Replies

1. 
   rjw | Jul 25, 2003 11:26am | #1

   Nope, nor under the mechanical codes.

   Another question: does it make any real life difference?

   _______________________

   10 .... I have laid the foundation like an expert builder. Now others are building on it. But whoever is building on this foundation must be very careful.

   11 For no one can lay any other foundation than the one we already have--Jesus Christ.

   1 Corinthians 3:10-11

1. 
   SageSwiger | Jul 25, 2003 02:15pm | #2

   I guess it would only be an issue if I want to have more electrical work done that has to be inspected.  It could be found at that time and be required to be changed with a penalty to be paid.  Florida seems to require permits and inspections for anything you want to do in a condo. 

   Thom

2. 
   CPopejoy | Jul 25, 2003 11:02pm | #3

   Thom,

   I assume you mean that the cable is run inside the duct for some distance, not just crosswise through the duct.  Using an air duct as a cable path is not allowed for a couple of good reasons, the main one being that if there's an electrical problem and the wires overheat, the insulation could burn.  That would release a lot of very toxic smoke.  Not exactly something you want in your air handling system.

   Also, if the metal clad cable is not properly grounded, and there's a fault, it could energize the ductwork.  And that could cause a fire under certain curcumstances.

   I'd be concerned about the electrical system in the whole house.  Often there isn't just one dangerously wrong change or addition to the wiring; an ingnorant or stupid person rarely makes only one modification.  For instance, I'd check the added circuit to see if it is correctly wired (polarity), especially that it has a properly connected equipment grounding conductor.  Also, that the metallic cable is connected to steel boxes, using the right kind of fittings.  Consider getting a qualified electrician to check the system.  And use his report to go after the previous owner.

   Good luck,

   Cliff 

1. 
   SageSwiger | Jul 25, 2003 11:36pm | #4

   Hello Cliff,

   Thanks for your through and thoughtful reply.  I agree with the issues you raise and will get it corrected.

   Thom

1. 
   CstlEng | Oct 26, 2003 06:14pm | #5

   I beleive this is covered in the NEC under paragraph 300-22 "Wiring in ducts, plenums, and other air handeling spaces" in subparagraph (b) "Ducts or plenums used for environmental air." 

    It is a long paragraph with some restrictions on things but the first sentence reads: "Only wiring methods consisting of Type MI cable, type MC cable employing a smooth or corrugated impervious metal sheath without an overall nonmetalic covering, electrical metallic tubing, flexible metalic tubing, intermediate metal conduit, or rigid metal conduit shall be installed in ducts or plenums specifically designed for the transport of environmental air." 

   I beleive that in contrast to the earlier respondents to this thread, you are meeting code, unless NEC has changed this specific part since 1996, the year of the copy of NEC i am quoting from.  Your local authority may be more stringent, I do not know if, for example, this would be acceptable in NYC. 

3. 
   Puff | Oct 29, 2003 10:19pm | #6

   Ditto to "CstlEng"'s message!!!

   I was just 'stabbed in the eye' by one reply to your question published in the Annual Kitchen & Baths issue (page 40). The reply is _not_ consistent with the 2002 National Electrical Code.

   A caveat is whether Thom's 'condominium' unit comes under 'residential' or 'commercial' codes. A rule of thumb that it is residential is if he has a circuit breaker panel located in his unit and if the plenum air begins and ends in his unit. 'Condominium' is a legal term; not an engineering term so the actual nature of his 'residence' may have some bearing under the permitting authority as to whether or not it is 'allowed'.

   NEC Article 300, paragraph 22, gives advice on conductors in ducts or plenums. Be advised the NEC is "advice", so, as your permitting authority adopts the code, your local authority may permit materials or techniques not in the code and vice versa. Also, lawful installations under previous versions of the code are generally considered "grandfathered". So you may find something in your house that was previously permitted but which may no longer be permitted in _new_ installations. (Or even something your inspectors may allow during remodeling that wouldn't be allowed in new construction).

