Hook-up fun?

[billybigspud]

would be quite easy to rig something up with an LED. if it lights up then polarity is correct. If it doesnt then it wont work anyway.

Reverse polarity does not stop it from actually working

If it has the diode I was talking about in it it would.

[1664]

would be quite easy to rig something up with an LED. if it lights up then polarity is correct. If it doesnt then it wont work anyway.

Reverse polarity does not stop it from actually working

If it has the diode I was talking about in it it would.

Oh, I thought when you said "If it doesn't then it won't work anyway" you were referring to the installation not working, not the LED. Had me wires crossed there - which considering the subject matter is a tad amusing

E D I T: Actually Billy, now I've thought about it, you're thinking in d.c.
An LED will only light up when connected the right way round in a d.c circuit, but it'll light up in an a.c circuit no matter if a circuit's reverse polarity or not because the current changes direction 50 times per second in both the live and neutral; so it will be lit every half cycle (ie, 25 times a second) which to the human eye will appear that it's simply 'on'.

[Oldiebut goodie]

must have been something else then; I can 100% assure you that reverse polarity does not affect incoming double pole RCD's and neither does it prevent any electrical equipment (kettle, lights etc) from operating (unless you are referring to RCBO's; single pole circuit breakers with an integral RCD facility which requires connection to both the neutral and earth busbars in the consumer unit)

Sure it wasn't an ye olde ELCB? Extremely defunct stuff these days

Yep - it's an olde worlde Crabtree elcb (500v 60A) - still a functional device though in some ways - though not for earthing via a person etc. I am not called OLDIEbut goodie for nothing!

[1664]

Yep - it's an olde worlde Crabtree elcb (500v 60A) - still a functional device though in some ways - though not for earthing via a person etc. I am not called OLDIEbut goodie for nothing!

Yes a moderately useful device in it's day - made completely ineffective by 'modern' ('80s onwards) earthing requirements creating parallel paths for the fault current to travel rather than through the ELCB. If your house is on a TT system (an earth rod or stake) I cannot impress on you enough the need to replace it with a suitably rated RCD, unless you have a new consumer unit with 30mA RCD protection provided by the incoming switch and/or RCBO's on the individual circuits.

[billybigspud]

I wonder if you used a 12v dc led would the driver be polarity concious?

It must be as it will be a wheatstone bridge. ( spelling )

As for them ELCB's. Awful things but served a purpose in their day. I would imagine oldies house is a TT as that is where I always seem to find them. Not saying its not though. As it is probably your primary protection I would, as already said, get an rcd fitted. If people do not want a board change then I usually fit them a 100mA rcd providing the resistance is low enough as you get a bit more tolerance with them over a 30mA.

[Oldiebut goodie]

TT =

Tumbledown tip? Yes!

[billybigspud]

Tyranosaurus Tina. It is Rex's sister.

Terra Terra. ie, uses the ground for your earth path. Have a look to see if you have a rod in the ground outside with an earth on it. your incoming main would probably come to your property over head from a post but not always. You may have an earth clamp around your incoming main or one that goes in the main fuse/cut out neutral side. If so then not so critical but still highly advised.

[Oldiebut goodie]

Yep nice earth rod outside ( it has been there since 1953 at least to my knowledge) - not in a box of sal ammoniac soaked earth though. (If you didn't know - it was an old trick to ensure dampness/circuit in the soil as the sal ammoniac forms an electrolyte)

[billybigspud]

no disrespect but this is the attitude I get quite a lot. It is probably not a nice earth rod and is probably not functioning as good as it could due to corrosion, especially on the clamp which is probably exposed. The usual line is ' well it has been fine for years ' to which I usually reply ' how do you know, is it because your dangerous old asbestos lined rewirable fuses never blow '. Please dont take this the wrong way as I just want to try and keep people safe. I expect 90% of the houses in the uk need work and that is just to get them safe, let alone upto regulation standard. I would imagine that your bonding is undersized as will be your main earth, As already said, you will have rewirable fuses, Lagging in your loft over the cables and to make a crazy stab in the dark, You live in a bungalow.

Probably wrong on all counts so I will jog on now.

[1664]

I wonder if you used a 12v dc led would the driver be polarity concious?

It must be as it will be a wheatstone bridge. ( spelling )

Doesn't change the fact that it will work either way round in an ac circuit regardless of whether a single diode or a wheatstone bridge configuration; they'll just polarise the alternating current to a unidirectional one but won't actually detect or indicate a 'reverse polarity' situation.

The word 'polarity' is a bit of a misnomer when used to describe this situation occurring in an ac circuit. The uk a.c mains supply changes 'polarity' 50 times a second so the expression 'reverse polarity', although instantly understandable, is not really a suitable description once you get down to the nitty-gritty of it. Perhaps 'reverse connected' or would be better?

[billybigspud]

I thought the bridge caught it before 0 degrees though?

[1664]

The voltage/current at 0, 180 and 360 degrees is zero as it is the exact point of directional changeover. A wheatstone bridge aligns both sides of the ac waveform into a dc unidirectional flow so it is an 'efficient' form of ac to dc conversion. A single diode will only allow one direction of flow but is only 50% efficient as the opposite direction of flow is blocked and discarded rather than used.

So a wheatstone bridge waveform looks like nnnnnnnn and a single diode waveform looks like n_n_n_n

Obviously neither of these are true dc as they are still rising and falling values of voltage rather than a fixed constant, but add a capacitor and inductor and you can smooth the resultant waveform out to mostly eradicate the resemblence to a big dipper.

[Oldiebut goodie]

no disrespect but this is the attitude I get quite a lot. It is probably not a nice earth rod and is probably not functioning as good as it could due to corrosion, especially on the clamp which is probably exposed. The usual line is ' well it has been fine for years ' to which I usually reply ' how do you know, is it because your dangerous old asbestos lined rewirable fuses never blow '. Please dont take this the wrong way as I just want to try and keep people safe. I expect 90% of the houses in the uk need work and that is just to get them safe, let alone upto regulation standard. I would imagine that your bonding is undersized as will be your main earth, As already said, you will have rewirable fuses, Lagging in your loft over the cables and to make a crazy stab in the dark, You live in a bungalow.

Probably wrong on all counts so I will jog on now.

You forgot to tell me that my wiring is wax impregnated cloth and rubber insulated also!

[ELSwervo]

That was a can of worms
Tried the re-wired hook-up for two weeks holiday. No problems, thanks for the comments.
I am going to add a couple of sockets to my system as one european style socket with a 3 gang extension lead is a bit of a pain in the ar*e to use. So question.....Spur or ring?

[1664]

So question.....Spur or ring?

Radial. The hook up is a maximum of 16 amps anyway so there's no point installing a ring. The circuit breaker will limit the current so it doesn't matter how many sockets you install, 16 amps will be the limit. Just make sure you use cable rated at 16 amps or over.