# ANSI dimmer switch plan symbol

Canonical URL: https://eloragrid.ai/symbols/ansi-dimmer-switch
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: SD
Drawing use: GA
Reference families: IEEE / ANSI

## Symbol convention

Convention: IEEE / ANSI
Form: Dimmer switch, SD
US architectural electrical plan practice in the ANSI Y32.9 lineage, read alongside IEEE 315 context; independently drawn, not a certified IEEE or ANSI graphic.

US plan symbol SD for a wall dimmer controlling a lighting group.

## In plain English

### What does ANSI dimmer switch plan mean?

A wall dimmer in US plan practice is drawn as S with subscript D, sometimes with a wattage note. The switch leg links it to the dimmed group, and three-way dimming is shown by pairing SD with S3 or with a companion device.

### A simple example

The reader should check dimmer type against LED driver compatibility, and whether the dimmer controls a low-voltage 0-10 V signal or switches line power directly. The plan symbol is identical for both. SD does not specify dimming technology, load or whether multi-gang derating applies.

### What the drawings help you do

Check dimming technology in the fixture schedule. Note multi-gang derating for ganged dimmers. The IEC dimmer uses a variability arrow on a switch mark; the US form uses the D subscript.

### This particular reference

US plan symbol SD for a wall dimmer controlling a lighting group. The IEC dimmer uses a variability arrow on a switch mark; the US form uses the D subscript.

### Terms

- Signal: Electrical information passed between devices, rather than necessarily the main power supply.
- Rating: A value stating the conditions for which equipment is specified.
- Schematic: A drawing showing function and connections rather than physical appearance.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [IEEE/ANSI 315-1975: graphic symbols for electrical and electronics diagrams](https://standards.ieee.org/ieee/315/515/)


## What it represents

A wall dimmer in US plan practice is drawn as S with subscript D, sometimes with a wattage note. The switch leg links it to the dimmed group, and three-way dimming is shown by pairing SD with S3 or with a companion device.
The reader should check dimmer type against LED driver compatibility, and whether the dimmer controls a low-voltage 0-10 V signal or switches line power directly. The plan symbol is identical for both. SD does not specify dimming technology, load or whether multi-gang derating applies.

## How to read it

- Check dimming technology in the fixture schedule.
- Note multi-gang derating for ganged dimmers.

## Information to show or reference

- State dimmer load rating.
- State control method.
- Link the dimmed group.

## Important distinction

The IEC dimmer uses a variability arrow on a switch mark; the US form uses the D subscript.

## Facts

- Graphic form: S with subscript D
- Key check: Driver compatibility
- Artwork scope: Original educational illustration; the exact ANSI or IEEE graphic and compliance are not certified

## Public references

- [IEEE/ANSI 315-1975: graphic symbols for electrical and electronics diagrams](https://standards.ieee.org/ieee/315/515/) — IEEE Standards Association. Graphic-symbol standards context; not a source of reproduced artwork.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.