Johnson Controls York VERSECON YSWD 012, Installation Operation & Maintenance

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JOHNSON CONTROLS
FORM 145.05-NOM1 (708)
FLEXSYS DEW POINT CONTROL
The unit can be configured to use Dew Point Control in
both economizer and mechanical cooling mode. This
feature will prevent the supply air temperature dewpoint
entering the under floor space from falling above the
Slab Temperature of the under floor space.
The following parameters must be programmed through
the
“Setpoints”
section of the Keypad / Display or by
a communicated input.
“AC-S/A DEW EN” – This value must be turned on in
order to use Dew Point Control. The default value is
ON
“AC-S/A DEW MIN” – This establishes the minimum
allowable derived Dew Point Control set point. The
default value is 48.0° F.
“AC-S/A DEW MAX”
– This establishes the maximum
allowable derived Dew Point Control set point. The
default value is 60.0° F.
“AC-DEW DIF”
- This establishes the differential below
the Slab Temperature that the unit will try and control
to. The default value is 5.0° F.
Sequence of Operation
The Unit Control takes the Slab Temperature and
subtracts the
“AC-DEW DIF”
value. It then compares
this value to the “AC-S/A DEW MIN” and the “AC-S/A
DEW MAX” . The derived “DEW POINT COOLING”
set point is determined as follows:
•
If the Slab Temperature minus the “AC-DEW
DIF” is less than or equal to the “AC-S/A DEW
MIN”
the control sets the
“DEW POINT COOL-
ING” set point to the “AC-S/A DEW MIN”
programmed value.
•
If the Slab Temperature minus the “AC-DEW
DIF” is between the “AC-S/A DEW MIN” and
the
“AC-S/A DEW MAX”
the control sets the
“DEW POINT COOLING” set point to the Slab
Temperature minus the “AC-DEW DIF” .
•
If the Slab Temperature minus the “AC-DEW
DIF” is greater than or equal to the “AC-S/A
DEW MAX”
the control sets the
“DEW POINT
COOLING” set point to the “AC-S/A DEW
MAX” programmed value.
ECONOMIZER OPERATION
There are three economizer options available – waterside
economizer, outdoor air economizer or none.
Based on the type of economizer that is installed the
following parameters must be programmed through
the
“Setpoints”
section of the Keypad / Display or by
a communicated input.
“H2O ECON EN” – This value can be turned ON, if
waterside economizer is desired, or OFF if not, the
default value is ON.
“ECON VALVE MIN” – If water economizer is enabled
this value must also be programmed. This is the
minimum allowable position for the economizer water
valve when water economizer is enabled in the Occupied
mode. The default value if 0.0%.
“O/A ECON EN” – This value can be turned ON, if
outdoor air economizer is desired, or OFF if not, the
default value is OFF.
“O/A MIN POS” – If outdoor air economizer is enabled
this value must also be programmed. This is the
minimum allowable position for the outdoor air damper
when outdoor air economizer is enabled in the Occupied
mode. The default value is 15%.
“ECON –S/A TMP EN” – When either the waterside or
outdoor air economizer is selected, the type of control,
supply air or return air must be selected. This value must
be turned ON to use Supply Air Temperature Control.
The default value is ON.
“AC / ECON S/A SP” - this is the set point the controller
will control to if the unit is configured for
“ECON –S/A
TMP EN” . The default value is 55.0° F.
“ECON – R/A TMP EN” – When either the waterside or
outdoor air economizer is selected, the type of control,
supply air or return air, must be selected. This value
must be turned ON to use Return Air Temperature
Control. The default value is OFF.
“AC / ECON R/A SP” – this is the set point the controller
will control to if the unit is configured for
“ECON – R/A
TMP EN” . The default value is 75.0° F.
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