Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums > AC Power and Grounding
RCD amp protection
Kev Parker:
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...
Tim McCulloch:
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.
Jonathan Johnson:
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.
richard_cooper:
--- Quote from: Kev Parker 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...
--- End quote ---
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.
Tim McCulloch:
--- Quote from: Jonathan Johnson on July 01, 2022, 01:14:07 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.
--- End quote ---
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.
Navigation
[0] Message Index
[#] Next page
Go to full version