of seconds it takes for one
revolution of the dial, calculate the cubic feet
of gas consumed per hour. (See example
below)
5. If necessary, adjust the high pressure
regulator as discussed in the section
"Manifold Gas Pressure Adjustment". Be
sure not to over-fire the furnace on second
stage. If in doubt, it is better to leave the
second stage of the furnace slightly under-
fired. Repeat Steps 1-5.
To determine the rate of gas flow (First Stage)
1. Turn off all other gas appliances connected to
the gas meter.
2. Turn on the furnace and make sure the
thermostat is calling for first stage heat.
3. Even when the thermostat is calling for first
stage heat, the unit will light on second stage
and will run on second stage for 1 minute.
Allow this one-minute time period to expire
and be certain the unit is running on first
stage.
4. Measure the time needed for one revolution
of the hand on the lowest increment dial on
the meter. A typical gas meter has a 1/2 or a 1
cubic foot test dial.
5. Using the number of seconds it takes for
one revolution of the dial, calculate the cubic
feet of gas consumed per hour (See example
below).
6. If necessary, adjust the low pressure regulator
as discussed in the section "Manifold Gas
Pressure Adjustment". Be sure not to under-
fire the furnace on first stage. If in doubt, it
is better to leave the first stage of the furnace
slightly over-fired. Refer to the table "Gas Rate
Cubic Feet Per Hour" for input value. Repeat
Steps 1-6.
Table 76: Gas Rate Cubic Feet Per Hour
Size of Test Dial
Seconds for One Rev.
1/2 cu. ft. 1 cu. ft.
10 180 360
12 150 300
14 129 257
16 113 225
18 100 200
20 90 180
22 82 164
24 75 150
26 69 138
28 64 129
30 60 120
32 56 113
34 53 106
36 50 100
38 47 95
40 45 90
42 43 86
44 41 82
46 39 78
48 37 75
50 36 72
52 35 69
54 34 67
56 32 64
58 31 62
60 30 60
Note: To find the Btu input, multiply the
number of cubic feet of gas consumed
per hour by the Btu content of the gas in
your particular locality (contact your gas
company for this information as it varies
widely from area to area).
EXAMPLE
By actual measurement, it takes 19 seconds for the
hand on a 1 cubic foot dial to make a revolution
with a 200,000 Btuh furnace running. To determine
rotations 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
INSTALLATION MANUAL ZY SERIES 3-10ton 60 Hertz R-410A 123
Johnson Controls Ducted Systems

Johnson Controls ZY Series Specifications

General

Brand	Johnson Controls
Model	ZY Series
Category	Air Conditioner
Language	English