4500w Element on two 110 outlets

So thinking about building a electric setup in my basement and at first I thought I needed to install a bunch of new 240 gfci breaker stuff. But since I'm really cheap and trying to figure out the easiest way of doing this, I was wondering if two 20 amp outlets on different poles hooked up to a 4500w element would work. I already have the outlets so all I would have to do is change them to gfci plugs. Wouldn't this work pretty much the same as a double pole 240 breaker?

ddahl84 said:

So thinking about building a electric setup in my basement and at first I thought I needed to install a bunch of new 240 gfci breaker stuff. But since I'm really cheap and trying to figure out the easiest way of doing this, I was wondering if two 20 amp outlets on different poles hooked up to a 4500w element would work. I already have the outlets so all I would have to do is change them to gfci plugs. Wouldn't this work pretty much the same as a double pole 240 breaker?

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The setup would be one Pid controlling a ssr and one pump. Much like all the BIAB setups found in the forum.

You know if this is in your basement you should probably just run the correct wire, have the correct receptacles and be able to sleep good at night. Cost is like $100 maybe seems like a lot but then there's the what if factor...

If the setup works from the pic attached wouldn't it work to just use line from plug 1 to a ssr then line from plug 2 to a contactor?

AC current has a frequency. That's the alternating part of AC. If I explain this correctly, 120v AC uses a single phase. It runs at 60Hz. It requires a neutral to complete the connection. With 240v, there are 2 120v lines, but they run in 2 phases which are 180 degrees from each other. There is no neutral. Since they are out of phase from each other, the opposite leg of each is the effective neutral. And because there are 2 legs there of 120v there is 240v.

Wiring 2 120v lines from the same circuit will likely overload the breaker for that circuit, be in the same phase and not produce the power you expect.
Wiring 2 120v from 2 separate circuits has a probability of not working because they might be fed from the same phase and thus not capable of producing 240v.

If you are considering using 240v for your ebrewery, you should really lay the foundation for it correctly and put in 240v for it. That way you know it's correct. Otherwise you'll likely be on here asking us to troubleshoot why your element isn't getting hot.

Thanks for your input. Still not 100% sure why it wouldn't work. If the circuit breakers are right next to each other in the electrical box that means they are on the two different legs just like a 240 circuit breaker right? And if your using a four prong outlet that has a neutral doesn't it? So putting the two hot wires, one to the ssr going to a contactor then the other hot also going to the contactor, that's two 120 lines from different legs making 240. I thought that's how 240 works? I wish I knew how P-J makes those nice schematics cause then I could post one and see what people's thoughts were about it. Maybe I'm not explaining myself well. I'm also not jumping into this without making sure its safe. That's why I posted the question to get feed back.

trying to figure out the easiest way of doing this

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The easiest way would be to do it properly with a dedicated 240 circuit.

Maybe I'm not explaining myself well.

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I think everyone knows what you want to do and stlbeer told you exactly why it would and wouldn't work.

Wiring 2 120v lines from the same circuit will likely overload the breaker for that circuit, be in the same phase and not produce the power you expect.
Wiring 2 120v from 2 separate circuits has a probability of not working because they might be fed from the same phase and thus not capable of producing 240v.

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If you can overcome those concerns by making sure they are out of phase it would work. You'll have to gauge how comfortable you are with that type of a setup which I think most would consider a hack at best.

ddahl84 said:

Thanks for your input. Still not 100% sure why it wouldn't work. If the circuit breakers are right next to each other in the electrical box that means they are on the two different legs just like a 240 circuit breaker right?

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Exactly like a 240 breaker with the exception of the little rod that goes through the holes in the two toggles and ties them mechanically together so that if one phase trips the other does too. In fact if you take two single pole breakers, glue them together and put in this little tie bar you will be hard pressed to tell the difference between the combo and a 240 V 2 pole breaker. So why not just buy a 240V breaker? It should be a GFCI breaker given the application (and that will cost a couple of bucks).

ddahl84 said:

And if your using a four prong outlet that has a neutral doesn't it? So putting the two hot wires, one to the ssr going to a contactor then the other hot also going to the contactor, that's two 120 lines from different legs making 240. I thought that's how 240 works?

