...and that is when I wonder if a RCCB with a sensitivity of 10mA at the stero will be ok for safety.
A human can take 10mA and still be ok as far as I know.
For now this is only a discussion that may also benefit others in similar situation.
I may end up installing earth on the stereo socket.
A human can take 10mA and still be ok as far as I know.
For now this is only a discussion that may also benefit others in similar situation.
I may end up installing earth on the stereo socket.
It's generally not a good idea to advise people to cut corners with safety.
If people understand electricity, maybe they can make up their own minds to some extent?
If you have a residual current circuit breaker between the electricity meter and the hifi, then you should be safe. 30mA RCCBs are generally held to be adequate to protect people from things like cutting the wire of the hedgetrimmer in the garden. It's still better not to cut that wire!
Likewise, safety with your amp is not just about picking the best grade of fuse or RCCB, it's also a matter of not taking silly risks and expecting the RCCB to save you. Don't leave the lid off while your kids are about, or anytime more than necessary. Make sure the mains parts are in good condition. Add a plastic cover to anything the manufacturer didn't. Be careful with tools etc. Keep your bench tidy, you are not Bob Pease. If you're fault-finding an amp with the mains on the same PCB, maybe you can power it from safer external bench supplies? It's all obvious numpty stuff, but we should remind one another and not encourage pointless bad behaviour.
I'm happy with my Cambridge Amp and its 2-wire mains lead. My house has RCCBs. But I've not yet tripped one fiddling with HiFi, and I intend to keep it that way. Other Amps I own, have labels on the back saying 'this device must be earthed'.
Generally, if there's no 'square within a square' double-insulated symbol, it should be earthed.
It's no effort for me to go along with that. But when you think about it, earthing the chassis is only protection against a limited range of problems and faults. It might be wrong to be complacent about other things because you've earthed the chassis.
Also, 'safe' and 'legal' are not always the same thing.
If people understand electricity, maybe they can make up their own minds to some extent?
If you have a residual current circuit breaker between the electricity meter and the hifi, then you should be safe. 30mA RCCBs are generally held to be adequate to protect people from things like cutting the wire of the hedgetrimmer in the garden. It's still better not to cut that wire!
Likewise, safety with your amp is not just about picking the best grade of fuse or RCCB, it's also a matter of not taking silly risks and expecting the RCCB to save you. Don't leave the lid off while your kids are about, or anytime more than necessary. Make sure the mains parts are in good condition. Add a plastic cover to anything the manufacturer didn't. Be careful with tools etc. Keep your bench tidy, you are not Bob Pease. If you're fault-finding an amp with the mains on the same PCB, maybe you can power it from safer external bench supplies? It's all obvious numpty stuff, but we should remind one another and not encourage pointless bad behaviour.
I'm happy with my Cambridge Amp and its 2-wire mains lead. My house has RCCBs. But I've not yet tripped one fiddling with HiFi, and I intend to keep it that way. Other Amps I own, have labels on the back saying 'this device must be earthed'.
Generally, if there's no 'square within a square' double-insulated symbol, it should be earthed.
It's no effort for me to go along with that. But when you think about it, earthing the chassis is only protection against a limited range of problems and faults. It might be wrong to be complacent about other things because you've earthed the chassis.
Also, 'safe' and 'legal' are not always the same thing.
As said..two designs are possible. Double isolation, difficult to handle if selfmade, or protective earth. The second design is required by using a metal case without double isolation...take it as the law for your own safety and the safety of other people in your house if you are building an amp, preamp...by yourself using a metal housing, case.
You can read about IEC rules https://en.wikipedia.org/wiki/Earthing_system#Purposes
Measure the earth protection, PE, with 0 ohm to all metal components of your amp case, housing. Choose a good firmly connection. Toothed washer and cable lug are necessary on the screw to give a good connection on anodized aluminum.
Other safety components additionally are a good idea either.
Greets
Peter
You can read about IEC rules https://en.wikipedia.org/wiki/Earthing_system#Purposes
Measure the earth protection, PE, with 0 ohm to all metal components of your amp case, housing. Choose a good firmly connection. Toothed washer and cable lug are necessary on the screw to give a good connection on anodized aluminum.
