Hi,
every power distribution ring in this and my last home had it's individual RCCB at the distribution board. Yes, 5 RCCB on 6 power rings.
Except the audio circuit in the lounge. It is breaker protected and uses fused plug tops.
Does that confirm my viewpoint?
"yes. "
Sometimes I worry that I seem to need really clear explanations of things that others just pick up straight away. Consequently I probably make my posts too long, needlessly attempting to anticipate the reader's questions...
Just to indulge me, what is wrong with using RCDs with audio equipment if you are worried about death by electricity? Isn't an RCD a good last resort, even if you wouldn't want to rely on it?
Admittedly, a plastic RCD costing £10 might tarnish the sound from your solid gold mains plug - but we don't really believe in that stuff do we..?
Sometimes I worry that I seem to need really clear explanations of things that others just pick up straight away. Consequently I probably make my posts too long, needlessly attempting to anticipate the reader's questions...
Just to indulge me, what is wrong with using RCDs with audio equipment if you are worried about death by electricity? Isn't an RCD a good last resort, even if you wouldn't want to rely on it?
Admittedly, a plastic RCD costing £10 might tarnish the sound from your solid gold mains plug - but we don't really believe in that stuff do we..?
My din rail mounted RCCBs cost about £40 each.
I don't want nuisance shutdown of my Audio Power due to detection of excess Earth Leakage.
It's bad enough in rural Borders with mains brown outs and total loss on an almost weekly basis.
Fortunately , this heavy snow fall has not been accompanied by strong winds. No power outs at all this week !
I don't want nuisance shutdown of my Audio Power due to detection of excess Earth Leakage.
It's bad enough in rural Borders with mains brown outs and total loss on an almost weekly basis.
Fortunately , this heavy snow fall has not been accompanied by strong winds. No power outs at all this week !
It could be, if you don't need to use standardized components that don't fulfull that requirement.
These components must have their own fuse which has to blow fast enough to avoid damage. Decent designs will comply with that demand.
That is called class II.
Power strips with built-in RCDs are available.
Correct. The regulations that force us to connect conductive cases of electrical devices to earth usually refer to external, but neighboring conductive bodies as well.
That is one of its purposes. Regulations require us to tune fuse and wire sizes to each other so that fires are avoided.
They also require us to ensure protection against indirectly touching dangerous voltage which class I devices do by making the fuse blow. In that case the fuse is also there to protect lives.
Another purpose of a fuse is to protect components other than wires according to the designer's choice.
Yes, you should test it on a regular basis. Here in Germany regulations dictate to do that once a month. Not many people know that they have to test it regularly. Those who know, don't do that, because it means to shut off the power resulting in all the inconvenient resetting of clocks, reprogramming of video recorders and such.
that's why my hardwired equipment (hob, dishwasher, oven etc) are on separate MCB protected circuit. The Utility room is RCCB protected.
@pacificblue
"Power strips with built-in RCDs are available."
I was anticipating that an objection might be that someone would inadvertently plug the equipment into an ordinary socket, hence the idea of building the RCD into the cable permanently.
Inline RCDs are available such as this:
Jo Jo | Connectors | Electrical/Power | Mains RCD Protected Connectors | RCD Protected Plugs And Sockets |400945
I guess a neater solution would be an IEC power entry module with RCD built in, but I haven't been able to find one yet.
What I am saying is that with such a device, one might feel justified in not connecting audio 0V to the chassis at all, hence the previous 40 pages of worry are rendered null and void! The same goes for my suggestions of fully shrouded (non-standard) audio connectors.
(As we have already established, this business of earthing the exposed shells of audio connectors is something of a dancing-on-the-head-of-a-pin exercise anyway, as the exposed 'tips' of plugs are not protected in the same way. The same for 4 mm speaker plugs).
However, I would like to know if there are any audio-related (NOT safety) reasons for connecting audio 0V to the enclosure.
"Power strips with built-in RCDs are available."
I was anticipating that an objection might be that someone would inadvertently plug the equipment into an ordinary socket, hence the idea of building the RCD into the cable permanently.
Inline RCDs are available such as this:
Jo Jo | Connectors | Electrical/Power | Mains RCD Protected Connectors | RCD Protected Plugs And Sockets |400945
I guess a neater solution would be an IEC power entry module with RCD built in, but I haven't been able to find one yet.