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Yes, that's how it works. Look at these symbols: >E The > represents a coil of wire with the left end being the end of the wire. This is hooked to high voltage on the pole. The E represents another coil of wire wound on the same core as the > coil. If the top of the > is positive with respect to the bottom the top wire on the E will be positive with respect to both the middle wire and the bottom wire and the middle wire will be more positive than the bottom wire. If one puts the common lead on an oscilloscope on the middle wire of the E the top wire will appear positive with respect to the middle wire by 120 V (at the peak of a cycle) and at the same instant of time the bottom wire will appear negative with respect to the middle wire by 120V. The top wire will thus be 240 V positive with respect to the bottom wire. In your breaker panel there are bars that run vertically from top to bottom one connected to the top of the E and one to the bottom. The middle is the neutral (and it is bonded to an earth rod at the service connection. Circuit breakers in a given column attach alternately to one bar and the other with double pole breakers attaching to both as noted. This is called a 'biphase' system.


So yes, it will work. I only have one remaining question. What do you think an insurance adjuster standing in the ashes of your house after an electrical fire would have to say about the proposed installation even if it had nothing to do with the actual cause of the fire?

I think you would be much better off installing two 2000 watt elements and powering each one from a separate 20 amp circuit. You would just need two SSR's instead of one.
I'm not saying your plan wouldn't work. It could if you use two circuits that were out of phase. I have done my share of "creative" wiring, but this plan makes even me cringe.

ddahl84 said:

Thanks for your input. Still not 100% sure why it wouldn't work.

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If the explanations so far are not good enough for you to understand why this is a bad idea then I don't think you should be working with electricity at all without a lot more research on your part. You need a better understanding of the functions of electricity before jumping into something like this. Circumventing safety to save cost when dealing with something that can easily kill you is a terrible idea.

ddahl84 said:

So thinking about building a electric setup in my basement and at first I thought I needed to install a bunch of new 240 gfci breaker stuff. But since I'm really cheap and trying to figure out the easiest way of doing this, I was wondering if two 20 amp outlets on different poles hooked up to a 4500w element would work. I already have the outlets so all I would have to do is change them to gfci plugs. Wouldn't this work pretty much the same as a double pole 240 breaker?

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Bad idea - PLUS - it will not work as you plan based on the highlited text of your post. With a GFCI circuit, the breaker is counting on the balance of the power being delivered in each conductor. With your stated plan, current delivered through one circuit is being returned through another circuit. The GFCIs will trip every time.

Do it right and don't play "You Bet Your Life".

ajdelange said:

So yes, it will work. I only have one remaining question. What do you think an insurance adjuster standing in the ashes of your house after an electrical fire would have to say about the proposed installation even if it had nothing to do with the actual cause of the fire?

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That might be the best answer I've got yet.

And yes I do understand electricity enough to build digital temp controls for my fridge and install new circuit breakers. I've also rewired and fired electric kilns. And I understand it enough to come up with this dumb idea. Just brain storming and asking questions. I thought that's what forums where for?

Here is an option. take one 20a circuit and make it 240v (two hot and a ground.) you will still have the other circuit for your 120v stuff

OMJ said:

\You need a better understanding of the functions of electricity before jumping into something like this.

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There is a bit more to it than that. It needs to be code compliant or your insurance goes out the window as I hinted in my earlier post. In addition to that there may be a requirement in your jurisdiction that electrical work be done by a licensed electrician. This is especially likely in blue states (strong unions) and by fiddling in your electrical box you may be violating local law. And there is doubtless a requirement that any electrical work be inspected. In any case if you do, or intend to do, anything like this you need a copy of the NEC (available from Amazon) and need to understand it. Good luck with that. It used to be a booklet. Now its a tome.

