Attributes (Waterside Economizer Suitability) - Johnson Controls - Metasys - LIT-12011147 - Software Application - Controller Configuration Tool - 13.1

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Johnson Controls
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Controller Configuration Tool
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The following table describes the attributes used by the Waterside Economizer Suitability modules:

Table 1. Waterside Economizer Suitability Attributes




Default Value

Building Load


Indicates the amount of energy the plant adds to the chilled water. The failsoft property on this element is set to true. If the input is unreliable (or not connected), the input uses its default value of zero.

0.0 tons (0.0 kW)

ECON IS AVAIL (Network Free Cooling is Available)


Indicates if waterside economizer cooling is suitable. Used as a network input.


Economizer Switchover Setpoint


Indicates the switchover setpoint, which is compared with the OAT (or OAWB-T) to determine waterside economizer cooling suitability. May be set to the CHWS-T Setpoint - (Cooling Tower Approach + HX Approach) to ensure outdoor air conditions are suitable for waterside economizer cooling.

50°F (10°C)

Free Cooling Available


Indicates if waterside economizer cooling is suitable.


HX Capacity


Indicates the available heat exchanger capacity.

28.4 tons (100.0 kW)

Load Margin


Indicates the differential applied to the HX capacity when comparing with the Building Load. The Load Margin may be used to account for a temporary increase in building load that may result when switching into economizer cooling due to the AHU's response to a warmer chilled water supply temperature.

5.7 tons (20.0 kW)

OA Econ Lockout Setpoint


Indicates the outdoor air setpoint for economizer lockout. When the outdoor air dry bulb temperature drops below this setpoint, waterside economizer operation is disabled.

32°F (0°C)

OA Econ Lockout Setpoint Diff


Indicates the differential for outdoor air economizer lockout. When the outdoor air rises above the OA Econ Lockout Setpoint plus this differential value, waterside economizer operation is reenabled.

4°F (2°C)

OA Humidity


Indicates the outside air relative humidity. Used to calculate the OA Wet Bulb Temperature (OAWB-T).


OA Temperature


Indicates the outside air dry bulb temperature.

70 °F (20 °C)

Switchover Diff


Indicates the differential applied to the Economizer Switchover Setpoint.

2 °F (1 °C)