Converting 110 to 220 electrical question

[lblair]

I told ya i was no electrician [img]/forums/images/icons/grin.gif[/img]
Larry

[karmakanic]

As you've found out, you only need two 110V inputs and a ground for a 220 circuit. No neutral is needed. However, you should use a true 220 breaker at the box instead of two individual 110 breakers. There are two reasons for this. The 220 breaker will pull the two 110 leads from different legs of the input. This keeps the current draw of the two legs even. You currently may or may not be pulling from different legs, it depends upon which breakers you selected to use. Generally, the row of breakers on one side of the box are on one leg, the other row is on the other leg. The 220 breaker is designed to tap into both rows of breakers. There is also a safety issue. With two separate 110 breakers someone who is not aware of how you wired the circuit could flip open one of the breakers and think he had killed all voltage to the circuit. The 220 circuit breaker has both breakers connected togeather, so flipping the breaker opens both legs of the circuit.

HTH,
Dave

[beenthere]

<font color="blue">""You currently may or may not be pulling from different legs""</font color>

I believe if hooked both wires to the same "leg", one could not get 220V. Each "leg" is 180 degree out of phase, and you get 220 between these two. When 110 is desired, it comes between one leg and the neutral wire (ground).

But the rest of your reasoning for a true 220v double breaker is valid. You want to break both "legs" if there is a problem on that circuit, not just one.

I don't mean to be correcting here, but it only is so others who read this get the correct information (or if I am wrong, I get corrected too [img]/forums/images/icons/grin.gif[/img] ).

[Inspector507]

There are only a few limited manufacturers that did things that way. Most are alternating phase A then phase B all on the same side.
Now I probably got everyone REALY confused.

[karmakanic]

Thanks for the accurate corrections guys. I need to learn to keep my mouth shut if I'm not sure of something, especially at 1am in the morning.

Dave

[exeter_acres]

this is all great info.. It's always good to see how much more I can try to learn!
Most of this actually makes sense to me!

[img]/forums/images/icons/wink.gif[/img] Thanks
Curtis

[MikePA]

I installed baseboard electric heaters in our three upstairs bedrooms. The rest of the house is forced hot air, but there was no easy way of getting ducts upstairs. (House is a 100 year old log cabin)

I ran a separate 10/3 with ground 220v circuit to each heater . The heater is on the longest outside wall in each room while the thermostat is on the opposite inside wall. It was real fun fishing 10/3 through the walls! In fact, one of the rooms required 10/4 with ground because of the need to go to the thermostat before the heater (or maybe it was the heater before the thermostat - can't remember - this was over 20 years ago!). I just followed the instructions that came with the heater.

[Pat]

Lots of comments posted but a quick scan and I didn't see anything along the lines of what I'm about to say...

A typical way construct a 110/220 heater is to have two equal sets of resistance wire, each getting 1/2 the current. Say for example (hypothetical) that the resistance each element was 11 Ohms. Each would get 10 amps and the heater should produce (I squared R or I times E whichever you prefer...I is current and E is voltage and R was resistance in Ohms) 1100 watts. The elements are in parallel so you draw a total of 20 amps (10X2) and a total output of 2200 watts.

Wired for 220V the elements are in series. You have 22 ohms with 220 volts and again there is 220/22 or 10 amps. And again 2200 watts total.

In tht above description the assumption is made that there are two different connection schemes for the two different voltages. If you just put 220 into a 110 volt heater it might not like it. If it is a 220 volt heater with only 110 applied, no doubt it didn't get very hot. Power produced varies as the square of the applied voltage P = E*E/R

A 110 volt heater with 220 volts applied will produce 4 times the heat, if it doesn't die trying. The original problem statement makes it sound as if it may have been a 220 volt heater wired to 110 volts which would produce 1/4 of its normal output.

For safety reasons the metal chassis of a heater should be grounded (not neutral...GROUND/Green wire) A 220 volt heater has no use for neutral unless there is a 110 volt fan or inidicator light involved. Power is supplied by two hot wires, one from each leg (both sides of the breaker box).

Most residential wiring is single phase. Your transformer supplies 220 volts via two wires. Neutral is a "center tap" on the transformer winding. A way to visualize that is to consider two 1 1/2 volt flashlight batteries in series to give 3 volts. If you measure across both batteries you get 3 volts. If you measure from the "center tap", analgous to neutral, to either end you get 1 1/2 volts.

Don't be confused by anyone confused by multi-phase power. Virtually all residential power is SINGLE phase. There are NOT two phases. The transformer has a secondary winding that supplies your 220 volts. A mid point, i.e. center tap, measures 110 volts to either LEG.

Assume a long and complete caveat and disclaimer follows. I am not a lisc electrician and it has been a long time since I stayed at a hotel wired by one. Note: Just this afternoon I wired up a 200 amp breaker pannel with 4 each GFCI 20 amp breakers and a 220 volt GFCI ($85). I wired up 8 duplex 20 amp outlets in 4 two gang outdoor boxes. Testing this I blew a house breaker twice and arc welded a couple times. Seems that I had miswired TWO of the duplex outlets, creating direct shorts. ALWAYS put the white wire to the silver screw and the black wire to the brass screw even when talking to someone while wiring.

Best of luck to you. Let us know how it turns out.

Patrick

[beenthere]

<font color="blue"> ""Don't be confused by anyone confused by multi-phase power. Virtually all residential power is SINGLE phase. There are NOT two phases. The transformer has a secondary winding that supplies your 220 volts. A mid point, i.e. center tap, measures 110 volts to either LEG."" </font color>

Are you saying that the 220v is not obtained between the two single phase legs that are 180 degree out of phase?

[Pat]

beenthere... Au contrair, mon ami... You have stated it precisely correctly. Unfortunately, folks frequently erroneously interchange the term leg with phase when discussing single phase home power circuits.

Phase has to be measured with respect to something. The phase relationship between the center tap and a leg takes some desciribing to unambiguously communicate with precision what is in fact relatively simple.

I'm sure, from your last post that we are in agreement. So that others can follow along, I have attached a precise engineering drawing of a power transformer. (too bad I never had mechanical drawing).

The neutral wire comes from the center tap. The voltage from the center tap to either end (leg) of the transformer) is 120 volts (nominal). The voltage across the entire secondary is 240 volts. For purposes of a simple explanation it is as if each side of the secondary of the trasformer were a "D" cell. Two D cells in series gives about 3 volts. Measureing from the middle of the two series cells to either end is about 1 1/2 volts.

Are the legs out of phase? Depends on your reference. If you use the center tap as a reference then the two legs are out of phase by 180 degrees as one leg is increasing in the positive direction and reaches max pos as the other leg is increasing in the negative direction and reaches max neg.

However, if you use one of the legs as a reference then the center tap and other leg are in phase with each other, with the leg being twice the voltage of the center tap. This changes nothing as far as the circuit is considered, just makes the description different and potentially less clear.

Note, I did not refer to a PAVM or O'scope.

Pat