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How to wire up a 240VAC receptacle
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Spork Schivago:

--- Quote from: Richard Crowley on May 19, 2018, 12:33:03 pm ---
--- Quote from: Spork Schivago on May 19, 2018, 07:20:11 am ---Because we don't have an L1 and L2,
--- End quote ---
But we DO have L1 and L2. Those are the names of the two "hot" wires coming into your house.  Between L1 and L2 are 240VAC.

In North America, the center-tap between L1 and L2 is grounded and all the 120V loads are connected between the center tap (called "Neutral") and EITHER L1 or L2, so you get half the incoming 240V  And 240V loads are connected BETWEEN L1 and L2.

In most of the rest of the world, they use L1 and L2 (240V) directly.  In many cases "L1" is grounded and called "Neutral". That is the industrial standard and that is what your PDU is designed for.

In some parts of the 240V world, BOTH sides (L1 and L2) are "above ground" and not even ground-referenced at all. They must treat ALL the wires as "hot" except the green-wire safety ground (which they call "PE" Proective Earth)  Because of this, much (most?) 240 volt equipment is designed with the assumption that BOTH sides are "hot".  That is why I find it so curious that you claim that your loads (servers) won't operate if both L1 and L2 are "hot".

--- End quote ---
HPE claims the loads won't work if I try wiring this PSU up to 120-0-120.   But I don't know if this matters, there's more inputs than just the three wires on the 1400 watt PSU.   There's actually a total of 7.   4 of which are made to communicate with the intelligent PDUs (which I don't have, and didn't want, because I don't like them but might  have been able to purchase one of those).   This was the only reason I was thinking HPE might have been correct, those four pads inside the connector there....but I'm going to try and send the PDU back now and purchase the ones made for 120-0-120 and see how it actually works, see if they're wrong and you guys are right.   You guys seem to really know your shit, and everything you guys have said has made since.


--- Quote from: Richard Crowley on May 19, 2018, 12:33:03 pm ---
--- Quote ---because the 240VAC is on the same phase, where do the electrons go if they're not hooked to a neutral or ground to complete the circuit?    Somehow they have to make it back to the breaker, correct? 
--- End quote ---
The electrons go BETWEEN L1 and L2.  When you say "because the 240VAC is on the same phase" it makes no sense.  That is like saying that a yard-stick is 36 inches long no matter if you hold it at one end or the other end.  Or if you hold it in the middle ("split-phase")


--- Quote ---I use the word ground, but all I mean is a completed circuit.   I know and understand that a completed circuit doesn't need a ground or a voltage potential of 0V.   I could technically power a circuit where the supply is 24V and the return is 12V.   So long as the return is at a lower voltage potential than the supply, we can have the electrons moving.
--- End quote ---
Yes, for 1/120th of a second. And then 1/120th of a second later, the 240V has changed to the opposite polarity (which is why it is called ALTERNATING current.


--- Quote ---Using the water analogy that everyone seems to like to use, we have our "pump" (the transformer I'd buy for the PDU, for example).   The "water" (electrons) flow out of L1 into the PDU.   But then what?
--- End quote ---
The current flows around the loop from L1 through L2 back to the transformer on the pole.  The center-tap is there to split the 240V in half so that our historic North American standard of 120V loads can get 120V and not the full 240V coming into your house.

--- End quote ---
But we're not talking about the center tapped 120-0-120VAC source.   I'm talking about the transformer, if I bought that.   But after you saying we still have an L1 and L2, I believe I understand.   It doesn't matter, to the PDU, if L1 and L2 are both hot (120VAC different phases) or one hot (240VAC) and the other neutral.   It acts the same.


--- Quote from: Richard Crowley on May 19, 2018, 12:33:03 pm ---
--- Quote ---They need to make it back to the "pump" (transformer) somehow.    I know you say ground / neutral is irrelevant, but in this case, I cannot imagine how those pesky little buggers would make it back to complete the circuit without using one of those other wires that are at 0V potential.
--- End quote ---
   
Neither L1 nor L2 are  "at 0V potential".  Even "Neutral" wouldn't be "at 0V potential" unless it was (artificially) grounded.  The current flow of a 240V load never sees neutral/ground.


--- Quote ---The components inside the PDU would be the loads
--- End quote ---
No. The things (computers) plugged into the PDU are the loads.  The PDU is just a fancy, expensive power-strip.

--- End quote ---
Yes, but each component inside the PDU is also a load.   And because there's circuitry that's running with nothing plugged into the PDU at all, the PDU is still considered a load itself.   If it wasn't, it'd be 100% efficient, instead of 80% efficient while running at x voltage, 85% efficient while running at y voltage, and 90% efficient while running at z voltage.


