More wiring???

[ed_denu]

240 volt circuits if they are 3 wire are (2) 120 volt legs and a ground. The ground is for safety considerations and the circuit would be complete and functional without the 3rd wire. A (4) wire 240 volt circuit has (2) hot legs, a ground and a neutral. The neutral allows for the circuit to provide a 120 volt source along with a 240 volt capability.

A 3 wire 240 volt circuit is not meant to supply a 120 volt source, while a (4) wire 240 volt circuit can supply both 240 volts and a 120 volt source. Typically for a (3) wire circuit, if romex is used, the black wire is hot, the white wire is marked black with either a marker pen or black electrical tape, and the green or bare is ground. With (4) wire cable, the hots are red and black, the ground is bare or sometimes green, while the 4th wire can be white, or another color. The NEC in most cases does not specify wire colors except for larger conductor sizes and 3 phase power.

Scott, I think you are referring to older dryer setups that sometimes used the ground as a neutral, but this is an exception to the rule and not the norm.

[philipd]

Originally Posted by SCOTTRODS

It's not a dumb question.... It is apparent there's not much electrical knowledge in your life though. That's nothing to be ashamed of at all.

Yeah, it is apparent. Most of my electrical training as been from "This Old House", "Hometime", and other shows on HGTV. Also to some extent from what I have read on the internet and gathered from DIY books. One drawback to this is that I have learned HOW to wire something but not WHY. So I guess my question should be: how come a 240v circuit doesn't require a neutral wire? I understand from Ed's post (thanks Ed) that a neutral is required in a modern home but what I don't understand is why it will work without a neutral.

If you look at the diagram in the original post you will see one leg (colored brown) goes to the SSR and then four wires exit, one to each of four elements. The other leg (colored black) exit the terminal strip and goes to the other side of each element. No neutral.

This really isn't important. I know it will work -- I just don't know why.

[ed_denu]

Originally Posted by philipd

Dumb question here: why doesn't a 240 circuit have a neutral? Does one leg act as a neutral for the other leg?

It's not a dumb question and you have the right idea. In a 240 volt single phase circuit the sine waves of the (2) hot legs are each 180 degrees apart and serve as a return path for the other to complete the circuit. When one conductor is positive, the other is negative, so the circuit is complete. A dedicated 'neutral' is not required. If the sine waves weren't 180 degrees apart, there would be no voltage present. The same as if you ran a (2) wire circuit with both feeds coming from the same hot leg, you would see 0 volts.

In 120 volt circuits, one sine wave(providing 120 volts) is used along with a neutral to complete a circuit. As the AC sine wave alternates between positive and negative, the circuit is positive 50% of the time, negative 50% of the time. This occurs 60 times a sec, hence the designation 60 hz.

[philipd]

Thanks Ed!

That makes perfect sense! As one leg goes above neutral the other leg is going below neutral. Don't know why I didn't think of it.

Well, I do know why I didn't think of it. I didn't know that the legs were 180° apart.

I love learning new stuff.

[SCOTTRODS]

Originally Posted by ed_denu

Scott, I think you are referring to older dryer setups that sometimes used the ground as a neutral, but this was an exception to the rule and not the norm.

Yes,... I use a dryer circuit on my oven.... At least it's wired like the one on my dryer....

[ed_denu]

Originally Posted by SCOTTRODS

Yes,... I use a dryer circuit on my oven.... At least it's wired like the one on my dryer....

Scott, If you are using a 3 wire circuit on your oven you should seriously consider converting it to a 4 wire circuit. 120 volt devices will place current on the ground. This can create a dangerous situation. The pid, lights, fan should have a dedicated neutral and the ground should be for short circuit, safety considerations only.