Checking Gas Heat Input; To Determine The Rate Of Gas Flow At Second Stage (Full Input); To Determine The Rate Of Gas Flow At First Stage (Minimum Input) - York Sun Select YV28 Manual

Checking Gas Heat Input

For two stage and modulating furnaces, input rate
should be checked at full input and minimum input.
The intended input for each furnace is shown in
and on the unit rating plate. The table applies to
units operating on 60 Hz power only.
To determine the rate of gas
flow at Second Stage (full input)
About this task:
To determine the rate of gas flow at Second Stage
(full input):
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
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 Step 1
to Step 5.
To determine the rate of gas
flow at First Stage (minimum
input)
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 (minimum
input) heat.
90 Installation Manual: YORK
Manifold
Sun™ Select YV28 to YV50
®
Johnson Controls Ducted Systems
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 cubic
foot 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
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. Repeat Step 1 to Step 6.
Table 69: Gas Rate Cubic Feet Per Hour
Seconds for one rev.
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
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).
Manifold Gas
Size of test dial
1/2 cu. ft 1 cu. ft
180 360
150 300
129 257
113 225
100 200
90 180
82 164
75 150
69 138
64 129
60 120
56 113
53 106
50 100
47 95
45 90
43 86
41 82
39 78
37 75
36 72
35 69
34 67
32 64
31 62
30 60