Home Wiring Question

You might want to check out mineral insulated (MI or MICC) cable. It can be directly embedded near the surface of concrete and has very good current carrying capacity. I think MI cable for a 15 amp circuit is about 1/4" in diameter so a 3/8" x 3/8" cut would be sufficient. As always you need to check with the AHJ before using exotic materials.

This is a specialty item and fairly expensive.

has a price quote form and it might be worth the extra cable expense if you can make a small trench that does not tear up the floor.

And what does an electrician, licensed to practice in your state, have to say? What does the planning office say to the plans you've submitted? Both are necessary if you ever expect your insurance to cover loss in the event the wiring sets the house on fire.

Bill,

That is not necessarily true. Insurance policies are to protect you from mistakes that cause fire, regardless if they're your own amateur mistakes or professional mistakes. Some insurance policies *might* require that all work be performed by a licensed tradesman but most don't (I've checked quite a few).

Needless to say, that doesn't mean you should just do "whatever" without regard for code and common sense. But anyone wishing to do his own work can do so in almost every jurisdiction and still get approval from the AHJ (inspector). I've been working with DIYers for many years. Many do their own electrical work as well as alarms, home automation systems, CCTV and whole-house entertainment systems. It is extremely rare that we hear of an inspector giving grief solely because the work is being done by a DIYer. They want the work done in accordance with code but a little reading, a dab of common sense and a bit of help from someone with knowledge of the trades involved will usually suffice.

And I know your "knowledge of the trade" and NEC is without equal.

This is why you pay for an inspector to inspect your wiring.

"Frank Ols>

Heh... right... Explain that to the thousands of people involved in the "Leaky Condo" debacle in Vancouver... Their buildings "passed inspection" too.

Point well taken.

I am trying to decide between doing a floor outlet(s) vice ceiling pendants to satisfy SWMBO desire for end table lighting in what is becoming the home theater. I can cost the latter, but was not sure what the former would require.

I get homeowner permits for electrical work and get it inspected so there is no insurance issue, go to the planning office next week for it, one way or the other. Its also part of a much larger project. With such a permit an electricians license is not required.

The NEC is not rocket science, but there was nothing I could find WRT to this kind of work, thus the post.

Although NEC doesn't help as much as one might hope, it isn't totally silent on the subject. The following is quoted from the 2002 NFPA 70 (NEC):

"300.6 Protection Against Corrosion. Metal raceways, cable trays, cablebus, auxiliary gutters, cable armor, boxes, cable sheathing, cabinets, elbows, couplings, fittings, supports, and support hardware shall be of materials suitable for the environment in which they are to be installed."

"(A) General. Ferrous raceways, cable trays, cablebus, auxiliary gutters, cable armor, boxes, cable sheathing, cabinets, metal elbows, couplings, fittings, supports, and support hardware shall be suitably protected against corrosion inside and outside (except threads at joints) by a coating of approved corrosion-resistant material such as zinc, cadmium, or enamel. Where protected from corrosion solely by enamel, they shall not be used outdoors or in wet locations as described in 300.6(C). Where boxes or cabinets have an approved system of organic coatings and are marked ?Raintight,? ?Rainproof,? or ?Outdoor Type,? they shall be permitted outdoors. Where corrosion protection is necessary and the conduit is threaded in the field, the threads shall be coated with an approved electrically conductive, corrosion-resistant compound."

"(B) In Concrete or in Direct Contact with the Earth. Ferrous or nonferrous metal raceways, cable armor, boxes, cable sheathing, cabinets, elbows, couplings, fittings, supports, and support hardware shall be permitted to be installed in concrete or in direct contact with the earth, or in areas subject to severe corrosive influences where made of material judged suitable for the condition, or where provided with corrosion protection approved for the condition."

See also:

"ARTICLE 342 ?INTERMEDIATE METAL CONDUIT: TYPE IMC"

"342.1 Scope. This article covers the use, installation, and construction specifications for intermediate metal conduit (IMC) and associated fittings."

"342.10 Uses Permitted."

"(B) Corrosion Environments. IMC, elbows, couplings, and fittings shall be permitted to be installed in concrete, in direct contact with the earth, or in areas subject to severe corrosive influences where protected by corrosion protection and judged suitable for the condition."

"342.42 Couplings and Connectors."

"(A) Threadless. Threadless couplings and connectors used with conduit shall be made tight. Where buried in masonry or concrete, they shall be the concretetight type. Where installed in wet locations, they shall be the raintight type. Threadless couplings and connectors shall not be used on threaded conduit ends unless listed for the purpose."

I've done exactly what you're wanting to do, except we planned it before the floor was poured so we laid the conduit first. The job was in my old church. The pastor wanted floor outlets at his desk for 110VAC, LAN and phones. We laid 2 separate runs of RNC and attached the boxes ~1/4" below finished floor height, then left pull cables in each one. We affixed blank covers so cement wouldn't get inside the boxes. When all was done we pulled the cables, attched brass finish plates and tested everything. There was no problem with the inspector or the insurance company (though the latter wasn't actually tested since we didn't have a fire... yet :)).

I've not yet had to retrofit power cable in a cement floor so I'd just ask the AHJ how deep he wants the conduit. You can rent a diamond-edged saw and a rotary hammer for a day to make the kerf.

Avoid cutting right through the slab. Do that and the two sides will move later and crack the new tiles. If possible consider laying the new tiles on an isolating membrain anyway.

Definitely don't want plated metal (except hot galv) pipe in contact with the concrete and plastic pipe needs expansion provisions on long runs.

snipped-for-privacy@yahoogroups.com

I understand the NEC. I have no idea if snipped-for-privacy@nospam.nospam knows what he is talking about when he says "Code requires conduit in concrete". My point is that MI cable is quite small and can be put into masonry without having to remove as much material as required by other products.

The relevant part of the NEC is:

330-3 Uses Permitted. Type MI cable shall be permitted as follows:

(6) Embedded in plaster, concrete, fill or other masonry, whether above or below grade.

Look it up. It is cool stuff.

When I suggested that you might have better things to do with your time a sudden interest in wiring methods did not spring to mind...

A more correct rendering of this would be: "What part of code requires conduit in concrete?"

I have the NEC and it doesn't *require* conduit. The code permits certain types of conduit and certain types of cable. It disallows certain types as well. But it does not *require* conduit.

To further that argument, what if we have concrete conduit as in ducted flooring slabs, the perfect conduit.

It will have to be protected when enter>>

Not having run across them I'd only be guessing but it doesn't seem particularly ideal.