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Author Topic: RCD amp protection  (Read 1578 times)

Kev Parker

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RCD amp protection
« on: June 30, 2022, 02:06:24 PM »

Ok, so i feel foolish asking such a basic question but here goes
I've never used RCD protection on my power amps (currently 2 x Crest pro-lite 7.5). I mainly play venues with standard 13 amp supply (UK) so my basic question is, should i use some form if circuit breaker in my chain and is there any particular model i should look for or is any standard 13amp breaker good enough?

Thanks and sorry again...
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Tim McCulloch

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Re: RCD amp protection
« Reply #1 on: June 30, 2022, 04:47:44 PM »

Do life-safety codes, regulations or laws require an RCD installed between the mains outlet and the device?  If not, I'd not.

We have a few UK folks here but you might get a faster response on the Blue Room Forums.
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Jonathan Johnson

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Re: RCD amp protection
« Reply #2 on: July 01, 2022, 01:14:07 PM »

Local codes trump anything I say here.

For power amps, I think there's limited utility of residual current/ground fault protection. The amps and speakers are unlikely to provide a current path to personnel.

For consoles and backline gear, there *can* be a current path to performers on stage. A faulty console can feed a hazardous voltage via the shield of a microphone cable, charging the grille. A performer contacting the microphone with lips while also contacting the grounded steel strings of a guitar could, conceivably, receive a shock. Or the opposite: a "vintage" guitar amp with a two prong plug and a faulty stinger cap could charge the strings, then the performer "grounds out" through the microphone. It's not just hypothetical; people have been killed this way.

The same techniques that are used to combat "ground loop" hum -- proper earthing/grounding of everything, with signal ground lifts between separately powered equipment where needed -- can also improve personnel safety. (Except for lifting the earth/ground of the mains power -- don't do this, ever!)

An RCD/GFI that trips during a performance harms the show. If it protects a performer or personnel from injury, that's a good thing. But if it is a nuisance trip, that's a bad thing. You'll need to weigh the risk of injury versus the risk of false trips and decide for yourself whether protection is needed.
« Last Edit: July 01, 2022, 01:17:04 PM by Jonathan Johnson »
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richard_cooper

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Re: RCD amp protection
« Reply #3 on: July 01, 2022, 01:26:11 PM »

Ok, so i feel foolish asking such a basic question but here goes
I've never used RCD protection on my power amps (currently 2 x Crest pro-lite 7.5). I mainly play venues with standard 13 amp supply (UK) so my basic question is, should i use some form if circuit breaker in my chain and is there any particular model i should look for or is any standard 13amp breaker good enough?

Thanks and sorry again...

Echoing Tim, you'll get better (more local) responses over on the blue-room, but IIRC you'll need to become a member to even see the "Electrical and Power" forum.

A good deal of 13A supplies in UK venues will already have RCD protection on them, but depending on age of the venue it's not necessarily a requirement. Venues should all have a recent (<5 years off the top of my head) Electrical Installation Condition Report, and I know that insurers are fairly hot on ensuring these are up to date and satisfactory.
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Tim McCulloch

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Re: RCD amp protection
« Reply #4 on: July 01, 2022, 02:05:54 PM »


For consoles and backline gear, there *can* be a current path to performers on stage. A faulty console can feed a hazardous voltage via the shield of a microphone cable, charging the grille. A performer contacting the microphone with lips while also contacting the grounded steel strings of a guitar could, conceivably, receive a shock. Or the opposite: a "vintage" guitar amp with a two prong plug and a faulty stinger cap could charge the strings, then the performer "grounds out" through the microphone. It's not just hypothetical; people have been killed this way.