--- Quote from: Richard Crowley on May 19, 2018, 12:33:03 pm ---
--- Quote ---and by the time the current / electricity had passed through the entire circuit and was ready to leave the PDU, it surely wouldn't just be traveling up the L1 wire again, would it? 
--- End quote ---
A 240V load current passes between L1 and L2.  It does not know or care whether either side (or the center-tap) is grounded or not.


--- Quote ---We'd have to use one of the additional neutral / ground wires in that instance. 
--- End quote ---
NO!  240V loads use the current between L1 and L2. Neutral/ground plays no part here.  Neutral is provided only for 120V loads.

--- End quote ---
You're saying if I kept the PDU, bought that transformer, neutral / ground plays no part?   L1 and L2 are still hot?    I thought the whole purpose of the transformer was to get one 240VAC L1....because we only have one-pole breakers inside of the PDU....If L1 and L2 both have current going through them, how would this transformer protect me if one of those internal breakers where to trip?   We'd still have current going through half the output.


--- Quote from: Richard Crowley on May 19, 2018, 12:33:03 pm ---
--- Quote ---Just like if we're dealing with 120VAC receptacles.   We cannot just hook up the hot wire.   That wouldn't do diddly squat.   We'd still have to hook up the neutral so the electrons could make it back to the panel.
--- End quote ---
Yes. From the hot wire (which is either L1 or L2) to Neutral is 120V.  But between L1 and L2 is 240V.  That is what 240V loads use.


--- Quote ---With the 120-0-120, I understand how it works now.   I also understand why if I were to not use a double pole breaker but tried wiring up a NEMA L6-30R using a 30-amp single pole breaker in slot 1 and slot 2 (opposites sides of the panel), it wouldn't work.   I'd have 120VAC, not 240VAC.
--- End quote ---
Huh?  There is no such thing as a "single pole breaker in slot 1 and slot 2". Each "slot" is a pole. Between each "slot" and Neutral is 120V. But between two adjacent "slots" is 240V because all the odd number slots are connected to L1 and all the even number slots are connected to L2.  Do not be confused thinking that the left side of the breaker panel is L1 and the right side is L2. The "slots" alternate between L1 and L2 so that you can use a double breaker to provide a 240V branch circuit from two adjacent slots.

Zoom in on this photo to see the details.  L1 and L2 come in at the top from the transformer out on the pole (or buried under the sidewalk). The Neutral comes in to that big terminal at the upper right.  And it is connected to the light-colored screw terminal strip on the right side.  If you look very carefully, you will see that one of the screws in the neutral strip is colored green.  That is where the Neutral is connected to Ground in the North American standard.

Then EVERY OTHER slot is connected to either L1 or L2.  So if you put in a single-pole breaker, you connect to EITHER L1 or L2 and the return path comes back through the Neutral.  But if you install a double-pole breaker one pole connects to L1 and the other pole connects to L2. Because between L1 and L2 is 240V and the load current comes from L1, passes through the load, and returns to L2.  At least for 1/120th of a second.  And in the next 1/120th of a second the current flows from L2, through the load and back to L1.

Notice that during the discussion of a double-pole, 240V circuit there was no mention of Neutral.  And I didn't have one up my sleeve, either.



--- End quote ---

Yes, that's exactly what I was saying.   Every other slot is connected to L1 or L2.   If you where to hook single pole breakers to slot 1 and 2 (where slot 1 is hooked to L1 and slot 2 is hooked to L1), you won't get the 240VAC.   You'd get 120VAC.   You'd just be able to draw more current.   This is why those people that suggest making a DIY plug that just plugs into the two inputs on the same receptacle and are supposed to provide 240VAC will never work.   You need the supply from L1 and L2, not L1 and L1, or L2 and L2.

What I was saying was you take two single pole breakers, if you connect one to slot number 1 in the panel, and connect one to slot number 3, you've essentially created a double-pole breaker.   It wouldn't be safe, because if one breaker tripped, there's no guarantee the other would.    slot number 1 and 3 are L1, for example, 2 and 4 are L2 for example.   If you were to connect two single pole breakers, one to slot 1 and one to slot 2, and wire them expecting 240VAC between them, you wouldn't get it because both breakers would be on L1 or both breakers would be on L2.   This was my way of showing that I understood it, describing back what I learned, in my own words.
IanB:

--- Quote from: Spork Schivago on May 19, 2018, 06:09:36 pm ---On my panel, double pole breakers go every other, slot 1 and slot 3, or slot 2 and slot 4.   So I'd think 1 and 2 would both be on L1, where 3 and 4 would be on L2.

