RCD over rated ?

[Nigel Goodwin]

I was always taught that 30 mA was the limit for humans and that it corresponded to 30/40 volts which is also considered the safety voltage.

That would correspond to 1000 ohms, which would be incredibly low for a human body.

30/40 volts is probably too low to even feel, it certainly doesn't pass 30mA through a body

But here is no 'limit', different people react in completely differnt ways.

And I'll ask again - how many people have died from electrocution in the house? - you seem panicked that not having a 30mA (or whatever) RCD means you're going to be killed at any monent

 

[Thunderchild]

No as far as i know no one has been electrocuted but that is not the way to look at it. The installation is also probably recent. Actually you bloody well would feel 30/40 volts, I used to have a 24 V transformer with DC and AC outputs, I could not feel the DC but could easily feel the AC, I would imagine 30/40 volts is very easy to feel, of course it's one thing running it from one finger to the other in the same hand and another to run it from one hand to another, like i said circumstances can be many hence to logic of a safety device is "never say never"

 

[Sceadwian]

30-40 volts isn't too low to feel, I've notice a very mild tingle from touching the tabs of Mosfets that are running on 12 volts. But that's with some pretty firm finger contact.

 

[Thunderchild]

I was able to feel current flowing through the earth wire and through me to ground when i was setting up our earth wire in Italy, that was the systems general leakage current to earth through the insulation

 

[Nigel Goodwin]

I was able to feel current flowing through the earth wire and through me to ground when i was setting up our earth wire in Italy, that was the systems general leakage current to earth through the insulation

That's because it was probably 120V at very low current, through all the devices connected to the mains.

 

[Nigel Goodwin]

30-40 volts isn't too low to feel, I've notice a very mild tingle from touching the tabs of Mosfets that are running on 12 volts. But that's with some pretty firm finger contact.

I've certainly never felt it, and have worked on hundreds of amplifiers with voltages of 40V and over with no precautions at all. I don't take precautions until you're looking at amps with around 60V HT rail.

 

[Thunderchild]

That's because it was probably 120V at very low current, through all the devices connected to the mains.

They use 230 in Italy, I guess it was the currect leaking through the capacitance of the wiring system plus the filters on any SMPS powered stuff although at the time we had few of those

If your only worrying about amps then you must have a thick skin

 

[Nigel Goodwin]

They use 230 in Italy, I guess it was the currect leaking through the capacitance of the wiring system plus the filters on any SMPS powered stuff although at the time we had few of those

It's from the filters on the SMPS's (and anything else with filters), which was why it's HALF the mains voltage (which will be 110V in Italy - not the 120V here).

While all the EU is officially 230V, in actuallity the UK is still 240V and the rest is still 220V - both of which fall within the permitted tolerance of the 230V.

 

[Thunderchild]

I think Italy may have uped it but can't swear to that, as i said at the time we had virtually no SMPS stuff so most of the discharge was via wiring capacitance

 

[Nigel Goodwin]

I think Italy may have uped it but can't swear to that, as i said at the time we had virtually no SMPS stuff so most of the discharge was via wiring capacitance

You only need ONE item with a mains filter, that would swamp any possible capacitance in the wiring - lot's of other items have filters as well, microwaves, washing machines, fridges - most stuff has filters.

I doubt Italy have upped their mains voltage?, there would be no point - basically it was for the manufacturers to ensure their equipment would work on either 220 or 240, not an actual mains change (previously that wasn't so).

 

[Thunderchild]

well a well known electronics magazine did a whole article on how the whole of Europe was conforming and they were now going to supply 230 V transformers with all their kits but that the previous 220 V ones were still fine due to the 10% tollerance

 

[Nigel Goodwin]

well a well known electronics magazine did a whole article on how the whole of Europe was conforming and they were now going to supply 230 V transformers with all their kits but that the previous 220 V ones were still fine due to the 10% tollerance

Exactly, they are obliged to provide 230V transformers - even though ther mains is actually either 220V or 240V.

 

[Thunderchild]

well I can't swear to it but I think when I did measure it was like 229 V

 

[Nigel Goodwin]

well I can't swear to it but I think when I did measure it was like 229 V

Mains voltages vary considerably, the UK has one of the best and most accurate - but even here you can get local faults which cause mains to be either high or low, and the Electricity Companies come out and cure the fault.

We had a problem with a customers TV years back, it was doing all kinds of wierd things, eventually we checked the mains - 280V

It's less of a problem now, particularly as TV's use SMPSU's, so aren't much affected by variations.

 

[Thunderchild]

well according to the manual Eric linked to 100ma is just to stop shorts and fires not save lives, so i believe I'm right in being concerned, who ever fitted my house up was a monkey

 

[Nigel Goodwin]

well according to the manual Eric linked to 100ma is just to stop shorts and fires not save lives, so i believe I'm right in being concerned, who ever fitted my house up was a monkey

I'll ask again, how many people have been electrocuted in the house?.

If you're not happy, then get the house rewired by a professional - it's a LOT more strictly controlled now than it was.

 

[Thunderchild]

well its a nice new box I'll be checking the place over myself. I guess the 100 mA RCD came with the box as a standard main RCD with the assumption that smaller ones would be be fitted which were not because the guy was obviously a bodger and did not understand RCD ratings, the main rewire was done by the council I'm told in 1987 when it was sold off to a private owner although "the bodger" has probably done some "maintenance"

 

[edeca]

You could just fit a 30mA RCD on the whole thing and enjoy resetting it every time an incandescant bulb blows

Seriously though, my house (built in 1980) was originally fitted with a Wylex fuse box with real fuse wire. I replaced it with a split consumer unit with outdoors and the shower on a 30mA RCD and the rest on standard breakers. Does this make me a "monkey"?

As Nigel says, regulations have got much stricter recently. The 16th edition went crazy with RCD protection and apparently the 17th edition relaxed this in part, but don't take my word for it.

I'd be more worried about the quality of what is hidden behind walls and under floors, the way sockets/lights are wired and the number of extensions which have been tacked onto things. All of these are potentially far worse than a perfectly safe consumer unit.

 

[Thunderchild]

well like you say you used 30mA, when i lived in italy everyone had a 30mA RCD which I think became law before they did in the uk, I never had problems with the 30mA version really and don't know why a bulb blowing should be a problem (its not an earth fault) I can't see what the hoo ha and machoness over "how many amps i work with before i'm worried" is about. Apparently 30mA is quite serious in fact fatal,

 

[edeca]

Yes but if you read what I wrote, no sockets or light fixtures in my house are protected by RCD. Not even in the kitchen (though that might change when we decorate it).

So really, I guess I'm a "moron"