# Demand switch (Netzfreischalter)

> A relay in the consumer unit that de-energises a circuit when no load is drawing current and re-energises it when a switch is thrown, eliminating the bedroom AC electric field overnight.

- Canonical URL: https://emfbase.com/shielding/demand-switch
- Collection: Shielding & remediation
- Record id: `shielding:shielding-demand-switch`
- Status: verified
- Last verified: 2026-08-12
- JSON: https://emfbase.com/api/shielding/demand-switch
- Also known as: Netzfreischalter, automatic circuit cutoff, demand shutoff

## Key values

- **Form:** filter
- **Targets:** elf electric
- **Grounding required:** No

## Failure modes

- Does nothing for magnetic fields, RF, or circuits other than the one it controls
- Standby loads on the protected circuit keep it energised, defeating the purpose
- Requires a qualified electrician and must not be fitted to circuits serving safety devices such as alarms or medical equipment

## Related records

- [Bedroom wiring AC electric field](https://emfbase.com/emitters/bedroom-wiring-electric-field): Live conductors in walls and in lamp flex create a power-frequency electric field that couples to the body whether or not any current flows; building biology grades below 1 V/m with ground reference as 'no anomaly'.
- [Building Biology SBM-2024 AC electric field bands](https://emfbase.com/limits/building-biology-ac-electric-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'.

## Sources

- `sbm-2024` Institut für Baubiologie + Nachhaltigkeit (IBN) (2024). *Building Biology Evaluation Guidelines for Sleeping Areas (SBM-2024)*. https://buildingbiology.com/site/downloads/SBM-2024_EVALUATION_GUIDELINES_EN.pdf — ngo, link checked 2026-08-12

Data licence: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Dataset version 2026.08.1. Retrieved from EMFBase, https://emfbase.com.

This record is reference data, not medical or legal advice. Regulatory limits, scientific guidelines and precautionary values are labelled separately and answer different questions.