What I am saying is that with such a device, one might feel justified in not connecting audio 0V to the chassis at all, hence the previous 40 pages of worry are rendered null and void! The same goes for my suggestions of fully shrouded (non-standard) audio connectors.
(As we have already established, this business of earthing the exposed shells of audio connectors is something of a dancing-on-the-head-of-a-pin exercise anyway, as the exposed 'tips' of plugs are not protected in the same way. The same for 4 mm speaker plugs).
However, I would like to know if there are any audio-related (NOT safety) reasons for connecting audio 0V to the enclosure.
RCCB for excessive Earth Leakage protection
An RCCB works by reading the imbalance between the Flow and Return currents and recognises the difference as the Leakage to Earth.
But a ClassII device and your PE isolated chassis have no easy route for leakage to take. It will leak via the Giga ohms of it's surroundings eventually back to Distribution Board Neutral. i.e. whether working properly or faulty the RCCB cannot see a significant difference in the Flow and Return currents. It cannot trigger.
Connect any of these ClassII pieces of equipment to any piece of ClassI equipment and now you have a good lowish impedance for the leakage current and fault current to pass. Either RCCB or MCB breaks depending on which reaches trigger value first.
In case you don't see it.
If you have only one piece of ClassI equipment in your interconnected system, it will act as the PE for all the pieces of mains equipment connected to the system. Except optical coupled.
Now back to that first paragraph.
"It cannot trigger" until someone provides a lowish resistance path to Earth. It might be a tingle sensation or a full blown Electrocution.
A ClassII device has two wires to connect to the mains. The Flow (Live) and the Return (Neutral).
An RCCB works by reading the imbalance between the Flow and Return currents and recognises the difference as the Leakage to Earth.
But a ClassII device and your PE isolated chassis have no easy route for leakage to take. It will leak via the Giga ohms of it's surroundings eventually back to Distribution Board Neutral. i.e. whether working properly or faulty the RCCB cannot see a significant difference in the Flow and Return currents. It cannot trigger.
Connect any of these ClassII pieces of equipment to any piece of ClassI equipment and now you have a good lowish impedance for the leakage current and fault current to pass. Either RCCB or MCB breaks depending on which reaches trigger value first.
In case you don't see it.
If you have only one piece of ClassI equipment in your interconnected system, it will act as the PE for all the pieces of mains equipment connected to the system. Except optical coupled.
Now back to that first paragraph.
"It cannot trigger" until someone provides a lowish resistance path to Earth. It might be a tingle sensation or a full blown Electrocution.
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Hi Andrew T
Not sure I follow you whether you're saying there is a problem with the RCD or not. The RCD is designed to trip if there's an imbalance between live and neutral currents, indicating that there's a leakage to earth - either an electrical fault or a person bridging live to earth. If someone bridges between Live and Neutral, the RCD will not trip - that, however, would be a 'double fault'.
In a class II device, the audio 0V is connected to its chassis (is there an 'audio' reason for simply not isolating the chassis completely?). I also notice one of my Japanese amplifiers has a screw terminal on the enclosure as if inviting the user to ground it to 'something' for whatever reason.
If I connect my home-built Class I amp to a Class II CD player via a phono lead, then I connect my 0V to its chassis. If, due to a screw-up in my amp, live touches my (non-earthed) 0V then the Class II amp chassis becomes live. Similarly, if live touches my line level input wire, the Class II device's chassis may become live also - depends on whether it's DC-coupled etc. In either case, if someone touches the Class II chassis they trip the RCD, which is what it's for.
If I had earthed my amp's 0V, then the fuse/MCB would have tripped immediately due to over-current (assuming my 0V wiring was robust and fused). However, in the case of live touching an audio signal cable, no fuse or MCB is guaranteed to trip. I can't see the 'harm' of including the RCD whether I earth my 0V in my amp, or leave it isolated.
I have a feeling I am missing something here..!
(And I still want to know any non-safety related reasons why the audio 0V should be connected to the chassis. I'm guessing that having a large, effectively-isolated antenna surrounding the circuitry is Bad in some way, but I would like to have that confirmed).
