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EMERSON PACSystems VersaMax MICRO PLC & NANO PLC. USER MANUAL (2019) - page 20

User Manual

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15.4.2

Dimensions of 14-, 20-, 23-, 28-, 40-, and 64-Point Micro
PLCs and Expansion Units

Figure 131

15.5

Grounding the Equipment

Equipment grounding procedures must be properly followed for safe operation of your PLC
equipment.

The maximum recommended resistance to ground is 200m



(equivalent to 100 feet of

AWG #12

–

3.29mm

–

copper cable).

•

Grounding installation must conform to National Electrical Code (NEC) standards.

•

Ground conductors should be connected with separate branches routed to a central
earth ground point.

Figure 132

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•

Ground conductors should be as short and as large in size as possible. Braided straps
or ground cables

–

AWG #12 (3.29mm

) or larger

–

can be used to minimize

resistance. Conductors must always be large enough to carry the maximum short
circuit current of the path being considered.

•

Install an external earth leakage breaker and take other safety measures according
to external wiring standards.

15.5.1

Grounding the Programmer

For proper operation, the computer for the programming software must have a ground
connection in common with the PLC. Normally, this common ground connection is

provided by connecting the programmer’s power cord to the same power source (with the

same ground reference point) as the PLC. If that is not possible, use a port isolator
(IC690ACC903) between the programmer PLC serial connection. If the programmer ground
is at a different potential than the PLC ground, a shock hazard could exist. Also, damage to
the ports or converter (if used) could occur when the programmer serial cable is connected
between the two.

WARNING

Failure to follow programmer grounding recommendations could result in personal injury,
equipment damage, or both.

15.6

Installing a PLC or Expansion Unit on a DIN Rail

VersaMax Nano PLC and Micro PLC equipment can be mounted on a 35mm DIN rail as
described below, or mounted on a metal panel using screws as described on the next page.
The equipment must be mounted on a vertical surface. Do not mount it on a horizontal
surface.

Figure 133

The DIN rail must be electrically grounded to provide EMC protection as described on the
next page. DIN rails compliant with DIN EN50032 are preferred.

For vibration resistance, the DIN rail should be installed on a panel using screws spaced
approximately 5.24cm (6 inches) apart.

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15.6.1

Mounting the PLC on a DIN Rail

Units mount on a 35 mm DIN rail as shown below. Using a small flat screwdriver or similar
tool, pull out the retaining clip on the bottom of the unit. Press the unit back and release the
retaining clip. Be sure the clip is holding the unit securely.

Figure 134

15.6.2

Removing the PLC from a DIN Rail

Pull down the retaining clip on the bottom of the module then pull the unit away from the
DIN rail.

15.6.3

Panel-Mounting

For greatest resistance to mechanical vibration and shock, units should be installed on a
metal panel.

Following the dimensions shown in this chapter or using the module itself as a template,

mark the location of the module’s panel

-mount holes on the panel. Drill the hole in the

panel. Install the module using 65x70 M4 (#8-32) screws at least 20mm (0.79 in.) long in
the panel-mount holes.

Figure 135

1.1  to  1.4Nm  (10  to  12  in/lbs)  of  torque  should  be  applied  to  M4  (#8-32)  steel  screws
threaded  into  material  containing  internal  threads  and  having  a  minimum  thickness  of
2.4mm (0.093in).

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15.6.4

Grounding the Metal Panel or DIN Rail

To prevent the risk of electric shock, the metal panel on which the PLC is installed must be
properly grounded to protective earth.

Connect the ground wire to the metal panel using a star washer. Where connections are
made to a painted panel, the paint should be removed so clean, bare metal is exposed.

Connect the metal plate, duct, pipe, door and sideboard etc. to protective earth.

15.7

Connecting an Expansion Unit to a Micro PLC

Up to four expansion units can be connected in series to a Micro PLC.

CAUTION

Power down the Micro PLC before connecting an Expansion Unit. Connecting an Expansion
Unit with the Micro PLC powered up will damage the unit.

