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JOHNSON CONTROLS
SECTION 8 – UNIT OPERATION
FORM 150.67-NM1
ISSUE DATE: 4/28/2017
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If a 4-20mA signal is supplied, it is applied to termi-
nals A+ and A- and jumper JP1 on the I/O board
must be installed between pin 1 and 2. To calculate
the chilled liquid setpoint for values between 4mA and
20 mA use the following formula:
Setpoint = Local Chilled Liquid Setpoint + °Reset
°Reset = (mA signal - 4) x (*Max Reset Value)
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Example:
Local Chilled Liquid Setpoint = 45° (7.22 °C)
*Max Reset Value = 10 °F (5.56 °C)
Input Signal = 12 mA
(English)
°Reset = 8mA x 10 °F = 5 °F Reset
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Setpoint = 45 °F + 5 °F = 50 °F
(Metric)
°Reset = 8mA x 5.56 °C = 2.78 °C Reset
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Setpoint = 7.22 °C + 2.78 °C = 10.0 °C
A 240-24 Volt Ratio Transformer (T3)
is used to derive nominal 12 volt out-
put from the 120 volt supply.
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