JOHNSON CONTROLS
110
FORM 100.50-NOM12
ISSUE DATE: 04/02/2019
SECTION 5 – SEQUENCE OF OPERATION
TABLE 40 -
RETURN AIR BYPASS DAMPER
CURRENT %
The amount of air the IPU board calculates is bypassed because the mixed SAT is not increasing. The IPU
board utilizes the current RAT, the current EAT, and the mixed SAT to perform a calculation to arrive at the
current %.
ACTIVE
SETPOINT %
How much the return air the IPU board calculates is needed to bypass to warm the mixed SAT from its
current value to the mixed SAT setpoint. The IPU board utilizes the current RAT, current EAT, and current
mixed SAT to perform a calculation to arrive at the active setpoint %.
BYPASS
DAMPER
POSITION
This is the actual position of the bypass damper. The bypass damper should be able to drive between 0%
and 40%.
MAX BYPASS
This is the maximum amount of return air that the IPU board allows to bypass around the evaporator coil
through the FlexSys bypass damper.
The IPU board utilizes internal logic and calculations to determine how much of the return air is being
bypassed.
This is not the same as the actual bypass damper position. This is an adjustable setpoint with a range of
20–40%. We recommend leaving it at 40% for initial start-up and then adjusting down later if needed.
NOTE
It is likely that the above mentioned parameters—return air bypass current %, return air bypass active setpoint %, and bypass damper position
%—do not have matching values. This is normal; do not be alarmed.
Heating
• Occ and Unocc Heating operates the same as Occ
and Unocc Heating for a VAV configured unit.
• It is recommended to limit the SAT heating setpoint
between 80.0–90.0°F.
• Keeping the SAT heating setpoint between 80.0–
90 .0°F keeps the underfloor slab from becoming
too warm and then radiating heat for an extended
period of time after heating operation has stopped.
Underfloor Temperature Control
•
A FlexSys configured unit has two specialized se
-
quences built in to help control the environment in
the underfloor plenum:
• Dew Point Reset
• Active Slab Control
•
Both of these sequences require an underfloor slab
temperature sensor and an underfloor humidity
sensor be installed.
•
Both of these sensors are field provided/installed.
Dew Point Reset
• This sequence changes the active EAT setpoint
from the EAT high setpoint to the EAT low
setpoint when the temperature of the underfloor
air approaches its dewpoint.
•
The unit must have an underfloor slab temperature
sensor and an underfloor humidity sensor installed
for this sequence to function.
• dew point reset must be set to User Enabled in the
PROGRAM-COOLING menu.
Sequence
• When the underfloor air dewpoint becomes
greater than the underfloor slab temperature
minus 2.0°F for 120 seconds, the IPU board
switches the active EAT setpoint from the
EAT high setpoint to the EAT low setpoint.
• The EAT low setpoint continues to be used as
the active EAT setpoint until the underfloor
air dewpoint becomes less than the under-
floor slab temperature minus 2.5°F.
Active Slab Control
• This sequence allows heat to be turned ON during
a transition from one occupancy state to another
when the underfloor air temperature is higher than
the underfloor slab
temperature.
• The Series 100 unit must have a heating source
installed and set to User Enabled.
• Active Slab Control must be set to User Enabled
in the PROGRAM-COOLING menu.
•
The unit must have an underfloor slab temperature
sensor installed for this sequence to function.
