jessechenven Posts: 34, Reputation: 1 Junior Member #1 Jun 22, 2006, 04:51 AM
Baseboard heater wiring circuit
I just finished intaling a baseboard heater and I have a question that has been nagging me. The heater is on 240 circuit. So, I ran 12/2 and used the black and white to run my two hot wires as is common practice. Please excuse my ignorance on this matter, but this got me wondering. I have always been told there is no need for a neutral wire (as you might find in the wiring for a 240 oven) because there is no need for 110/120 on the heater. My basic understanding of electricity tells me that electricity runs alond a circuit and must have a return path (normally the neutral wire in a regualr 110 outlet or light, etc.) Does this mean that the return current from my 240 heaters is coming back on the uninsulated ground? If so, is that not more dangerous than with a insulated wire? If I am missing something, please enlighten me.
Thanks, Jesse
 tkrussell Posts: 9,659, Reputation: 725 Uber Member #2 Jun 22, 2006, 01:49 PM
No the bare equipment ground connects only to the metal frame of the heater to ground the exposed metal.

The working current only flows between the black and white of the 2 wire cable. Testing the voltage across the black and white should read 240 volts. Since 60 cycle AC (Alternating Current) changes direction 120 times per second, you can imagine that the black is the return for the white, and the white is the return for the black, 60 times per second for each wire.

If the black, or the white, or even the heating element, were to short out to the metal frame/housing of the heater, then the ground wire will provide a path to drain off, so to speak, the voltage that all of a sudden is now in the metal housing. This current flow, since now no longer is going through the heating element, will try to rise to infinity, and the high current flow will trip the circuit breaker or blow the fuse.

So be sure to connect the bare ground wire to the metal housing of the heater, there is usually a green screw in the junction box for this. And be sure the bare ground is connected to the equipment ground bar back at the panel.

Both legs or wires of a 240 volt circuit are live, in a 120 volt circuit only the black is live, since the white (neutral) is grounded. In theory, if the neutral was not grounded, then the white would be live also. In North America, the neutral is grounded so that there is only one wire live in a 120 volt system.

In Europe, they use a 220 volt system, and similar to here, they ground one leg of their system, so that one leg is hot and the other appears to dead, since it is grounded.

I hope this makes sense to you, if not or need more info , get back with those questions.
 ptnoble Posts: 42, Reputation: 1 Junior Member #3 Jul 30, 2007, 05:46 PM
Good explanation Tkrussell. I am in the process of running wires for a 2500 watt, 240v baseboard heater. I am using 12/2 with the white taped black for the supply. My question is about the thermostat, the wire required for this, and how to wire it.

The owners manual for the unit I have is here:

Does the thermostat and the current supply get wired together on the heater? Is standard "thermostat wire" good for this? I am also being introduced to the concept of double and single pole thermostat. Can someone explain the difference and advantages. Any difference in the thermostat wire for either. I have not bought my thermostat yet but plan on something very simple.
 ptnoble Posts: 42, Reputation: 1 Junior Member #4 Jul 30, 2007, 06:27 PM
Okay, I'm answering part of my own question. It seems a baseboard heater thermostat works at line voltage (in this case 240v) rather than the small small volatage of other heating system thermostats. So it seems to me, the thermostat in the case of a baseboard just acts as a switch and is wired preety much the same way you would wire a switch to a light. That is current goes in one side of the stat, out the other, and then travels on to the baseboard heater. Do I have this right?
 gabriolastyle Posts: 1, Reputation: 1 New Member #5 Apr 9, 2011, 10:14 PM
Each breaker on your double pole breaker installed in panel is out of phase so the negative and positive can travlle back and forth down both hot wires ;)
 tkrussell Posts: 9,659, Reputation: 725 Uber Member #6 Apr 10, 2011, 04:22 AM
Please take an electrical course, as this is incorrect:

Originally Posted by gabriolastyle
each breaker on your double pole breaker installed in panel is out of phase so the negitive and positive can travlle back and forth down both hot wires ;)
A typical home has a single phase service, so how can two legs be "out of phase"?

In North America, and most of the world, alternating current is used, there is not positive and negative wires.
 rovo Posts: 3, Reputation: 1 New Member #7 Dec 2, 2012, 01:08 PM
While standard 240VAC house wiring is referred to as single phase, it really depends on the point of reference. Think of the 240VAC as being sourced from a center tapped transformer where the center tap is grounded. As such, each leg is 120VAC referenced to ground but is 240VAC when measured across the two hot legs. The reality is each leg is 180 degrees out of phase to the other leg. A simple (and correct) way of describing the wiring is 2-phase 120 VAC when referenced to ground.

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