Should house electrical cables be kept out of new thermal insulation
So I am thinking of insulating my attic.l have a slab foundation and all my
electrical runs through the attic.l know certain hot features (light
fixtures, transformers, etc) need a certain amount of clearance around
them so they can dissipate heat - that is in the electrical code.Do runs
of individual cable, runs of multiple cables (which have to be derated
just because they're near other cables) or junction boxes need to be kept
clear of insulation too?The derating business makes me think they need space to dissipate heat, but l can not find anything on the topic.Also, if they are on the house side of the summer heat (it easily reaches 140 up there) would not that be better anyway?
I wouldn't worry about the actual electrical cable touching the
insulation. If properly installed, electrical cable does not get hot to
start a fire. The Junction boxes are the same way, you can cover them,
just make sure they are accessable & the insulation can be easily pushed
aside if you need to get into them.
The only thing I would be worried about is if you have recessed lighting. There are 2 types of recessed lighting, one which can be completely covered in insulation, & others which have to have an air space around it. It usually says it right on the fixture if you can have insulation touching the fixture. If you got recessed lighting that cannot touch insulation, then its just a matter of determing how much clearence it requires & if ur laying fiberglass you can just not insulate that area, or if ur using blown in insulation, just build a little wooden box to go around each fixture to prevent the insulation from touching it. I don't have the specs infront of me, but if you go to home Depot look at the fixtures there & it should give you an idea of what you have to do.
i have to laugh occasionally, when i think about how the NEC
(National Electrical Code) has gotten folks so scared..Article 310 has
always stated the ampacities of wires.#12 guage copper, according to Code,
can handle 30 amps of current. (Article 310-16) although it stipulates that
#12 will be attached to no more than a 20 amp breaker or fuse.
Think of ur average bedroom in a house. 6 to 8 receptacles. per. room..max current load.1 clock radio.1 lamp. 1 television.potentially 5 amps on a set of wires meant to carry at least 30.Unless you have a factory in ur house, with the continuous load factor figured..no more than 80% load per circuit breaker.don't worry about it.your house is never gonna get hot enough, to affect the wires. keep the NEC rated clearances for the inductive loads..i.e. transformers,,,flourescent lites.Can lites need space to breathe, as they are resistive loads.both produce heat.give em room.. Continuous loads are a major factor with the NEC & NFPA.These are loads of three hours or more. i doubt that anyone on these boards has a continuous load.unless they are growing.something.. Keep ur cables as best as you can on top of the insulation.let everything breathe.and unless ur growing weed or making beef jerky, with lites.don't worry about the heat factor.remember.CONTINUOUS LOADS.
The insulation will not affect ur electrical wiring, even
around junction boxes. There is one area of concern, however. If you
have recessed can lighting, you need to determine whether they are
designed for contact or non-contact with insulation. If they're not
rated, & a re newer fixtures, they will automatically turn off when they
reach a certain heat limit. If they're really old, they might be a
hazard. But many of today is recessed cans are designed to be fully covered with insulation. If they're not, simply leave a space around the perimeter of each can & they will function safely & properly.
don't worry about it. the wires won't set your insulation on
fire.
You're right about recessed lighting needing to be kept a certain distance
from insulation, but they make a special type of can/recessed lighting to
keep that from being an issue.
You can not find anything on it because it isn't a problem. Very smart of you to ask, not enough people worry about fire safety when they remodel.
the insulation can go over the top of the cables
yes they do need to be derated if in or near thermal insulation
for the exact figures check the IEE wiring regulations
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