Two Phase House Mains 220v Oven - Page 1
Forum section: electronics / general

author: vidarr
author_rank: Frequent Contributor
timestamp: March 28, 2025, 02:24:05 pm
content: Most houses where I am have two phase electric and often have three phase also. I am pretty sure what I have is two phase.We just got a 220V oven and we need a line from the breaker box run about one meter to where the oven goes.According to the pics, it looks like there are two, two phase breakers (on the right side of both rows), and a separate, single phase, in the top row and bottom row that powers everything (there are no 220v receptacles right now).We are going to have a guy come and do this work, but I want to fully understand how this should be done. This is Brazil and there are a lot of hacks. The last time we had electrical work done, the guy got it working, but it was a total mess and so far from code. (Not this house, another.)So, on the bottom row, all the way to the right, there are two 110V lines coming in to a double switch breaker. I tested the lines, each are 110v and tested together they are 220v.Will two lines screw into the two terminals on the bottom of the double breaker? Then run that to the oven?Again, I am Not doing this work. I just need to know what is going on, so I can have some authority over this. I don't want to be the clueless homeowner guy.Thanks.

author: rdenney
author_rank: Regular Contributor
timestamp: March 28, 2025, 06:43:38 pm
content: As I understand it, Brazil only supplies three-phase power. An appliance can get 127VAC by being wired to one of the phases plus neutral and 220VAC is available by wiring to two of the phases. The breaker (disjuntor) at the bottom right--labeled MW263E--is a 220VAC breaker that is two-pole and is wired to two phases, just like the two at the upper left, which are also 220V breakers that might serve, for example, a water heater and an air-conditioning system, neither of which would use receptacles. All the others are single-pole breakers that are tied only to one phase.The three phases are 120 degrees out of phase with each other, and 120 degrees out of phase with the earth-ground zero potential. Think of it as an equilateral triangle with a dot right in the middle. The dot in the middle is at zero potential. The points of the triangle are 127VAC away from that zero-potential center, and 220VAC from each other.It appears that the part numbers printed on those breakers follow the format MYxyyE, plus Cyy below it. x is 1 for single pole (127VAC, but probably nominally known as 110V) and 2 for two-pole (220VAC). yy denotes the current rating (63 amperes in the case of that 2-pole breaker at the lower right). You'll need an MW2yyE, where yy is the current requirement for the oven you are installing (63 amps might be correct--U.S. range/ovens are usually 50 amps at 240VAC--but you'll need to look at the installation manual).A possible issue that I see is there is no space in your panel for an additional two-pole breaker, but your electrician will tell you what your options are. You should not tie two branch circuits into one breaker, especially for high-current appliances like an oven. In the U.S., that would be a violation of the electrical code. But maybe in Brazil they do that and just know that they can't use the two appliances being served at the same time.I can't be sure, but it appears breakers get their power from the backpanel to which they are mounted, and the wires screwed into them are the branch circuits they are serving. I think I see three of the big black wires going behind the panel to which the breakers are attached--those might feed power from the electric utility to the panel. The terminal strips on the sides are where that center tap is wired to provide zero potential, and they are bonded to earth ground at that one point.Rick "guessing at those part numbers after reviewing examples in a Brazilian catalog" Denney

author: vidarr
author_rank: Frequent Contributor
timestamp: March 29, 2025, 03:16:33 pm
content: Quote from: rdenney on March 28, 2025, 06:43:38 pmI finally get it. No one ever explained this so good and so clear. I can finally picture it in my head and understand it. Thank You for the whole comment.edit: I wrote the breakers out in English a while back when someone in another country was helping me figure this out. The one labeled "office receptacles" is a double switch, but none of the receptacles in my office are 220v. It appears that they are two separate lines going to the same room and share that switch. The stuff not labeled goes no where (I should actually shut the switches off).

author: EPAIII
author_rank: Super Contributor
timestamp: April 01, 2025, 11:47:40 am
content: Of course I could be wrong; the wires are quite the spaghetti bowl, but here is what I see.The double breaker on the bottom right is the main cutoff for the panel. It appears to have two feeder lines connected at the top. Those two lines (larger black wires) seem to be entering at the bottom of the box. They would come from the pole or whatever holds the power coming to your house. Since there are only two of them that would mean you have two of the three phases in that box.That bottom right breaker feeds a pair of buss bars under the bottom row, distributing the two phases to the other slots in the bottom row. Those breakers would alternate on which phase they are connected to. On the bottom of the bottom right, double breaker there is another connection with heavier, black wires. They appear to supply power to the top row through the top, right breaker in much the same way that power is fed to the bottom row.The rest of the breakers in the top row are single breakers so they should be feeding 115 V circuits only. There are two double breakers in the bottom row on the left. Normally they would be used for 220 V circuits. The other breakers in the bottom are singles and should be feeding 115V circuits only. That is how it should be done, but I don't know if there are any make-shift installations there.It appears to me that all the breakers in the box are in use except for one single breaker in the top row. So there is no obvious way to connect a new, 220 V circuit.But there are two possibilities that I can speculate about. The first is the top right breaker which does not have any connections at the top. If is is the same type as the bottom right, it MAY be usable for your oven. I emphasize the word "MAY" as I do not know your local codes or practices.The second possibility would be to remove two of the existing, single breakers and replace them with special, double breakers that fit in the same spaces. This is OK by the US code and I have several such breakers in my house's box. Different wiring arrangements are possible depending on how the double breakers function, but one possible one would be that one of the double breakers would be used for the two circuits that were on the two breakers that were removed. And the other double breaker would be used for your oven.Of course I have never been to Brazil so all of the above is my best guess only.

