How to Wire an A30-30-10 Contactor Safely

An A30-30-10 is a 3-pole ABB A-Line AC contactor with one normally open auxiliary contact. Wiring it means making three sets of connections: the supply to the three line terminals, the three load terminals to the overload relay and motor, and the control circuit to the coil terminals, which are commonly marked A1 and A2. All of it is done with the equipment de-energized, locked out and tested for absence of voltage.

This guide walks through that work in order. It does not give tightening torques or conductor sizes, because those come from the marking on the device and from the electrical code that applies to your installation. It also lists the BRAH Electric replacement for the A30-30-10 with each coil voltage.

A30-30-10 wiring at a glance

• Lock out and tag out every source, including a separately fed control circuit, then test for absence of voltage.
• Check the new contactor against the old one: part number, coil voltage, auxiliary contact and rating.
• Supply conductors go to the line terminals. The load terminals feed the overload relay and the motor.
• The control circuit connects to the coil terminals, commonly marked A1 and A2. The coil voltage must equal the control voltage.
• Tighten every terminal to the value marked on the device or given in its instructions, then inspect and test in stages.

Safety: lockout/tagout and verifying absence of voltage

A motor starter usually has more than one source of energy. The power circuit feeds the line terminals. The coil may be fed from the same circuit through a control transformer, or from a separate control supply that stays live when the main disconnect is open. Interlock wiring from another panel can also bring voltage onto the auxiliary contact terminals.

In the United States, OSHA 29 CFR 1910.147 is the general lockout/tagout standard for the control of hazardous energy during servicing and maintenance, and OSHA 29 CFR 1910.333 sets the work practices for electrical work, including locking and tagging de-energized circuits and verifying that they are de-energized. NFPA 70E describes how to establish an electrically safe work condition. Follow your employer’s written energy control procedure. In outline:

• Stop the motor through its normal controls, then open the disconnecting means for the starter.
• Open the disconnecting means for any separate control supply and any interlock circuit that enters the starter.
• Apply your own lock and tag to each disconnecting means. A selector switch, a stop button or a control-circuit device is not a disconnecting means.
• Release or block stored energy. That includes capacitors on the circuit and any mechanical energy in the driven machine that could turn the motor.
• Test for absence of voltage with a tester rated for the circuit. Prove the tester on a known live source before and after. Test phase to phase and phase to ground on the line terminals, the load terminals and the coil terminals.
• Do not treat a breaker handle position or a dark pilot light as proof that the circuit is dead.

Until absence of voltage has been verified, treat every terminal as energized and wear the protective equipment your site requires for that task. The work should be done by qualified personnel.

The BRAH replacement for the A30-30-10, by coil voltage

BRAH Electric’s replacement for the ABB A30-30-10 is the BA30-30-10. The BRAH part number is the ABB number with a B in front. The catalogue lists it as a 3-pole, 3-phase AC contactor with a catalogue rating of 34A at 600V, 10HP at 240V, 25HP at 480V and 30HP at 600V, supplied with a 120VAC coil and one normally open auxiliary contact. The two digits added after A30-30-10 on the ABB number identify the coil, and each one has its own BRAH listing:

The listing without a suffix and the -84 listing both carry a 120VAC coil. Treat the amperage as a catalogue value and match the replacement to the old contactor’s nameplate and the motor nameplate. For anything not in the table, call (855) 355-2724 with the part number. Other sizes are under replacement contactors.

Step 1: check the new contactor against the old one

• Part number. Read the full number from the old nameplate, including any digits after A30-30-10.
• Coil voltage and frequency. Read them from the marking on the coil and compare them with the control circuit voltage on the drawing.
• Auxiliary contact. The A30-30-10 has one normally open contact. Note any add-on auxiliary blocks fitted to the old contactor.
• Load. Compare the motor nameplate voltage, full-load current and horsepower with the rating marked on the replacement.
• Fit. Compare the mounting points and terminal positions of the two devices.

Step 2: label and record the existing wiring

Mark each conductor with the terminal it comes from before you loosen anything. Photograph the starter with the labels in place and check them against the wiring diagram. If the diagram and the installed wiring disagree, resolve that before you go further. Then disconnect the conductors, remove the old contactor and mount the new one securely in the same position.

Step 3: connect the line and load terminals

On a contactor of this type the line terminals are commonly marked 1/L1, 3/L2 and 5/L3, and the load terminals 2/T1, 4/T2 and 6/T3. Go by the marking on the device in front of you.

• Land the supply conductors on the line terminals, in the same phase order as before.
• Connect the load terminals to the overload relay, and the overload relay to the motor leads. Where the relay mounts directly on the contactor, follow the relay instructions for that connection.
• Keep the phase order the same from line to load. Swapping two phases reverses the motor.
• Seat each conductor fully in its terminal, with no insulation under the clamp and no stray strands.
• Use the conductor material, size and temperature rating that the device marking and the applicable code call for.

Step 4: connect the coil terminals A1 and A2

The coil pulls the contactor in when the control circuit puts voltage across it. Its two terminals are commonly marked A1 and A2. Connect them as the wiring diagram shows.

In a typical three-wire start/stop circuit, a normally closed stop button, a normally open start button, the coil and the normally closed contact of the overload relay are all in series across the control supply. Pressing start energizes the coil. Pressing stop, or a trip of the overload relay, opens the circuit and the contactor drops out. A two-wire circuit replaces the two buttons with one maintained device such as a float switch or a PLC output.