Other safety components additionally are a good idea either.
Greets
Peter
Ideally test the earth bonding at high current (10 amps is good)... Should be <=0.1 ohms to the plug earth pin.
Never earth-bond to anodized aluminium without first filing/machining off the ozide layer, aluminium oxide is very hard and very insulating!
Never earth-bond to anodized aluminium without first filing/machining off the ozide layer, aluminium oxide is very hard and very insulating!
The double square symbol, meaning reinforce insulation, seems to be abused by many commercial brands. I see single insulated AC wires, that if they fail or come loose, may make the case live.
I have also come across IEC leads with molded on plugs, where the earth is not connected. Your best bet is a 30mA RCCD in the circuit. This is the value required in the Commonwealth countries that follow the UK BS7671 regulations for any socket outlet. Obviously you should press the RCCD Test button from time to time.
My condo was incorrectly built with 100mA RCCDs. This may not save my life, so I had them changed.
Any equipment that has a AC RF filter, must have an earth connection. These filters can have a fairly high leakage current
I have also come across IEC leads with molded on plugs, where the earth is not connected. Your best bet is a 30mA RCCD in the circuit. This is the value required in the Commonwealth countries that follow the UK BS7671 regulations for any socket outlet. Obviously you should press the RCCD Test button from time to time.
My condo was incorrectly built with 100mA RCCDs. This may not save my life, so I had them changed.
Any equipment that has a AC RF filter, must have an earth connection. These filters can have a fairly high leakage current
I like to follow the instructions in Rod Elliott's article on grounding. https://www.sound-au.com/earthing.htm#s9
I'm using this chassis from a blown out gfa 5400 i got on Craigslist for $40 to build Shaan's PeeCeeBee V4H. I'll probably replace the 2 pronged plug with a 3 pronged receptacle and then add the parallel resistor-capacitor-bridge ground loop breaker to it.
For the first time I just noticed that this chassis creates a loop around the transformer. Isn't that a bad idea?
I'm using this chassis from a blown out gfa 5400 i got on Craigslist for $40 to build Shaan's PeeCeeBee V4H. I'll probably replace the 2 pronged plug with a 3 pronged receptacle and then add the parallel resistor-capacitor-bridge ground loop breaker to it.
For the first time I just noticed that this chassis creates a loop around the transformer. Isn't that a bad idea?
Attachments
Correct. You must not create a shorted turn around a toroidal transformer.
I just remembered I’ve seen this before as a technique to secure a heavy transformer, but the trick is to make sure the loop is not electrically conductive. So you have to use an insulating bush and washer. If you do, it’s perfectly safe.
All RCCDs have a test button. Anything involving the consumer unit has to be signed off by a qualified electrician.
If the chassis is made up of aluminium plates then every plate should be checked to have <=0.1ohms to earth pin.
It might be more helpful to think about what failures can happen and how the earthed chassis protects against those failures, rather then inventing or quoting arbitrary 'rules'.
If there is a possibility that a metal part could conceivably become live, then earthing that part protects you by blowing the fuse.
Does that require 0.1 ohm?
If it does, then perhaps a smaller fuse might be called for?
If there is a possibility that a metal part could conceivably become live, then earthing that part protects you by blowing the fuse.
Does that require 0.1 ohm?
If it does, then perhaps a smaller fuse might be called for?
You can have RF chokes without an earth connection. Also L-N capacitors.
IT's a good point to be aware of leakage currents due to L-E caps etc, these can trigger your RCCB.
Double isolation is not ever so difficult for DIY.
You could enclose all the mains parts in a plastic box of some sort.
Or maybe a rigid plastic sheet over that part of the circuit, on plastic pillars?
I think it's good practice to have some extra protection of the mains parts, even if the case is earthed.
Some commercial amplifiers have everything on one PCB, so it's hard to faultfind without risk of contacting the mains.
I prefer to use bench supplies for working on some equipment.
Audiolab amps have torroidal transformers and no ground. My 8000 series amps appear to have double-insulated mains wires, but I don't know what they do about the transformer.
The current 6000A also has a torroidal transformer and no mains ground.
