120/240 hookup for Jenn-Air cooktop

jroho · 01-20-2009, 05:32 PM

I am replacing an older Jenn-Air cooktop (mod # C-201) with a new Jenn-Air cooktop (mod # JED8430). My problem/concern is that the 120/240 circuit feeding the cooktop is fed via Greenfied conduit housing 4 wires [ (2) black, (1) white (1) bare copper ]. The new cooktop attached junction box has 4 wires [ (1) black, (1) red, (1) white and (1) green. It seems intuitive enough to me that white connects to white as a neutral and that green connects to bare copper as an appliance ground. BTW, white and bare copper are bonded together at the service panel, i.e. continuity is read between the 2 wires as well as at the neutral and ground bus bars. No problem so far. My concern is the proper connection of the two "hot" black wires which normally would be (1) black and (1) red. Since the two hot wires are phase reversed and together provide the 240v energy I'm concerned that if they are incorrectly connected backwards some form of polarity problem may exist which could cause damage to the unit.
A related issue is that the exhaust fan motor (120v) is fed from Hot wire L1 and the neutral wire (white). I don't know which of the (2) blacks is L1 and which is L2. At the time the fan is working and drawing current from L1 some imbalance would exist between L1 and L2 which might imply that it is critical to connect the two correctly. It may well be that if I wire L1 and L2 backwards the fan may not work or worse, some damage to the unit might occur.

I would be most grateful for your advice on this matter.
Thanks

Stubbie · 01-20-2009, 05:39 PM

It doesn't matter which black wire of the supply you connect to the red and black of the cooktop. There isn't a phase reversal only a 180 degree offset of the single phase source between the two. Both wires are 120 volts to neutral, the exhaust fan could care less which hot L1 or L2 it uses.

jroho · 01-20-2009, 05:45 PM

Thanks, Stubbie. Relieves my worries.
BTW, good luck to the UAW during this economic crisis. We need US cars and US jobs!
Thanks

Stubbie · 01-20-2009, 06:49 PM

This is pretty much what you have going on with your cooktop. I didn't show the safety ground or the cooktop junction box (you will have to use your imagination...

) You can see that it will not matter which supply wire the two hots connect to nor which one supplies the 120 volt loads.

jroho · 01-20-2009, 07:06 PM

Thanks, Stubbie. That makes it much clearer. As I always say "A day without learning is like no day at all!" My day is now complete. Thanks