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230v sub. well pump

Discussion in 'General Electronics Discussion' started by jackorocko, Aug 5, 2011.

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  1. jackorocko

    jackorocko

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    Apr 4, 2010
    How does a 2 wire 230 volt w/ ground pump work exactly without no neutral leg? Can someone please explain to me how this works. Don't you need to make the "loop" so that current can flow, or is that what the ground does?
     
  2. poor mystic

    poor mystic

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    Apr 8, 2011
    Hi :)
    Probably the neutral is fixed to ground at the pump, a sensible precaution in the circumstances, and the return path is then via the combination ground/neutral leg.

    Somebody must have a copy of the regs?
     
    Last edited: Aug 5, 2011
  3. jackorocko

    jackorocko

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    What do you mean "a copy of the regs?" I read the manual and the only thing they tell you is how to hook it up.
     
  4. poor mystic

    poor mystic

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    Well that's a bit boring.
    I'd hoped it would have been some kind of special earth provision application. Sorry.
     
  5. duke37

    duke37

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    There must be two wires, one out and one back. These are normally called line and neutral. In the UK two wire devices without ground are permitted if the insulation is to a high standard and the case is insulaiting. You could show a diagram of the connections.
     
  6. daddles

    daddles

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    In the US, your home's power comes from a transformer that is center-tapped; the center tap is grounded typically both at the pole and at one location in your circuit breaker panel. The two legs of the transformer have 220/240 VAC on them. It is these two lines that are run to the pump. In addition, these lines are also typically run to power-hungry devices like the dryer, air conditioning, water heater, stove, etc.

    See the attached schematic. The picture of the power pole is typical, although many neighborhoods now put these in power boxes to eliminate the poles. The 220/240 VAC is gotten from terminals A and C. Note the grounding of the neutral B -- it's connected to the grounded high voltage side and, through a 12 gauge bare wire to a ground buried in the earth when the power pole was installed. The 7200 VAC primary power is referenced to Earth ground (which should be obvious from the schematic).

    Thus, to run any 220/240 VAC device, the device's terminals are connected to terminals A and C to make up the circuit. There is no neutral involved at all. It would have been better for the neutral to have been called the center tap, but unfortunately the nomenclature is pretty well fixed.

    Note that the voltage between terminals A and B is 120 VAC, as it also is for the terminals B and C. These two terminals are used for the 120 VAC branch circuits in your house; you can see that a neutral connection is always involved and that the neutral is always near ground potential.

    Typically, the three wires going to your pump are a grounded wire and these two 240 VAC power lines.
     

    Attached Files:

  7. poor mystic

    poor mystic

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    Apr 8, 2011
    Thanks for all that about US mains reticulation, Daddles. I had no idea and didn't know it!
     
  8. daddles

    daddles

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    Well, I should add that the pictures I gave are specific to the wiring at my house, which was built around 40 years ago. One day I got curious about how this is done and mapped things out. I'd be loath to say it represents every possible configuration, but I know it's pretty typical.
     
  9. jackorocko

    jackorocko

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    Yep, I think I get it. I even learned a bit about my old ass breaker box. I tried putting in a 2 pole breaker into two slots but both were attached to the same pole. So while each had 110 reference to ground I got 0 voltage from what you called A-C.

    As soon as I realized this, I switched the breaker out and put it into a split slot and I miraculously had 220 across A-C. My question is, how far apart where the phases under both condition? I would imagine that when I tapped into the single pole slot the phase angle would have been 180 degrees?(that don't make sense, same pole same phase angle???) But what about the split slot, what phase variance do you need to get the additive supply of 220?
     
  10. TBennettcc

    TBennettcc

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    I think 110VAC and 220VAC are both single-phase (at least in the US). 480VAC is three-phase. I don't think the 110/220 bit has anything to do with in-phase/out-of-phase. It just like using a center tapped transformer to go from 110/220 to 18 volts. If you have a center-tapped secondary, the voltages on the secondary are really 9v-0v-9v. If you measure the voltages between each end and the center, you get 9 volts. if you measure between both ends, you get 18 volts. This has to do with the number of windings in the transformer.
     
  11. poor mystic

    poor mystic

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    According to Daddles' description, the 220V is centretapped to give 2 110V domestic supplies. These are 180* apart.
     
  12. jackorocko

    jackorocko

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    Apr 4, 2010
    so that is why the rms voltage is additive, but why is a double pole breaker hooked into one leg read 0 voltage across it's to polls. Never mind I think I just answered my own question. For a voltage to be present you need to have a voltage difference between two points, if both points are at 110V potential then the difference is 0
     
  13. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    What do you get in the US if you have 3 phase power supplied to your house?

    Here in Australia, if you have a single phase to your house you get one of the three phases plus neutral. If you have 3 phase (as I do) you get all three phases plus neutral. Each phase id 240VAC, the difference between the phases is 440VAC.

    Looking at the US system It initially concerned me that you'd have to balance the two 110V split phases, but I guess it is no different to the way we need to balance the loads on the three phases we have.

    As a bit of trivia, our three phases are "red", "white", and "blue". If you touch them together you see stars, and on our earth wires you can see stripes (albeit yellow and green).
     
