Pull a new Allen-Bradley 509 out of the box and open the cover. Before you land a single field conductor, three wires are already installed inside the starter. They were put there at the factory in Mequon, Wisconsin, and they are not optional — they establish the coil return path, the overload protection, and the seal-in connection per NEMA ICS 2-2000.
Pull a new Schneider TeSys D off the shelf and snap it onto a DIN rail. Open the auxiliary contact module. Nothing is pre-connected. Every control wire is yours to land.
Same function. Same circuit logic. Different starting points. The difference is the design standard: NEMA or IEC.
NEMA: Three Jumpers, Three Fewer Mistakes
NEMA-rated motor starters — Allen-Bradley 509 and 709 series, Eaton Freedom and AN16, Square D 8536 and 8538, Siemens Class 14 — ship as integrated assemblies. The contactor and overload relay are mechanically coupled and electrically pre-connected at the factory. The starter arrives with three internal jumper wires that establish the core of the control circuit before the electrician opens a spool of wire.
Jumper 1: Coil A2 to OL Terminal 95
The most consequential factory connection. This wire routes the return side of the contactor coil through the normally-closed overload contact. If the motor draws sustained overcurrent, the OL relay trips, terminal 95-96 opens, the coil loses its return path, and the contactor drops out.
Without this jumper, the overload relay's auxiliary contact is not in the circuit. The coil energizes and de-energizes through the STOP/START chain alone, and the overload relay — despite being physically present and monitoring motor current through its heaters — cannot shut the motor down. The protection exists mechanically but not electrically. Factory installation eliminates this failure mode.
This jumper also establishes the return-side OL placement that is the NEMA/JIC convention. The coil's A2 terminal connects to OL 95; OL 96 connects to L2. The overload contact sits between the coil and the return conductor, downstream of the entire control chain. The alternative — hot-side placement per IEC 60204-1 — puts the OL contact upstream, between L1 and the STOP button. Both are electrically equivalent; the factory jumper enforces the NEMA position. For the engineering rationale behind each convention and where you'll encounter them in the field, see NEMA vs IEC overload relay placement.
Jumper 2: Terminal 14 to Coil A1
The seal-in connection. Terminal 14 is the output of the built-in normally-open auxiliary contact (the IEC 60947 designation for the first NO pair is 13-14; NEMA starters historically label these 2 and 3). This jumper connects the auxiliary output directly to the coil input.
In the field, you land the START button output on terminal 14 — which, thanks to this jumper, is the same electrical node as coil A1. You then run a wire from terminal 13 (the auxiliary input) back to the STOP/START junction to complete the seal-in parallel path. The factory jumper saves one field wire and ensures the seal-in contact feeds the coil through a verified internal connection rather than a field splice.
Jumper 3: OL Terminal 96 to L2
The return path completion. This jumper connects the output of the OL contact to the L2 common bus terminal on the starter. Combined with Jumper 1 (A2 to 95), it creates the complete coil return path: Coil A2 → OL 95 → OL 96 → L2. The field electrician does not need to wire any part of the return path between the coil and the supply return.
In a line-voltage control circuit, L2 is the return conductor (another ungrounded phase in a 208V delta system — not a neutral). In a transformer-fed control circuit, this jumper would be removed and OL 96 would be field-wired to the transformer secondary X2 instead.
See the Factory Jumpers
Click the highlighted jumpers in the text below to see each factory connection inside a NEMA motor starter:
Instrument: NEMA Factory Prewiring
Every NEMA starter ships with two internal jumpers already installed. The first jumper, A2 → 95, routes the coil return through the overload relay — if the motor trips the overload, terminal 95 opens and the coil drops out. The second jumper, 14 → A1, connects the seal-in auxiliary contact output directly to the coil input, completing the latch path.
What the Field Electrician Adds
With the three factory jumpers in place, the field wiring for the control circuit is four conductors:
L1(or control transformer hot) → STOP terminal 1 — brings control power to the first device in the chain- STOP terminal 2 → START terminal 3 — series connection through the pushbutton station (often pre-wired inside the control station enclosure)
- START terminal 4 → Starter terminal
14— START output to the seal-in/coil junction - Starter terminal
13→ START terminal 3 — seal-in return to the STOP/START junction
Plus six power conductors: three from the disconnect (L1, L2, L3 to the starter) and three to the motor (T1, T2, T3).
That is the complete job on a NEMA starter. Ten field wires. The factory handled the rest.
IEC: The Same Circuit, Built from Components
IEC starters — Schneider TeSys, ABB AF-series, Siemens 3RT, Eaton DILM — are modular. The contactor is one device. The overload relay is another. Auxiliary contact blocks snap onto the side or top. They share a DIN rail and connect mechanically, but the control circuit is entirely the field electrician's responsibility.
