Selector Switch 3-Position Symbol
Definition: The Selector Switch 3-Position symbol represents a maintained-contact rotary switch with three discrete cam positions used in schematic and wiring diagrams per IEC 60617 and ANSI Y32.2 / IEEE 315, most commonly deployed in HOA (Hand-Off-Auto) control schemes where a single operator-accessible knob selects among manual, off, and automatic operating modes.
Also known as: 3-position selector switch, HOA switch, Hand-Off-Auto switch, 3-position rotary switch, 3-pos cam switch.
What the Selector Switch 3-Position symbol means
The 3-position selector switch symbol identifies a maintained-contact rotary switch that can be set to one of three stable positions. In industrial control diagrams the three positions almost universally correspond to HAND (manual), OFF, and AUTO (automatic), giving operators direct local override, a safe off state, and a return to automated sequence control.
The symbol has four pins: a Common input that feeds the shared contact, and three separate outputs for Pos 1, Pos 2, and Pos 3. Depending on the selector's cam profile, each position closes the contact between Common and one output while leaving the other two outputs open, or can provide a springless centre-off with two outer positions.
How to identify the Selector Switch 3-Position symbol
The 3-position selector switch symbol is drawn as a rotary operator circle with an arc showing three position stops, connected to a common contact and three position contacts. The Common pin is at the top of the symbol and the three position outputs (Pos 1, Pos 2, Pos 3) fan out from the lower half. The rotation arc typically spans 90° for three positions (45° between adjacent positions).
Function in a circuit
A 3-position selector switch routes the Common input signal to one of three output contacts depending on which cam position is selected. In position 1 (e.g. HAND), the circuit between Common and Pos 1 is closed, energising the manual-control path; in position 2 (e.g. OFF), all outputs are open; in position 3 (e.g. AUTO), the Common-to-Pos 3 path closes, enabling automated control.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60617-07 defines control switch symbols; a 3-position selector uses the same rotary-operator symbol as the 2-position type but with three position stops indicated. IEC 60947-5-1 governs electrical performance. |
|---|---|
| ANSI/IEEE 315 | ANSI Y32.2 / IEEE 315 uses a rotary arc with three position markers for the 3-position selector. The designator is S. NEMA ICS 5 specifies application requirements for industrial control components including multi-position selectors. |
| Key difference | IEC and ANSI selector-switch symbols are graphically equivalent: both use a rotary-operator arc with position markers. The primary difference is in nameplate labelling conventions — IEC uses 0/I/II, ANSI/NEMA panels use OFF/HAND/AUTO or 1/2/3. |
Terminals / pins
| Pin | Name |
|---|---|
| com | Common |
| pos1 | Pos 1 |
| pos2 | Pos 2 |
| pos3 | Pos 3 |
Typical values
Typical contact ratings: 10 A at 600 V AC (NEMA); 4 A–10 A at 230 V–690 V AC (IEC). Number of positions: 3. Rotation angle between adjacent positions: 45°–90°. Total rotation arc: 90°–180°. Panel-cutout diameter: 22 mm or 30 mm. Operating life: ≥1 000 000 mechanical operations per IEC 60947-5-1.
Where the Selector Switch 3-Position symbol is used
- HOA (Hand-Off-Auto) control panels for pumps, fans, and compressors — the most common 3-position selector application worldwide
- VFD (variable frequency drive) local/remote/off mode selection from the motor-starter panel
- HVAC air-handling unit fan speed selection: Low / Off / High
- Transfer switch mode selection: Normal / Off / Generator for generator control panels
- Motor protection relay test panels: Service / Off / Trip for relay testing and commissioning
- Industrial machine cycle mode: Setup / Off / Run for CNC and assembly equipment
Example
In a pump control panel wiring diagram, a 3-position HOA selector switch SA1 has its Common pin wired to the 24 V DC control bus; Pos 1 (HAND) connects to the manual-run relay coil, Pos 2 (OFF) is left unwired, and Pos 3 (AUTO) connects to the PLC output that enables the pump run command. Only one relay path is energised at a time depending on which position SA1 is in.
Key facts
- The Selector Switch 3-Position symbol uses the designator S (switch) per IEC 60617 and ANSI Y32.2 / IEEE 315, commonly written SA for selector-auto applications; a reference number follows, e.g. SA1.
- In HOA wiring diagrams, the three positions map as: Pos 1 = HAND (manual run), Pos 2 = OFF (all outputs open), Pos 3 = AUTO (PLC or automatic control enabled).
- The Common pin is the shared electrical feed point; only one of Pos 1, Pos 2, or Pos 3 is connected to Common at any time depending on the cam position selected.
- IEC 60947-5-1 mandates a mechanical endurance of at least 1 000 000 operating cycles for panel-mount selector switches, ensuring long service life in industrial environments.
- A 3-position selector with a spring-return to centre is a non-maintained variant: it reverts to the centre (OFF) position when the operator releases it, used for jogging or pulse applications.
- Key-operated 3-position selectors use a removable key at each position as a security measure, preventing unauthorised mode changes in safety-critical machinery.
- The 22 mm panel-cutout is the most common mounting size for 3-position industrial selectors and is compatible with Siemens, ABB, Schneider Electric, and Eaton operator head families.
Frequently asked questions
What does the selector switch 3-position symbol look like?
The 3-position selector switch symbol shows a rotary operator (a circle with an arrow or arc) with three stable position marks spaced along the arc, connected to a Common pin and three output pins (Pos 1, Pos 2, Pos 3). The Common pin is the shared input and each position pin is closed to Common only when the selector is rotated to that position.
What does the HOA selector switch symbol mean?
HOA stands for Hand-Off-Auto. The 3-position selector switch symbol in an HOA configuration means: HAND (Pos 1) = manual operator-controlled run; OFF (Pos 2) = circuit open, motor stopped; AUTO (Pos 3) = automatic or PLC-controlled operation. The selector maintains its last-set position without operator hold.
What is the designator for a 3-position selector switch?
The designator is S (switch) in both IEC 60617 and ANSI Y32.2 / IEEE 315. In HOA applications it is typically labelled SA (selector-auto) or S followed by a reference number. Full example: SA1.
What standard defines the 3-position selector switch symbol?
IEC 60617-07 defines graphical symbols for control switches including multi-position selectors. ANSI Y32.2 / IEEE 315 is the North American equivalent. Electrical performance requirements are specified in IEC 60947-5-1 and NEMA ICS 5.
What is the difference between a 2-position and 3-position selector switch symbol?
A 2-position selector has two output pins and two position stops on the rotary arc; it switches between two states (e.g. On/Off). A 3-position selector has three output pins (Pos 1, Pos 2, Pos 3) and three stops, enabling three distinct circuit states — most commonly HAND, OFF, and AUTO.
Can a 3-position selector be used for speed control?
Yes. A 3-position selector can select between three speed references: for example, Pos 1 = low speed resistor, Pos 2 = off, Pos 3 = high speed direct. Each position closes the Common contact to a different output path, which can be wired to different motor-speed configurations or VFD preset speeds.
What is the current rating of a 3-position selector switch?
Panel-mount IEC 3-position selectors are rated 4 A to 10 A at 230 V to 690 V AC. NEMA selectors are typically rated 10 A at 600 V AC. The contact rating must be appropriate for the control-circuit current — most selector contacts are used in low-power control circuits, not as power switching devices.
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