Johnson Controls 40 25 TON, Installation Operation & Maintenance

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147
JOHNSON CONTROLS
5276178-JIM-C-0118
5
TABLE 74 - CFM
UNIT SIZE CV UNITS CFM
VAV UNITS
FLEXSYS UNITS
CFM
25 – 40 TON
15000 7500
TABLE 75 - HEAT STAGES
“ELEC HEAT CAPACITY”
(KW)
MAXIMUM STAGES
40 (40KW, 80KW) 2
40 ( 200V ) (108KW) 3
During the initial call, the Unit Controller uses the
following formula to determine how many stages
of electric heat to bring ON. After which the Unit
Controller uses the procedure above for staging
additional capacity ON or OFF.
N =
SAT - SATSP
2 x HCO
Where:
•
N = Number of Heat Stages Required (Rounded
Down to the Nearest Integer) .
•
SAT =
“SUPPLY AIR TEMP”.
•
SATSP = “SUPPLY AIR TEMP ACTIVE SP”.
•
HCO = “HEATING CONTROL OFFSET”.
If the Number of Heat Stages required calculates to less
than 1, the Number of Stages is set to 1.
If the Number of Heat Stages required calculates to
be greater than the derived “HEAT STAGES” value
the Number of Heat Stages required will be set to the
“HEAT STAGES” derived value.
When the UNIT MODE is “COMFORT VENT
HEATING” or “SUP AIR TEMPERING” is active the
initial number of heating stages will not be estimated.
Instead, one stage of heat will be brought ON at a
time.
When UNIT MODE is “STANDBY ” and “UNDER
FLR TEMP OVRD” is active, one stage of heat is
turned ON.
STAGED GAS HEAT
Programmed Data
The following parameters programmed into the Unit
Control:
•
“HEATING SYSTEM”
must be set to USER EN-
ABLE through the PROGRAM key, HEATING
subsection of the User Interface.
•
“HEATING SYSTEM TYPE” must be set to
STAGED GAS through the OPTIONS key,
HEATING subsection of the User Interface.
•
“GAS HEAT CAPACITY” must be set to the
rating plate value through the OPTIONS key,
HEATING subsection of the User Interface.
If the unit rating plate shows a capacity of 266
MBH, set this parameter to 375 MBH. If the unit
rating plate shows the capacity as 532 MBH, set
this parameter to 750 MBH. If the unit rating
plate shows the capacity as 798 MBH, set this
parameter to 1125 MBH.
•
“HEAT LIMIT TEMPERATURE” must be pro-
grammed using the SETPOINTS key, HEATING
subsection of the User Interface.
•
“1ST STG HEATING SETPOINT”
must be
programmed for CONSTANT VOLUME units
through the SETPOINTS key, HEATING subsec-
tion of the User Interface.
•
“2ND STAGE HEATING SETPOINT” must be
programmed for CONSTANT VOLUME units
through the SETPOINTS key, HEATING subsec-
tion of the User Interface.
•
“HEATING SAT”
must be programmed for
“VARIABLE AIR VOLUM”
and
“FLEXSYS”
units through the SETPOINTS key, HEATING
subsection of the User Interface.
Heating Control Offset
The Unit Control calculates a “
HEAT CONTROL
OFFSET” (HCO)
using the following formula
HCO =
180000
2.16 x CFM
Where:
•
HCO = “HEAT CONTROL OFFSET”
•
CFM = (See Table 67)