In anticipation of this sort of thing when they built my garage I had them pull (2) 4-wire (+ phase, - phase, neutral and earth) circuits wired to 4 prong outlets and fed by 240 V GFCI breakers. I can plug in one of those octopus things that comes with generators for 120V circuits or plug in directly for 240 V for bigger loads (smoker, pump, welder...).

ajdelange said:

It needs to be code compliant or your insurance goes out the window as I hinted in my earlier post. In addition to that there may be a requirement in your jurisdiction that electrical work be done by a licensed electrician.

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And that's one of the reasons that I was trying to figure out a way to use the 120 outlets that are already there. I wouldn't have to install anything new.

As separate circuits usually go to different parts of the house I'm picturing an outlet in the brewery cabled to one in the next room. Doesn't give me a warm tummy feeling. What would make more sense would be to pull out the 120V outlet in the brewery and replace it with a 240 V outlet and remove the white (neutral wire) from the neutral strip in the panel and tie it to the pole of another breaker on the opposite phase or better still install a two pole breaker in the panel and connect white and black to its poles. This is doubtless a code violation because those wires are supposed to be black and red but at least you now have a more or less normal installation with the exception of the color of the wires. This assumes you installed a 2 pole breaker. Using two existing breakers or adding a second single pole for this circuit would be a code violation because the two breaker poles are not mechanically linked. I guess if you put them adjacent to one another (which would give opposite phases as desired) you could put the link in thus removing that objection practically speaking if not in terms of strict adherence to the book.

Also be sure to consider wire size when choosing a breaker. The breaker is there to protect the wiring - really to protect the house by keeping the wiring from getting too hot. It's been a while but as I recall you need 12 gauge for more than 15 amps. The important consideration is that you can't just decide you want to increase the amperage and do that by replacing the breaker with a bigger one.

ajdelange said:

As separate circuits usually go to different parts of the house I'm picturing an outlet in the brewery cabled to one in the next room.

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Nope. One is a 30 amp 10g wire with one outlet installed on it only. The other is a 20 amp 10g wire with only one outlet on it as well. Both are right next to each other about three feet from the main breaker. This is another reason it would be nice to use what is already there rather than install new stuff. From the sounds of it though its not going to work.

Given that a new 20 amp 2 pole breaker would cost you about $15 it just really seems penny wise and pound foolish not to install one of those and wire to one of the existing boxes with a proper 240 V outlet. If you wrap red tape around the white wire then that would even get you kosher wrt the wire colors.

is your clothes dryer in your basement?

Unplug your dryer and use that plug when you brew, then plug it back in when you are done so that your wife doesn't get upset with you.

stlbeer said:

AC current has a frequency. That's the alternating part of AC. If I explain this correctly, 120v AC uses a single phase. It runs at 60Hz. It requires a neutral to complete the connection. With 240v, there are 2 120v lines, but they run in 2 phases which are 180 degrees from each other. There is no neutral. Since they are out of phase from each other, the opposite leg of each is the effective neutral. And because there are 2 legs there of 120v there is 240v.

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FWIW, 240 isn't two phase power. It's just single phase power, typically with a center-tapped secondary on the transformer. Using the full winding of the transformer gives you 240V, using the center tap to either end gives you the two 120V legs.

The common terminology for this arrangement is 3-wire split phase.

In addition to some of the things already mentioned, using two single pole breakers for 240V circuit is a dangerous situation (and quite likely a Code violation) unless the handles are tied for common trip (essentially making it a 2-pole breaker). If only one leg tripped out using separate breakers the circuit could/would still be hot through the other leg.

whoaru99 said:

FWIW, 240 isn't two phase power. It's just single phase power, typically with a center-tapped secondary on the transformer. Using the full winding of the transformer gives you 240V, using the center tap to either end gives you the two 120V legs.

