voltage drop regulations

[climberjim]

Hi,

Hope you don't mind me pesting you lot again. Although my house is fairly small it has been wired with only one ring main which runs front to back under the middle of the upstairs floor branching off as required (if you see what I mean). Currently the ring is off a 30A rewirable fuse (although I intend to replace the unit with a modern cu with rcd & mcb in the near future. I've extended part of the ring and added a couple of spurs). As I understand it at a load of 30A the max length of the ring (assuming voltage drop is the limiting factor - do I have to assume max current is the fuse rating for this?) will be around 37m. Given the number of time the wires have to go up and down I'm probably not that far off this figure. Is there an easy way to check this ?(I don't really want to do it on distance as for one thing I haven't yet worked out exactly where all the cables run). Can I disconnect the ring at the cu and measure the resistance of the individual wires (applying a correction for typical cable temps under load, 30 degrees? )

Should I be concerned about this reg anyway - I can't see many (any?)appliances being upset by a drop of 4% - is this figure plucked out of the air or is there some reasoning behind it?. If I am outside would there be any real probs with living with it until such time that I change the cu, put the kitchen (or at least part of it) on a separate circuit and use a 20A mcb on the ring.

Many Thanks

Jim

 

[breezer]

i shouldnt worry too much. but when you get a new consumers unit you could split the ring, one up. two down. one down for most things the other for the kitchen

voltage drop comes in when you have long cable runs and an appliance that draws a lot of current.

the regs say (so i recall) one ring should not cover more than 100 square yards of floor space.

But nothing says you can have more rings in smaller space, it depends on what the ring is to be used for. for argument sake a place that tests kettles say 10 at a time ,one ring with 30 A fuse would not be a lot of use (since each kettle could draw 13 A

 

[spark]

It's 100 sq. metres not yards . Those were the days eh breezer.... . Maximum Zs to give you a disconnection time of 0.4 seconds is also a consideration along with lots of other things which I won't go into tonight. I failed a ring circuit today which was covering 325 sq.metres .

 

[supersparks]

It's 100 sq. metres not yards . Those were the days eh breezer.... . Maximum Zs to give you a disconnection time of 0.4 seconds is also a consideration along with lots of other things which I won't go into tonight. I failed a ring circuit today which was covering 325 sq.metres .

alittle oversized and this in someones house? or commercial?

 

[spark]

A Police Station

 

[supersparks]

A Police Station

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!UR JOKIN!! LMAO
did you fail anything else there?

 

[ban-all-sheds]

Were they using copper cable?

And was it all mains, or did they have some dry cells as well?

If I keep this up, will I become a victim of assault and battery?

 

[ban-all-sheds]

Undervoltage can damage some motors, and (I think?) fluourescent lights.

Where does the figure of 37m come from?

 

[masona]

Were they using copper cable?

And was it all mains, or did they have some dry cells as well?

If I keep this up, will I become a victim of assault and battery?

No, keep it up,I need cheering up specially when my missus taken laughing beans off the shoping lists

 

[ban-all-sheds]

What worries me is that unless one of the employees did it in their spare time, that wiring in the police station must have been done by a professional electrician.

Of course there are cowboys around - look at Spark's signature (joking! ), but despite what the NICEIC are trying to imply, the 53,000 out of 61,000 firms that aren't registered with them are not all bandits, but what on earth was a "public" body like the police doing using someone so incompetent?

 

[climberjim]

Undervoltage can damage some motors, and (I think?) fluourescent lights.

Where does the figure of 37m come from?

Sorry for replying earlier but I've had a busy week. I got the distance from the a table (I actually mis rembered it it was 36m) given in this article

http://www.kevinboone.com/cableselection_web.html

Essentially assumes the cable carries 30A and then calculates the voltage drop over its length from the overall resistance of the cable (farthest point from cu) based on length which should be less than 4% of 230 (240).

Of all the regs it seemed the least safety (i.e. shock/fire) related (I'm not sure my supply voltage doesn't drop more than that on a regular basis). I've more power cuts that hot dinners recently (the pubs not doing badly)! I came home one evening to discover I had a whole 10V - lights were a bit dim to say the least!

Thanks to all for the replies

Jim

 

[ban-all-sheds]

Sorry for replying earlier but I've had a busy week. I got the distance from the a table (I actually mis rembered it it was 36m) given in this article

http://www.kevinboone.com/cableselection_web.html[/QUOTE]

Thanks - useful site that. Glad you misremembered - when I did the calculation and got 35.56m, I thought "where did I go wrong?".

Not that there's much difference between 35.56/36/37.

I came home one evening to discover I had a whole 10V - lights were a bit dim to say the least!

Not sure it's lawful for the supply company to give you 10V

 

[spark]

What you have to remember is that the electrician installing it doesn't necessarily always design it. We have a consultant who also works for the force concerned and we have to install to his design. Unless it's unsafe there's not a lot you can say. We've just partially rewired (too tight for a full rewire!) a depatment within the station and we're using all of the original switch positions which are behind the doos! People will probably question our abilities when they see how it's been left, but our hands are tied. Unless you can say that a particular aspect of the installation (existing or new) is immediately dangerous to persons or property then it doesn't matter to anyone what your opinion is compared to that of the gratuate consultant.