Dimmer switch and phase-cutting controls
Phase-cutting dimmers chop the mains waveform and inject harmonics from a few kilohertz up to about 1 MHz onto the building wiring — the classic source of what practitioners call dirty electricity.
Last verified 12 August 2026.
Also searched as: light dimmer, triac dimmer
- Category
- dirty electricity
- Emission bands
- Harmonics 2 kHz–1 MHz
- Environments
- home, workplace
- Duty cycle
- Whenever the dimmed circuit is on and not at full brightness.
Field strength by distance
Mitigations, most effective first
- Replace phase-cutting dimmers with plain switches, or with dimmable LED drivers designed for low conducted emissions.
- Removes the harmonic source rather than filtering its symptoms.
- Measure conducted harmonics on the circuit before and after any filter installation.
- Plug-in filters shift and sometimes increase harmonic content; only measurement shows the net effect.
Why no value is published at 30 cm
Assessed as conducted harmonic content on the circuit, not as a distance profile. Building-biology practice grades harmonics from 2 kHz–1 MHz more severely than the 50/60 Hz field by a factor of roughly 10–100.
Measure with
- Dirty-electricity (line harmonics) meter
- Oscilloscope line adapter
Related records
- Building Biology SBM-2024 AC electric field bands
Sleeping-area grades with ground reference: below 1 V/m no anomaly, 1–5 weak, 5–50 strong, above 50 V/m extreme; body voltage below 10 mV is 'no anomaly'.
Exposure limits
- Dirty electricity
High-frequency harmonics and transients riding on mains wiring, typically from dimmers, switch-mode supplies and inverters. Not a term used in any exposure standard.
Glossary
Sources
- sbm-2024 Building Biology Evaluation Guidelines for Sleeping Areas (SBM-2024) — Institut für Baubiologie + Nachhaltigkeit (IBN), 2024. ngo, link checked 2026-08-12.
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