In almost all cases, usually when the inside of the oven was on (boil or broil), both wires had the same current going through them (I only have one meter, so I couldn't check them simultaneously). But when I would power the top external burner, one "phase" had 15A, and the other "phase" had 8.3A.If the stove top burners have thermostatic controls that continuously dial from low to high, they should always run from 240. If it has controls that have warm-low-med-high click positions, then they may use 120 V for warm and low, and 240 for med and high, with two separate resistance elements in the burner. That could explain the different current on the two hots.
If its to calculate power used, amperage at 240V is not equivalent to amperage at 120V,
Why is current at 240 different? If I measure 10A on 240, then it's still 10A going through the breaker panel.
As for why I'm doing this, long story short, it's to roughly calculate current through the panel on some of the higher power appliances; the electric stove in this case.
Initially I thought 240V was "two phase"Strictly and accurately speaking, it IS two phase.
That's a matter of semantics really. The split phase 240V we use in North America is still called single phase, it comes from a single one of the 3 phases that come from the power grid.The semantics is about how the power is generated/derived. The resulting "signal" speaks for itself. On the bench, with a scope, you'd describe the two "hot" wires as each being a separate phase with 180 degrees of separation between the two. The fact that it's high(er) voltage, or that its symmetry doesn't automagically yield a rotating magnetic field, doesn't obviate that there are two phases, easily distinguished. For confirmation, "single phase" has one phase (a single sine wave) and "three phase" has three sine waves, which (like two phase) are equidistantly separated at (360 / # of phases) degrees. If we had 5, 6, 7, or 11 phase power this relationship would still hold true. There's no reason to discount two phase power just because it (might) originate from a center-tapped transformer secondary.
Which raises an interesting question: On a portable gasoline generator, do the two phases come from two generator windings 180 degrees apart? Or is there a transformer in there with a center tap? I strongly suspect the former, in which case the argument for "two phase" is strengthened.
Fairly common at point of use yes, but I've never seen 2 phase power brought into a structureEvery house I've lived in had two phase power. 120V per phase, 180 degrees out of phase, use one or both phases depending upon the load.
Fairly common at point of use yes, but I've never seen 2 phase power brought into a structure, there is no real savings over just bringing in all 3 phases if you're going to bring in two of them. Service is either single phase or 3 phase, individual appliances on a 3 phase service may use anywhere from 1 to 3 of the available phases.Quite common in US apartments since it would be overkill to have 3 phase in every room but very reasonable for the whole building. Each room gets 2 of the 3 phases, spread out to even the load.
Strictly and accurately speaking, it IS two phase.
Why refer to 180 degrees of phase offset "differently" than 0 or 120 degrees of offset, other than in magnitude?
Fairly common at point of use yes, but I've never seen 2 phase power brought into a structure, there is no real savings over just bringing in all 3 phases if you're going to bring in two of them. Service is either single phase or 3 phase, individual appliances on a 3 phase service may use anywhere from 1 to 3 of the available phases.Quite common in US apartments since it would be overkill to have 3 phase in every room but very reasonable for the whole building. Each room gets 2 of the 3 phases, spread out to even the load.
I can't quite agree. In every case, a voltmeter across different phases will show a voltage potential which can cause current to flow.
Indeed, the 90 degree offset case is the oddball. It is the exception to the (360 - # of phases =) phase offset relationship that describes the others. I understand the convenience of having the built-in rotating magnetic field behavior but other than Philadelphia(?) I know of nowhere in the United States that has offered such utility power for decades. Literally everywhere else uses one phase (no offset), two phase (in every case 180 degree offset), or three phase (in every case 120 degree offset). I suspect that's true worldwide.
Why refer to 180 degrees of phase offset "differently" than 0 or 120 degrees of offset, other than in magnitude? The sine waves do not know what you plan to do with them... resistive loads, inductive loads....
I found the manual online, and I also found the installation instructions that were stuffed in a drawer (see attached pictures).
Unfortunately it doesn't seem to specify much about the electrical connections - or at least I didn't see anything pointing to whether it feeds off the 120V too.
To answer some previous questions: when I turn the top dial s for the top burners (are they actually burners since they are electric?) they click past 'off', but seem to be smooth turning.
