What electrical installation and safety-disconnect requirements apply to resistance welding equipment under 29 CFR 1910.255? Answer in under 100 words.
Details / How it works
All resistance welding equipment shall be installed by a qualified electrician in conformance with Subpart S of 29 CFR Part 1910. A safety-type disconnecting switch or circuit breaker must be provided to open each power circuit, conveniently located at or near the machine so that power can be shut off when the machine or its controls are to be serviced.
Numbers & thresholds
| Requirement | Threshold |
|---|---|
| External weld initiating control circuit voltage | Not over 120 volts |
| Portable welding gun initiating switch voltage | Not exceeding 24 volts |
| Capacitor discharge equipment (high voltage over 550 volts) | Complete enclosures with interlocks and manual discharge switch required |
Exceptions & edge cases
For capacitor discharge or stored energy resistance welding equipment involving high voltage (over 550 volts), the regulation requires complete enclosures with interlocks that interrupt power and short circuit capacitors when doors are open. Additionally, a manually operated switch or suitable positive device must be installed as an added safety measure to assure absolute discharge of all capacitors. Grounding of the secondary of welding transformers is required where technically practical; where not, center-tapped grounding reactors or safety disconnect switches are acceptable alternates.
Sources
- [1]U.S. National Archives, Electronic Code of Federal Regulations — 29 CFR 1910.255 — Resistance welding · as of 2026-08-26
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