Loft electrics - new socket or extension on fused spur

[myxiplx]

Hi folks,

We've just had our loft boarded and I'm looking to move a small server up there. I could do with some advice on what's the recommended way to add the necessary electrics.

I'm planning to use an old circuit which fed an electric shower. It's a 40A supply from the main consumer unit (on the RCCB side), which is totally unused now and terminates in a box in the loft.

My first thought was to re-label that on the consumer unit as the loft circuit, and then add a 13A fused spur up in the loft and run a 4 way extension lead from that, with the cable tacked safely out of the way.

Does that sound reasonable?

Myx

 

[JohnW2]

I'm planning to use an old circuit which fed an electric shower. It's a 40A supply from the main consumer unit (on the RCCB side), which is totally unused now and terminates in a box in the loft. ... My first thought was to re-label that on the consumer unit as the loft circuit, and then add a 13A fused spur up in the loft and run a 4 way extension lead from that, with the cable tacked safely out of the way. ... Does that sound reasonable?

You could do that (provided that the current cable is not too big to fit in the terminals of an FCU). You could alternatively run a socket from that cable and plug the extension lead into that (the plug will have a 13A fuse). However, wouldn't you prefer to do it 'properly', with hard-wired sockets, rather than an extension lead? If you did want to do the latter, there are various options as to how you could do it, which could be discussed.

Kind Regards, John

 

[flameport]

Electrically no problem.

As for putting a server there - not a good idea. Lofts are dusty, have temperature variations from freezing to +50C and humidity from nothing to dripping wet.

 

[myxiplx]

Hi John,

This was more of a convenience thing, I have a 4 way extension lying around already, so I'd just need to add the fused spur. I was planning to leave the existing cable terminated as is, and connect the fused spur to the side of it. The alternative as you say is 2.5mm cable and a hard wired socket.

I'm ok with either option, the main reason I wanted to check here was I wasn't sure what the "proper" way was

You could do that (provided that the current cable is not too big to fit in the terminals of an FCU). You could alternatively run a socket from that cable and plug the extension lead into that (the plug will have a 13A fuse). However, wouldn't you prefer to do it 'properly', with hard-wired sockets, rather than an extension lead? If you did want to do the latter, there are various options as to how you could do it, which could be discussed.

Kind Regards, John

 

[myxiplx]

Electrically no problem.

As for putting a server there - not a good idea. Lofts are dusty, have temperature variations from freezing to +50C and humidity from nothing to dripping wet.

Heya flameport. We've just had the loft boarded and insulated, so it's boarded corner to corner, with insulation covering every exposed inch of the rafters too. It's about as stable an environment as you're going to get for a loft.

Sure there's going to be a decent temperature swing in the summer, but the server is under very light load and the components are rated to 60 degrees C. Worst case scenario would be the CPU overheating (definitely possible in the summer), but it's got temperature sensors on the motherboard and does a controlled shutdown if that happens.

 

[JohnW2]

Hi John, This was more of a convenience thing, I have a 4 way extension lying around already, so I'd just need to add the fused spur. I was planning to leave the existing cable terminated as is, and connect the fused spur to the side of it. The alternative as you say is 2.5mm cable and a hard wired socket.
I'm ok with either option, the main reason I wanted to check here was I wasn't sure what the "proper" way was

I suspect you know the real answer to that - 'hardwiring' an extension lead to an FCU cannot really be described as 'proper'. However, provided you take steps to keep the cable out of harm's way, its electrically OK.

Kind Regards, John

 

[bernardgreen]

The concerns about temperature effects on servers in a loft are valid.

The temperature on the PCB can be 20°C higher than the ambient temperature.

Some components, especially electrolytic surface mount devices have a life span that is reduce when operated at or near their maximum rated temperature. Life span of the components and thus life span of the equipment at different ambient temperatures is part of the design process.

It can be as bad as 1000 hours at 60°C and 100,000 hours at 25°C for the same capacitor

 

[deadshort]

I'm planning to use an old circuit which fed an electric shower. It's a 40A supply from the main consumer unit (on the RCCB side), which is totally unused now and terminates in a box in the loft. ... My first thought was to re-label that on the consumer unit as the loft circuit, and then add a 13A fused spur up in the loft and run a 4 way extension lead from that, with the cable tacked safely out of the way. ... Does that sound reasonable?

