I replaced my double wall oven this weekend. The wiring for the old oven came off the top of the oven in the back through a metal conduit and in to a junction box in the wall back behind the oven.

The new oven has the wires coming out of the bottom in a metal conduit and the instructions say to put the junction box below the oven. They are assuming there is a drawer or empty space below the oven. Makes sense, otherwise it will sit too low. (See page 2 of this PDF)

I had to go buy a longer conduit and run it up alongside the oven and over the top to the junction box.

Then I noticed that in the installation manual it says they use wire that has a higher heat rating on the shielding and a lower wire gauge. It says the current rating of wire isn't determined by the gauge alone, it is also determined by the heat rating of the shield. The service has to be #8, but the wire coming out of the oven is #10 with a higher heat tolerance on the individual wire shielding. I replaced it with #8, but with a lower heat rating.

Do you think I'll be ok with the #8 I ran inside the conduit going up alongside the oven, or should I take it back out and use the original wire and put it underneath? Anyone know how hot it actually gets back there? There's not enough room for me to get my hands in below it, so I'm going to have to take a long drill bit and hook it up in the joists below. I can access that from the basement.

Any thoughts appreciated. I checked on line and couldn't find any information on how hot it gets behind a wall oven.

Bub

As long as you have a clean unbroken run of #8 from the breaker to your outlet for the stove in the conduit, IMO should be fine.

If I recall correctly #8 is good for a 30amp circuit.  The Oven is set up for 20amp if it is wired with #10 indicating that the main line feeding the appliance wont get warm on ya.

If you can reach this spot from the basement Id just stab a fresh new circuit in thru the bottom directly to it as suggested in the install instructions.

NEC  Table 310-16 says   #10 COPPER THHN wire is good to 40 amps  THHN is rated 90 C or 194 F

I would however, if it was my house run #8 copper THHN which is good to 55amps @90C  Circuit breaker at 50a unless the range nameplate tells you otherwise

Aluminum is rated lower current for the same size wire. I would NOT use AL wire. Special connectors are required that are AL rated.... or they will burn up. 

Always opt for the higher temp rating on the insulation.  The cost difference is negligible compared with the lower temp rated insulation. 

Thanks guys. What I'm ultimately concerned about is, the temperature of the oven causing problems with the lower heat rated wire I installed. I can't decipher from the manual if the higher heat rated wire they used was to save on copper, or to protect from the oven itself.

Yeh I was way off, been too long

14 for 15 amp
12 for 20
10 for 30
8 etc...

Thanks Herb  

But back to my point LOL  I believe thats why they went with the larger on the main ckt feeding the appliance so heat would not an issue.

Bub


Thanks guys. What I'm ultimately concerned about is, the temperature of the oven causing problems with the lower heat rated wire I installed. I can't decipher from the manual if the higher heat rated wire they used was to save on copper, or to protect from the oven itself.

I agree... there is a derating factor to be applied with excess heat.. the advice to have the JB below the oven is clearly associated with this in mind....as is their choice of wiring guage..  if you need to run the conduit up behind the oven i would err on the safe side and have higher heat rated and higher guage. (its only a few feet so cost isnt an issue)

just wondering..

how is this a 'heating, ventilation and air conditioning' problem/issue?

Thats funny .... i was thinking in my head, which is in a flabberghasted state at the moment for reasons im not at liberty to say, high voltace a. c. as in alternating current.

high voltage a.c.


LOL
that's good, i'm gonna use that one with my engineer geek dudes...

Ask them about my oven wiring will ya.

:-)