JOHNSON CONTROLS
134
FORM 145.05-NOM7
ISSUE DATE: 10/31/2019
SECTION 5 – SEQUENCE OF OPERATION
HEAT OPERATIONS
Electric Heat
Programmed Data
The following parameters must be programmed into
the Unit Controller through the User Interface:
• PROGRAM key, HEATING subsection: “HEAT-
ING SYSTEM” must be set to USER ENABLE
• OPTIONS key, HEATING subsection:
• “HEATING SYSTEM TYPE” must be set to
ELECTRIC
• “ELEC HEAT CAPACITY” must be set to
the nameplate KW on the unit's tag
• SETPOINTS key, HEATING subsection:
• For CV units: “1ST STAGE HEATING
SETPOINT” (default is 85.0°F) and “2ND
STAGE HEATING SETPOINT” (default
is 100.0°F) must be programmed for CON
-
STANT VOLUME
• For VAV and FlexSys
units: “HEATING
SAT” (default is 100.0°F) must be pro
-
grammed for VARIABLE AIR VOLUME or
FLEXSYS
Heating Control Offset
The Unit Controller calculates a “HEATING CON-
TROL OFFSET” (HCO) based on the KW of heat in
-
stalled, the CFMs (see
), and the
stages of heat (see
).
The “HEATING CONTROL OFFSET” is rounded up
to the nearest 1/2 degree. If “HEATING CONTROL
OFFSET” is calculated to be less than 2.0°F, it is set
to 2.0°F.
If the UNIT MODE “COMFORT VENT HEATING”
or “SUPPLY AIR TEMPERING” is active, the “HEAT-
ING CONTROL OFFSET” is fixed at 5.0°F.
Active SAT SP
See
to determine what the
“SUPPLY AIR TEMP ACTIVE SP” value is for Con-
stant Volume units. On VAV and FlexSys units, the
“SUPPLY AIR TEMP ACTIVE SP” is the “HEATING
SAT” setpoint.
Sequence of Operation
The Unit Controller enters an active HEATING mode:
a. OCC HEATING
b. UNOCC HEATING
c. COMFORT VENT HEATING
d. SUPPLY AIR TEMPERING
e. MORNING WARM-UP
The Unit Controller determines the initial stages of
heat needed and starts the required stages of heat.
COMFORT VENT HEATING and SUP-
PLY AIR TEMPERING bring on one
stage at a time
After expiration of the 3.5-minute Interstage Delay
Timer, the Unit Controller cycles ON/OFF stages of
heat based on the Heating Control Logic.
TABLE 24 -
CFM
UNIT SIZE
(TON)
CV UNITS
(CFM)
VAV UNITS OR
FLEXSYS UNITS (CFM)
25
8800
4400
35
12200
6100
40
14000
7000
50
17500
8800
60
21000
10500
70
25000
12500
85
27600
13800
95
31500
15700
105
34000
17000
TABLE 25 -
HEAT STAGES
ELEC HEAT CAPACITY (KW)
MAXIMUM STAGES
17.5
1
35
2
52.5
3
70
4