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Old 09-23-2009, 09:39 AM   #1
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Help identifying 8/3 AWG NM-B vs 6/3 AWG NM-B


Hi,

I am getting a new kitchen range installed with specs that require a 50 amp dedicated circuit. My current kitchen range line is using a copper wire with 3 wires (black,red,white) + ground split off from the sheathing inside my breaker box. The breaker on the line right now is 40 amp which matches the maximum amperage my current range can take. However the 4-prong outlet my range cord plugs into on the other side of the line has 50 amp stamped on it, which makes the situation somewhat ambiguous. I have run across some discussion boards indicating that one can have a 50 amp outlet wired to a line that only supports 40 amps.

Unfortunately very little of the range line's outside sheathing is visible in my breaker box and none is visible at the other end. I am only able to make out what looks like a UL and NM-B without tearing out sheet rock around the breaker box. According to my best online research this indicates that I most likely have either a AWG 8/3 NM-B or a AWG 6/3 NM-B, both of which are possible configurations for the range line in modern construction.

My research also tells me that the 8/3 ampacity is only rated at 40 amp vs a 6/3 ampacity of 55 amp. Clearly I am hoping that I have a 6/3 line otherwise I am looking at a few hundred dollars to replace the line along with the hassle and mess of tearing out a lot of sheet rock to have an electrician do the job.

I was hoping someone on this board can help me determine which kind of line I have without having to tear out sheet rock around my breaker box. All my online research is frustrating because both lines are composed of red and black lines with 7 copper wires in a hexagonal configuration with identical sheathing diameter. It seems virtually impossible to my untrained eye to spot the difference between the two wires. Would it be possible to identify a difference by measuring the diameter of one of the copper strands in the red or black wire patched into the circuit breaker? I imagine an electrician might be able to tell the difference just by looking at the wire, but I would like to know asap without calling in an electrician and possibly wasting his time. Building inspectors familiar with code in my local area are not returning my calls, so I am posting here.

My house was built in NC in 2004 and it seems to me that electricians would want to wire a 6/3 range line since so many ranges today require 50 amp. As a side note, I notice now that almost all new construction nowadays uses the lower resistance RG-6 cable wire to support satellite television rather than the RG-11 of yesteryear. It seems to me that the same reasoning should apply to electrical wiring for today's demanding appliances. No?

Cheers.

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Old 09-23-2009, 09:44 AM   #2
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Help identifying 8/3 AWG NM-B vs 6/3 AWG NM-B


If you really can't see enough of the label on the sheath, go to the hardware store and get a 6" piece of #8 or #6. Compare sizes vs the known size.

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Old 09-23-2009, 09:44 AM   #3
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Help identifying 8/3 AWG NM-B vs 6/3 AWG NM-B


Most electric ranges will satisfactorily operate on a 40 Amp circuit, using the 50 Amp NEMA14-50R receptacle.

I would not worry about it at all, nor change a thing.
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Old 09-23-2009, 10:10 AM   #4
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Help identifying 8/3 AWG NM-B vs 6/3 AWG NM-B


Thanks for the reply. I have heard similar advice from a few others, albeit not experienced electrical contractors such as yourself.

The range model my wife and I want is an Electrolux EW30DF65GS which indicates the following relevant items in the specs:

Main Specs

Voltage Rating: 240V/60Hz/50A
Connected Load (kW Rating) @ 240 Volts: 4.4
Minimum Circuit Required (Amps): 50 Amps
Dedicated Circuit Required: Yes

Installation Page
• Electrical Requirements – 240 Volts AC, 4-wire, 60 Hertz, 50 Amps Dedicated Circuit
• Connected Load (kW Rating) @ 240 Volts = 4.4kW
• Amps @ 240 Volts = 18.3 Amps

It's actually a gas range (which I understand typically has lower electrical needs that an electric range), however it is dual fuel with a double oven, both of which are electric convection for more even heating. I suspect it is the fact that it has a double electric oven which is jacking up the power requirement. Of course I cannot expect a guarantee, but would you think given this limited info that we won't likely see problems with this range even keeping a 40 amp breaker on the current line?

Incidentally just to satisfy my voracious curiosity, would you know what the third bullet point means?

Amps @ 240 Volts = 18.3 Amps


Does this mean that a typical running amp requirement is 18.3? I'm just trying to understand the complexities here. It mentions a requirement for a 50 amp line, but then says Amps @ 240 Volts = 18.3 Amps.

Thanks again.

Last edited by metcalfjm; 09-23-2009 at 11:11 AM.
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Old 09-23-2009, 05:43 PM   #5
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Help identifying 8/3 AWG NM-B vs 6/3 AWG NM-B


Quote:
I would not worry about it at all, nor change a thing.
I concur.

#8 SE is good for 50A

#8 ThHN is good for 50A

For some reason, #8 NM is technically only good for 40A

Just leave the circuit and breaker as is.
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Old 09-24-2009, 07:01 AM   #6
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Help identifying 8/3 AWG NM-B vs 6/3 AWG NM-B


I can't for the life of me understand why they would spec a 50 Amp circuit when a circuit with half that ampacity would work just fine.

Considering this new information, I would leave it as is.

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