You will most likely not be pulling the full load of the range. That is just the maximum if all is on at the same time. In addition, each burner will cycle off and on continually. Not to outguess your inspector, but 8-3 what is standard. Perhaps put it on a 40 amp breaker for inspection and only change it if needed. #6 only if it is a long run like over 100 feet.

 

I don't know what the NEC says, but that site is contradictory. In one chart is use 8/3 for 45 amps for ovens. In the chart below it, it says 8/3 has a 40 amp rating.

 

Most inspectors will follow the manufacturers guidelines. When you apply for the permit include a copy of the manufacturers instructions. Also write a brief note to the inspector asking what size circuit breaker to use. When you pick up the permit the inspector may have responded with a notation on the permit. If not, call the inspector for clarification.

It may be a situation where the maximum current draw is less than 40 amps, but in order to keep the total load draw at 80% of breaker capacity they recommend a 45 amp breaker. What is the maximum wattage of the cooktop?

I just did a Google search and found that there are 45 amp circuit breakers available. You probably won't find them in a home center. Check with an electrical supply company.

Double oven ranges usually get a 50 amp circuit.

 

Their documentation is confusing, its for both their 30" and 36" models... in one spot it refers to making sure your 40A breaker is off, in the other section it says "required on a dedicated double pole circuit breaker of at least 45 amps". It also says to use 8ga solid copper wire....

Interestingly, while most of the 8-3 wiring on Home Depots site says 40A, this particular one from Cerrowire says "Good for double oven up to 45A": https://www.homedepot.com/p/Cerrowire-75-ft-8-3-NM-B-Wire-147-4003B9/202206571

The 36 inch cooktop is 10800 watts @ 240V. The smaller cooktop is rated at 8400 watts.


In my city's permit checklist, I just noticed this after their amp / gauge guide:
Note: Conductors that supply motors, air-conditioning units, and other equipment may have overcurrent protection that exceeds the limitations in the above chart.

 

I found 45 amp breakers listed on Home depot and Lowes websites. I was surprised.

 

I wouldn’t take a Home Depot comment to heart. Could be a simple typo.
If it appeared on the Cerro wire packaging, I’d give it a bit more credence.

10,800w at 240v is 45amps. I’d go with the #6nm-b. If I wanted to pursue the #8, I’d talk with my AHJ.

What’s the make/model of this cooktop?
Looking at a 10,800w thermador, they recommend a 50a circuit.

The note about motors, a/c, etc, are items that have a large starting surge and quickly settle down to a lower running current. Using a larger breaker prevents the breaker from tripping with the starting surge. An induction cook top doesn’t fall into this category, AFAIK.

 

Its a Samsung, here is their URL: https://www.samsung.com/us/support/owners/product/induction-cooktop-nz36k7880

 

Would I be better off I pulled flex conduit through my basement ceiling and then pulled 8-AWG THHN conductors which are rated for 55 Amps?

 

Your circuit breaker won’t be 90C rated, so you can’t use the 90C column for conductor sizing.
Best you can do is 75C which would be 50 amps for #8.

That’s 5 amps less than the 55amp rating for #6 NM-B in the 60C column.

Don’t know what your wire prices are, but in my area four conductors of #8 THHN cost than $1+ per foot more the #6 romex, before you add in the extra cost of the conduit and fittings.

 

Alright, I guess I'll go with NM-B. I was thinking about how hard it will be to work with fishing those cables, they are pretty stiff...

Having done my own solar and geothermal wiring, I didn't think i'd spend this much time thinking this over

 

But to add to the confusion, when I go to Cerrowire and pull up this following chart: https://www.cerrowire.com/products/resources/tables-calculators/applications-charts/

They say 8/3 works on double-oven ranges up to 45A...

They say that 8/3 works on ranges up to 45A. Induction cooktops are sized according to load (nameplate)

Alright, I guess I'll go with NM-B. I was thinking about how hard it will be to work with fishing those cables, they are pretty stiff...

There is nothing stopping you (apart from a few $$) running #8 in conduit, if that's what you would rather work with.