Johnson Controls System 350T A350P User Manual
Features and Benefits
FANs 930, 930.5, 125, 121
Product/Technical Bulletin A350P
Issue Date 0414
System 350
TM
A350P Electronic Proportional Plus Integral
Temperature Control
The A350P is an electronic, proportional plus int egral
temperature control with analog 0 to 10 VDC and
0 to 20 mA outputs. The control is equipped with
three user-selectable time integration constants and
an adjustable throttling range of 2 to 30F° (1 to 17C°).
Two models cover a setpoint range of -30 to 130°F
(-35 to 55°C) and 90 to 250°F (32 to 121°C).
As are all System 350™ products, the A350P control
is housed in a NEMA 1, high-impact plastic enclosure.
The modular design provides easy, plug-together
connections for quick installation and fut ure
expandability.
Modular Design Enables stage, display, and power modul es to
be purchased and installed a s needed
Plug-Together Connectors
and 35 mm DIN Rail
Mounting
Eliminates wiring between m odules, whi ch
reduces installation costs
Figure 1: A350P Electronic Proportional Plus
Integral Temperature Control
Two Models Cover a Wide
Setpoint Range of -30 to
250°F (-35 to 121°C)
Minimum Output Adjustable
from 0 to 60%
Adjustable Throttling
Range of 2 to 30F° ( 1 to 17C°)
Field-selectable Rev erse
or Direct Acting Mode
Three User-Selectable
Integration Time Constants
Interchangeable
Temperature Sensors
Reduces inventory by encom passing
temperature ranges requi red to suppo rt the
majority of Heating, Ventilat ion, Air C onditioni ng,
and Refrigeration (HVAC/R) applications
Tailors the output to the req uirements of the
controlled device; can be us ed to set m inimum
valve or damper position
Enables the user to tune the system for optimum
stable performance
Works in heating or cooling applications
Provides selection of the int egration constant fo r
applications requiring propo rtional pl us integral
control
Increase versatility and serviceability
© 2014 Johnson Controls, Inc. 1
Part No. 24-7664-192, Rev. G www.johnsoncontrols.com
Code No. LIT-930020
Cover Screw
(One of Four)
Setpoint
Dial
Throttling Range
Potentiometer
Minimum Output
Potentiometer
LED Indicator
(Percent of Output)
V: 0-10 VDC Ou tp ut
I: 0-20 mA Output
SN: Sensor Input
24V: 24 VAC (+)
C: Common (-)
VDC: +5 VDC (not used)
Operation Mode
Jumper Positions
Reverse
Acting (RA)
Direct
Acting (DA)
Module
Connector
Integration DIP switch is
shown in proportional-only position.
THROT
RANGE
MIN
OUTPUT
VIS
NVD
C
C
2
4
V
Fast
Medium
Slow
Off
On
1 2 3 4
Integration
DIP Switch
pplication
A
The A350P Temperature Control can be used as a
standalone device or in conjunction with plug-together
accessory modules. The addition of S350 Stage
Modules allows for the control of multiple stage
HVAC/R applications. Typical application for the
A350P includes:
• proportional heating control with staged direct
expansion cooling
• simple temperature control for air handling units
• modulating damper actuators for mixed air control
• simple proportional mixed air control
A typical System 350 Temperature Control setu p
includes the following:
• A350P Temperature Control
• A99B Series Temperature Sensor
• Y350R Power Module (or 24 VAC Class 2
transformer)
• S350 Stage Modules
• D350 Digital Temperature Display Module
peration
O
The A350P control operates on 24 VAC/VDC and
provides two simultaneous analog outputs:
0 to 10 VDC and 0 to 20 mA. A cover-mounted,
10-segment Light-Emitting Diode (LED) bar graph
indicates percentage of output.
Features include:
• adjustable setpoint
• adjustable minimum output
• adjustable throttling range (proportional b and)
• selectable integration time constant
• selectable Reverse Acting (RA) or Direct Act ing
(DA) mode of operation
IMPORTANT: All System 350 controls are
designed for use only as
operating controls. Where an
operating control failure would
result in personal injury and/or
loss of property, it is the
responsibility of the installer to
add devices (safety, limit controls)
or systems (alarm, supervisory
systems) that protect against, or
warn of, control failure.