  14. jackorocko

    jackorocko

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    As I understand it, 3 phase here comes in two flavors a wye and a delta configuration even though I don't really understand the fundamental differences. There will be three transformers, tapped into the three wires on the pole with three wires coming from the transformers to your building.

    But if you only have single phase, as most people here in the states do, then you are correct in that they run a transformer off just one of the 3 legs. This much I know...

    As for balancing the load, you mean across the 2 110V supplies? I might be wrong but I think the design of the breaker box helps in this, without too much extra effort on the part of the electrician. That is another good question and I would be curious to know more about it myself now that you brought it up steve.
     
    Last edited: Aug 7, 2011
  15. daddles

    daddles

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    It is pretty rare for someone to have 3 phase power at their home in the US -- there isn't much demand for it. I would love to have it because I'd then be able to use 3 phase motors for my machinery. But there can be a hefty demand charge or it can be quite expensive to get the power company to run it to you. I'm sure if I wanted it, it would cost me many tens of thousands of dollars, as the high voltage line that feeds our area is only single phase. It's common on farms, though (usually running irrigation pumps and processing equipment).

    When an electrician wires a house, it's part of his job to balance the loads on the 120 VAC legs. It's not hard -- I did it on a 1000 square foot addition that we added on to our house a couple of decades ago. I did the wiring as half of that was for my shop and I wanted it just so. I put in lots of 120 VAC and 240 VAC outlets -- but, as usual, I wish I had put in double or triple what I did. That seems to be a common lament of most people. As I recall, it only cost a few dollars in parts to add an outlet when I did it, so there's no reason to not add lots of outlets (NEC requirements excepted, of course :p).
     
  16. poor mystic

    poor mystic

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    This is weird and screwy! Daddles says only 1 phase goes round his whole area!
    In New Zealand (and Australia) the 3-phase is split at about block level and alternate dwellings are fed alternate phases.

    In Australia are some marvellous systems for electrical reticulation, including SWER, or "single wire earth return". This marvel of modern engineering sends electricity to the most distant parts of the continent. Trouble is, the elelctricity has to find its own way back. SWER households know a bit about load-varying supply voltages. Little heavy machinery is run on SWER lines.
     
  17. daddles

    daddles

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    The local substations all have three phase power coming in to them. Then the power company distributes each phase throughout the neighborhoods. It is pretty rare to find 3 phase power at a residential home where I live.
     
  18. poor mystic

    poor mystic

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    D you use 20A, 110V domestic circuits?
    I wonder how the domestic wiring is arranged.
    In Australia and New Zealand, power is led in from the street to a switchboard, and several fused sub-circuits are responsible for lighting (unearthed) and pluggable appliances (earthed). The lighting circuits are often 5A fused, and the appliances are fused at 10A. Hot water is often run from a circuit switched at the electricity company's discretion - "off-peak" electricity is sold at a discount.
     
    Last edited: Aug 7, 2011
  19. daddles

    daddles

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    Most 120 VAC branch circuits in a house use 15 A or 20 A circuit breakers. I've attached a picture of my home's circuit breaker panel which is about 40 years old. You can see most of the breakers are 20 A with a few 30 A and 40 A ones. The 30 A and 40 A circuits are all 240 VAC. The whole panel is a 200 A panel, which is a bit small by today's standards (typical houses often have 400 A panels).

    The second panel is a 100 A panel for my shop. This is a 1000 square foot addition to our house that we added about 20 years ago; there are the shop, two other rooms, and a full bath. You can see all the circuits are 20 A, both 120 VAC and 240 VAC. There are 8 double outlet boxes around the shop; each box includes a 20 A 240 VAC circuit and a 15 A 120 VAC duplex outlet. There's a 30 A circuit that runs two wall heaters (we never use them) and a 50 A 240 VAC outlet for welding.

    The 20 A circuits run both lighting, outlets, and appliances. Most of the 120 VAC outlets are actually rated to 15 A, as it's somewhat unusual to find appliances that need more than that (but there are 20 A 120 VAC NEMA outlets that are available for such things). A microwave oven we used to have (it gave up the ghost a week out of warranty) and my air compressor take a bit more than 15 A.

    Older homes like my mother-in-law's use the round fuses and date from the 1940's or before. Most houses I've seen built from about 1950 and on use circuit breakers.

    In my shop, I have a 20 A circuit that runs the 13 fluorescent lighting fixtures (I don't use all of them at once). Each fixture has a 15 A duplex outlet next to it to power it. This was quite convenient, as I can plug appliances into the ceiling wherever needed (the lighting only takes 500 W worst-case, so that leaves about 1500 W to run an appliance if needed).
     

    Attached Files:

  20. poor mystic

    poor mystic

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    Apr 8, 2011
    Thank you Daddles.
    The only thing left to ask about the American power reticulation system is earthing. I imagine that each house is earthed at the neutral on the switchboard, and that the earth is taken up to the pole transformer?
    In Australia and New Zealand the neutral is earthed at the substation transformer, where the 240V (Australian) or 230V (New Zealand) is generated. The earthed neutal and the 3 phases are reticulated over what can be quite a large area. At each domestic switchboard a local earth is tied to the neutral via a removable link.



    Is that Daddles the Bear, btw or is it Daddles the Duck? This could well become an interesting question. Is it likely to be answered by a choice of avatar... ?
     
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