Spur query

[far2complicated]

Hi all

I'm currently checking some wiring in an outbuilding that I want to use as an office. There aren't many sockets in the space, but there is one I want to plug a 2kw heater in to.

The socket is on a 2.5mm t+e spur, which then goes into a junction box, and changes to 1.5mm t+e. The 1.5mm is buried under plasterboard and insulation, and arrives at a single socket.

Is this a safe socket to use for the heater, or anything?

Thanks in advance.

 

[deadshort]

Hi, it depends on the fuse that is protecting the cabling, are you saying that the socket is on a fused spur ?

Regards,

DS

 

[far2complicated]

Hi DS, thanks for the reply. The spur isn't fused anywhere, it's taken straight from the back of a double socket. The double socket is on a ring that is obviously fused.

 

[ban-all-sheds]

The double socket is on a ring

You're absolutely sure, as a result of 100% visual inspection, or proper testing, that that is the case?

 

[JohnW2]

The double socket is on a ring

You're absolutely sure, as a result of 100% visual inspection, or proper testing, that that is the case?

A valid question although, in electrical terms, I'm not sure that it matters what sort of circuit it originates from, does it? IF, as the OP says, the 1.5mm² cable is supplying just as single socket (hence a downstream 13A fuse at the largest), and IF the cable is not actually 'buried in insulation', then I would say that, electrically, it's OK, regardless of the nature of the circuit it originates from, and regardless of what the upstream protection of that circuit may be. On the basis of regs, rather than electrical principles, some may try to argue otherwise.

Kind Regards, John

 

[ban-all-sheds]

A valid question although, in electrical terms, I'm not sure that it matters what sort of circuit it originates from, does it?

Yes, if the "donor" socket is already a spur from a ring final.

 

[JohnW2]

A valid question although, in electrical terms, I'm not sure that it matters what sort of circuit it originates from, does it?

Yes, if the "donor" socket is already a spur from a ring final.

True. I somewhat misread/misinterpreted the question, which I was thinking was just about whether or not the circuit was a ring, rather than whether the donor socket was part of a ring (if that's what it is) or a spur.

Kind Regards, John

 

[far2complicated]

Hello All, thanks for the input. The donor socket is definitely on a fused ring. It is on surface mounted conduit coming from and going to a consumer unit. I have taken the original double socket face off and can see the spur coming out the back and through the wall. The junction box where it drops from 2.5 to 1.5 is at the top of the wall, then the 1.5 goes under plasterboard and insulation to the single socket. Obviously I didn't want to plug my heater in and melt the cable.

 

[JohnW2]

Hello All, thanks for the input. The donor socket is definitely on a fused ring. It is on surface mounted conduit coming from and going to a consumer unit. I have taken the original double socket face off and can see the spur coming out the back and through the wall. The junction box where it drops from 2.5 to 1.5 is at the top of the wall, then the 1.5 goes under plasterboard and insulation to the single socket. Obviously I didn't want to plug my heater in and melt the cable.

You won't melt the 1.5mm² cable with a 2kW heater, even if it were 'buried in' (completely surrounded by) thermal insulation.

The issue that BAS and I were discussing relates to cable supplying the double socket from which the 2.5mm² spur originates, which isprobably 2.5mm² cable. If you are certain that that double socket is part of the ring, then there is no problem. However, if that socket were already a spur from a ring, wired in 2.5mm² cable, then taking a further spur from that would mean that the cable feeding that double socket would be having to carry the total current being drawn by both the double socket and the single one (with 2kW heater). That total current could exceed the capacity of 2.5mm² cable, which is why it would be non-compliant with regs and potentially unsafe. However, you seem certain that you do not have that situation.

Kind Regards, John

 

[far2complicated]

Thank you so much for your input John. I understand your points, and am happy it is how I've described. Thank again.

 

[JohnW2]

Thank you so much for your input John. I understand your points, and am happy it is how I've described. Thank again.

You're welcome.

Kind Regards, John