You could do that (provided that the current cable is not too big to fit in the terminals of an FCU). You could alternatively run a socket from that cable and plug the extension lead into that (the plug will have a 13A fuse). However, wouldn't you prefer to do it 'properly', with hard-wired sockets, rather than an extension lead? If you did want to do the latter, there are various options as to how you could do it, which could be discussed.

Kind Regards, John

I was not aware that fcu and socket terminals were a different size ?

Regards,

DS

 

[ban-all-sheds]

the server is under very light load

How many different power states does it have?

Doesn't matter whether it's running code or running the idle loop, GHz is GHz. If the clock speed doesn't get reduced when it's not busy it will use the same amount of power, and get just as hot.

and the components are rated to 60 degrees C

I would be gobsmacked if that means that you can run it at 60°C ambient.

 

[Maxatoria]

If you are going to put a server in a loft by which we mean an old PC to do some file serving normally don't put it on the floor but raised a bit and leave the keyboard/mouse and a monitor up there with it unless its a proper lights out unit and before popping it up there give it a good clean out of dust and remember to every now and again check up on it physically

Personally i wouldn't go with a FCU but a few sockets as you never know what you'll decide to do in the future and with the prices of sockets it might be better to sort of flood the place with them as now its boarded it'll probably get more use and things could get moved around

 

[JohnW2]

You could do that (provided that the current cable is not too big to fit in the terminals of an FCU). You could alternatively run a socket from that cable and plug the extension lead into that (the plug will have a 13A fuse). However, wouldn't you prefer to do it 'properly', with hard-wired sockets, rather than an extension lead? If you did want to do the latter, there are various options as to how you could do it, which could be discussed.

I was not aware that fcu and socket terminals were a different size ?

I wasn't clear. The bit in brackets about cable/terminal size should have gone after the reference to the alternative to using a socket (rather than an FCU) - since, as you imply, the same issue applies to both, and I didn't intend to imply that using a socket would alleviate that potential problem.

If I were doing it, and only wanted one or two sockets, I would probably run them as (separate) 2.5mm² branches from the end of the present cable. You might then possibly moan about a 2.5mm² cable being protected by a 40A OPD. I think that is an unwarranted concern but, if one were worried, the MCB could be downrated to 32A, which would make it a perfectly standard A2 radial with 2.5mm² single-socket branches.

Kind Regards, John

 

[deadshort]

If i moaned every time you bend the regs i would sound like a caravan park after the pubs close on a saturday night

Kindest regards,

DS

 

[JohnW2]

If i moaned every time you bend the regs i would sound like a caravan park after the pubs close on a saturday night

What I do, in my home, is obviously a very different matter, but I'm surprised you say that in terms of what I write here - which is almost always an attempt to interpret, not 'bend', the (sometimes unclear, and often necessarily non-comprehensive) regs, since I would not want to advise an OP (who was not in a position to make their own judgements) on the basis of what I thought were 'bendings of the regs'.

I'm not sure what position you're taking in relation to this particular issue, hence whether or not you think I'm trying to do any 'bending' on this occasion. You presumable accept that it is acceptable to have one (single or double) socket supplied by a 2.5mm² unfused spur/branch from a 32A ring/radial circuit (as illustrated in App 15). In those cases, the seemingly 'under-protected' cable is acceptable because of the implicit downstream fuse(s) in the plugs which are providing overload protection to the spur/branch cable - but they would provide that same degree of protection whether the upstream OPD protecting the circuit as a whole was 32A, 40A, 50A or whatever, wouldn't they?

Kind Regards, John

 

[EFLImpudence]

Yes.

 

[ban-all-sheds]

but they would provide that same degree of protection whether the upstream OPD protecting the circuit as a whole was 32A, 40A, 50A or whatever, wouldn't they?

They would. But there would come a point when the upstream device no longer provided fault protection. ICBA to do the sums, but I'd be surprised if a 40A was unacceptable for 2.5mm²