I don't recall ever hearing of a mixing console sending mains voltage down a mic cable - although I'm sure it's possible - but I've heard of multiple (usually 'vintage') guitar amps with 2 wire cords and a "polarity" switch sending mains voltage to the guitar via the 1/4" cable.  When the player's lips touch the (properly grounded/earthed) vocal mic, a circuit is completed.  IIRC there was a case a year or so before the Deadly Phlegm Pandemic (in the Philippines?) where this happened.  Pretty sure there's a thread here in this subforum.

Often the old guitar amps are already leaking current and trip RCDs/GFCIs.  Players think these are nuisance trips and lead them to use unprotected outlets.
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John Roberts {JR}

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Re: RCD amp protection
« Reply #5 on: July 01, 2022, 02:35:45 PM »

I don't recall ever hearing of a mixing console sending mains voltage down a mic cable - although I'm sure it's possible - but I've heard of multiple (usually 'vintage') guitar amps with 2 wire cords and a "polarity" switch sending mains voltage to the guitar via the 1/4" cable.  When the player's lips touch the (properly grounded/earthed) vocal mic, a circuit is completed.  IIRC there was a case a year or so before the Deadly Phlegm Pandemic (in the Philippines?) where this happened.  Pretty sure there's a thread here in this subforum.

Often the old guitar amps are already leaking current and trip RCDs/GFCIs.  Players think these are nuisance trips and lead them to use unprotected outlets.

It is not uncommon for console mic grounds to become the vector to shock a muso holding a hot guitar (faulty amp)... Rare but a RPBG outlet at FOH could energize a console mic ground with mains voltage.

RCD/GFCI should protect all the meat puppets....

IMO not bad idea to provide GFCI protected outlets for back line.

JR 
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Tim McCulloch

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Re: RCD amp protection
« Reply #6 on: July 01, 2022, 03:05:52 PM »

It is not uncommon for console mic grounds to become the vector to shock a muso holding a hot guitar (faulty amp)... Rare but a RPBG outlet at FOH could energize a console mic ground with mains voltage.

RCD/GFCI should protect all the meat puppets....

IMO not bad idea to provide GFCI protected outlets for back line.

JR

Exactly, on all accounts.  I've had some old-skool guitarists not like it when I say "if you're tripping the GFCI, you need to get your amp fixed." 
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Riley Casey

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Re: RCD amp protection
« Reply #7 on: July 06, 2022, 06:34:19 PM »

In my part  of the country it's  code to require GFIs on all outlets on outdoor stages. First time I learned this was during 2 am load in on an outdoor festival in the middle of the city decades ago. That was exciting making that happen in time for morning sound checks.


 
...

IMO not bad idea to provide GFCI protected outlets for back line.

JR

Tim McCulloch

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Re: RCD amp protection
« Reply #8 on: July 06, 2022, 06:44:31 PM »

In my part  of the country it's  code to require GFIs on all outlets on outdoor stages. First time I learned this was during 2 am load in on an outdoor festival in the middle of the city decades ago. That was exciting making that happen in time for morning sound checks.

I had to work out what that means with an inspector - compliance hinged on what "for use by personnel" meant.  Eventually he called his boss who said "that means a worker can walk up and plug his saw, drill, or computer into the outlet."  That exempted everything except 15/20 amp Edison connectors.  Compliance got easier. :D
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Stephen Swaffer

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Re: RCD amp protection
« Reply #9 on: July 11, 2022, 01:09:45 PM »

I had to work out what that means with an inspector - compliance hinged on what "for use by personnel" meant.  Eventually he called his boss who said "that means a worker can walk up and plug his saw, drill, or computer into the outlet."  That exempted everything except 15/20 amp Edison connectors.  Compliance got easier. :D

How long ago was that?  The 2020 code added 50 amp single phase and 100 amp single phase less than 250 volts to ground to the lists of required circuits with the key phrase being "supplied by".  Doubt anyone is plugging a saw, drill or computer into a 100 amp 3 phase receptacle?
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Steve Swaffer

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Re: RCD amp protection
« Reply #9 on: July 11, 2022, 01:09:45 PM »


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