Note:

The Micro PLC and Expansion Unit(s) should be wired to a common power source and powered up
together. If an attached Expansion Unit is left unpowered, the Micro PLC may not power up
properly.

15.7.1

The Expansion Cable

A 0.1-meter ribbon cable (IC200CBL501) is provided with each expansion unit. Cables are
also  available  in  0.5-meter  (IC200CBL505)  and  1  meter  (IC200CBL510)  lengths.  The
maximum  total  overall  length  is  2  meters.  This  cable  has  keyed  connectors  to  prevent
incorrect  installation.  Powering  up  the  system  with  the  cable  improperly  installed  can
damage  the  Expansion  Unit.  Do  not  substitute  a  different  cable.    If  you  need  to  order
replacements, expansion cables are available in various lengths. Connect the units as shown
below.

Figure 136

The Expansion Unit(s) and Micro PLC must be connected in the same orientation.

Connecting an Expansion Unit “upside down” will damage the DC input circuit when the

system is powered up. After installing the ribbon cable on a unit, close the hinged door.

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15.8

System Wiring Guidelines

In addition to the following wiring suggestions, we strongly urge that you follow all wiring
and safety codes that apply to your area or to your type of equipment. Failure to do so could
lead to personal injury or death, property damage or destruction, or both.

Four types of wiring may be encountered in a typical factory installation:

•

Power wiring

–

the plant power distribution, and high-power loads such as high

horsepower motors. These circuits may be rated from tens to thousands of kVA at
220Vac or higher.

•

Control wiring

–

usually either low voltage DC or 120Vac of limited energy rating.

Examples are wiring to start/stop switches, contactor coils, and machine limit
switches. This is generally the interface level of discrete I/O.

•

Analog wiring

–

transducer outputs and analog control voltages. This is the interface

level to I/O analog blocks.

•

Communications and signal wiring

–

the communications network that ties

everything together, including computer LANs, MAP, and field busses.

These four types of wiring should be separated as much as possible to reduce the hazards
from insulation failure, miss-wiring, and interaction (noise) between signals. A typical
control system may require some mixing of the latter three types of wiring, particularly in
cramped areas inside motor control centers and on control panels.

Wiring which is external to equipment and in cable trays should be separated following
National Electrical Code practices.

15.8.1

Safety Measures

Appropriate emergency stop circuitry, interlock circuitry and similar safety measures should
be added to the system in accordance with accepted practices.

Appropriate safety measures should be included in the design of the overall system to
ensure safety in the event of incorrect, missing or abnormal signals caused by broken signal
lines, momentary power interruptions or other causes.

15.8.2

Installing Additional Suppression

External MOV suppression can be installed at the power line input of a system enclosure (see
below). The axial leaded ZA series of MOVs from Harris is often used. The MOV should be
able to handle most line transients. Measurement of actual transients may be required in
extreme cases to decide what MOV is best.

Ideally, MOVs should be used at each cabinet in the system for maximum protection. The
following illustration shows suppression on both power lines and a communications bus
entering an enclosure.

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Figure 137

Periodic Inspection and Replacement of MOVs

MOVs do a good job of absorbing transients on communications, control, and power lines,
provided the total energy of those transients does not exceed the rating of the device.
However, if the energy of the transient exceeds the rating of the device, the MOV may be
either damaged or destroyed. This failure may not be visibly or electrically evident. MOVs
should be regularly inspected for signs of damage to assure continued protection against
transients. For some applications, periodic replacement of critical MOVs is recommended,
even if they do not show signs of damage.

15.9

I/O Installation and Wiring

Wiring diagrams are located in the individual module sections of this manual.

WARNING

•

The PLC must be grounded to minimize electrical shock hazard. Failure to do so could
result in injury to personnel.

•

You should calculate the maximum current for each wire and observe proper wiring
practices. Failure to do so could cause injury to personnel or damage to equipment.

