Why Range/stove require larger wire on 50 amp plug

[brother]

Was reading the instructions on a new range, it requires 2 phases 6 AWG, 1 neutral 8 AWG, 1 ground 8 AWG with the plug. The male plug is a 50 amp 4 prong plug. 120/240 volt.

Is there a reason they wanted an # 8 ground and # 6 circuit conductors since they have a 50 amp plug that # 8 phases and # 10 ground would work? 50 amp plug has to be on 50 amp breaker.

 

[LarryFine]

The smaller neutral and grounding conductors are actually allowances, not requirements.

Yes, a #10 grounding conductor is permissible in the circuit cable.

The range cord assembly contains the sizes it does because that's how their cables are made.

 

[infinity]

If you're using NM cable #8 (40 amps) is too small for 50 amps so that is why #6 is required. Not sure why the EGC required isn't the standard size (#10) for a 6/3 NM cable. Just curious what is the KW rating of the unit?

 

[RRJ]

Was reading the instructions on a new range, it requires 2 phases 6 AWG, 1 neutral 8 AWG, 1 ground 8 AWG with the plug. The male plug is a 50 amp 4 prong plug. 120/240 volt.

Is there a reason they wanted an # 8 ground and # 6 circuit conductors since they have a 50 amp plug that # 8 phases and # 10 ground would work? 50 amp plug has to be on 50 amp breaker.

Not necessarily a 50 amp plug for a 50 amp breaker. (Seems like it’s not your case)They don’t make a 40 amp plug. So if the 40 amp breaker is enough for the wattage demand it is allow to put a 50 amp plug on a 40 amp breaker. As far as The neutral there is an allowable 70% reduction in wire size since neutral is only use for the clock and lighting in the appliance.


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[Carultch]

Was reading the instructions on a new range, it requires 2 phases 6 AWG, 1 neutral 8 AWG, 1 ground 8 AWG with the plug. The male plug is a 50 amp 4 prong plug. 120/240 volt.

Is there a reason they wanted an # 8 ground and # 6 circuit conductors since they have a 50 amp plug that # 8 phases and # 10 ground would work? 50 amp plug has to be on 50 amp breaker.

If it is an electric range, it uses the 240V circuit to power the heating elements that are the most Watt-intensive circuits. The 120V circuit is used for powering circuits such as indicator lights and the ventilation fan motor, that may be more voltage-sensitive, but less wattage/operating amps. A gas range that may replace it in the future, might only use the 120V circuit to operate the sparkers. In any case, current on the neutral is significantly less than the current on the black and red wires, which is why it gets to be lower in size. You can make it the same size neutral as the ungrounded conductors, if you desire to unify, or if you can't find a manufactured cable assembly that has a reduced neutral. But instead, you get to use smaller neutrals no smaller than either what is necessary for the neutral current, or no smaller than the 250.122 EGC, due to less total current on the neutral.

A 50A circuit requires #6 Cu wiring, if it is only rated for 60C terminations, which is the default for 100A and less, unless both sides are listed and labeled otherwise. If using Romex, it that wiring method requires 60C termination sizing, unlike the alternative of using THWN-2 wire in EMT or FMC raceways, where you get to take credit for a 75C terminal listing.

 

[brother]

If you're using NM cable #8 (40 amps) is too small for 50 amps so that is why #6 is required. Not sure why the EGC required isn't the standard size (#10) for a 6/3 NM cable. Just curious what is the KW rating of the unit?

This is not residential (no NM Cable) its commercial. A new stove for a break room they want installed. The KW on the nameplate was 18, 15 kw. One of the concerns I have is that the existing circuit is 120/208. Most stoves will work even with the name plate for this new stove is 120/240, but it takes longer to cook and heat up (will try to reach the manufacterer to be sure). That was one of the complaints with the old range.

To answer someone elses question, when I stated a 50 amp plug need to be on 50 amp breaker, I was referring to the MAX ocd, not the minimum. I was just curious as to why the manufacturer wanted a larger ground wire when a #10 would do, was checking to see if I missed something in the NEC.

 

[Carultch]

One of the concerns I have is that the existing circuit is 120/208. Most stoves will work even with the name plate for this new stove is 120/240, but it takes longer to cook and heat up (will try to reach the manufacterer to be sure). That was one of the complaints with the old range.

Only the heating elements are powered off of the higher voltage, and heating elements are the simplest kind of load you can have, since they are resistors whose purpose is to directly generate heat. Reducing the voltage from 240V to 208V, means that it generates only 75% the total amount of heat as if you were to run it on the full 240V. This means it will take longer to cook and heat up, but it will not result in any damage to the heating elements because of it. Parts of the appliance that are more voltage sensitive, will be powered off the 120V. Electric ovens and clothes driers are also designed with the same concept of selective use of 240V and 120V, so that they can run off both 120/240V and 120/208V.