Attic insulation and cables

Payton

I got 200mm insulation to put on top of what I already have in the attic and hopefully do it this Saturday, it states on the packageing that electrical cables shouldn't be covered now what I have up there is a shower cable, 1 socket ( just for a light when I go up there) and tv cables plus the cable for the lights which are a bit tight. Would I be right in saying only the socket and shower cables should be on top of the insulation?

tomdempsey200

you might be ok
the shower may be the only concern
I presume it's only used for short periods?

Payton

tomdempsey200 wrote: »

you might be ok
the shower may be the only concern
I presume it's only used for short periods?

Cheers yes it is but I think I'll keep it on top for peace of mind.

Bruthal

Wouldn't make a bit of difference IMO.

Cycling Dumbasses

Payton wrote: »

Cheers yes it is but I think I'll keep it on top for peace of mind.

+ 1 there Payton.

All electrical cables of high amperage uses (cooker and shower cables) should be raised and clipped to a conventional rafter or tie above the level of the insulation to meet the requirements of ETCI publication EF 207:2003: Guide to the National Rules for Electrical Installation as Applicable to
Domestic Installations. All other electrical cables should be laid above the insulation once installation is complete.

Payton

Cycling Dumbasses wrote: »

+ 1 there Payton.

All electrical cables of high amperage uses (cooker and shower cables) should be raised and clipped to a conventional rafter or tie above the level of the insulation to meet the requirements of ETCI publication EF 207:2003: Guide to the National Rules for Electrical Installation as Applicable to
Domestic Installations. All other electrical cables should be laid above the insulation once installation is complete.

The shower cable is running along the gable end inside the attic so I may just batten it to the wall once and for all.

Cycling Dumbasses

Payton wrote: »

The shower cable is running along the gable end inside the attic so I may just batten it to the wall once and for all.

One cannot presume a shower be only used for short periods, you are right to be cautious and following regs and good work practices is a must always, enjoy the insulating not the most pleasant place to be or pleasant job to be at.

Payton

True but at €21 per roll for 200mm thick of knuaf insulation I had to avail of it :-)

Bruthal

Cycling Dumbasses wrote: »

One cannot presume a shower be only used for short periods,

They are not designed for prolonged continuous use really.

But either way, attic insulation on the cable is not going to cause problems. If it did, then in the summer, we are all in trouble, as the cable will endure higher temperatures on top of the insulation than under it in attics on hot sunny days, and higher temperatures on top on hot summer days than under it in winter.

In other words, the cable would have to be on the threshold of overheating already, for insulation on it to cause problems.

Proper sized cables, and there will be no problems.

Put it on top if handy, but no major worries if insulation goes over it.

Cycling Dumbasses

They are not designed for prolonged continuous use really.

I never said they were designed for prolonged continuous use, i cannot presume or assume how long the OP uses his shower for, rather than other people presuming things might be ok isnt it much more correct to follow ETCI publication EF 207:2003:
I dont think ETCI quote the words presume or assume.

Bruthal

Cycling Dumbasses wrote: »

I never said they were designed for prolonged continuous use, i cannot presume or assume how long the OP uses his shower for, rather than other people presuming things might be ok isnt it much more correct to follow ETCI publication EF 207:2003:
I dont think ETCI quote the words presume or assume.

The cable will reach equilibrium with regards to wattage output v wattage absorbed by surroundings within a shorter time than the average shower time, so how long its on makes little difference to the cable.

If you believe the cable will overheat simple because of etci writings, then so be it.

The shower cable will dissipate about 4 to 6 watts per metre. I think we are safe.

2011

Table A52-F1, ET101:2008 is for multi-core Cu/PVC cables. Continuous current carrying capacity of a 6 sq. T&E is 34 amps with an ambient temperature of 30DegC, method of installation A1 (cable direct in insulation).
For a 10 sq. it is 46 amps.

So if the load is up to 9.5kW and the cable is a 10sq. T&E installed directly in insulation at an ambient temperature up to 30DegC the cable can withstand the load for hours on end and comply with the regulations (in terms of current carrying capacity). In reality an instantanious shower such as a Triton T90 that is rated at 9.5kW is only 8.8kW at 230VAC as illustrated on page 4 of this link. Therefore it only draws 38 amps.

Most instantaneous showers in Ireland are rated at 8.5kW which at 230VAC is only 7.9kW (34.3 amps).

