DIY, difficulty new cooktop, present wiring & breaker

[RaeJaye]

I am at a standstill installing the new cooktop until I can determine if the new one works with the present wiring/breaker. (I am keeping in mind the contractor may not have installed the right wiring/breaker for the original (current) cooktop either, so tell me if you determine this is the case.)

Photo one is my current house wiring to the original cooktop. The breaker to this is a 30 amp, double breaker. Photo two is the original cooktop appliance wiring. In the junction box, the black was wired to black, the red to white, and the bare grounds together. The new cooktop instructions in the booklet are confusing regarding what wiring to connect.

Photo three is a closeup of the writing on the black wire of the original cooktop appliance.

Photo four is the wiring of the new cooktop I wish to install. Photos five and six are electrical requirements from the instruction booklet of the new cooktop. The seventh photo is the sticker off the new cooktop that has information needed according to the instructions in photos five and six.

Photos eight, nine, and ten show instruction booklet wiring instructions and warnings.

As best as I can figure it out, the new cooktop wants a 40 amp breaker. This means it wants a heavier wire too. If so, I have to replace the wire and the breaker in order to install the new cooktop. Please advise on this.

I am in the USA.

 

[Lucien Nunes]

The original connection seems to be correct, except that per the NEC I think the white wire of the NM house wiring should have a colour coding tape on it to show that it is hot rather than neutral, i.e. it has the function of the red wire of the appliance. This would be the case if the white is connected into the second pole of the double-pole breaker. There is no neutral in the house wiring (just hot/hot/ground) but that is OK because the new appliance does not need a neutral.

As for the ampacity, on paper the existing circuit does not meet with the manufacturer's recommendation, because a 7.4kW appliance operating at 240V requires 31A. It will work OK, but whether it would meet code will need someone on your side of the Atlantic to answer. In the UK we have a formula for domestic cookers to assess how much current they will use in real life as a fraction of the theoretical maximum, but it is different under the NEC and you would have to justfiy why you did not follow the manufacturer's recommendation to install a 40A breaker and circuit.

This is assuming that it is coming from a normal domestic 120/240V panel, and not from a 3-phase panel with only 208V line to line, in which case it would function as a 5.6kW appliance with reduced current draw.

 

[RaeJaye]

The original connection seems to be correct, except that per the NEC I think the white wire of the NM house wiring should have a colour coding tape on it to show that it is hot rather than neutral, i.e. it has the function of the red wire of the appliance. This would be the case if the white is connected into the second pole of the double-pole breaker. There is no neutral in the house wiring (just hot/hot/ground) but that is OK because the new appliance does not need a neutral.

As for the ampacity, on paper the existing circuit does not meet with the manufacturer's recommendation, because a 7.4kW appliance operating at 240V requires 31A. It will work OK, but whether it would meet code will need someone on your side of the Atlantic to answer. In the UK we have a formula for domestic cookers to assess how much current they will use in real life as a fraction of the theoretical maximum, but it is different under the NEC and you would have to justfiy why you did not follow the manufacturer's recommendation to install a 40A breaker and circuit.

This is assuming that it is coming from a normal domestic 120/240V panel, and not from a 3-phase panel with only 208V line to line, in which case it would function as a 5.6kW appliance with reduced current draw.

 

[RaeJaye]

That is the label inside my breaker box if it helps.

 

[RaeJaye]

The original connection seems to be correct, except that per the NEC I think the white wire of the NM house wiring should have a colour coding tape on it to show that it is hot rather than neutral, i.e. it has the function of the red wire of the appliance. This would be the case if the white is connected into the second pole of the double-pole breaker. There is no neutral in the house wiring (just hot/hot/ground) but that is OK because the new appliance does not need a neutral.

As for the ampacity, on paper the existing circuit does not meet with the manufacturer's recommendation, because a 7.4kW appliance operating at 240V requires 31A. It will work OK, but whether it would meet code will need someone on your side of the Atlantic to answer. In the UK we have a formula for domestic cookers to assess how much current they will use in real life as a fraction of the theoretical maximum, but it is different under the NEC and you would have to justfiy why you did not follow the manufacturer's recommendation to install a 40A breaker and circuit.

This is assuming that it is coming from a normal domestic 120/240V panel, and not from a 3-phase panel with only 208V line to line, in which case it would function as a 5.6kW appliance with reduced current draw

 

[RaeJaye]

"This is assuming that it is coming from a normal domestic 120/240V panel, and not from a 3-phase panel with only 208V line to line, in which case it would function as a 5.6kW appliance with reduced current draw" How can I determine which panel I have for certain?

 

[Megawatt]

I am at a standstill installing the new cooktop until I can determine if the new one works with the present wiring/breaker. (I am keeping in mind the contractor may not have installed the right wiring/breaker for the original (current) cooktop either, so tell me if you determine this is the case.)

Photo one is my current house wiring to the original cooktop. The breaker to this is a 30 amp, double breaker. Photo two is the original cooktop appliance wiring. In the junction box, the black was wired to black, the red to white, and the bare grounds together. The new cooktop instructions in the booklet are confusing regarding what wiring to connect.

Photo three is a closeup of the writing on the black wire of the original cooktop appliance.

Photo four is the wiring of the new cooktop I wish to install. Photos five and six are electrical requirements from the instruction booklet of the new cooktop. The seventh photo is the sticker off the new cooktop that has information needed according to the instructions in photos five and six.

Photos eight, nine, and ten show instruction booklet wiring instructions and warnings.

As best as I can figure it out, the new cooktop wants a 40 amp breaker. This means it wants a heavier wire too. If so, I have to replace the wire and the breaker in order to install the new cooktop. Please advise on this.

I am in the USA.

That wiring is # 10 which is good for 30 amps and it looks like you don’t need a neutral. As @Lucien mentioned the white wire needs to be sleeved or taped up with red tape so it’s easy to identify that it is a being used as a live wire. Your old cooktop was smaller in KW’s than your new one. You will need to change the wiring which will be # 8 wire on a 40 amp double pole breaker.

 

[Megawatt]

I am at a standstill installing the new cooktop until I can determine if the new one works with the present wiring/breaker. (I am keeping in mind the contractor may not have installed the right wiring/breaker for the original (current) cooktop either, so tell me if you determine this is the case.)

Photo one is my current house wiring to the original cooktop. The breaker to this is a 30 amp, double breaker. Photo two is the original cooktop appliance wiring. In the junction box, the black was wired to black, the red to white, and the bare grounds together. The new cooktop instructions in the booklet are confusing regarding what wiring to connect.

Photo three is a closeup of the writing on the black wire of the original cooktop appliance.

Photo four is the wiring of the new cooktop I wish to install. Photos five and six are electrical requirements from the instruction booklet of the new cooktop. The seventh photo is the sticker off the new cooktop that has information needed according to the instructions in photos five and six.

Photos eight, nine, and ten show instruction booklet wiring instructions and warnings.

As best as I can figure it out, the new cooktop wants a 40 amp breaker. This means it wants a heavier wire too. If so, I have to replace the wire and the breaker in order to install the new cooktop. Please advise on this.

I am in the USA.

I’ve been thinking about your cooktop and done the math. Its 7.4kw, so take 7400kw divided by 240vac = 30.8 amps which according to the NEC it exceeds the capacity of 30 amps. Having said that at no time will your cooktop will pull 30 amps. Leave it at # 10 wire and you will be fine.