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Technically it is. It is just that the two phases are 180 ° apart as opposed to some other angle such as the (approximately) 90° phase shift between the phases in a 2 phase motor that uses a running capacitor. It it often referred to as bi-phase, as opposed to three phase or polyphase and sometimes as split phase to recognize that it can be obtained from a center tapped winding as explained in #8 with the >E 'diagram'. If you ask an electrician what the black, red and white wires connected to a 240 V 4-wire outlet are he will answer 'phase, phase and neutral'.

whoaru99 said:

In addition to some of the things already mentioned...

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This was mentioned explicitly in #16 and alluded to in #8. But as the potential hazard is great enough it is probably worth mentioning again. Another aspect of it is that it would be impossible to use GFCI breakers in the box though one could use a GFCI outlet (in a single outlet arrangement - not the originally proposed dual outlet scheme).

ajdelange said:

Technically it is.

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No, it is not two phase power. It is a single, split phase. Just because lots of people call the legs "phases" doesn't make the correct. Almost everyone refers to the neutral wire in a 120V circuit too, but technically it's the grounded wire. There is no neutral wire in a 120V circuit yet that's the parlance.

L1 and L2 being 180 out of phase is merely a matter of the reference point. Using the full winding of the transformer to obtain 240V is decidedly single phase with no relevance to 180 in or out of phase.

The system is 240V, center tapped, which facilitates also providing two 120V legs; not two 120V legs that can also provide 240V.

whoaru99 said:

No, it is not two phase power.

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Yes, actually it is. Any system with 3 or more wires in which two or more (called phases) are at potentials with respect to one designated as the 'neutral' which peak at different times is a polyphase system. If there were a total of 4 wires and their voltages with respect to the neutral peaked 1/3 of a cycle apart I think you'd agree that we have a 3 phase system. Now suppose there are 2 wires and the voltage on one phase wire peaks 1/4 cycle later than the voltage on the other. This is a biphase system with 90 ° shift. Power used to be generated and distributed this way. Each phase was developed by a coil on the stator of a generator and these were at right angles. If I took a notional generator in which the coils could be moved to any position and shifted the one at right angles to 120 ° we'd have biphase with a 120 ° phase relationship. Thus is exactly what is done in 3-phase generation except that an third coil at 240 ° is also added and that is connected to the 3rd phase wire (we're ignoring number of poles considerations here). If I moved the 2nd coil to 179 ° we'd have a biphase system with a 179 ° relationship and if we moved it to 180 ° then we'd have a biphase system with 180 ° phase shift.

As my generator is a bit impractical and I'd have to build it I'd probably just buy a three phase generator, connect one end of one stator coil to neutral, connect the other end to a red wire, then take the coils from the other two phases and connect them in series with one end of the series chain connected to neutral and the other to a black wire. This would give me biphase with a 180° phase relationship. I actually worked briefly at facility where someone installed a trailer wired for 120 biphase 60 Hz and the facility had 408 three phase 50 Hz. They got the 120V biphase they needed by wiring the generator on an MG set exactly as I described.

Simpler than generators or MG sets is to center tap the coil of a secondary of a transformer. You still get a neutral and 2 phases and its still biphase with a 180° relationship. The fact that you can get it by center tapping a single winding doesn't somehow remove the biphase properties.

whoaru99 said:

It is a single, split phase.

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You can get it by 'splitting' a phase but you can also get it by combining 3 phases or by combining 2 as with my hypothetical generator or by wiring two inverters to a common (neutral). In your house you may know that it came from splitting a phase but at my overseas site it didn't and if you are in an industrial setting or large apartment building it probably comes from 2 out of 3 phases of a Y connected 3 phase distribution with the neutral being the neutral of the 3 phase system (in which case you would have two 120 V circuits and/or one 208 V circuit).

whoaru99 said:

Just because lots of people call the legs "phases" doesn't make the correct.

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What makes it correct is wide acceptance by engineers who work with this stuff. And it's probably in the IEEE dictionary because I know I didn't invent it.

whoaru99 said:

Almost everyone refers to the neutral wire in a 120V circuit too, but technically it's the grounded wire. There is no neutral wire in a 120V circuit yet that's the parlance.