Not sure I follow you whether you're saying there is a problem with the RCD or not. The RCD is designed to trip if there's an imbalance between live and neutral currents, indicating that there's a leakage to earth - either an electrical fault or a person bridging live to earth. If someone bridges between Live and Neutral, the RCD will not trip - that, however, would be a 'double fault'.
In a class II device, the audio 0V is connected to its chassis (is there an 'audio' reason for simply not isolating the chassis completely?). I also notice one of my Japanese amplifiers has a screw terminal on the enclosure as if inviting the user to ground it to 'something' for whatever reason.
If I connect my home-built Class I amp to a Class II CD player via a phono lead, then I connect my 0V to its chassis. If, due to a screw-up in my amp, live touches my (non-earthed) 0V then the Class II amp chassis becomes live. Similarly, if live touches my line level input wire, the Class II device's chassis may become live also - depends on whether it's DC-coupled etc. In either case, if someone touches the Class II chassis they trip the RCD, which is what it's for.
If I had earthed my amp's 0V, then the fuse/MCB would have tripped immediately due to over-current (assuming my 0V wiring was robust and fused). However, in the case of live touching an audio signal cable, no fuse or MCB is guaranteed to trip. I can't see the 'harm' of including the RCD whether I earth my 0V in my amp, or leave it isolated.
I have a feeling I am missing something here..!
(And I still want to know any non-safety related reasons why the audio 0V should be connected to the chassis. I'm guessing that having a large, effectively-isolated antenna surrounding the circuitry is Bad in some way, but I would like to have that confirmed).
Hi,
The way i interpreted your post, the equipment needs to be connected to safety-earth for the rccb to trip.
If the equipment isn't connected to safety-earth, someone touching it will/might trip the rccb.
Afaik most rccb's are tripping at 30mA or more, this means there's a potentially life-threatening current through the person touching the equipment BEFORE the rccb trips.
Did i interpret your previous post wrong as well ?
Klaas
The way i interpreted your post, the equipment needs to be connected to safety-earth for the rccb to trip.
If the equipment isn't connected to safety-earth, someone touching it will/might trip the rccb.
Afaik most rccb's are tripping at 30mA or more, this means there's a potentially life-threatening current through the person touching the equipment BEFORE the rccb trips.
Did i interpret your previous post wrong as well ?
Klaas
Hi Andrew
I was not proposing that you fit an RCD in an exclusively-Class II system - as we know, they are certified as perfectly safe(!) and do not have an earth connection, nor do they need a PE in the system at all.
I *was* suggesting that if I am going to include a home-built piece of Class I equipment in the system, an RCD can only add safety.
I interpreted your post as suggesting that an RCD in a mixed Class I/II system is a problem in some way.
I was not proposing that you fit an RCD in an exclusively-Class II system - as we know, they are certified as perfectly safe(!) and do not have an earth connection, nor do they need a PE in the system at all.
I *was* suggesting that if I am going to include a home-built piece of Class I equipment in the system, an RCD can only add safety.
I interpreted your post as suggesting that an RCD in a mixed Class I/II system is a problem in some way.
The nub of my questions is: can we safely avoid connecting 0V to earth in our home-built (and therefore Class I) equipment if it is the source of so many hum loop headaches. However, I am perfectly open to the idea that 0V must be connected to the chassis, and therefore earth, for a non-safety related reason.
A fall-out from this discussion is that I am now aware of the idea that audio 0V connections should be as robust as a main protective earth which I never really thought about before.
A fall-out from this discussion is that I am now aware of the idea that audio 0V connections should be as robust as a main protective earth which I never really thought about before.
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Even in class II equipment 0V must be connected to the chassis for safety reasons. If a wire of the audio supply comes lose and touches the case the corresponding fuse must blow to protect the equipment.
A non-safety related reason is shielding. If the case is not grounded, it acts like an antenna. If it is grounded, it acts like a shield. That screw terminal you found on your class II amp is there for the same reason. Turntables use to be grounded there, because their very low-power signals are extremely sensitive and all the metal parts of a turntable make for good antennas too.
A non-safety related reason is shielding. If the case is not grounded, it acts like an antenna. If it is grounded, it acts like a shield. That screw terminal you found on your class II amp is there for the same reason. Turntables use to be grounded there, because their very low-power signals are extremely sensitive and all the metal parts of a turntable make for good antennas too.