Wiring New Cooktop

[nsomniac]

Just wanting some thoughts on my situation...

I'm replacing an ancient Jennair downdraft cooktop with a new Whirlpool...

My supply is black, red, and white (note the absence of green )...the Jennair, I discovered, was wired red to red, black to black, white to white, with the green from the cooktop just hanging bare in the junction box.
The new cooktop is 3 wire, black/red/ground. Installation instructions say, red to red, black to black, cap the white supply and ground the green.

So, I guess all this means that the old cooktop was wired improperly (that is to say, ungrounded) all this time?
Do I have any recourse but to have the circuit rewired?

Thanks for any guidance.

 

[glennjanie]

Welcome Tim:
Follow the instructions to the letter; they are part of the UL approval on the cooktop and must not be changed or altered in any way to keep the UL seal in force.
Glenn

 

[guyod]

The White can be used as a ground wire it is connected to the same place as the ground would be in your service panel.. 240 volts circuits do not need a return(neutral/white). Some 240 devices need a neutral some don't. I think it has to do with powering 120v components of that device(fan,clock). So you old stove was not grounded but your new one will be using the same wire.

Make sure the wire is heavy enough gage though. 40amp needs a 8 awg wire and 50 amp needs 6 awg.

 

[speedy petey]

The old circuit was legal and still is for replacement units. Yes, this was an "ungrounded" circuit, but there was an exception for appliances like this that they could be "grounded" to the neutral of the circuit under specific circumstances.

It is important to not this DOES NOT work in reverse. You CANNOT use a ground wire for a neutral under ANY circumstances. Never could.

Also, guy makes a very good point. The voltage is only half the equation. What is the amperage/wattage of the new unit and what is the size of the wire/circuit?

 

[user 4883]

If you use the old neutral as a new ground, wrap some green marking tape around both ends (panel and stove).

 

[nsomniac]

Thanks for the guidance here, I really appreciate the education....

I should be ok on the amps...its not exactly a high end high-power unit...the manual recommends at a 30 amp circuit, which is what I've got.

Might be a chore sorting out the proper neutral to label at the panel...which looks like this: