Knauf Saver Value Triple Loft Insulation
200 mm x 1140 mm x 4825 mmNow £3 at B&Q
(1) Allowing adequate ventilation, of course.
Chris
Is there a fire risk due to overheated cables? I hear of that quite a lot here in the US, where old houses might be using ancient cables and carrying far more load than their electrical systems were originally designed for.
cheers
Jules
nah
we are much more advanced here in the uk
or we cannot afford to use that much electricity as to overload the wiring
You should see how much it costs here
UK regs are fairly good in that respect.
Each ring is fused to be relatively safe.
Tend to get more fires from shorted cables and rat or mouse damage to insulation.
UK loft (lighting) cables tend to be run against the ceiling or on the joist. Thus at least one side of the cable is against a thermally conductive material.
The problem, however, is when people have existing insulation (say
100mm) and cables run across the top of that, then add another 250mm of insulation on top. In that situation you do have cables "run through insulation >500mm" which as I recall requires 1.5mm cable if not higher temperature 6242BH (XLPE 90oC) 1.5mm cable due to the temperature derating.The bigger fire problem is / will be from downlights without adequate protection on the reverse. Admittedly few bedrooms will have such lights, but where they are used continuity of fire protection is important. UK does not tend to have heat alarms in the loft, and smoke alarms would false or fail pretty quickly anyway.
There is *some* risk and its generally better to avoid insulating over heavily loaded cables. (lighting circuits are fine since they cabling has plenty of spare capacity). The worst thing to do is to completely enclose a cable in insulation. One that for example is resting on a plasterboard (sheet rock) ceiling, or clipped to a joist is far better off since it can still cool from one side.
Its a situation that will be noticeably worse there as a result the use of 110V circuits. That means double the current, and hence four times the heating effect for the same load.
Add to that there is quite a bit of Ali cable in use which is prone to suffering from high resistance terminations, and the (in)famous quality of US wiring accessories in general; suggests it pays to take great care when insulating.
Yeah, I'm sure they are now - no different here in the US, really. But there's still an awful lot of old installations here that are using any old crap, and I'd assume that the UK is the same way.
I think that's part of the problem over here - radials (no rings here) using old wiring via the loft to sockets sometimes get left in place, even when people go adding more sockets to the system to cope with the need for lots of things plugged in these days. I suspect breakers sometimes get twiddled to be higher-capacity, too. It works, but puts a much bigger load on often-ratty old bits of cable.
I don't think there are many areas over here which don't have some form of electrical code - but of course that doesn't mean that people don't often ignore the regs and need for inspection, and just do whatever work they feel like. I'm sure that happens in the UK, too :-)
Whether anything can ever get hot enough below masses of insulation to actually cause a fire, though, I don't know - that might just be a spot of urban legend.
cheers
Jules
Indeed. It's surprising how warm things such as the cable for the vacuum cleaner get after it's been running for a while.
I'm not sure about that - I don't know how much alumin[i]um cable there is left, or how much there ever was. It's certainly been a problem, but I'm just not sure how widespread (and potentially a regional thing). I've seen wiring from various houses 1920s and newer around here, and they've all used copper.
No argument there. they're utter shit :-)
cheers
Jules
There can be a risk from concealed downlighters
I still find some 50 - 60 year old rubber insulated installs about - but they are getting rarer. Usually folks don't mess with those too much these days on the grounds that the cable is often so flaky the insulation falls off it the moment you touch it. Even relatively "brave" folks usually think better of reusing that!
Many of the appliances in use these days tend to be low power kit (kitchens excluded!) which helps a bit.
Probably happens everywhere. If you stick to one of the "standard" circuit designs, then there is usually enough latitude in them to allow for less than perfect installation. Also since we commonly use 7.2kw circuits for general purpose sockets, its actually quite hard to cobble together enough long term load to exceed that by any margin.
The most likely result is damage to the cable and reduced lifespan. Most household insulating materials won't actually ignite until they get to several hundred degrees C - and the cable insulation will be toast long before that (at which point a short is likely, and the breaker / RCD (GFCI) will hopefully of done its job!)
They can also be bad news in multi storey properties, not only from the fire risk caused by their overheating, but also from the fact that they pierce the ceiling, and hence create a path for the faster spread of fire. Fire retarding hoods are made for the things, but you rarely seem them used.
Well after phoning 3 of my local stores (Shropshire) they all have ZERO stock and none expected til tuesday at the earliest.
Tim.
We still have some in our place, actually. Previous owners rewired the 'easy' stuff (having a full basement means that getting to the wiring for the ground floor sockets, basement lighting, and things like the water heater and well pump was easy) but left ground floor lights, upstairs sockets + lighting.
Not sure why they didn't do the upstairs lights + sockets at least, because the wiring for that is all easily accessible via the loft. Getting to the downstais lights is going to be a sod though - I need to pull upstairs boards for that, I think.
True. Still a lot of CRT TVs about, though. And electric heat isn't that uncommon here (we have about 14kW, thankfully all on new wiring :-)
I think there's probably additional paranoia this side of the Pond due to having so many timber-framed houses. Typically external walls are tar- papered, and roofing is done with bitumen shingles, and that stuff burns
*really* well.We get a lot of bugs, too; when we moved in, I found the fusebox in the garage full to the gills with dead ladybirds. I'm not sure what the ignition temperature of a dessicated ladybird is ;-)
cheers
Jules
Mmmm. Timber houses, aluminium wiring and volunteer fire brigades. Yum.
:
Yes, and also a great deal of incredibly-old wiring. Nothing unusual to come across lots of knob-and-tube wiring from the 1920s and earlier still in common use and running very hot -- as does much US wiring -- due to the 110v supply. Actually, the knob-an-tube may be quite OK as long as it's in the open. Blanket it in loft insulation and you may have a very different story. Aluminum cable from the 1960s and 1970s used with the typical desperately-poor-quality US fittings not designed for it is a disaster area, especially bearing in mind that US receptacles (sockets) typically run very, very hot indeed.
The only aspect of UK domestic fittings which approaches the depths to which American receptacles descend is the typical, self-destructing, BC lampholder.
Ask "Jerry", he seems to know about electrical installations.
;-)
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Man at B&Q" saying something like:
I wouldn't want to live in any house he'd built.
Leave him alone, his ice-cream is triffic (i'm told) -
A few years ago I went to investigate a house where a couple of sockets were not working. I discovered that the immersion heater supply that was using
1.5mm T&E had been used to power two double sockets. Extra loft insulation had been added and the cable under the insulation had melted to cause a LE short. The maximum current for 1.5 T&E surrounded by insulation is 10A and this cable had really suffered as the house had no central heating, only fan and oil filled heaters.I am sure that many electric shower installations will also suffer in the same way due to badly installed loft installation.
Especially the ones wired in 2.5mm cable - not unusual according to Triton
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