The power circuit auto-connects when the overload relay snaps onto the contactor base — internal bus bars carry L1/L2/L3 through the main contacts and into the OL heaters without any field wiring. But no control jumpers exist. The coil terminals, auxiliary contacts, and OL auxiliary contacts are all open and waiting.
Every wire described above — including the coil return through the OL contact, the seal-in connection, and the return path to the supply — is field-installed. The electrician lands all of them.
IEC convention (per IEC 60204-1) places the overload contact on the hot side of the control circuit — between the supply hot and the STOP button — rather than the return side. The wiring path reads: L1 → OL 95 → OL 96 → STOP → START → Coil A1 → Coil A2 → L2. This is a deliberate engineering choice for ground fault isolation, not a consequence of the modular design.
IEC starters use different terminal designations for the auxiliary contacts: 13/14 for the first NO pair, 21/22 for the first NC pair. Some NEMA starters use these IEC designations as well; others use the legacy NEMA labels 2/3. Check the terminal markings stamped on the device.
NEMA vs IEC: The Field Difference
The 3-wire circuit logic is identical. The same coil, the same seal-in, the same OL protection, the same start/stop behavior. What changes is where the electrician's work begins.
On a NEMA starter, you are completing a circuit that the factory started. The critical internal connections — the ones most likely to be forgotten or miswired — are already done. Your job is to connect the field devices (control station, power supply, motor) to the pre-wired assembly.
On an IEC starter, you are building the entire control circuit from the rail up. Every connection that the NEMA factory installed is now your responsibility. The advantage is flexibility — you choose the OL placement, the auxiliary configuration, and the exact control architecture. The tradeoff is that nothing is pre-verified.
Neither approach is better in absolute terms. NEMA starters reduce field errors through standardization. IEC starters accommodate a wider range of control architectures through modularity. Most North American industrial facilities have both types installed, often in the same building, depending on when each system was specified and which OEM supplied the equipment.
Reading is one thing — wiring it yourself is another. Open the interactive trainer and build this circuit from scratch.
Practice wiring a NEMA starter →Frequently asked questions
Which wires come pre-installed in a NEMA motor starter?
Three internal jumpers per NEMA ICS 2 conventions: coil A2 to OL terminal 95, OL terminal 96 to L2, and starter terminal 14 to coil A1. The first two route the coil return through the overload contact and complete the path back to the supply. The third connects the seal-in auxiliary output to the coil input. Allen-Bradley Bulletin 509, Eaton Freedom Series, Square D Class 8536, and Siemens Class 14 NEMA starters all ship this way.
Why do NEMA motor starters come pre-wired but IEC starters don't?
NEMA starters are sold as integrated assemblies — the contactor and overload relay are mechanically coupled and electrically pre-connected at the factory. IEC starters are modular: the contactor, overload relay, and auxiliary contact blocks are separate devices that share a DIN rail and snap together mechanically, but the control circuit is entirely field-installed. NEMA's approach standardizes the wiring and reduces field errors. IEC's approach trades that standardization for flexibility in OL placement and auxiliary configuration.
What happens if the A2 to 95 jumper is missing or broken?
The OL contact is no longer in the coil path. If the field electrician didn't notice and the coil ends up energized through some alternate return — a stray wire, a damaged factory jumper that was bypassed during troubleshooting — the motor runs without overload protection. The heaters still sense motor current and the bimetallic mechanism still trips on sustained overcurrent, but the trip has nothing to interrupt because the contact is no longer in the coil path. The contactor stays in. The motor runs until something burns. NEMA factory installation is what makes this failure mode structurally hard to create.
How many wires does an electrician land on a factory-prewired NEMA starter?
Ten. Six power conductors — three from the disconnect (L1, L2, L3) and three to the motor (T1, T2, T3). Four control conductors — L1 to STOP terminal 1, STOP terminal 2 to START terminal 3, START terminal 4 to starter terminal 14, and starter terminal 13 back to the STOP/START junction. The factory jumpers handle the coil-to-OL-to-return path.
What's the difference between IEC 13-14 and NEMA 2-3 terminal designations?
They are different labels for the same auxiliary contact pair. 13-14 is the IEC 60947 designation for the first NO contact pair and is now standard on most modern starters. 2-3 is the legacy NEMA designation that still appears on older or NEMA-only equipment. The terminals are functionally identical — input and output of a normally-open auxiliary contact driven by the contactor armature. Read the markings stamped on the device rather than assuming the convention.