College tutor - rcd issue

[Lip.82]

On thing I do know is that at the moment AFDD don’t work on ring finals(what I’ve read and seen anyways) so if they eventually become mandatory then if the manufacturers can’t get them to work with rings then the ring final may become obsolete?
Just a thought

 

[Lip.82]

Hi
I'm new on here and still learning the trade so please forgive any, what may seem to you as silly questions but what does AFDD stand for?
I can't find it anywhere
Thanks

 

[Richard Burns]

Hi
I'm new on here and still learning the trade so please forgive any, what may seem to you as silly questions but what does AFDD stand for?
I can't find it anywhere
Thanks

Arc fault detection devices.
Supposedly meant to identify things like loose connections arcing and so prevent fires, they are mentioned, I think, in the draft to the 18th Edition as a possible consideration for fire protection. However they are in use in the USA (as arc fault circuit interrupters, AFCI) and generally appear to be considered not very good.

 

[The Ghost]

An RCD is additional protection against an earth fault. If you weigh inconvenience/danger against a live part due to an earth fault then I think you would obviate the earth fault with additional protection as a priority over inconvenience. Obviously where life support systems which cannot be turned off are in operation I would use a high integrity DB to get around having an RCD on it. I often recommend people have emergency lights when there is a possibility of being plunged into the dark when things go off, to avoid that inconvenience.

 

[Pete999]

My tutor at college is really good. Explains things well and is very knowledgable. He has mentioned a few times that the use of RCD’s doesn’t comply with the regs. By this he means that in the regs it states that rcds cannot effect other circuits upon operation.

So the use of rcds protecting more than 1 circuit is not in occordance to bs7671.

As my tutor explains, if I was to be standing in the dock having to explain why, when the rcd tripped on the downstairs sockets it tripped the upstairs lights and led someone to fall down the stairs and die, they would just point to this reg and I wouldn’t have anyway out of it.

I get it but, they are so widely used in this way. In the fact the only real to avoiding this is rcbo’s. If you quoted every rewire or board change on just rcbos you would hardly get any jobs because Alan the electrician down the road can do a split board with rcd protection at half the cost.

Sometimes I feel this industry is a little contradicting or unrealistic

Have you got the regulation number your tutor is referring to ? just want to take a look at it for my own peace of mind.

 

[telectrix]

methinks tutor bin talking to niceic about how to make up your own rules, irrespective of what the bible (7671) says.

 

[SparkyChick]

Have you got the regulation number your tutor is referring to ? just want to take a look at it for my own peace of mind.

It would be nice to know if the tutor has other ideas, but I think it's in 314, the most pertinent part of which I've quoted above.

 

[Pete999]

It would be nice to know if the tutor has other ideas, but I think it's in 314, the most pertinent part of which I've quoted above.

I agree SC I think 314.2 is the sticker, and the last sentence of 314.2 in particular, think Tel has hit the nail on the head with his comment as well.

 

[telectrix]

my parents and grandparents never fell down the stairs ( not when sober anyway) due to all the lights failing. the whole house only had 1 light circuit anyway. talk about nanny state? next thing is they'll be stipulating emergency lighting in all dwellings and mandatory purchase of candles. pfff.

 

[gazdkw82]

Yep it’s 314.2

Iv read it again and it’s pretty clear. It does say circuits shall be designed in a way that the protective devices are designed in a way that they do not effect other circuits.

Wheather that would be an important factor if I was ever in the dock for something related is very unclear

 

[Ian1981]

The Protective devices would be the OCPD I’d imagine and not the rcd.
Interpretation again I guess

 

[Lip.82]

Arc fault detection devices.
Supposedly meant to identify things like loose connections arcing and so prevent fires, they are mentioned, I think, in the draft to the 18th Edition as a possible consideration for fire protection. However they are in use in the USA (as arc fault circuit interrupters, AFCI) and generally appear to be considered not very good.

 

[Lip.82]

Thank you, I thought it was something to do with arcing, when I was trying to look it up all that was coming up was what you mentioned AFCI.