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I've got some festoons for a theatre show but the theatre is quite old and I was told they need to have 15amp round pin plugs. Can I just get some ordinary festoons and swap the plug into a 15amp round pin plug? And is changing them a very tricky undertaking? Or are there any adapters for that for those sort of plugs? Any answers would help thank you very much Lia

  • 15amp round pin plugs are always certainly used for dimmable lights - be careful. If the festoon can't be dimmed, then whacking a 15amp plug on it and attempting to dim it will result in erratic behaviour at best, and a blown light at worst. – berry120 Jun 18 '19 at 8:12
  • Or a blown dimmer. Replacing a blown dimmer pack could be expensive. – Owain Jun 18 '19 at 12:45
  • I'm far from an expert, but my understanding is that some theaters in the UK (I am assuming from the use of the phrase "round pin plug" that the OP is in the UK) use 15A sockets for everything that is controlled by the lighting guys, whether it is dimmed or simply switched. – Peter Green Mar 12 at 18:34
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Nate Strickland's answer is correct for the USA.

If you are in the UK, you'd need a similar adapter

British 15 amp to 13 amp adapter

Stage Electrics

15 amp round pin plugs are used for stage work in the UK for the additional reason that our 13 amp standard power plugs have fuses in them. A blown fuse on a lighting grid is difficult to change quickly, so unfused plugs are preferred. In schools the smaller 5 amp round pin plugs were often used.

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Yes, you either change out the plug or get an adapter. Adapters from round pin (more commonly known as stage pin) to whatever the common mains socket where you live will be easily available at any theatrical supply store near you, or online. If you'd like to make it permanent, instead just buy a stage pin plug and change out your current cord end -- if you've ever changed a plug before, it'll be the same straightforward process.

Here's a link to an adapter that will work with standard North American plugs: https://www.lighttheatrics.com/lex-edison-female-to-stage-pin-male/

Edison to Stage Pin adapter

Also note that use of these plugs is not because the theatre is 'quite old' -- this style is still used in new theatres today. The reason they use a different plug style and make you use an adapter is because all of these circuits are on dimmers, which are really only meant for incandescent lamps, and don't play nicely with other types of electronics, so the incompatible plugs serves as a reminder that it isn't a general purpose circuit that you can plug just anything into.

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  • Sounds like this falls under the "you can't dim a (standard NEMA 5) receptacle" rule. In which case, yeah, that cheater should not exist, because it would let you plug in (and then accidentally dim) an air conditioner. You should put the standard theatrical plug on your festoons. The cheater going the other way 'round would be safe. – Harper - Reinstate Monica Jun 17 '19 at 21:23
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    @Harper, there's a bit more to it than that -- theatres have their own whole section in NEC, section 520, because they do all sorts of wacky electrical stuff. – Nate S. Jun 17 '19 at 21:28
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    In particular, those plugs aren't always on a dimmer -- usually there's either a panel where different circuits can be either patched into a dimmer or a regular circuit, or there's interchangeable dimmer/relay modules which can be switched out as appropriate for the load. – Nate S. Jun 17 '19 at 21:30

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