quick question for a sparky

[LaserTam]

Just trying to see if this is possible before I get a sparky to come in and check it and do the work.

Here you see my consumer unit, to the left is a fused un-switched spur which feeds my house alarm system (in a box just out of picture) and it has its own 'switch' on the consumer unit. I want to install a PIR security light outside and the ideal source of power is right here (otherwise its a much longer run round the garage to a plug socket the other side. Is it conceivable that a switched fused spur could take a feed from the existing fused spur, for the power for the security light?

Maybe the 'switch' in the consumer unit may need to be up-rated? Its says B6 on it (not sure what that means or is relevant)

electrics by LaserTam, on Flickr

Thanks.

[LooneyTunes]

Not a spark, but with 6A to play with you should be fine with the ratings (unless the security light is a monster and/or the unswitched FCU has a tiny fuse in it), but aren't you overlooking the fact that the alarm probably has its own circuit breaker in order avoid a failure elsewhere causing it to trip?

[LaserTam]

See thats why I ask these dumb questions on here, because it uncovers stuff that I have not thought about! Cheers LT.
Having said that, we actually never put the house alarm on, but doesn't mean to say we won't in the future.
Perhaps plan A then, longer run around the garage.

[megaphone]

You'll have a lighting circuit breaker on the consumer unit, it will likely be another 6 amp breaker. Run your security light from this, you can go via a switched spur if you want, so you can isolate the security light if necessary.

Or there is spare 'way', the one with the blank plate, you can fit another 6 amp breaker here for you security lighting.

Edited by megaphone on Sunday 6th September 10:03

[Jefftav]

For a security light the best thing would be a separate circuit using the spare way on the CU. I can't tell the rating of the supply circuit to your garage but it would probably take a security light using a switched fused spur from a ring main but as the garage supply looks as though it comes from the RCD in your CU if there are any electrical problems in the garage it will knock off the other supplies coming through the RCD as well as your security light. I don't think there are any specific requirements to have the security light fed through a supply controlled by an RCD so a separate circuit might be better in the long term.

[p1esk]

On modern consumer units with MCBs, can you take out individual MBCs and put them back in your preferred order, or are they permanently fixed in place along the row?

For example, I might like the first two to serve lighting circuits, the next two to serve power point ring mains, then immersion heater, cooker, shower, external lighting, then two or three spares etc.

[dazwalsh]

^ do not do this.

[Pheo]

My sparky recommends it be on its own way on the CU - otherwise it could take something out which you don't want... Like your lights. And outside lights have a propensity to do this as they all get water in them eventually!

[LaserTam]

Ummm - No spare slots on the CU! There was me thinking this would be easy....

[ch427]

Im sure i see a spare way on the right hand side, why dont you just use this as its not rcd protected and wont cause any nuisance tripping.

[Yabu]

LaserTam said:

Ummm - No spare slots on the CU! There was me thinking this would be easy....

Looks like a spare way on the right hand side of the board, 2nd space is blanked off, rcd could be added after the board if required

[Yabu]

Pheo said:

And outside lights have a propensity to do this as they all get water in them eventually!

If they are properly sealed they will not get water in them

[Pheo]

Yabu said:

If they are properly sealed they will not get water in them

Agree when new but over time likely to degrade. Anyway I am just passing on my sparky's advice to me, OP can take it or leave it!

[LaserTam]

I appreciate the advice, and yes, well spotted, there is a spare way in there. I didn't notice, just recall the sparky telling me it was now full when I had an extension completed a year or so ago - clearly not.

So, looks like I have a plan. Now to get the fella round - could be easier said than done, but I have another little job for him once he is here.
Thanks.

[p1esk]

dazwalsh said:

^ do not do this.

If that's a reply to my question, please can you explain further.

Are you saying it's not physically possible to re-arrange the order of the MCBs; or that it can be done, but it is likely to create a problem?

[Jefftav]

Are you saying it's not physically possible to re-arrange the order of the MCBs; or that it can be done, but it is likely to create a problem?

It is physically possible but CB's are arranged usually in an order of highest rating closer to the CU Isolator so yes if you move things around it could cause an issue with the internal loading in the CU. So unless you know what you are doing leave as it is.

[p1esk]

Jefftav said:

Are you saying it's not physically possible to re-arrange the order of the MCBs; or that it can be done, but it is likely to create a problem?

It is physically possible but CB's are arranged usually in an order of highest rating closer to the CU Isolator so yes if you move things around it could cause an issue with the internal loading in the CU. So unless you know what you are doing leave as it is.

OK, thanks for the explanation.