Garage consumer unit...are tails needed?

Precisely! My natural instinct would have been to write 110cm - but I knew someone would jump on me for using non-preferred units! Also, I did say

*about* 1100mm - to give an indication of the size of gap to be spanned, rather than implying accuracy to the nearest mm.

I think Mr Hansen must be having a bad day!

Reply to
Roger Mills
Loading thread data ...

I'll answer your questions to the best of my ability!

I've never been totally clear about these! The supply comes underground (1960's build), and up to the main fuse in what looks like SWA cable. L & N tails go from the main fuse to the consumer unit. There is an earth tapping on the side of the main fuse block, from which an earth feed goes to the consumer unit. I assume that the earth is derived from the sheath of the SWA rather than from the neutral conductor, but I cannot say for sure since I can't access the internal connections of the fuse block.

I propose to use a 40A MCB in the consumer unit. [There is currently a much lower rated one, since it only feeds a shower pump]. I have in mind to use a garage consumer unit the other end, such as Screwfix 63138. This has overall RCD (40A 30mA) protection, plus MCB protection on the individual power and lighting circuits.

Approx 10 metres of T&E and 5 metres of SWA.

Your further comments will be much appreciated.

Reply to
Roger Mills

On Thu, 22 Jun 2006 09:54:15 +0100 someone who may be "Roger Mills" wrote this:-

What's wrong with 1.1m? Far more appropriate to the measurement concerned (and fewer characters to type:-)

Don't take up mind reading.

Reply to
David Hansen

On Thu, 22 Jun 2006 10:43:03 +0100 someone who may be "Roger Mills" wrote this:-

The supply cable probably has a central energised conductor, surrounded by a protective earth and neutral conductor. The latter is connected to the neutral tail and the earth block inside the unit that contains the fuse. TN-C-S

Reply to
David Hansen

When did the concentric cable come in? I thought it was the 70s, so a 60s installation would more likely be the standard SWA cable.

Reply to
<me9

Split concentric (for TN-S) was certainly in use by the late 60's. I remember the MEB, as was, replacing the service to my parents' house around that time. I filched an offcut of the cable for examination - phase & neutral were 7/0.064 (neutral being seven individually insulated

0.064 strands) and there were four somewhat larger uninsulated strands for earth.

AFAIK, SWA was and is seldom, if ever, used for service cables.

Reply to
Andy Wade

Try the FAQ:

formatting link
The supply comes underground (1960's build), and up to the main fuse

Give the date, I suspect TN-S. TN-C-S/PME didn't come into use until the 70s (AFAIK). I've assumed TN-S (Ze max = 0.8 ohm, in what follows).

With a 40 A MCB, the 2.5 mm^2 CPC in the T&E leg is looking a bit puny. With a Type B MCB you should just about be OK, provided those circuit lengths are correct. With a Type C it certainly wouldn't comply. Since cables always tend to end up a bit longer than you expect, I strongly suggest that you either upgrade the T&E section to 10 mm^2, or run SWA all the way, or reduce the MCB at the feeding end to 32 A, Type B.

HTH

Reply to
Andy Wade

On Thu, 22 Jun 2006 16:36:56 +0100 someone who may be Andy Wade wrote this:-

My house has such a cable and it was built in the 1960s.

Reply to
David Hansen

But is it TN-S or TN-C-S?

Reply to
Andy Wade

On Thu, 22 Jun 2006 21:23:25 +0100 someone who may be Andy Wade wrote this:-

The latter.

Reply to
David Hansen

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.