Kitchen Island Wiring

Discussion in 'Electrical Forum discussion & Blog' started by swaimm, Jun 25, 2013.

  1. swaimm

    swaimm New Member

    Messages:
    3
    Location:
    Houston, TX
    25 year old cooktop currently installed on my kitchen island is a Jenn-Aire Downdraft. The wiring is 10 ga. The island has no outlets. So, I've been trying to come up with a wiring solution for a new cooktop and outlets. It's a two story house and running a column down to the island isn't a good solution. My plan is to install an overhead range hood and then use the old downdraft duct to run wires to the island. Any problems with this solution? Any special cables that I need to use? Any secrets to attaching conduit to the side of the old pvc pipe? The old downdraft duct is pvc pipe (6" or 8") which goes down through the slab, over to the side of the house and then up just outside the house. It has a vented cap a few feet above ground. I was thinking of capping it at the ground and connecting new underground pvc to the side (24" deep).
  2. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Hold on.

    HOW is the cook top wired? Is it some sort of NonMetalic? Is it some sort of armored cable?

    Or is it conductors in (hopefully) 3/4" conduit of some sort?

    The island would be adequately served by one 20 amp circuit.

    I don't know if your new cooktop is going to be happy with only a 30 amp circuit, although I have never seen one that was not.

    If you have conduit with individual conductors in it, you have no problems. Two hots at 10 ga for the cooktop. Don't know if it needs a neutral, but that would be 10 ga as well.

    Nowadays we only allow metal conduit to serve as a ground path for a 20 amp circuit. Larger than that and you need a ground wire. And you almost certainly will be required to use a 10 ga. But you should check with your local inspector, he might be in a good mood and let you use 12 ga for the neutral and the ground.

    So all you need now are a 12 ga hot and a 12 ga neutral for the island outlets. The two circuits can certainly share the ground. Change the old wires if they are not THHN. And use green for the ground and white for the neutrals. Don't confuse which neutral is which, tape them to the corresponding hots in both the panel and where they enter the box under the cabinet.

    If, however, you cannot change the wire going into the island, do the simple thing:

    Reassign the 10 ga (assuming there is a neutral) to a very small sub panel mounted in the cabinet below the cook top.

    You can use one that has only two spaces (but is rated for four circuits), and buy a triplex breaker: a two pole 30 amp breaker in the middle and two single pole breakers on either side. You only use one of the 20 amp breakers.

    This is a Murray sample, although this one is for outdoors. I'd be astonished if they did not have just the same thing for indoors without the hub on top or a door.

    http://www.homedepot.com/p/Murray-6...02GS/202253181?N=1z122bnZ1z121pj#.UcqW4dhi0Zk

    Such a box is very small, barely larger than a 4" sq junction box.

    Continue to protect it at the main panel with a 30 amp breaker. You will need to be trying very hard to trip it.

    And do not connect the neutrals to the subpanel's chassis. The neutral and the ground should only be bonded in one place in the system: the main service panel.

    If that does not serve, let me know as I am pondering your original, somewhat convoluted question.
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,641
    Location:
    Cave Creek, Arizona
    wire

    If you think his question is convoluted, reread your answer. The wire to the island is probably a 10/3 w/g cable inside a conduit. Whether he could snake a pair of #12s thorough it is debatable. BUT, there is NO WAY he could "confuse" the neutrals since they will be different sizes. And I also doubt that they would require his outlet to be #10 wires as you intimate. If you can get the wires to the PVC "safely" then use metallic wiring from there to the island.
  4. swaimm

    swaimm New Member

    Messages:
    3
    Location:
    Houston, TX
    Sorry. I didn't mention that the new cooktop will be electric and require 6/2 with ground. The existing conduit is 1/2" and I think it comes up through the wall behind a cabinet. In any event, its hard to get to and much too small for 6/2. I hadn't thought of using a subpanel to feed the outlets. I guess I could run 6/3 w ground and add the subpanel. Yes, I can get the wires to the PVC safely. I would run underground conduit from the breaker box to the side of the pvc vent. If I use PVC coated MC cable, could I run the cable through the PVC vent and continue to use it as a vent?
  5. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    I'm NOT saying that his 20 amp counter circuit needs #10. Obviously that is #12. "So all you need now are a 12 ga hot and a 12 ga neutral for the island outlets." The cooktop needs #10, which he currently has.