CAUTION

When connecting stranded conductors, ensure that there are no projecting strands of
wire. These could cause a short circuit, thereby damaging equipment or causing it to
malfunction.

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15.9.1

Wiring for Power Supply and I/O Connections

•

Each terminal can accept solid or stranded wires, but the wires into any given
terminal must be of the same type and size.

•

Use copper conductors rated for 75°C (167°F) for all wiring.

•

Micro PLC wire sizes: one AWG #14 (2.1 mm

) conductor or two smaller conductors

–

AWG #16 (1.3 mm

) through AWG #20 (0.36mm2) per terminal. The suggested

torque for the terminal connections is 5 in-lbs (5.76 kg-cm).

•

Nano PLC wire sizes: each terminal accommodates one AWG #14 (avg. 2.1mm

cross section) to AWG #22 wire (avg. 0.36mm

cross section), or two wires up to

AWG #18 (avg. 0.86mm

cross section). The suggested torque for the terminal

connections is 3 in-lbs (3.75 kg-cm).

15.9.2

Removable Wiring Terminals

Figure 138

The terminal block assemblies of a Micro PLC can be removed to perform wiring. For
example, a 14-point unit (shown above) has two removable terminal assemblies.

CAUTION

Do not insert or remove a terminal assembly with power applied to the PLC/Expansion Unit
OR TO FIELD DEVICES. Injury to personnel and damage to the equipment may result.
Potentially dangerous voltages from field devices may be present on the screw terminals
even though power to the PLC or Expansion Unit is turned off. Care must be taken any time
you handle the removable terminal assembly, or any wires connected to it.

A  new  Micro  PLC  or  Expansion  Unit  is  shipped  with  its  terminal  block  assemblies  firmly
installed.  To  remove  a  terminal  assembly,  use  a  small  Phillips  or  flat  screwdriver  to
alternately loosen the two captive retaining screws. Hold onto the terminal assembly; when
the  screws  have  been  backed  out  of  the  holes,  the  terminal  assembly  is  completely
detached from the module.

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Figure 139

When re-installing terminal assemblies, be sure to place each one in the correct location to
avoid miss-wiring the module. The terminal assemblies are not keyed or labeled.

15.9.3

General Wiring Procedures

Follow the procedures below when routing and connecting field wiring from user devices to
the PLC inputs and outputs. The individual PLC and Expansion Unit sections of this manual
provide detailed wiring information for connecting input and output devices and power
sources.

•

Turn off power to the PLC before connecting field wiring.

•

All low-level signal wires should be run separately from other field wiring.

•

All channels must be fed from the same phase for AC power lines.

•

Install AC power cables and signal or data lines in separate cable trays or bunches
from DC field wiring.

•

Field wiring should not be routed close to any device that could be a potential source
of electrical interference.

•

Route the signal and data lines as close as possible to grounded surfaces such as
cabinet elements, metal bars and cabinets panels.

•

If severe noise problems are present, additional power supply filtering or an isolation
transformer may be required.

•

Ensure that proper grounding procedures are followed to minimize potential safety
hazards to personnel.

•

Label all wires to and from I/O devices.

•

Do not attempt to disassemble, repair or modify any part of the PLC.

•

Do not pull on cables or bend cables beyond their natural limit. The lines may break.

•

Always use the power supply voltage listed in the module specifications. Using other
voltages may damage the equipment.

•

Do not apply voltages to the inputs in excess of the rated input voltage. The
equipment may be damaged if the rated voltage is exceeded.

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•

Do not use voltages with outputs in excess of the maximum switching capacity. The
PLC may be damaged if the maximum switching capacity is exceeded.

•

Use shielded cable for analog inputs and outputs and connect shields to a functional
earth ground.

Wiring Connections

The following types of wiring terminals are recommended for use with VersaMax Micro PLC
modules:

Figure 140

When using wiring terminals, be sure to tighten screws adequately, so the wiring terminals
will not become loose.