Figure 2: Interior View Showing A350P Control’s Featur es
2 System 350 A350P Electronic Proportional Plus Integ ral Temper ature Cont rol Prod uct/Tech nical Bulleti n
Deviation Above Setpoint (F°)
Output
(mA)
0
2 4 6 8 10 12 14 16 18 20
0
4
10
20
50%
20%
0%
Throttling Range
Minimum Output Adjustment
The minimum output adjustment sets the minimum
voltage or milliampere output provided by t he A 350P
control. It can be adjusted from 0 to 60% (0 t o 6 V DC
or 0 to 12 mA) of the output range.
Example:
A controlled device responding to a 4-20 mA out put
would require the minimum output to be adjusted t o
20% or 4 mA. (See Figure 3.) The minimum output
adjustment may also be used to set valves or dam pers
to minimum positions.
Throttling Range (Proportional Band)
The throttling range is the range over which a control
is active. Throttling range for the A350P control can be
adjusted from 2 to 30F° (1 to 17C°). Make the
adjustment at the throttling range potentiometer
marked THROT RANGE (see Figure 2).
Integration Function
Proportional-only controls cannot hold a process at the
exact setpoint. A proportional offset is alway s present
because the control output is 0% at setpoint. Any load
on the system will cause the control point to be offset
from the setpoint. The greater the load on the system,
the further the control point will be offset from the
setpoint. (This is commonly referred to as proportional
offset, and under maximum load this error will
approach the throttling range.)
Some proportional-only controls are designed with
their setpoint located midway through the proporti onal
band to help compensate for this offset. This results in
a plus/minus error from the setpoint rather t han a
single-ended error. Refer to Figure 4.
Figure 3: Output vs. Deviation from
Setpoint for: Minimum Output = 0, 20, and
50%, Throttling Range = 20°F (DA)
Make the adjustment at the minimum output
potentiometer marked as MIN OUTPUT.
(See Figure 2.) For each 10% increase in output, the
next bar on the LED indicator will light (only one bar is
lit at any time).
Note: Before setting the minimum output
potentiometer, verify that the control reads
zero output (that is, no LEDs are lit).
System 350 A350P Electron ic Proportio nal Plus Int egral Tempe rature Control Prod uct/Tec hnical Bullet in 3
Proportional
Offset
Setpoint
Load Change
System Load
Contr ol Point
Follo ws the Load
Temperature
Time
Throttling
Range
Proportional Only Control
Temperature
Proportional
Offset = 0
Setpoint
Load Change
System Load
Integration adjusts the
proportional output to
bring the process to
setpoint regardless of load.
Time
Proportional Plus Integral Control
Figure 4: Comparison Between Proport ional Only and Proportional Plus Integral Control
The A350P control has an integration feature that
forces the control point to match the setpoint . Over
time, the A350P will control the heating/cooling
equipment to balance the system load at t he cont rol
setpoint. (See Figure 4.)
On traditional proportional plus integral controls, the
amount of correction will become too large if the
system load exceeds the capacity of the equipment.
When the actuated device (valve or damper) is ful l y
open or closed and the setpoint still cannot be
reached, the integration error continues to grow. The
result is called integral windup.
The A350P control avoids integral windup with a
patented circuit that puts a dynamic ceiling on the
integrator. This resets the integration error when the
sensor goes just above the setpoint plus the throttling
range (in DA mode) or just below the setpoint minus
the throttling range (in RA mode). This allows the
process to recover from an out-of-range condition
without a large overshoot.
The A350P control has three field-selectable
integration constants and an off position. The
integration DIP switch selects the integration constant.
(See Figure 2 for location.)
The field-selectable integration constant s i nclude:
• OFF: Switch 1 to On position, all others Off
provides proportional-only operation.
Note: In open-loop (without feedback) applications,
select OFF (proportional-only) operation.
Slow (C3): Switch 2 to On position, all others
•
Off is the slowest integration constant (26 minut e),
and is suitable for most proportional plus integral
applications. Slow is the recommended init i al
setting.
Medium (C2): Switch 3 to On position, all
•
others Off selects a 13-minute integration
constant. If the rate of system recovery to set point
is sluggish with the control set to slow, and if the
system has enough capacity to drive the process
to setpoint at a faster rate, the medium sett i ng
may be used.
Fast (C1): Switch 4 in On position, all
•
others Off is the fastest integration constant
(6.5 minutes). Use fast only in instances where the
rate of change at the sensor is extremely rapid
and system capacity can compensate for that
rapid change.
4 System 350 A350P Electronic Proportional Plus Integ ral Temper ature Cont rol Prod uct/Tech nical Bulleti n
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