Correct me if I'm wrong, but I assume the heating elements are controlled by triacs controlled by the hand dials. When I measured the currents, it seemed the current didn't change (within reason - obviously the current changed a bit from initial turn on to steady state - although I didn't keep the oven on long) regardless of the temp setting, however, the heating elements I think get more red the higher I set the temperature.
It occurred to me right after I posted my reply that someone would probably mention this. As far as I'm aware, the buildings are still fed by the full 3 phase feed from the transformer, and then the panels in the individual units get two of the three phases. I guess it's fair to call that 2 phase to the dwelling, but it isn't 2 phase power fed into a building.It's also possible for there to be a 3 phase transformer in the area with each building connected to 2 of the three phases, that might be the case for apartments with a few rooms each in many smaller buildings. It's also possible for individual houses to be connected that way in a neighborhood although I don't think it's very common.
I'm not saying triac controlled burners don't exist but I've never seen one. The classic infinite controller is actually a cycling thermostat. Internally it has a heating element wrapped around a bimetal strip, this heater is fed from the same output that cycles power to the burner. The knob you turn is a mechanical adjustment that controls the spring tension against the bimetal strip thus adjusting the duty cycle. When you turn it all the way off the contacts are held open and when you turn it all the way up to high they're held closed but the rest of the time it will cycle. This design has been around a lot longer than triacs, it's more reliable and less likely to fail shorted.Some higher end electric stoves use triacs in order to modulate the heat at a faster rate to make it more like a gas stove, but I think those have largely been replaced by induction cookers.
from the viewpoint of an electrician, it's single phase because a two phase system is wired differently.
If the spring pushes against a heating element, then why do the plastic knobs not get hot?
Note: do not wire loads between phase (hot) and earth. The drawing is just an illustration showing the voltages with respect to earth. Always connect loads between phase and neutral, or phase-to-phase!
Two phase is 90° out of phase. Split phase is a centre tapped transformer.
I zoomed in on the top coil and looks like it's engraved with 108V / 140V.
After some research, I read both top and bottom turn on during 'bake' to heat the oven, and then the top turns off once temp is reached.
Maybe this accounts for the difference in current since the top may be going through the 120V leg and the bottom through the 240 leg?
Maybe this accounts for the difference in current since the top may be going through the 120V leg and the bottom through the 240 leg?
Yes, and if you do the math it adds up perfectly.
One (hopefully) last question.
Since I measured 15A in one leg and 8.3A in the other, while on 'bake', and we determined the top element must be on from 120V, does this mean it's 23.3A draw total?
As I mentioned (or believe I mentioned) some messages ago, I am trying to get an idea of how much current is going through the breaker box.In a split-phase system "the current through the breaker box" doesn't have a useful or well defined meaning. It better to say the current is X on L1, Y on L2 and Z on Neutral, or perhaps to say the highest current is on L1 and is X Amps.
No, you don't add anything. You have a 15A load on one side and an 8.3A load on the other, with a 6.7A neutral current due to the imbalance. The highest current anywhere is 15A.
The two questions I have (since it seems 240 wiring is a bit confusing to me than I thought - especially since some of the oven uses 120V). The simplest question: if I have a 100A breaker box, am I using 15A leaving me with 85A for the rest of the house or 23.3A leaving me with 76.7A for the rest of the house?A 100 A breaker box allows you to have up to 100 A on each phase. So you have 85 A left on L1 and you separately have 91.7 A left on L2. You could therefore add another 85 A worth of 240 V load (leaving you 8.3 A spare on L2), or you could add 85 A of 120 V load to L1 and 91.7 A of 120 V load to L2.
As for a 6.7A neutral current due to the imbalance, where is the rest of the current going from the 15A and the 8.3A?The 6.7 A of neutral current is the rest of the current. 15 A flows from the breaker box on L1. At the appliance this passes through some loads and splits, 6.7 A flows back to neutral and 8.3 A flows through other loads and into L2.
The two questions I have (since it seems 240 wiring is a bit confusing to me than I thought - especially since some of the oven uses 120V). The simplest question: if I have a 100A breaker box, am I using 15A leaving me with 85A for the rest of the house or 23.3A leaving me with 76.7A for the rest of the house?
The fully-loaded-neutral is sufficiently rare that historically some jurisdictions have allowed the neutral to be smaller (1/2 to 2/3 the line conductors). No idea if it was ever allowed in the USA.