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The NEC calls the white wire the 'grounded conductor' and the bare or green wire the 'grounding conductor'. Little wonder that most of us prefer to refer to the neutral as the neutral.

whoaru99 said:

L1 and L2 being 180 out of phase is merely a matter of the reference point. Using the full winding of the transformer to obtain 240V is decidedly single phase with no relevance to 180 in or out of phase.

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Yes that's so and once that reference is available you have created a polyphase system as I explained above at some length above.

whoaru99 said:

The system is 240V, center tapped, which facilitates also providing two 120V legs;

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As I noted above I have worked in several places (including here in the US) where it is not 240V center tapped. To assume that it always is (though that may almost universally be the case for home brewers in the US - I have been to one country where I noticed that the homes are wired 3-phase) is not only incorrect but obscures the fact that a split phase system is indeed a polyphase (biphase) system even in this case.

whoaru99 said:

...not two 120V legs that can also provide 240V.

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But that's exactly what they are that's exactly how they are used in house wiring! There are two windings on the transformer on the pole that are connected in series to provide 240 and are used separately to provide 120 circuits relative to the point where those windings interconnect. The two windings may be made by spooling on half the turns, bringing out a loop and then winding the other half of the turns but they are in fact two series connected windings with their common point available.

Perhaps it's all just semantics. If I point out a dog to you and you say no, it's not a dog, it's a Leonberger you are right to some extent but the fact of it being a Leonberger does not mean it is not a dog.

No. It is not two phase and those two legs are not 180 deg out of phase.

Perhaps the transformer drawing I marked up (showing just a half cycle to keep it less cluttered) will clarify it. It's clear the two 120V legs are in phase. They have to be because it can't go both ways simultaneously as would be the case in the lower illustration. If that even worked, the neutral would see the sum of the currents not the difference which is further evidence to support the single, split phase illustrated at the top, not the 180 degrees out of phase myth.

It's all about the transformer windings in series, nothing about phase in this case.

If you want to run that 2-phase thing higher up the flag pole I suggest trying it on a dedicated electrical forum such as forums.mikeholt.com.

I'm not your EE prof. but what your drawing is missing is the little dots that go at one end or the other of the coils. If you wind two separate windings on a core in the same direction the start of the windings would be unmarked on the drawing and the end of the windings would be marked with a dot (or the dots could go at the start ends - it's arbitrary as long as it's consistent). A biphase transformer, as found on a power pole, would have the dots at the tops of the two windings i.e. on your top drawing there would be dots at the top of the upper winding and at the top of the lower winding (adjacent to but below where you have the neutral wire). If you separate the place where the winding are connected and put an oscilloscope (triggered from the primary - carefully, it's 13.8 kV) with the common on the start wire and the probe on the finish (dotted) wire you will observe a sine wave in phase with the primary (assuming the dot is at the top of the drawing for the primary winding too.) If you move the scope leads to the bottom winding you will see the same thing (again with the probe at the dotted wire) you would see the same thing. The two windings, considered separately, each produces 120V. At the peak of a cycle they are like 120V batteries. If you join the windings (the dot on one to the unmarked on the other) they are like two batteries connected in series. The voltage from the bottom most wire to the topmost wire is 240 Volts. If, in this case, you connect the common wire of the oscilloscope to the common connection and move the probe to the top wire you will see + 120V (at the peak) i.e. a waveform in phase with the primary. But when you move the probe to the bottom wire you will see -120V at the peak (a waveform that is 180° out of phase with the top coil and the primary. Thus: 3 wires, 2 phases. It's a biphase system.

Your bottom drawing is intended to represent the case where the dot is at the top for the top winding and at the bottom in the bottom winding. It is like connecting two batteries in series with the two negative terminals in common. The potential relative to the connection (reference) of the one battery is +120 and the potential referenced tothe common point of the other battery is +120. The potential difference between the two (non common) terminals is 120 - 120 = 0. The same thing happens if you connect transformer winding in a 'bucking' connection.

