5742637-YIM-D-0620
Johnson Controls Ducted Systems
57
Adjustment Of Temperature Rise
The temperature rise (or temperature difference between the
return air and the heated air from the furnace) must lie within
the range shown on the rating plate and the data in the Gas
Heat Application Table 11.
After the temperature rise has been determined, the cfm can be
calculated as follows:
After about 20 minutes of operation, determine the furnace
temperature rise. Take readings of both the return air and the
heated air in the ducts (about six feet from the furnace) where
they will not be affected by radiant heat. Increase the blower
cfm to decrease the temperature rise; decrease the blower cfm
to increase the rise. Refer to the In Door Blower Specification
Table 18.
Start Up For Units Equipped for FER
This section applies to single phase gas heat only.
Direct Drive
Direct drive FER units come from the factory with the following
three leads that lead to the indoor motor.
• A yellow cooling lead
• A red heating lead
• A white, fan only lead
Each lead is put on a different tap on the motor and provides
different speeds. The leads are set on default taps from the
factory. See the wiring diagrams for details on factory default
speeds. During installation, you may need to move the leads to
different taps depending on the airflow and static requirements
of the application.
NOTE:
During installation, the tap chosen for the heating
speed must produce a temperature rise that lies within
the rise range stated on the rating plate and the data in
Table 11.
Belt Drive
Belt drive FER units come with a VFD that provides heating,
cooling, and fan only speeds. The units are controlled by a 2-10
vdc output from the Smart Equipment™ control to the supply
fan VFD.
You may need to adjust the speeds for specific applications as
factory defaults may not always be suitable. To make airflow
changes, adjust the variable pitch sheave pulley. If pulley
adjustments fail to achieve the required airflow, you may need
to adjust the factory default speed settings for the Smart
Equipment™ control, see
Adjusting the fan speed percentages
.
NOTE:
During installation, the speed chosen for the heating
speed must produce a temperature rise that lies within
the rise range stated on the rating plate and the data in
Table 11.
Adjusting the fan speed percentages
1.
On the unit control board, use the joystick to select
Details
,
Fan
,
Setup
and press ENTER.
or
From the Mobile Access Portal (MAP) Gateway, select the
indoor fan section.
2.
Make the required changes to the fan speed commands.
The following table shows available fan speed commands.
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
1. By actual measurement, it takes 38 seconds for the hand on
the 1-cubic foot dial to make a revolution with a 100,000 Btuh
furnace running. Using this information, located 38 seconds
in the first column in the table above. Read across to the
column headed “1 Cubic Foot”, where you will see that 95
cubic feet of gas per hour are consumed by the furnace at
that rate. Multiply 95 X 1050 (the Btu rating of the gas
obtained from the local gas company). The result is 99,750
Btuh, which is close to the 100,000 Btuh rating of the furnace.
Table 25: Gas Rate-Cubit Feet per Hour
1
Seconds for
One Rev.
Size of Test Dial
1/2 cu. ft.
1 cu. ft.
CFM
Btuh Input x 0.8
=
108
.
.
x F Temp Rise
o
Table 26: Fan setup commands
Command
Adjustment
Setting
Fan Only-% Cmd
Adjust based on application
(CV IS Fan Only)
1ClgStg-% Cmd
Adjust based on application
(CV IS 1 Stg Cool)
1HtgStg-%Cmd
Adjust based on application
(Occupied: One
Stage of Heat %
Command)