Here were I am the chassis of a commercial product has to be grounded, unless its double insulated. However, the amplifier circuitry grounds even on exposed connectors can be isolated somewhat by a so-called hum breaker circuit which connects the amplifier circuit common to AC line ground.
Example image from:
https://www.diyaudio.com/community/threads/ground-breaker-isolation.384927/post-6989127
(component values may vary somewhat in different designs)
Example image from:
https://www.diyaudio.com/community/threads/ground-breaker-isolation.384927/post-6989127
(component values may vary somewhat in different designs)
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In some applications, like boats, yo usee 'Galvanic Isolators', which are a bit like the hum-breaker circuit above, minus the 10R resistor.
The idea is, it prevents small DC voltages between mains ground and the water from creating currents.
In the event of a fault, a couple of diode drops makes no difference to blowing the fuse.
The diodes need to be 'stout'.
In other areas, you may find a similar circuit where any current through the 10R resistor is detected and used to trigger a breaker.
The idea is, it prevents small DC voltages between mains ground and the water from creating currents.
In the event of a fault, a couple of diode drops makes no difference to blowing the fuse.
The diodes need to be 'stout'.
In other areas, you may find a similar circuit where any current through the 10R resistor is detected and used to trigger a breaker.
Hi, been otherwise occupied.
Thank you all for your replies.
I don't look at this as trying to cut corners with safety. There will be a few million homes in Europe with this situation. Most places will have a 30 mA RCD in the main fuse box as wet rooms and outside sockets will be grounded. AFAIK the reason for this is that your body has to be grounded for the electricity to be lethal.
I read in another thread about a brave diy'er who stretched an earth cable down 8 stories to get "good" earth to his stereo.
Most builds here have safety earth and grounded sockets. I was mainly wondering if there was an alternative for rooms with no grounded sockets. I did find a wall sockets with built in RCD at 10mA like bonsai mentioned, but I guess those work best in a grounded socket also.
So it looks like it's either grounded sockets with safety earth or floating chassis.
I have had a floating chassis on homebrew power amps for some decades without any problems.
I assume that the most important thing with having a floating chassis is to have a solid and tidy build with little or no chance for any wires to come loose and touch the chassis.
If something should happen to the amps circuitry the amps mains fuse should handle that. So having a mains fuse in your amp that is not too big but very close to what is needed is also important.
For me the most interesting approach for an alternative solution is what Briz mentioned in the last post
Say for the live mains wire (or neutral as well), a circuit with a mosfet switch that is triggered by any current through a 10R resistor connected between amp ground and chassis and thereby cutting mains to the amplifier if any faults occur. This circuit could also act like a mains power switch for the amp. Anyone up for a challenge? 🤔
Anyway , my mono blocks have a bit of double insulation as they are living in a cage 😉
Thank you all for your replies.
I don't look at this as trying to cut corners with safety. There will be a few million homes in Europe with this situation. Most places will have a 30 mA RCD in the main fuse box as wet rooms and outside sockets will be grounded. AFAIK the reason for this is that your body has to be grounded for the electricity to be lethal.
I read in another thread about a brave diy'er who stretched an earth cable down 8 stories to get "good" earth to his stereo.
Most builds here have safety earth and grounded sockets. I was mainly wondering if there was an alternative for rooms with no grounded sockets. I did find a wall sockets with built in RCD at 10mA like bonsai mentioned, but I guess those work best in a grounded socket also.
So it looks like it's either grounded sockets with safety earth or floating chassis.
I have had a floating chassis on homebrew power amps for some decades without any problems.
I assume that the most important thing with having a floating chassis is to have a solid and tidy build with little or no chance for any wires to come loose and touch the chassis.
If something should happen to the amps circuitry the amps mains fuse should handle that. So having a mains fuse in your amp that is not too big but very close to what is needed is also important.
For me the most interesting approach for an alternative solution is what Briz mentioned in the last post
Say for the live mains wire (or neutral as well), a circuit with a mosfet switch that is triggered by any current through a 10R resistor connected between amp ground and chassis and thereby cutting mains to the amplifier if any faults occur. This circuit could also act like a mains power switch for the amp. Anyone up for a challenge? 🤔
Anyway , my mono blocks have a bit of double insulation as they are living in a cage 😉