Alternatively, each module screw can accept:

•

One wire, size AWG14 to AWG22 (2.1 to 0.36 mm2) or:

•

Two wires, size AWG16 to AWG22 (1.3 to 0.36 mm2)

Terminal Screws

Should any of the terminal screws be lost or damaged, they can be replaced with M3 x
0.6mm pitch screws of the type shown below.

Figure 141

15.9.4

Providing Fusing for Outputs

Outputs with electronic short-circuit protection are available on several Micro PLCs and
Expansion Units. All other module outputs should be externally fused (1 Amp to 2 Amp fuse)
to protect the output point contacts. For lighter loads, the internal common fuse (3.15
Amp) can be replaced with a 1 amp fuse to protect the output point without adding the
external fusing.

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15.9.5

Providing Suppression Circuits for Inductive Loads

Figure 142: Typical Relay Output Circuit

Installing suitable suppression across inductive loads enhances reliability of relay contacts.
When switching inductive loads, relay contact life approaches resistive load contact life if
suppression circuits are used. The 1A, 100V diode shown in the typical DC load suppression
circuit is an industry standard 1N4934.

15.9.6

Typical DC Input Circuits

All DC inputs can be connected as either positive or negative logic.

Figure 143: Typical 12/24Vdc Positive/Negative Logic Input Circuit

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Positive and Negative Logic Definitions

The IEC definitions for positive logic and negative logic, as applied to the PLC I/O circuits, are
shown below.

Input Points

–

Positive Logic

•

Equivalent to IEC sink input points.

•

Sink current from the input device to
the user common or negative power
bus.

The input device is connected between the
positive power bus and the input terminal. The
negative bus is connected to the input circuit
common.

Input Points

–

Negative Logic

•

Equivalent to IEC source inputs.

•

Source current through the input device
to the user common or positive power
bus.

The input device is connected between the
negative power bus and the input terminal. The
positive bus is connected to the input circuit
common.

15.9.7

Typical DC Output Circuits

Typical Transistor Output Circuit 12Vdc

Figure 144

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Typical Transistor Output Circuit 24Vdc

Figure 145

For Micro 10-, 14-, 23- and 28- PLCs, when using the outputs as PWM or Pulse Train Outputs,
and for duty cycles in the lower ranges (5% and lower), a pulldown resistor must be
connected between the output point (Q1-Q3) and the common terminal (C1). A 1.5 k

Ω,

0.5-watt resistor is recommended.

Micro 20-, 40-, and 64- PLCs do not require a pulldown resistor.

Output Points

–

Positive Logic

Figure 146

•

Equivalent to IEC source output points.

•

Source current to the loads from the user common or positive power bus.

The load is connected between the negative power bus and the module output.

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Output Points

–

Negative Logic

Figure 147

•

Equivalent to IEC sink output points

•

Load is connected between positive power bus and module output.

15.9.8

Typical High-Speed Counter Connections

High-Speed Counter Circuit

–

Positive Logic Connection

Figure 148

High-Speed Counter Circuit

–

Negative Logic Connection

Figure 149

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When I1-I6 on a Micro PLC are used as High-Speed Counter inputs, the input switches should
be solid state to prevent switch bouncing, which could cause unintended High-Speed
counter counts or strobe input signals.

15.9.9

Added Resistance for 20-, 40-, and 64-Point Micro PLCS
at Higher Count Rates

When using count rates about 30kHz on a 20-, 40-, or 64-Point Micro PLC, a 1k



, 3W resistor

should added between the common and the Count input as shown below.

High-Speed Counter Circuit

–

Positive Logic Connection

Figure 150

High-Speed Counter Circuit

–

Negative Logic Connection

Figure 151

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15.9.10

Typical AC Input and Output Circuits

Typical 120Vac Input Circuit

Figure 152

Typical 120/240Vac Triac Output Circuit

Figure 153

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15.9.11

Typical Analog Input and Output Circuits

Analog Input Circuit

Figure 154

Analog Output Circuit

Figure 155

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