As we've just seen, transformer winding in series is all about phase. I mentioned in my last post that you can also get 120/240 biphase from a 3 phase system by connecting 3 transformer windings in series but they must be phased correctly. I brought that up to get you to think in broader terms IOW to understand that a center tapped transformer isn't the only way to get 120/240. This should help you to see that the center tapped transformer is indeed a biphase hookup.

If this is a myth I've surely known hundreds of engineers, not only in power but audio and rf design where exactly the same principles apply, who have been taken in by it and a lot of text books will need to be burned.

[EDIT] Where I say 'peak' here I am neglecting to mention that the actual peak voltages are sqrt(2)*120. As we're confused enough here without bringing in that aspect I though this would best be omitted but in retrospect I think it should at least be mentioned. Thus this edit.

stlbeer said:

AC current has a frequency. That's the alternating part of AC. If I explain this correctly, 120v AC uses a single phase. It runs at 60Hz. It requires a neutral to complete the connection. With 240v, there are 2 120v lines, but they run in 2 phases which are 180 degrees from each other. There is no neutral. Since they are out of phase from each other, the opposite leg of each is the effective neutral. And because there are 2 legs there of 120v there is 240v.

Wiring 2 120v lines from the same circuit will likely overload the breaker for that circuit, be in the same phase and not produce the power you expect.
Wiring 2 120v from 2 separate circuits has a probability of not working because they might be fed from the same phase and thus not capable of producing 240v.

If you are considering using 240v for your ebrewery, you should really lay the foundation for it correctly and put in 240v for it. That way you know it's correct. Otherwise you'll likely be on here asking us to troubleshoot why your element isn't getting hot.

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That is about the best explanation I have ever read.

The neutral is the reference point with respect to which phase voltages are measured (where you connect the black wire from the scope). As in a 240V outlet you only have 2 wires either one or the other has to be the neutral. But if I only give you 2 wires in a 120V circuit it is exactly the same thing. You have to connect the black wire somewhere. In the 240V case you can choose either the red or black wire to be the neutral because neither is the system neutral. That's the white wire which you don't find in older clothes dryer installations, for example (but the earth wire is connected to the neutral at the panel). In a 120V circuit you don't have a choice. The neutral is the white wire though in terms of making a measurement you could just as well connect the black wire of the scope to the black wire in the outlet and the probe to the white wire.

So the explanation is a fairly good one except for the 'uses a single phase' part. Each 120V circuit is connected to one or the other of the two antipodal (or approximately antipodal) phases available in a biphase system. Each 240 V circuit is connected across those two phases in series.
[EDIT] But connecting across one of the available phases is using that phase so I guess what I'm 'objecting' to is failure to mention that the other phase is there and that a different 120V circuit may be connected to it.

As phase is so confusing think of two AA batteries connected in series. You can get several voltages from that connection simultaneously
1) + 1.5 V between common point and + terminal on one battery
2) - 1.5 V between common point and - terminal on the other.
3) + 3 V between - terminal one battery and + terminal on the other.

ajdelange said:

I'm not your EE prof. but what your drawing is missing is the little dots that go at one end or the other of the coils. If you wind two separate windings on a core in the same direction the start of the windings would be unmarked on the drawing and the end of the windings would be marked with a dot (or the dots could go at the start ends - it's arbitrary as long as it's consistent). A biphase transformer, as found on a power pole, would have the dots at the tops of the two windings i.e. on your top drawing there would be dots at the top of the upper winding and at the top of the lower winding (adjacent to but below where you have the neutral wire). If you separate the place where the winding are connected and put an oscilloscope (triggered from the primary - carefully, it's 13.8 kV) with the common on the start wire and the probe on the finish (dotted) wire you will observe a sine wave in phase with the primary (assuming the dot is at the top of the drawing for the primary winding too.) If you move the scope leads to the bottom winding you will see the same thing (again with the probe at the dotted wire) you would see the same thing. The two windings, considered separately, each produces 120V. At the peak of a cycle they are like 120V batteries. If you join the windings (the dot on one to the unmarked on the other) they are like two batteries connected in series. The voltage from the bottom most wire to the topmost wire is 240 Volts. If, in this case, you connect the common wire of the oscilloscope to the common connection and move the probe to the top wire you will see + 120V (at the peak) i.e. a waveform in phase with the primary. But when you move the probe to the bottom wire you will see -120V at the peak (a waveform that is 180° out of phase with the top coil and the primary. Thus: 3 wires, 2 phases. It's a biphase system.

