50
JOHNSON CONTROLS
FORM 145.05-NOM1 (708)
Sequence of Operation
Waterside Economizer
If the “IN WATER TEMP” is less than the “MIXED
AIR TEMP”, the control will switch to the economizer
mode. The unit will remain in the economizer mode
until the “IN WATER TEMP” is 1.0° F greater than the
“MIXED AIR TEMP”.
If the unit is configured to use Supply Air Temperature
Control, the control will compare the actual supply air
temperature to the “AC / ECON S/A SP” and generate
an analog output based on the difference and the amount
of response to a given change in output.
If the unit is configured to use Return Air Temperature
Control, the control will compare the actual return air
temperature to the “AC / ECON R/A SP” minus 1.0° F
and generate an analog output based on the difference
and the amount of response to a given change in
output.
If both Supply Air and Return Air Temperature Control
is selected, the Unit Control will use the lower of the
two outputs to control the economizer water valve.
On a FlexSys unit if Dew Point Control is selected,
the control will compare the derived “DEW POINT
COOLING” set point minus 2.0° F and the dew point
of the supply air; and generate an analog output based
on the difference and the amount of response to a given
change in output.
If Supply Air Temperature Control and Dew Point
Control are selected, it will pick the higher of the two
outputs to control the economizer water valve.
If Return Air Temperature Control and Dew Point
Control are selected, it will pick the higher of the two
outputs to control the economizer water valve.
If Supply Air Temperature Control, Return Air
Temperature Control, and Dew Pont Control are
selected; the Unit Control will compare the Supply
Air Temperature Control output to the Return Air
Temperature Control output and select the lower of
the two outputs. It will then compare it to the Dew
Point Control output and select the higher of the two
values.
The 2 to 10 volt analog output is located at the AO-
1 terminals 1 and 2 and is used to control the water
economizer valve. As long as water economizer is
enabled and the unit Air Flow Switch is closed the
output will never be less than the “ECON VALVE MIN”
setting.
Outdoor Air Economizer
If the “OUTSIDE AIR TEMP” is less than the “RETURN
AIR TEMP” the control will switch into the economizer
mode. The unit will remain in the economizer mode
until the “OUTSIDE AIR TEMP” is 1.0° F greater than
the “RETURN AIR TEMP”.
If the unit is configured to use Supply Air Temperature
Control, the control will compare the actual supply air
temperature to the “AC / ECON S/A SP” and generate
an analog output based on the difference and the amount
of response to a given change in output.
If the unit is configured to use Return Air Temperature
Control, the control will compare the actual return air
temperature to the “AC / ECON R/A SP” minus 1.0° F
and generate an analog output based on the difference
and the amount of response to a given change in
output.
If both Supply Air and Return Air Temperature Control
is selected, the Unit Control will use the lower of the
two outputs to control the economizer outdoor damper
actuator.
On a FlexSys unit if Dew Point Control is selected,
the control will compare the derived “DEW POINT
COOLING” set point minus 2.0° F and the dew point
of the supply air; and generate an analog output based
on the difference and the amount of response to a given
change in output.
If Supply Air Temperature Control and Dew Point
Control are selected, it will pick the higher of the two
outputs to control the economizer water valve.
If Return Air Temperature Control and Dew Point
Control are selected, it will pick the higher of the two
outputs to control the economizer water valve.
Sequence of Operation
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