Cable leaving house to underground.

[Simon35]

And the point of all this was what? An actual installation in your house? Or purely hypothetical?

 

[Simon35]

sorted.

First part answered. Now interesting. As thread went on, the point of spurs on a ring being protected by only a maximum of 13A, even though the spur cable is rated 26A, came up.

Scenario.

• A 32A ring, 2.5mm cable.
• Junction box in ring then 2.5mm to a garage or out-building.
• In garage/out-building a small CU.
• CU has a 20A MCB/fuse protecting the garage/out-building and the 26A rated spur cable.
• Spur cable protected as it is rated at 26A - all safe.
• After the 20A mcb, which protects the whole garage/out-building, a couple of 16A radials for sockets, say one for inside and for the outside for garden socket use.
• Another mcb at 3A for LED lighting.
• Circuits off garage/out-building split, so divide & rule.

Looks very legal to me now. Clearly electrically sound and safe for sure.

Legal? There are no laws defining or requiring any of the above.

 

[hard-work]

Is it longer than 3M?
Reg 433.2.2

433.2.2
"The device protecting a conductor against overload may be installed along the run of that conductor if the part of the run between the point where the change occurs (in cross sectional area, method of installation, type of cable or conductor, or in environmental conditions) and the position of the protective device has neither branch circuits nor outlets for connection of current-using equipment and fulfils at least one of the following conditions:

(i) It is protected against fault current in accordance with the requirements stated in section 434
(ii) Its length does not exceed 3m, it is installed in such a manner as to reduce the risk of fault to a minimum, and it installed in such a manner to reduce to a minimum the risk of fire or danger to persons (see also Regulation 434.2.1)"​

(i) applies.

 

[hard-work]

Legal? There are no laws defining or requiring any of the above.

So legal, as BS is recommendations.

Hypothetical.

 

[Simon35]

So legal, as BS is recommendations.

Hypothetical.

?

If we are talking about BS7671, then they are regulations, not recommendations, not laws. Compliance with BS7671 is evidence of compliance with the applicable statute law, PUWER, EAWR and the like.

 

[DetlefSchmitz]

434.2 Position of devices for protection against fault current
A device providing protection against fault current shall be installed at the point where a reduction in the crosssectional
area or other change causes a reduction in the current-carrying capacity of the conductors, except where
Regulation 434.2.1, 434.2.2 or 434.3 applies.
The requirements in Regulations 434.2.1 and 434.2.2 shall not be applied to installations situated in locations
presenting a fire risk or risk of explosion or where special requirements for certain locations specify different
conditions.
434.2.1 Except where Regulation 434.2.2 or 434.3 applies, a device for protection against fault current may
be installed other than as specified in Regulation 434.2, under the following conditions:
In the part of the conductor between the point of reduction of cross-sectional area or other change and the position
of the protective device there shall be no branch circuits or socket-outlets and that part of the conductor shall:
(i) not exceed 3 m in length, AND
(ii) be installed in such a manner as to reduce the risk of fault to a minimum, AND
NOTE: This condition may be obtained, for example, by reinforcing the protection of the wiring against external
influences.
(iii) be installed in such a manner as to reduce to a minimum the risk of fire or danger to persons.

 

[SUNRAY]

sorted.

First part answered. Now interesting. As thread went on, the point of spurs on a ring being protected by only a maximum of 13A, even though the spur cable is rated 26A, came up.

Scenario.

• A 32A ring, 2.5mm cable.
• Junction box in ring then 2.5mm to a garage or out-building.
• In garage/out-building a small CU.
• CU has a 20A MCB/fuse protecting the garage/out-building and the 26A rated spur cable.
• Spur cable protected as it is rated at 26A - all safe.
• After the 20A mcb, which protects the whole garage/out-building, a couple of 16A radials for sockets, say one for inside and for the outside for garden socket use.
• Another mcb at 3A for LED lighting.
• Circuits off garage/out-building split, so divide & rule.

Looks very legal to me now. Clearly electrically sound and safe for sure.

I struggle big time to work out what you are actually trying to achieve with these nonsensical questions. To add insult you then argue with people giving perfectly adequate answers. So why have you come up with this stupid scenario after so much excellent advice?
What is 26A rated cable? Probably what the sheds call 2.5mm² cable but as nearly everyone on her can tell you it TOTALLY DEPENDS on many factors and quite often 2.5mm² is significantly derated by installation conditions.

Anyway just in case you are silly enough to start installing the above, the maximum OCD for a spur off a 'standard' RFC is 13A fuse or 16A MCB.

 

[hard-work]

Mr Sunray, it is best you read the first post first and work your way through.

 

[SUNRAY]

Mr Sunray, it is best you read the first post first and work your way through.

Oh I've read it OK, all the way through and as has become the custom your questioning is becoming more confusing.

I'm still trying to work out if these are schoolboy questions, curiosity, serious learning, wind-up.

 

[hard-work]

Anyway just in case you are silly enough to start installing the above, the maximum OCD for a spur off a 'standard' RFC is 13A fuse or 16A MCB.

Different to what EFLImpudence wrote.
BTW, I know about derating, etc. 20A will cover a 2.5mm cable unless it is very long and/or deep in thermal insulation unable to dissipate heat.

 

[hard-work]

Oh I've read it OK, all the way through and as has become the custom your questioning is becoming more confusing.

I'm still trying to work out if these are schoolboy questions, curiosity, serious learning, wind-up.

If you cannot understand the first post you have comprehension problems. It seems it is common here.

 

[JohnD]

... Of course it cannot have more than one socket off spur....

However, since you have now confessed that you intend to hang a garage CU off it, with lights and sockets, you must protect your spur with a 13A FCU or similar.

 

[SUNRAY]

If you cannot understand the first post you have comprehension problems. It seems it is common here.

Indeed I understand the OP perfectly and, as has become your trademark, you have turned the thread into gobbletygook.

Let us into the reason for your unorthadox questions.

 

[hard-work]

However, since you have now confessed that you intend to hang a garage CU off it, with lights and sockets, you must protect your spur with a 13A FCU or similar.

Not this loony - more noise. He follows me around the forums.

 

[hard-work]

Indeed I understand the OP perfectly and, as has become your trademark, you have turned the thread into gobbletygook.

Let us into the reason for your unorthadox questions.

I was a simple question. You even understood it, you wrote so. Then noise enters wanting know my shoe size, not understanding simple questions, or other irrelevant tripe coming in like the recent insertion.

What gobblegook? You answered differently to EFLImpudence. Which is the gobblegook, your answer or his?