author: vidarr
author_rank: Frequent Contributor
timestamp: April 01, 2025, 12:31:08 pm
content: Quote from: EPAIII on April 01, 2025, 11:47:40 amIn top row, the double breaker to the right went to an air conditioner (220V) that is no longer here (previous owner). It was "installed" with two wires running on the floor with tape across two bedroom floors. I removed the lines and terminated in a junction box.So, that double breaker is technically free, but maybe better to leave it.That top row single breaker with no connection is there because I have no idea.If you come to Brazil, you might be rich. The exchange rate is $1 USD equals R$5.5 +/-. A beer (Good Beer) costs about $0.40 here. A 12 pack is less than $7 USD.Quote from: EPAIII on April 01, 2025, 11:47:40 amI think that the thing you said "MAY" about, might be what the electrician is thinking. Very few follow code here, which is why I posted this; I don't want to get screwed again."remove two of the existing, single breakers and replace them with special, double breakers"I like this idea. I will ask the electrician.Thank You so Much!

author: vidarr
author_rank: Frequent Contributor
timestamp: April 02, 2025, 03:32:28 pm
content: How far away from the oven does the electrical outlet (or junction box) need to be? I see people putting the outlet right behind the oven. Is that legit?

author: nctnico
author_rank: Super Contributor
timestamp: April 02, 2025, 03:46:02 pm
content: Quote from: rdenney on March 28, 2025, 06:43:38 pmThis looks like it is a split phase (two phases being 180 degrees out of phase) supply. So you have 220V between the phases and 110V between phase and neutral. The breaker box seems to have some 110V circuits and some 220V circuits.Probably the oven supports connecting it to two 16A 220V circuits (using four connected breakers) or a single 25A 220V circuit. The latter will need 4mm^2 wires and a special plug while two 16A circuits can use more standard 2.5mm^2 wires together with a multi-pole plug. Over here a plug style called 'Perilex' is common for ovens.Quote from: vidarr on April 02, 2025, 03:32:28 pmThis is a question you have to ask a local electrician (which is a good idea anyway instead of taking forum posts for granted). Over here it is common to have the outlet behind the oven so the idea is not weird but I don't know the regulations in Brazil.

author: Siwastaja
author_rank: Super Contributor
timestamp: April 02, 2025, 04:14:08 pm
content: Quote from: nctnico on April 02, 2025, 03:46:02 pmNo, Googling confirms what others have said: Brazil has "127/220V" supply, from which you can see that ratio is 1.73, same as our 230/400. So it must be simply normal 3-phase system, with phase-to-phase voltage of 220V (unlike our 400V), which results in 127V phase-to-neutral. Then if you bring neutral and two phases into a house (leaving one phase unconnected), you can have either 220V or 127V. It's then neither split-phase nor two-phase system: it's three-phase system with one phase missing.Split phase would have 1:2 ratio (like 240V/120V in the US).

author: vidarr
author_rank: Frequent Contributor
timestamp: April 03, 2025, 11:43:58 pm
content: Quote from: Siwastaja on April 02, 2025, 04:14:08 pmAdd to the complexity, no one follows code here. New construction that is done legit has to have inspections, after that, anything can happen. We still have people electrocuted from our showers. The water pours over a nichrome coil to heat and that water pours down on you. Sometimes, you get a shock when you touch the faucet. If you have a cut on your finger and it touches the faucet, you will get a shock you feel. Some people put rubber mats on the shower floor. People also wrap their faucets with rubber, so you make no contact with the metal faucet. The showers are not grounded.Nothing is grounded. No Thing.The electrician comes tomorrow. Let's see what he proposes and does. I'll post an update so you can see how it works here in Brazil.Thanks Guys!

author: JoanBS
author_rank: Contributor
timestamp: April 04, 2025, 12:56:13 am
content: Quote from: vidarr on April 01, 2025, 12:31:08 pmI don't know, but I don't see a double-circuit breaker in the upper right cornerI also don't see a residual-current circuit breaker anywhereAs already mentioned, two phases are used to obtain 220V, and one of the phases and the neutral are used to obtain 125V.I wouldn't be crazy to connect an oven without using a residual-current circuit breaker and, of course, with a good ground connection. The oven breaker must be two-pole and have a capacity of 25A (maximum) and the connection wires must be 4mm.The electrician has the obligation to know this!