--- End quote ---

Fair enough, I probably just used the wrong words. I'm just trying to say that for a 240 V circuit the double pole breaker connects between L1 and L2, and this gives 240 V single phase. In the house wiring L1 would be the black wire and L2 would be the red wire (or vice versa--it doesn't really matter). To wire a 240 V circuit from this breaker you would use a three conductor cable with red, black and ground wires.
IanB:

--- Quote from: Spork Schivago on May 19, 2018, 06:26:19 pm ---This was the only reason I was thinking HPE might have been correct, those four pads inside the connector there....but I'm going to try and send the PDU back now and purchase the ones made for 120-0-120 and see how it actually works, see if they're wrong and you guys are right.
--- End quote ---

Please don't say "120-0-120" or "split phase" or anything like that to the sales people. It will cause confusion and get you into trouble.

What you need to say is "200 to 240 V AC single phase for use in the USA". A compatible PDU should be provided with 2-pole breakers for complete isolation of the supply, and the PSUs actually don't care. As long as the PSU is designed for "high-line" 200 to 240 V AC input it will be fine.
IanB:
A quick summary.

Here are the PDU specs:



The P9S13A says "North America/Japan, single phase 200 to 240 V input, 24 amps input, fitted with two 2-pole 20 A breakers." Therefore it can distribute 24 A to servers or other equipment.

Here are the PSU specs:



It can run off 200 to 240 V AC, single phase, at 50 to 60 Hz. Running at full load at 240 V it will draw 6.5 amps. Therefore you could probably run four of these PSUs from one P9S13A PDU, assuming that the PSUs are not going to be running flat out. (Notice it also gives the heat rating in BTU/hr to estimate the required cooling in the server room. The air conditioning unit has to remove 5300 BTU/hr for each one of these power supplies.)
Spork Schivago:

--- Quote from: IanB on May 19, 2018, 04:44:56 pm ---
--- Quote from: Spork Schivago on May 19, 2018, 07:32:38 am ---I'm sorry, I haven't gotten a lot of sleep lately, but yes, you are correct.   The NEMA L6-30P / L6-30R only has 3 wires, not four.    So in Europe and other parts of the world that use 240VAC, it's just like ours, where 120V goes down one wire, 120V goes down another?
--- End quote ---

No, there's no 120 V anywhere. Recall that voltage is measured as the difference between two wires. There are only two power conductors in the L6-30 and they carry 240 V. There is simply 240 V between the two power conductors. That's it. End of story. There is no 120 V in a correctly wired L6-30 plug or receptacle. Only 240 V. (Ignore the ground for this discussion, it is there for safety, not for power delivery.)

--- End quote ---
I think you're misunderstanding what I'm saying.   I correctly wired my NEMA L6-30P.  When L1 is referenced to L2 there's ~240VAC.   When L1 is referenced to Ground there's ~120VAC.   When L2 is referenced to Ground there's ~120VAC.   I understand the Ground is solely for safety purposes, trust me.   I'm asking, in Europe and other parts of the world, where most appliances are designed to run off 240VAC, not 120VAC, on their receptacles, when L1 is referenced to Ground, is it ~240VAC or ~120VAC?   When L2 is referenced to ground, is ~120VAC or 0VAC?   That's what I'm asking.   I know what it is in the USA with the NEMA plugs.   I know the 240VAC is acquired by referencing L1 and L2...


--- Quote from: IanB on May 19, 2018, 04:44:56 pm ---
--- Quote ---This is what my European friend was talking about I think when he said it was a language barrier and that Neutral was meant to be hot.   If that's the case though, and they have two wires carrying the 240V load, then my PDU wouldn't work over there either, would it?   Because we still have single pole breakers.   They'd need 1-phase 240VAC, not two-phase.
--- End quote ---

Breakers are about safety and system protection. If both power conductors are "hot" then each power conductor needs a breaker (a "2-pole breaker"). In North America the 208 V AC or 240 V AC supply typically has two hot conductors, so it needs the 2-pole breaker. This is what the NA/Japan models of PDU provide.

In other parts of the world only one power conductor may be "hot", in which case only the hot conductor needs a breaker (a "single pole breaker"). This is what the INTL or WW models of PDU provide. They are suitable for parts of the world like Europe, but they are not code compliant for use in North America.

Again, this is all about safety and system protection and code compliance. It is not about voltages or power requirements.

--- End quote ---
That's what I was asking.   In Europe, are there two power conductors that are hot or just one?   In America, with 240VAC using our 120-0-120 split phase, both conductors, L1 and L2 are hot, each providing 120VAC out of phase from each other by 180°.   Why 180°?   Because 180° + 180° = 360° so when L1 is +120VAC, L2 will be -120VAC, give or take.   L1 and L2 will should always be the same voltage, but opposite signs of each other.   So when L1 is at +20VAC, L2 should be at -20VAC.   That's why they're 180° out of phase from each other.   If they where something like 120° out of phase with each other, L1 might be +120VAC, and L2 wouldn't be -120VAC.
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