Your bottom drawing is intended to represent the case where the dot is at the top for the top winding and at the bottom in the bottom winding. It is like connecting two batteries in series with the two negative terminals in common. The potential relative to the connection (reference) of the one battery is +120 and the potential referenced tothe common point of the other battery is +120. The potential difference between the two (non common) terminals is 120 - 120 = 0. The same thing happens if you connect transformer winding in a 'bucking' connection.

As we've just seen, transformer winding in series is all about phase. I mentioned in my last post that you can also get 120/240 biphase from a 3 phase system by connecting 3 transformer windings in series but they must be phased correctly. I brought that up to get you to think in broader terms IOW to understand that a center tapped transformer isn't the only way to get 120/240. This should help you to see that the center tapped transformer is indeed a biphase hookup.

If this is a myth I've surely known hundreds of engineers, not only in power but audio and rf design where exactly the same principles apply, who have been taken in by it and a lot of text books will need to be burned.

[EDIT] Where I say 'peak' here I am neglecting to mention that the actual peak voltages are sqrt(2)*120. As we're confused enough here without bringing in that aspect I though this would best be omitted but in retrospect I think it should at least be mentioned. Thus this edit.

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It is not two phase power and the legs are not 180 out of phase.

The explaination with the oscilloscope is a common one, albeit flawed, because both leads have to be moved, not just one. Using the center tap as reference is the reason that oscilloscope example is flawed. This is akin to putting the black lead of a multimeter on the positive battery post and the red lead on the negative post, the proclaiming the battery polarity has miraculously reversed because the multimeter shows negative voltage.

So I think I've decided I'm going to go with two 1500 or 2000 watt 120 v elements and two ssr. Just like the diagram I posted on page 1 which i think was from P-J.
Next question I have is can I use the 30 amp 120v circuit and run both elements or should I still use two separate circuit breakers? The 30 amp breaker I have has one outlet and doesn't have anything else installed on it. And thanks for the input this is really helping me decide what system I'm going to go with.

ajdelange said:

As phase is so confusing think of two AA batteries connected in series. You can get several voltages from that connection simultaneously
1) + 1.5 V between common point and + terminal on one battery
2) - 1.5 V between common point and - terminal on the other.
3) + 3 V between - terminal one battery and + terminal on the other.

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I'm glad you posted that because it illustrates exactly why saying the legs are 180 out of phase is flawed.

Sure, measuring from an improper point of reference gives that appearance, but if you actually put the batteries 180 out of phase, negative to negative or positive to positive, (or if the two power legs were 180 out of phase) you still get 1.5V (or 120V) across each one, but you don't get 3V (or 240V) because they cancel.

ddahl84 said:

So I think I've decided I'm going to go with two 1500 or 2000 watt 120 v elements and two ssr. Just like the diagram I posted on page 1 which i think was from P-J.
Next question I have is can I use the 30 amp 120v circuit and run both elements or should I still use two separate circuit breakers? The 30 amp breaker I have has one outlet and doesn't have anything else installed on it. And thanks for the input this is really helping me decide what system I'm going to go with.

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2x 1500 would work on a 120V-30A circuit with a little cushion.

