Originally Posted By: roconnor This post was automatically imported from our archived forum.
A dedicated circuit for an oven doesn’t appear to be required, and I dont see an issue as long as the equipment ratings match the feeder capacity. How are ya reading its a tricky issue?
– Robert O’Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: rmoore This post was automatically imported from our archived forum.
Jeff…
Can I assume that you would be using 6AWG(cu) conductors for that tap?
Manufacturers recommendations for circuit size for the cooktop would come first. After that I guess the total possible draw of both units comes into play. If the oven required a 50amp circuit in the first place I suspect that an additional range top would be "overcooking".
-- Richard Moore
Rest Assured Inspection Services
Seattle, WA
www.rainspect.com
Originally Posted By: jremas This post was automatically imported from our archived forum.
Bob Badger, you win the prize. A #12 wire may be tapped off of a 50amp circuit (#6 as an example) in this instance IF it meets 4 very specific criteria…
Yes, you WILL see this occasionally and YES, you will look like an idiot if you say it is wrong and it DOES meet code IF the 4 criteria are in place.
What are they?????
I have decided to start posing questions to which the official answers are known for the purposes of education for all of us, including me. I feel this will be better than having 3 different (opinions) answers to a question. I will be taking these questions directly from official NEC literature.
Is this fun or what? !!!
--
Jeff Remas
REMAS Inspections, Inc.
Northeastern PA & the Poconos
www.NEPAinspector.com
Originally Posted By: rmoore This post was automatically imported from our archived forum.
With my head hung in shame for my previous answer?let me try again.
Tap conductors must be at least 12AWG for a 50amp circuit (and not less than needed by the cooktop).
They should be no longer than necessary to serve the cooktop.
The oven and cooktop must be in the same room.
A disconnecting means is required unless the circuit breaker can be locked off.
The nameplate ratings of both are added together to determine demand load (table 220.19?still a fuzzy area for me)
Not sure if those are THE criteria you speak of.
Jeff?keep them coming?obviously I still need the education. 
-- Richard Moore
Rest Assured Inspection Services
Seattle, WA
www.rainspect.com
Originally Posted By: rmoore This post was automatically imported from our archived forum.
Bob…
This is what I'm reading...(slightly condensed)
"Tap conductors supplying ranges, ovens and cooktops from a 50-amp circuit shall have an ampacity of not less than 20 and shall be sufficient for the load served"
Doesn't that infer 12AWG at least?
Ahhhh... ...after a moments thought....14AWG can handle 20 amps can't it? I forgot about the asterisks. So it would be OK in this situation?
-- Richard Moore
Rest Assured Inspection Services
Seattle, WA
www.rainspect.com
Originally Posted By: Bob Badger This post was automatically imported from our archived forum.
David while I am comfortable with my understanding of taps defining one is not so easy.
In the most basic sense it is when you protect a conductor from overload after the run of conductor instead of before the conductor starts.
In this case leave the panel with 6 AWG copper from a 50 amp breaker, this is normal.
Now we get to the kitchen that has a wall mount oven and a counter mounted cook top.
The oven needs lets say 24 amps and the cook top 15 amps.
Run the 6 AWG copper into a suitable junction box and splice on a set of 10 AWGs to run the oven and a set of 14 AWGs to run the cook top.
These 10 and 14 AWGs are taps of the original circuit and can not be overloaded as each supplies a fixed load.
If a short or ground fault occurs the 10 or 14 AWGs are still sufficient to trip out the 50 amp breaker due to their short length and the fact the breaker will trip before the conductors will get hot enough to damage the insulation.
In a way the service conductors from the power company are transformer taps but we do not call them that.
Originally Posted By: rmoore This post was automatically imported from our archived forum.
Jeff…
Obviously the answer to your first question is yes.
As to the four criteria, I'm not sure what I'm missing from the 210.19(A)(3) exceptions other than the neutral size. So..I'm stumped.
As this is was posed for the sake of education would you give us the four criteria in English? Robert Oconnor's answer may be correct but the code numbers alone aren't going to help much in the field.
-- Richard Moore
Rest Assured Inspection Services
Seattle, WA
www.rainspect.com
Originally Posted By: Bob Badger This post was automatically imported from our archived forum.
Well directly in the exception I come up with 3
Exception No. 1: Tap conductors supplying electric ranges, wall-mounted electric ovens, and counter-mounted electric cooking units from a 50-ampere branch circuit
1)shall have an ampacity of not less than 20 and
2)shall be sufficient for the load to be served.
3)The taps shall not be longer than necessary for servicing the appliance.
The above is right from the NEC itself.
Now if we go to the NEC handbook they show four items.
It is worth noting that it is not an enforceable document, but still an excellent resource.
(1)The taps are not longer than necessary to service or permit access to the junction box.
(2)The taps to each unit are properly spliced.
(3)The junction box is adjacent to each unit.
(4)The taps are of sufficient size for the load to be served.
Number 2 is not a direct part of 210.19(A)(3) but of coarse applies to any splice. 110.14
RC
Quote:
where is the tricky part?
I think most people would be concerned with conductors smaller than 8 AWG protected by a 50 amp breaker.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
Bob Badger wrote:
I think most people would be concerned with conductors smaller than 8 AWG protected by a 50 amp breaker.
Okay, I see where that could go. So even though it's a short 20A minimum tap conductor run that should be able to trip the 50A breaker, it might be a concern even though it's allowed by the NEC? Do some electrical professionals question that exception and allowing that?
It's curious that I don't see the same exception in the IRC now that I looked, but that doesn't mean it's not allowed ... it just means ya have to look at the more detailed provisions of the NEC to do that [and pretty much "prove" it's okay] ... hmmmmm.
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: rmoore This post was automatically imported from our archived forum.
Quote:
I think most people would be concerned with conductors smaller than 8 AWG protected by a 50 amp breaker.
Yep...that was pretty much my initial "knee-jerk" reaction to Jeff's original question. I now know better, including the reasoning. I would like to thank all concerned for this excellent thread.
-- Richard Moore
Rest Assured Inspection Services
Seattle, WA
www.rainspect.com