author: vidarr
author_rank: Frequent Contributor
timestamp: April 07, 2025, 08:43:37 pm
content: Quote from: JoanBS on April 04, 2025, 12:56:13 amNot in the upper right corner. I wrote, "In top row, the double breaker to the right went to an air conditioner (220V) that is no longer here (previous owner)." I wrote, "to the right" because there are two double breakers in the top row and one is on the left, the other is on the right. The one on the right was for the AirCon.He ended up using that AirCon double breaker. Also, he ran a line from the unused breaker next to the former AirCon and ran a 120 line to the same box. So, in the receptacle, the two on the right are 220 and the two on the left are 120. All of this will be inside built in cabinets ---not exposed.And that is how it ended up.

author: vidarr
author_rank: Frequent Contributor
timestamp: April 07, 2025, 08:50:00 pm
content: Quote from: Siwastaja on April 02, 2025, 04:14:08 pmWhy do they do this? I don't get it.

author: Siwastaja
author_rank: Super Contributor
timestamp: April 09, 2025, 07:29:25 am
content: Quote from: vidarr on April 07, 2025, 08:50:00 pmSomeone thought that having two different voltages for different types of appliances is a good idea - just like the USA did with their transformer center-tapping.Implementing it like this is a slightly different way to the US split phase, and does not result in 180deg phase difference but 120deg, and the voltage difference isn't 2x but 1.7x.Both are simple to implement.The real question is, though, is it useful to have two different voltages? The US heavily uses this concept, with nearly every house having both 240V and 120V appliances and stuff. Maybe you do the same? Like, the voltages are close enough to the US equivalents. Here, 99.9% of our households manage with just 230V stuff. We have 400V available similarly from 3-phaseness, but it has very little use in households (we never connect anythingbetween the phases, but we surecould).

author: bitwelder
author_rank: Super Contributor
timestamp: April 09, 2025, 08:59:05 am
content: Quote from: Siwastaja on April 09, 2025, 07:29:25 amI'd guess the lower is the 'basic' voltage, the higher will be the average currents to carry, and with it will go also the need for thicker copper cables, etc.So it will be easier to reach a 'breaking point' where it gets more convenient to distribute also a secondary, higher voltage, for high-power devices.

author: Siwastaja
author_rank: Super Contributor
timestamp: April 09, 2025, 09:32:47 am
content: Quote from: bitwelder on April 09, 2025, 08:59:05 amThis being said, most of the world ended up distributing only 220 .. 240V to residential and light commercial end users and it seems high enough for decent copper use. Since 120V does not offer any significant savings in insulation requirements or shock safety, 120/240V dual system does not seem to have any point; they could usethe highervoltage for everything, like the rest of the world.But I guess it's the tradition. It makes no sense to make large fundamental changes to a working system.

author: bitwelder
author_rank: Super Contributor
timestamp: April 10, 2025, 07:52:57 am
content: Yeah, it's the burden of the legacies. If there is a large installed base that follows a certain (working) standard, there needs to be a very compelling reason to move everything to a new one.

author: EPAIII
author_rank: Super Contributor
timestamp: April 12, 2025, 01:47:28 pm
content: Why two Voltages? It probably all comes down to economics. First mention was made of that being how the US does it. For better or worse, a lot of equipment is designed for use here. And when some company expands it's line to include additional countries, the equipment that is already designed for the US will be less expensive than new designs that are specific to only the smaller markets that those countries represent. So if an existing design can have only minimum changes and function in other countries it will be less expensive and will sell better.Another economic reason is the materials involved. Copper wire, for one, tends to be expensive due to and in proportion to the amount of copper in it. If you add to that the economics of standardization and volume production and sales, you get another economic advantage in having limited, standard sizes of wire. Example: when I retired, I rewired my garage for a shop. I wanted circuits for a number of different purposes from low power things like LED lights at the various work locations to high power things like heating and AC. I could have sized the wire for each circuit according to the individual needs: some 14 gauge, some 12 gauge, and, if I stuck to one Voltage, some even larger gauges for machines that use a lot of power. And I would have either paid top price for each run by just purchasing what was needed for that run or I would have needed to purchase 50 or 100 foot coils of several different sizes, each of which would have generated a scrap of unknown length.Instead I decided to standardize on just one gauge of wire, 12 gauge. With two different Voltages I could run 115 Volt circuits which could handle 20 Amps. that would cover the majority of my needs. But when higher power was needed, instead of forcing me to use a heavier gauge of wire, the US dual Voltage system allowed me to get twice as much power delivered with that same same, 12 gauge wire. I wound up purchasing several 50 foot coils of armored cable and I used it for everything. By buying the standard sized coils the price was kept to a minimum because that is a common wire size here and, with careful planning, I had only one sizeable scrap.Not only that, but the power wasted in the wiring (i^2 x R) is held to a minimum by keeping the Amperage as low as possible. The Amperage is the squared term in that equation. So I continue to save money every time I use something in my shop. Much of the original wiring in my home is 14 gauge and I pay for the extra lost power every day.There are other economic arguments in that single phase, split phase, two phase, three phase thing. For one thing, different transformers are often needed and there's a lot of copper and steel as well in those things.Basically it is all economics. Economics at various different levels.