It is important to note that the tables in the regulations provide very conservative values. Also 30DegC is a very high ambient temperature, higher than most attics in Ireland and that is what the values in the table are based on.

Cycling Dumbasses

2011 wrote: »

Table A52-F1, ET101:2008 is for multi-core Cu/PVC cables. Continuous current carrying capacity of a 6 sq. T&E is 34 amps with an ambient temperature of 30DegC, method of installation A1 (cable direct in insulation).
For a 10 sq. it is 46 amps.

So if the load is up to 9.5kW and the cable is a 10sq. T&E installed directly in insulation at an ambient temperature up to 30DegC the cable can withstand the load for hours on end and comply with the regulations (in terms of current carrying capacity). In reality an instantanious shower such as a Triton T90 that is rated at 9.5kW is only 8.8kW at 230VAC as illustrated on page 4 of this link. Therefore it only draws 38 amps.

Most instantaneous showers in Ireland are rated at 8.5kW which at 230VAC is only 7.9kW (34.3 amps).

It is important to note that the tables in the regulations provide very conservative values. Also 30DegC is a very high ambient temperature, higher than most attics in Ireland and that is what the values in the table are based on.

Again one is assuming the OP has his shower installation wired in 6sq or 10sq but i have seen several installations where 4sq has been used and in 3 cases i have seen 2.5sq used, and one assuming the electric shower is 8.5kw whereas it could be 10.8kw and it could be wired in 4sq or 2.5sq, but is this relevant?
I dont think so whats relevant is there is that there is a ETCI publication ET 207 : 2003 and it gives guidelines and information to deal with the OP first post, if people have issues with this publication then they should debate or contest it with the regulatory body that issued the publication.
I am not disagreeing with any ones statements made in this thread, i feel i have provided relevant information to the OP, i will not debate what the capabilities of what the OP installation is as i dont know it and dont need to know as its irrelevant.

2011

Cycling Dumbasses wrote: »

Again one is assuming the OP has his shower installation wired in 6sq or 10sq

Read my post carefully.
I am not assuming anything.

I just gave examples of current carrying capacity for the 2 most common sizes of cables used for instantaneous showers when the cables they are "installed directly in insulation". To back this up I showed exactly where the information came from.

tomdempsey200

Cycling Dumbasses wrote: »

Again one is assuming the OP has his shower installation wired in 6sq or 10sq but i have seen several installations where 4sq has been used and in 3 cases i have seen 2.5sq used, and one assuming the electric shower is 8.5kw whereas it could be 10.8kw and it could be wired in 4sq or 2.5sq, but is this relevant?
I dont think so whats relevant is there is that there is a ETCI publication ET 207 : 2003 and it gives guidelines and information to deal with the OP first post, if people have issues with this publication then they should debate or contest it with the regulatory body that issued the publication.
I am not disagreeing with any ones statements made in this thread, i feel i have provided relevant information to the OP, i will not debate what the capabilities of what the OP installation is as i dont know it and dont need to know as its irrelevant.

2.5 and 4sq cable and 230v/10.8kw showers would be at the extreme end

i'm not sure that there's any calculation in et 101 for attic insulation

apart from the general good advise that cables should be laid above it

Payton

Job done guys and I have it battend to the wall roughly 6 inches above the insulation. Sorry if I started a "heated" no pun :-) debate.

Cycling Dumbasses

Payton wrote: »

Job done guys and I have it battend to the wall roughly 6 inches above the insulation. Sorry if I started a "heated" no pun :-) debate.

I presume your house is much warmer now assuming you installed the insulation correctly.

2011

tomdempsey200 wrote: »

i'm not sure that there's any calculation in et 101 for attic insulation

As explained here the cables can be derated for this using table A52-F1, ET101:2008.

Payton

Yep so far so good. I used 200mm earth wool on top and at right angle of the 100mm yellow stuff that was already there, all that is required is a couple of shelves for the Xmas decorations and a couple of suit cases.