    As I write, IF he has 3/4" conduit, things might go pretty easy. He should be able to fish in new #10 (four conductors) and two #12 (two conductors). He needs all the conductors to be thhn to avoid derating. And it is much easier in my experience to fish in all new rather than adding to existing. Pull out the old and start fresh.

    The only reason to lash the neutrals to their hots is if his inspector cuts him some slack and lets him use #12 for the cook top neutral and ground. Stranger things have happened.

    The alternate solution is to mount a sub panel in the cabinet (there likely being issues of the mandated access for panels, possibly he would need to cut the back of the panel out and have the box facing out.

    That makes use of the existing wire and permits the addition of a 20 amp circuit.

    I freely admit that I would not start down that path without getting a full OK from my inspector.
  6. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Oh, oh, oh.

    I have no idea if you could use a vent as a conduit, but I would be astonished if you could. That is a greasy environment, and I am sure that code and the inspector will not buy it. But don't quote me.

    The original 10 ga? Easy as pie. Change the breaker to 20 amp and use the 10 ga for your counter top circuit on the island. There is no reason that you cannot use wire larger than the rated circuit, if it happens to go where you want it.

    Happens all the time here in Los Angeles, where gas is commonly plumbed in, but lots of houses were set up with a 50 amp circuit for a stove. Just change the breaker and the outlet, and you have a circuit for the electronics of the new gas stove. No reason to pull out the conductors.

    Forget the subpanel.
  7. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    no! .
  8. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    He says the vent is large. 6" or 8". Assuming that were the case, and assuming that a 4" vent met code, could he fish a new, narrower vent (and assuming that it even could be done physically) and also fish his cable next to it?
  9. swaimm

    swaimm New Member

    Messages:
    3
    Location:
    Houston, TX
    The wife says that in spite of the additional work, she wants an overhead range hood. So, I will be using the existing duct only to run cable. Do I really need MC? Couldn't I use UF-B since its in a conduit all the way? Or, does the PVC duct not qualify as conduit? Perhaps I could use a variation of Homeowninburb's idea and run conduit inside of the duct.
  10. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Good about the overhead vent, that seems to me to be the only likely solution.

    You could use the UF-B, but it cannot be out in the open where it can be damaged, just as any non-metalic.

    You could run water-tight conduit down the vent, and fish conductors down that. 3/4" for 3 #6 conductors is workable. Definitely use lube. The conduit could come up with the vent on the side of the house, enter a water tight junction box, and then change over to non-flexible conduit of some sort that you could bury as it runs to the panel.

    And certainly consider using the existing 10 ga for your new outlets. No problem there. Is there a neutral? We are no longer permitted to use white tape to mark a black wire as a neutral (except for switch legs using nm) but I'm sure the inspector will let you slide on a thing like that. "It was the existing conductors and I just re-purposed them!"
  11. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    no! .
  12. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Huh.

    Could you elaborate? If he is not running cable in the vent, but rather next to it, where is the problem?
  13. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    (A) Ducts for Dust, Loose Stock, or Vapor Removal. No wiring systems of any type shall be installed in ducts used to transport dust, loose stock, or flammable vapors. No wiring system of any type shall be installed in any duct, or shaft containing only such ducts, used for vapor removal or for ventilation of commercial-type cooking equipment.
  14. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    So if one duct is "coaxial" with another duct, the inner one being that which actually carries the cooking vent fumes, no wiring can be carried in the outer duct parallel to the inner duct?

    I don't deny that is is news to me, but it certainly is the sort of arrangement that I would run past my local inspector before I even started measuring anything. I see it as being reasonable.

    Does this mean that if a duct is running up a stud cavity in a wall, that wiring cannot be in the same stud cavity?
  15. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    This is correct. We don’t want any grease that might leak out to be in the area of an electrical spark. Grease will compromise the insulation of conductors
  16. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Well, if your attitude is better safe than sorry, I can certainly go along with that.
  17. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,015
    Location:
    New England
    I wouldn't characterize it as 'his' attitude...it's what the code says. The code book doesn't elaborate WHY certain things are not allowed, only that they are...that is what jwelectric was relating. Over the years, lots of 'whatif' situations have come up and the codes get modified to account for them. Generally, the goal is to improve safety and avoid one of those 'whatif' situations.
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