   Funny story (potentially hair raising?)... I was replacing a wall outlet in the tony Georgetown (District of Columbia) apartment of my girlfriend back in the 1990's. To my surprise, the old outlet was not in a splice box (!!!) and the receptacle yoke itself, was dated 1915 (!!!). The building was built before the 'days of electricity' so when electricity came along they just dug a hole in the shoe moulding for the outlet and pulled in wiring! All perfectly legal (in 1915) and <gulp!> technically 'up to code' (in 2003)! I still cringe when I think of those apartment dwellers (still) in ignorant bliss in that building and reflect how we would publicly 'lynch' any contractor who would so much as suggest such an installation today! <shrug>

   As to the 'reasons' expressed in the published reply... a lot of things produce toxic smoke when they oxidize and are of general concern. _Ideally_, nothing should be added to air ducts or plenums except air, but sometimes there is no other practical way to wire when in remodeling mode and the code forsees this. Wiring in particular does not present any more of a philosophical concern whether it is burning inside the plenum or outside (the code allows conductors to be exposed to the air in unfinished rooms, for example)-- best not to dwell on this but rather, when you, or, your sensors detect smoke, don't try to maintain normal respiration but rather -- get the H*LL OUT!!!

   As for the notion of accidentally energizing your HVAC system or a portion of it, this also is of _general_ concern. In practice, a simple NM (non-metallic sheathed cable, aka 'ROMEX') conductor lying across a metal duct in your ceiling could accidentally energize your HVAC system or a portion of it. If you don't think contractors do this all the time... (I've got a bridge you might like to buy!!!). But this is one reason why the current code requires that the cables _in_ ducts and plenums be type MC or MI (or in various types of conduit protection) -- suitabley grounded. With all the non-conducting materials used these days in plumbing and HVAC, it can be tough or impossible to get complete continuity all the way back to ground. Anything made of metal in your house could get energized by some fluke and send you to that big electric utility in the sky (even Ground Fault Interupters can be fooled!).

   There is just no end to the aspects of your house that can potentially kill you. A death trap from 1915 might never kill anyone and a house built a couple of years ago and inspected 'three ways to Sunday' might come within a hair's breadth of taking an entire family...

   Another true story: A new house of a nearby neighbor recently burned up and almost took their neighbor's house with it. The word on the street was that 'surges' caused the circuit breaker box to blow up (and miraculously spared everybody elses house on that transformer, ...right!). I have no idea who started this rumor nor what the 'official' reason for the cause is, but, I'm willing to bet that the offical cause will never be found <wink>. Early on the scene of the confligration, I noticed that the meter box was attached to the circuit breaker box in the garage via a 'drip loop'. Putty was slapped around the cable where it pierced the vinyl siding. These precautions might be okay for a cable supplying an airconditioner compressor outside but it stands to reason that if the meter box is higher on the outside wall than the circuit breaker box is on the inside wall, then moisture is going to get into the circuit breaker box, and, when the alluminum conductor in the SER cable oxidizes enough... fireworks!!! NEC specifies a direct internal connection whenever possible and a connection impervious to water otherwise. The building inspectors signed off on a whole slew of houses (maybe 60 built at the same time) where the house was connected to meter boxes via these silly drip loops. ...Nope... no cause will ever be found here -- obviously 'God's fault'!

   The reply's advice that, "...when in doubt, check it out", is still _good_ and applicable here. First, you could request a visit from your local building inspector (you already paid for him/her with your tax dollars, but, like all government, they are there to _help_ you so they may be too busy 'helping you' to help you). If the building inspector (shows up, and,) gives you a thumbs down or otherwise unsatifactory answer, you could then call in the 'hired guns' ($$$$$ <sniff, sniff>...that's the smell of your credit card bursting into flames).

   A note of caution with the permitting office (building inspectors) I wouldn't make a lot of assertions as to 'who' installed the circuit in the first place (it may have been installed by a licensed electrician who did or didn't 'pull' a permit). It may be true that you have recourse to the pocket book of the former owner but, as a practical matter, he is probably in proverbial 'Brazil'. If the permitting authorities want to get _ugly_, they will get ugly with _YOU_!!! _Not_ the former owner. Hmmmm...(you think?) maybe best not to open that can of worms! All you should care about at this point (if you still have any doubts) is if the installion was performed in a 'professional' manner and if it is still 'safe'.

   ...And SMILE! Things could be WORSE! You could live in a 'historic' building in the District of Columbia!!!

   With sincerest empathy,

   PUFF

   (WARNING: I am not a licensed electrician or attorney!)

1. 
   CPopejoy | Oct 30, 2003 08:17am | #7

   Cstleng & PUFF--

   The original post states that "armored cable with 3 wires" was run through the duct.

   To me, that means AC cable.  And as Cstleng's post summarizing the NEC points out, AC cable is not one of the wiring methods allowed in 300.22.

   Cliff

1. 
   CstlEng | Nov 04, 2003 12:44am | #8

   "The original post states that "armored cable with 3 wires" was run through the duct.

   To me, that means AC cable. "

   To me it meant MC.  Guess we have to see just what size and construction that 3rd conductor is.