• Confirm again that the coil voltage marked on the contactor equals the control circuit voltage. A coil on too high a voltage overheats. A coil on too low a voltage may chatter or fail to pull in.
• Wire the overload relay’s normally closed contact in series with the coil, so a trip de-energizes the contactor.
• Keep the control circuit protection that the drawing shows, such as the fuses on a control transformer.

Step 5: wire the auxiliary contact

An auxiliary contact switches control current only. A normally open contact closes when the contactor pulls in. The terminals of a normally open auxiliary contact are commonly numbered 13 and 14. Check the marking on your device.

In a three-wire circuit this contact is the holding, or seal-in, contact. It is wired in parallel with the start button, so the coil stays energized after the button is released and drops out when the stop button is pressed or control power is lost.

Other uses need more contacts than the one built in: a run indication to a pilot light or PLC input, or an electrical interlock between two contactors, which uses a normally closed contact on each contactor wired in series with the other one’s coil. BRAH lists add-on blocks for A-Line contactors including the A30: the BCA5-10 (1 NO), the BCA5-01 (1 NC) and the BCAL5-11 (1 NO / 1 NC). See auxiliary contacts. An electrical interlock on a reversing starter is normally used together with a mechanical interlock, not in place of one.

Step 6: set and connect the overload relay

A contactor switches the motor. It does not protect it against overload. That is the job of the overload relay, which is selected so that its current range covers the motor full-load current and is set from the motor nameplate following the relay instructions. If the old relay stays in service, check that its setting still matches the motor that is connected today. The guide to troubleshooting an overload relay covers the usual causes, and replacement relays are under overload relays.

Step 7: tighten terminals to the device marking

A loose terminal heats up under load, and an over-tightened one can be damaged. The correct tightening torque for the power, coil and auxiliary terminals is marked on the device or printed in the instructions supplied with it. Use those values with a torque screwdriver or wrench that is in calibration. Conductor sizing, overcurrent protection and the other installation requirements come from the code in force where the equipment is installed, which in most of the United States is based on NFPA 70, the National Electrical Code. Do not take a torque value or a wire size from a general guide, including this one.

Step 8: inspect, then test in stages

Before the locks come off:

• Check every terminal against your labels and the drawing.
• Remove tools, offcuts and loose hardware from the enclosure, and refit covers and barriers.
• Confirm the overload relay is set and reset.

Remove locks and tags only as your procedure allows, with everyone clear of the driven machine. Where the starter has a test position or the motor can be isolated, prove the control circuit first: start, hold-in, stop and overload trip. Then run the motor. Check the direction of rotation, listen for a clean pull-in without chatter or loud hum, and measure the current in each phase against the motor nameplate.

Common A30-30-10 wiring mistakes

• Wrong coil voltage. The replacement was ordered by the base number alone and its coil does not match the control circuit.
• Control supply left live. The main disconnect was locked out but a separate control source was not.
• Overload contact left out of the coil circuit. The relay trips but the contactor stays in.
• Holding contact on the wrong terminals. The motor runs only while the start button is held, or will not stop.
• Two phases swapped. The motor runs backwards.
• Add-on auxiliary blocks not transferred. An interlock or a status signal stops working.

Before you order a replacement A30-30-10

Copy the full number from the nameplate, read the coil voltage from the coil, count the auxiliary contacts in use, and compare the motor nameplate with the rating on the product page. BRAH Electric designs its parts in-house and tests them at its Carlsbad, California facility. It is an aftermarket manufacturer and is not an authorized ABB distributor. Contactors carry a 2-year warranty from the date of invoice, and in-stock orders placed before 3:00 PM Pacific ship the same business day. For help identifying a part, call (855) 355-2724, Monday to Friday, 6AM to 5PM Pacific. If you are replacing the smaller A16 size, see the guide to replacing an ABB A16-30-10.

A30-30-10 wiring FAQs

What is the most important safety step when wiring an A30-30-10 contactor?

Lockout/tagout of every source, followed by a test for absence of voltage on the line, load and coil terminals. Never assume the power is off because a disconnect is open.

How do I know which terminals are line and which are load?

Read the marking on the contactor. Line terminals are commonly marked L1, L2 and L3 and load terminals T1, T2 and T3, often with the numbers 1 to 6 alongside. The wiring diagram for the starter shows the same designations.

Can I use any coil voltage on an A30-30-10?

No. The coil must match the control circuit voltage. The table above lists a separate part number for each coil voltage from 24VAC to 500/600VAC. Order the one that matches the coil you are replacing.

Do I need an overload relay with this contactor?

For a motor load, yes. The contactor only switches the circuit. The overload relay protects the motor against sustained overcurrent, and its normally closed contact must be wired in series with the coil.

What torque should I use on the terminals?

The value marked on the device or given in the instructions supplied with it. Torque values differ between terminal types and sizes, so they are not quoted here.

References

• OSHA 29 CFR 1910.147, The control of hazardous energy (lockout/tagout).
• OSHA 29 CFR 1910.333, Selection and use of work practices. Covers work on de-energized electrical parts, including lockout and tagging.
• NFPA 70E, Standard for Electrical Safety in the Workplace.
• NFPA 70, National Electrical Code. The installation code for conductors, overcurrent protection and motor circuits.