Baseboard Heater

ron schenker

Anyone out there have a simple explanation as to why a 240V. baseboard heater has no neutral wire? I've heard a few explanations, but they just don't seem to sink in

Speedy Petey

Because they are straight 240v loads, not 120/240.
240v is line to line, not line to neutral.

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ron schenker

But is there no path to ground?

Speedy Petey

A 240v circuits needs no path to ground to complete the circuit.
The white is NOT the ground. The bare or green is, and ALL new circuits must have a ground, regardless of voltage.

That is what 12/2 (etc.) w/g means. W/G = "with ground".

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Atricaudatus

Ron,
Pete is dead on, but I sense you may be trying to understand the underlying principle of the thing. I'll try to put it in layman's terms for you (and I'll probobly botch it up )

Alternating current is a sinusiodal wave form, meaning that the potential to "ground" (the voltage) of each phase swings from 120volts in a "positve" direction in relation to your reference point ("ground") to 120 volts in the other or "negative" direction. Now it's not quite negative and positive, since it's not a polarized or DC ciruit, but that may help you visualize it.

The two phases in your panel (I know it's a "single phase" system, but don't let that throw you) are 180 degrees "out of phase" with each other. Meaning that when one phase is 120volts (to ground) in one direction, the oposite phase is "negative" 120volts (or rather it's 120 volts in the other direction) to the same refernce point. So there is 240 volts BETWEEN them.

When thinking about a 120 volt circuit, the path of current flow is changing direction 120 times per second (60 hertz) so it "flows" from the "hot" to the neutral, then back the other way. The neutral IS a current carrying conductor, even though its voltage is zero in reference to ground.

On a 240 volt load, the path for the current is "from" one phase TO the other phase, because they are at oposite potentials TO EACH OTHER, so one pulls and the other pushes, then they switch places and the first one pushs while the other one pulls, if that makes it easier for you.

So the bare wire in the 240 volt system is a ground or "bond" (see Art 100 of the NEC) and has nothing to do with the operation of the equipment. It's required for safety. The appliance or load would work just as well without it.

Now, before I get jumped by the really smart guys, I KNOW this isn't a 100% technically correct explanation from an engineering stand point. Think of it as a metaphor to illustrate the concept to those who are trying to grasp the idea of how it works.

Not sure if I helped, or just muddled things up.

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-Rhett
Licensed electrician and plumber

MSSI

Awsome ,except 60 Hertz is 60 cycles per second

CE1

Try this:

Take a 3000 watt baseboard heater;

The baseboard heater must be grounded, no exceptions!

If you connected it to 120 volts AC (one hot & a neutral)it would draw about 25 amps
This circuit would require a copper 10/2 w/ground

If you connected it to 240 Volts AC (2 hots)it would draw about 13 amps
This circuit would require a copper 12/2 w/ground

The 240 VAC circuit would be cheaper to install and would balance the load on the main circuit breaker panel. This is good!

The 120VAC circuit would be more costly to install and unless the circuits are installed very carefully you would end up with an unbalanced circuit breaker panel. Which causes other problems to long to list.

Ron ->recomended handbook for about $10.00

Attachment 1968

Atricaudatus

Correct, but the current still changes direction 120 times per second. One full wave form equal two changes of direction on a 60 cycle system.

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-Rhett
Licensed electrician and plumber

CE1

Technically the current in an AC system changes 4 times a cycle. At 0 degrees (increasing from no current flow), at 90 degrees (decreasing from maximum current flow), at 180 degrees (increasing from no current flow) at 270 degrees (decreasing from a maximum current flow) and at 360 degrees (increasing from no current flow) Current is at its maximum 2 times in a cycle and at zero 2 times a cycle.

Current on an AC system does change directions 2 times in one cycle but you have to understand what it is really going on in an AC system circuit.

Now do you want to talk voltage?

I think we have probably lost the original poster and have drifted away from his original question. So if you guys want to talk electrical theory maybe we should start another thread?

CE1

Atricaudatus
Canebrake Rattlesnake???

Atricaudatus

True. I didn't want to get too deep in the weeds, and was only trying to give the poster a general idea of why he didn't need a "neutral" on a 240V load. Sometimes too much tech jargon creates more confusion than it clears up.
And your're right, let's not even start trying to explain RMS, peak, peak to peak, etc voltages and their constantly changing values on an AC waveform.

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-Rhett
Licensed electrician and plumber

Atricaudatus

Correct! Crotalus Horridus Atricaudatus. A subtle play on a nickname I've had since boyhood, due an unusual choice of "pets."
I sense I may have found a fellow amatuer herpetologist. You're familiar with that species?

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-Rhett
Licensed electrician and plumber

King of Crown

can you die from 120 volt shock?

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Real nice guys

mas2006

Its the path current takes through the body that determines cardiact disruption. Example: if you complete a circiut path from your fingers to say to your elbo, it would hurt like hell, but not stop your heart. But don't try it.

ron schenker

YOU GUYS ARE KILLING ME HERE

Atricaudatus

Sorry Ron.

I'll give it one more shot.
All that is needed for current to flow is a difference of potential between two points (the voltage across them.) Current doesn't have to have a path to ground, only to a different (lower or higher) voltage.

So, like Pete pointed out early on: on a 240 volt load, the path for current is from one phase (or leg) TO the other, not to ground.

A "neutral" isn't needed, and it's only called a neutral because its voltage is zero to ground. Ground is simply a reference point (Now it does serve other functions related to safety, but has nothing to do with the operation of the loads.)

Hope that helps. It's about as concise as I can make it.

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-Rhett
Licensed electrician and plumber

locofoco

It's my understanding that the ground ( cabinet ground) on 220v is for safety, not functionally necessary for the operation of the device.

As for the question- can 120v kill you? I had a co-worker whose wife was helping him in the wet crawlspace of their home. Electrocuted when she tried to move a drop light. She was 30 years old with two kids.

ron schenker

I get it now Thanks guys, especially you Rhett

mdcorreia

A 240 v 3000 watts heater connected to 120v does not draw 25 amps.