Bruthal

Cycling Dumbasses wrote: »

Again one is assuming the OP has his shower installation wired in 6sq or 10sq but i have seen several installations where 4sq has been used and in 3 cases i have seen 2.5sq used,

Yes, the solution to a shower wired in 2.5 is to run the cable above the insulation:pac:

tomdempsey200

2011 wrote: »

As explained here the cables can be derated for this using table A52-F1, ET101:2008.

ya? i'll check tomorrow when i sober up ..thought that was for cables in thermally insulated wall

2011

tomdempsey200 wrote: »

ya? i'll check tomorrow when i sober up ..thought that was for cables in thermally insulated wall

You are correct, it is. But I doubt the cable will know if it is an attic or a wall that is thermally insulated

Crazy Eye

whats the story with cables lying optop of existing attic insulation and then fitting xtratherm insulated loft boards for extra insulation and walking storage space ?

tomdempsey200

2011 wrote: »

You are correct, it is. But I doubt the cable will know if it is an attic or a wall that is thermally insulated

http://www.voltimum.es/files/gb/others/3/2005100479087614Summer05_EQ.03-10-05.pdf
excellent document on attic insulation and cables

your figure of 34amps for 6sq is about right

but notice how the capacity drops sharply for cables on top of joist when extra insulation is applied but little difference for cables at bottom of joist
an important point!


points 1 and 2 in article..point 1 backs up your statement that the capacity for cables buried in thermally insulated wall can be used as a guide


ambient temp of 30 degrees? wonder if that would apply in a hot summer

excellent graphs also in the document

cerastes

Payton wrote: »

True but at €21 per roll for 200mm thick of knuaf insulation I had to avail of it :-)

Where did you get your rolls, its a job I need to do really and I think one of the cheapest quickest ways to improve insulation and possible as a DIY solution too.
whats the length in the rolls you got? any U/R values.

Glad someone started this thread as I was thinking about my lighting wiring, as its laid with no room to move it at all, its practically pinned down to the beams tight the way its been put in, minimum usage I suppose.
Reading so far, it seems I might not have any problem with the current carrying capacity of the light wiring, or even the shower wire, which I think is at least 6mmSQ, maybe even 10 square.

Im just off to read the pdf few posts back, whats de-rating the cables mean? I copped what it is, if Im correct Id say its other additional factors that mean the actual current carrying capacity a cable might be able to carry would have to be reduced.

Ok, the pdf article, suggests cables carrying higher loads may have to be increased in size, but table 1 suggests the time (is it in minutes? I assume so, but cant see where it says what time unit its in) if thats the time to reach 63.2% of the max temp reached. If thats meaning the cable is within the operating temp tolerance of the cable? if so then that seems ample time to use a shower as an example.
Looks like I could work away and lay insulation over my wiring, without a concern or even having to consider upgrading the wiring, to a larger size.
I had thought it might be necessary and as simple to get the accessible light wiring upstairs increased to the next size up, presumably 2.5 square, from this pdf, looks like it wouldnt be necessary.

Payton

Smith's builders providers on the greenhills road walkinstown Dublin, I have an average semi detached and it took roughly 7.5 rolls and each roll is just under 6m in length (Knuaf Eko earthwool 200mm). Just clear out everything and start with a blank canvas. The R value of each roll is 4.5 and looking at a couple of sites with the 100mm plus the 200mm earth wool the total R value is just above 7

cerastes

tomdempsey200 wrote: »

http://www.voltimum.es/files/gb/others/3/2005100479087614Summer05_EQ.03-10-05.pdf
excellent document on attic insulation and cables

your figure of 34amps for 6sq is about right

but notice how the capacity drops sharply for cables on top of joist when extra insulation is applied but little difference for cables at bottom of joist
an important point!


points 1 and 2 in article..point 1 backs up your statement that the capacity for cables buried in thermally insulated wall can be used as a guide


ambient temp of 30 degrees? wonder if that would apply in a hot summer

excellent graphs also in the document

is table one minutes to reach 63.2%?

tomdempsey200

I wouldn't worry about time graphs
they're not part of calculations for cables here

Cycling Dumbasses

Bruthal wrote: »

Yes, the solution to a shower wired in 2.5 is to run the cable above the insulation:pac:

Are you saying that i imply this? You have a quote from me in that post so please clear this up as i did not mention this.

Bruthal

Cycling Dumbasses wrote: »

Are you saying that i imply this? You have a quote from me in that post so please clear this up as i did not mention this.

I think trying to clear anything up is pointless.

Cycling Dumbasses

Bruthal wrote: »

I think trying to clear anything up is pointless.

Its not pointless to me, you have a quote included in that post and i want you to explain it and clear the matter up please.