2x 2000 wouldn't be a good plan because that's 4000W and is greater than the 3600W a 120V-30A circuit should be called on to provide at max nominal load.

whoaru99 said:

2x 1500 would work on a 120V-30A circuit with a little cushion.

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Would that little cushion be enough to also run a pump? Or should that be separate

whoaru99 said:

It is not two phase power and the legs are not 180 out of phase.

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It is indeed as we shall see in a moment.

whoaru99 said:

The explaination with the oscilloscope is a common one, albeit flawed, because both leads have to be moved, not just one.

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No. That's not true. Reread what I wrote. The low side of the scope is connected to the common point between the two phases. If the probe is connected to one phase of the system you will see a wave form in phase with the primary. If you then move only the probe lead, leaving the low lead in place, to the other phase you will see a waveform 180 ° out of phase with the primary.

But a picture is worth a thousand words. You'll have to look closely to pick up some of the details but they are all there. The yellow cable is connected to a 4 prong 120/240 biphase system (right of the panel in the brewery). This cable makes both phases available in, respectively, cable marked with a black stripe and unmarked. There is a plug in a striped (but the stripe is barely visible at the right edge) and another in an un striped line. As you can see, though again you have to look closely, a red aligator clip is hooked to the gold (hot) terminal in one phase and a red one to the gold terminal on the plug connected to the other phase. You will also see a white wire connected to the silver (neutral) plug on the striped phase. No need to run this wire again from the unstriped as the neutral is common to both - it is the neutral of every circuit connected to this panel. It is connected to the center tap of the transformer on the pole.The white wire runs to the low wire of oscilloscope channel B (gray probe) and is jumpered (yellow) to the low wire of the other (A, red) oscilloscope channel. Thus both oscilloscope channels are measuring relative to the neutral. The oscilloscope shows two waveforms of identical amplitude but opposite (180 °) phase.

whoaru99 said:

Using the center tap as reference is the reason that oscilloscope example is flawed.

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You now have solid visual evidence that the oscilloscope example is not flawed. If you have an oscilloscope you can repeat what I did (just in case you think I photoshopped this - and I did, I used unsharp mask to make the picture a little clearer) and you will get exactly the same result which is, very plainly, two phases in a 180° relationship to one another.

whoaru99 said:

This is akin to putting the black lead of a multimeter on the positive battery post and the red lead on the negative post, the proclaiming the battery polarity has miraculously reversed because the multimeter shows negative voltage.

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No, it is akin to connecting two batteries in series and hooking the black lead of a voltmeter to the common point then measuring the two voltages at the other ends of the two batteries. You would get, with 1.5 volt batteries, + 1.5 and - 1.5 and, of course 3 across the outside.

So you've now had detailed theoretical explanations from an electrical engineer, multiple examples and visual evidence. Plus the 'step back from the trees to see the forest' concept which is that if you are right electrical engineers, the professors that taught them, GE, Westinghouse and Siemens and all the textbooks have all been wrong from the days of Steinmetz and Tesla (who invented 3 phase power) to the present.

If you can't take in what your eyes show you then I fear there isn't much else I can do for you.

It is not two phase power with two legs 180 degrees out of phase.

That connection of the o-scope doesn't hold water for this purpose. Neutral isn't the correct reference in this regard. Use the waveform math on that scope and add those two together. Do you get 240V or zero?

You have to use an end point for reference because it's the only place you can get 120 AND 240, and as you see below they are in phase and that the voltage on CH B is 2x that of CH A because it's taken at the correct reference for a 120/240V circuit (disclaimer, I'm using a small step down transformer from the line but net result is the same, just lower voltage).

I do like your newer ScopeMeter though, but for my uses this old dog still hunts.

ddahl84 said:

Would that little cushion be enough to also run a pump? Or should that be separate

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IDK. What's the draw on the pump?

I believe it's 1.4 amps.

The heating elements and the pump would still be a few amps less than 30.

sudbuster said:

Are you stupid, or just ignorant?

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I guess stupid. This will teach me not ask questions. Thank you for your informative response.