JOHNSON CONTROLS
195
SECTION 8 – SERVICE
FORM 145.05-NOM7
ISSUE DATE: 10/31/2019
8
ANALOG INPUT OPERATION
This section describes the control operation of the (22)
twenty-two analog inputs. These inputs are used by
the control to monitor and respond to unit tempera-
tures, pressures, enthalpy, etc. The location of each of
these connections on the Unit Controller is contained
in
. The ID gives the jack con-
nection designated as “J” and the identifying number
of the connector, followed by a – and the pin number
of the connector. For example the SUPPLY AIR TEM-
PERATURE analog input would be found at J9-1. This
is connector J9 – Pin 1. As the Unit Controller board is
positioned in the control box the right hand row of the
J series connectors is the input, the middle row is the
common, and the left hand row is the 5VDC input to
the sensor. Also the pin in the lower right hand bottom
corner is pin 1.
Temperature Sensors
The temperature sensors are all 10K Type III Thermis-
tors. The relationship between the temperature and the
voltage output and resistance is contained in
The following analog inputs are of this type: Supply
Air Temperature, Flex Evap Temp, Outside Air Temp,
Return Air Temp, Zone Temp, Under Floor Temp and
Mixed Air Temp. and Leaving Water Temp.
Duct Pressure Transducer
The Duct Pressure Transducer is located in the electrical
control box. The purpose of the transducer is to sense and
convert the static pressure in the supply-side of the duct to
a 1 to 5VDC voltage. The DC voltage is sent to the Unit
Controller and compared against the “DUCT STATIC
PRESS ACTIVE SP.” The transducer is factory wired, but
pneumatic tubing must be field supplied and installed
(re-
fer to Section 2
“INSTALLATION”
in this manual).
The
duct static pressure transducer measures differential pres-
sure between the pressure in the duct and atmospheric pres-
sure. When verifying transducer operation, the technician
must insert a tee in the pneumatic tubing and connect a ma-
nometer to the tee to verify the pressure being applied to
the transducer. Once this pressure is known, a comparison
can be made of the duct pressure vs. output VDC from the
transducer.
shows the relationship
between the pressure applied to the duct pressure transduc-
er and the output voltage. The output is linear between 0"
WC and the SPAN. The “DUCT PRESS TRANSDUCER
SPAN” can be set to .25, 1.25, 2.5 or 5.0 "W.C.
The unit is shipped with a transducer with a 0 to 5 "W.C.
span. In order to use the .25, 1.25 or 2.5 "W.C. span avail-
able through the Unit Controller, the transducer would
have to be changed. The “DUCT PRESS TRANSDUCER
SPAN” must always be set based on the span of the trans-
ducer installed.
Units built prior to 2012 used an AutoTran
1-5vdc output transducer for Duct Static
Pressure. The AutoTran transducers are
no longer available. Units built after the
start of 2012 use a Setra 0-5vdc output
transducer. If the 1-5vdc transducer is
defective, it must be replaced with a 0-5vdc
style transducer. Also, the software must
be upgraded as the old software version
was setup for the 1-5vdc style transducer.
SECTION 8 – SERVICE