Conduit Sizing & Placement

Reply

  #1  
Old 02-02-08, 08:57 PM
Member
Thread Starter
Join Date: Jun 2003
Location: NY
Posts: 32
Conduit Sizing & Placement

I'm remodeling my kitchen and need to replace the circuits for my separate oven and stove. I'd like to use some leftover red, white and black #6 wire and #8 green wire from an earlier project.

Despite the effort involved, I'm tempted to run Schd 40 PVC conduit to separate junction boxes for the oven and stove.

1) Can the two circuits (8 wires total) be run in a common conduit to the point they would need to separate? If so, what size conduit would that need to be? Also, what size conduit do I need from where the bundles split to the junction boxes?

2) I suspect the oven and stove will come with an attached 4 wire segment of armored cable. Provided there are 4 wires inside, is there any issue with my running that cable into my PVC junction box?

3) I assume that it is ok to run my Schd 40 PVC conduit on the bottom of the floor joists? However, there are a couple places where I'll need to go up into the floor joists (drilling holes to get through) to get around obstructions. Assuming I'm willing to expend the effort to run the Schd 40 PVC there (heat bending, cutting and gluing as necessary) is there any reason I can't run Schd 40 PVC conduit through the floor joists?

Thank you very much for the help.

Mark
 
Sponsored Links
  #2  
Old 02-03-08, 10:10 AM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
Multiple circuits can be placed in the same conduit, however there are specific requirements that you must meet.

1) You would have 4 'current carrying conductors', which means that you must derate the ampacity of the conductors. This means using a smaller breaker than usual for that size of wire.

2) You can share a single properly sized equipment grounding conductors between both circuits.

3) You can find conduit fill calculators on the web; it won't hurt to use a conduit that is larger than the minimum.

4) Generally, flexible metallic tubing needs to be run to a metallic junction box. You can run your PVC to a suitable threaded coupler to a metallic junction box, and be kosher as long as you land the ground on that junction box.

5) Given the size of the conductors being run, you will need a large junction box. Search for 'box fill calculations'.

6) There is no electrical problem with running conduit through floor joists, however drilling large holes can be a structural problem. I don't know enough to assist on that point.

7) Depending upon the ratings of oven and stove, they may be able to share a single circuit.

8) Remember that a conduit system must be complete between 'pull points' before pulling the conductors in.

-Jon
 
  #3  
Old 02-03-08, 10:28 AM
Member
Thread Starter
Join Date: Jun 2003
Location: NY
Posts: 32
Thanks Jon,

Two more things if I may?

1) I was just looking in the panel at the circuits I'll be replacing and have found that they're run with aluminum wiring. Since I'll be running copper should I assume that I need to replace the breakers?

2) I was hoping to run conduit along much of the path of the existing wiring and have found one set of joists with sheet metal on the bottom that is used as a cold air return. The existing wire runs through those joists within the enclosed area. Can I run my PVC conduit through there as well?

Thanks again,

Mark
 
  #4  
Old 02-03-08, 11:29 AM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
1) You have to use a breaker with terminals rated for the conductors. Most breakers are dual rated for copper and aluminium, so you shouldn't have a problem. It is very unlikely that you will find a breaker rated for aluminium only, but I suppose it is possible.

2) I don't know the rules for running conductors through air return ducts, so you will need to get that answer from someone else.

3) If you use copper in place of aluminium, smaller conductors can safely carry the same current. What are the ratings of your oven and cooktop? Ideally look at the data plates, which should report the KW rating, the voltage rating, and possibly the maximum breaker size.

-Jon
 
  #5  
Old 02-03-08, 01:44 PM
Member
Join Date: Aug 2001
Location: owego, new york
Posts: 110
I don't beleive you can run Pvc in a plenum. I know you can't in a commercial building, not sure about residential.If it burns it is toxic and if it is in a plenum it will spread the toxins.
You should have a "means of disconnect" some way to turn off the appliances within sight of the appliance, Either an outlet/cord and plug or a switch rated for the appliance
 
  #6  
Old 02-04-08, 06:05 PM
Member
Thread Starter
Join Date: Jun 2003
Location: NY
Posts: 32
The specs on the built-in double oven say it requires a separate 40amp, 240V circuit. The cooktop says it requires a 50amp, 240V circuit.

My 200amp service splits to two 100amp panels, one of which services the kitchen and adjacent areas. Given the other appliances in the kitchen (refrigerator, dishwasher, toaster, microwave, etc.) and the requirements of the two items above, is there an easy way to determine if I'm likely to be exceeding the 100 amps? Am I right in thinking that if it does exceed the 100 amp capacity it's just going to trip the breaker and I can then make the decision to either not run everything at once or upgrade the service?

As to one of my earlier questions, if I'm reading 300.22(B) correctly, by omission it prevents me from running the PVC conduit through the cold air return. I'm tempted to sleeve a hole through the return with an oversized RMC section and run the PVC conduit through it.

Finally, do I really need a "means of disconnect" for a built-in wall oven? I suppose I could put an appliance outlet and cord in there but I've never seen built-in appliances hooked up in anything other than a junction box?

Thanks again for the help...

Mark
 
  #7  
Old 02-05-08, 09:38 AM
Member
Join Date: Aug 2001
Location: owego, new york
Posts: 110
After checking the code,I don't beleive that a means of disconnect is required. If the unit has an on off switch and it is a one family home. Sorry!
What is the wattage of both units?
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes