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  • Manual transfer switch from generator to inverter

    I posted a related question a week or so ago, but the thread got diverted somewhat from my original question, so I'm starting a new thread here. I'm attempting to use a 15 amp DPDT switch as a transfer switch between my Honda EU2000i generator and my Xantrex X-Power 1500 inverter to power my off-grid cabin. The generator and inverter also power several other buildings, but I'm only interested in using the transfer switch on the lines to the cabin which never draws more than 350 watts.

    I've bought a Levitron 1282, 15 amp, DPDT switch which is usually used to switch a single power source between two different loads (or to power a motor between forward and reverse). What I want to do is to wire it so that it switches my cabin (the load) between two different sources (my inverter and my generator). I got a pretty clear answer from cariboocoot, but since actually getting the switch, I'm confused anew. First off, the wiring diagram for the 1282 on Levitron's website does not show the terminals in the same configuration as the diagram that came with the switch--and, to top it off, the terminals on the actual switch itself are labeled differently than either of Levitron's own diagrams!

    Before proceeding, I want to be sure that cariboocoot's suggestion is correct. It sounded perfectly logical to me, but the conflicting information from Levitron is confusing me. I have tested the switch in it's two "on" positions (it also has an "off" position in the center) to determine where there is continuity, and I have attached some drawings to this post. The first one is the switch with the terminals as they are marked on the switch itself, and I have indicated where the continuity is in each position. The second and third drawings are of the conflicting wiring diagrams (which I didn't intend to follow anyway) that have come from Levitron. If cariboocoot or anyone else can help clarify my predicament, I would be most appreciative.

    A few other points. The Honda does not have any neutral-ground connection and neither does the inverter. The generator is not grounded, but the inverter is. There is no kind of box at the entry point to the cabin, but I'd also appreciate advice on where to install fuses. Of course the generator and inverter have internal circuit breakers, but it seems prudent to add some fuses when I put in the transfer switch.

    Thanks in advance for any suggestions.
    Attached Files

  • #2

    Re: Manual transfer switch from generator to inverter

    Re: Manual transfer switch from generator to inverter

    Perhaps you've already seen this, but here is a link to this switch. It does seem to be a rather unnecessarily complicated connection arrangement that isn't as one might naturally expect. I know that personally, I would use an ohm meter to verify which terminal is switched to what, before I'd dare wire it up.
    http://communities.leviton.com/servl...260%201262.pdf
    1900 watts PV, (1000 watts PV feeding MidNite Classic 150; 900 watts PV + 160 watts micro hydro both feeding into a single shared Morningstar TS-MPPT-60) ; Xantrex Pure Sine 1800/12 for heavy loads; Xantrex Pure Sine 1000/12 on 24/7 for everything else; six Rolls Surrette 2 volt L16 @ 12 volts.
    Domestic hot water totally provided by the sun 8 months out of every year via thermal panel.

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    • #3

      Re: Manual transfer switch from generator to inverter

      Re: Manual transfer switch from generator to inverter

      The wiring looks consistent to me, think of the L1 and L2 as load (cabin), and A1 A2 as source 1 (generator) and B1 B2 as source 2 (inverter) for your application.
      15 assorted solar panels 1800 watts
      MX 60 charge controller
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      MikeO

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      • #4

        Re: Manual transfer switch from generator to inverter

        Re: Manual transfer switch from generator to inverter

        Using your top diagram as reference:

        L1 Hot to cabin (load)
        L2 Neutral to cabin (load)

        A1 Hot from Inverter
        A2 Neutral from Inverter

        B1 Hot from generator
        B2 Neutral from generator

        When switch is up: B1 hot from generator --> L1 Cabin hot
        When switch is up: B2 neutral from generator --> L2 Cabin neutral

        When switch is down: A1 hot from inverter --> L1 Cabin hot
        When switch is down: A2 neutral from inverter --> L2 Cabin neutral

        --vtMaps
        4 x 235w Samsung, Outback fm60 & vfx3524 & mate, Midnite E-panel, four Interstate L16, Trimetric monitor, Honda eu2000

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        • #5

          Re: Manual transfer switch from generator to inverter

          Re: Manual transfer switch from generator to inverter

          Originally posted by Lifetide View Post
          The Honda does not have any neutral-ground connection and neither does the inverter. The generator is not grounded, but the inverter is. There is no kind of box at the entry point to the cabin, but I'd also appreciate advice on where to install fuses. Of course the generator and inverter have internal circuit breakers, but it seems prudent to add some fuses when I put in the transfer switch.
          As I understand it (and I might be confused) when a power source has neutral bonded to ground you need only fuse the hot. Otherwise you should fuse both hot and neutral.

          You wrote that neither the inverter or generator has a neutral-ground connection, but then you wrote that the inverter is grounded. Therefore I am confused.

          --vtMaps
          4 x 235w Samsung, Outback fm60 & vfx3524 & mate, Midnite E-panel, four Interstate L16, Trimetric monitor, Honda eu2000

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          • #6

            Re: Manual transfer switch from generator to inverter

            Re: Manual transfer switch from generator to inverter

            Can you find anywhere in the spec, that the switch IS : Break-Before-Make ? I'm pretty sure (98%) that it would be, and not even need to be stated, but KNOWING for sure would be better. Maybe an LED would make a good test device.
            http://tinyurl.com/LMR-Solar
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            Grundfos 10 SO5-9 with 3 wire Franklin motor (1/2hp 240V 1ph # 214505 ) on a timer for 3 hr noontime run - Runs off PV
            Powerfab poletop PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe battery | 15, Evergreen 205w "12V" PV | Midnight ePanel || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT

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            • #7

              Re: Manual transfer switch from generator to inverter

              Re: Manual transfer switch from generator to inverter

              It is not necessary to add additional fusing on either the generator or the inverter if they already have built-in circuit protection on their outputs.

              Normally portable generators do not have a neutral-ground connection nor any permanent Earth ground, although there is a terminal for one. Don't use it.

              Pure sine wave inverters should have no trouble with a neutral-ground connection, but consult the manual for your particular inverter to be sure.

              There can be only one neutral-ground connection, and that should be at the point where the loads meet with the two inputs. It should be Earth grounded.

              I don't know who designed that switch, but its connections aren't very logical. Probably made sense to someone. Given its wiring, I totally agree with Mike about checking its operation before trying to use it. With a "center off" it should be safe but ...

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              • #8

                Re: Manual transfer switch from generator to inverter

                Re: Manual transfer switch from generator to inverter

                The gen is rated for more current than the switch for 2KW let alone surge. Never draw more than 350W means it will draw more than that amount for a variety of reasons. Personally I would use at least a 20A rated DPDT switch with center off.

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                • #9

                  Re: Manual transfer switch from generator to inverter

                  Re: Manual transfer switch from generator to inverter

                  Having gone through this exercise recently, switching between the AC shore power and the inverter in the trailer I looked for a 30A DPDT and found one at Allied.

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                  • #10

                    Re: Manual transfer switch from generator to inverter

                    Re: Manual transfer switch from generator to inverter

                    To CATraveler: Thanks for the advice. I wish I had ordered the 20 amp model. These switches are not available in my area, so it's a hassle to send it back for an exchange. I realized the current could surge over 350 watts, but I don't see any way it could approach 15 amps. However, after your suggestion, I'm considering going through the time and expense of exchanging it..

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                    • #11

                      Re: Manual transfer switch from generator to inverter

                      Re: Manual transfer switch from generator to inverter

                      To cariboocoot: My modified sine wave inverter (Xantrex X-Power 1500) is not designed for a system with a neutral-ground connection. I found that out the hard way when I tried to hook one up to my main house (a completely separate system) that has a conventional service box. The only points at which I have the system grounded now are from the solar panels and the inverter chasis to a common grounding rod. The cabin is about a hundred feet from the solar panel/batteries/inverter shed and fed by a 12 gauge line. Any more grounding suggestions.

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                      • #12

                        Re: Manual transfer switch from generator to inverter

                        Re: Manual transfer switch from generator to inverter

                        To mike90045: I've searched the web and all of Leviton's on-line information, but there is no mention of whether the switch is a break-before-make or open transition type. Since one of the manufacturer's suggested uses is in reversing the direction of motors, I'm thinking it would have to be break-before-make; but i would like to be sure. Just not sure how to go about testing it. How would you go about using an LED when the switch has a center-off position?

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                        • #13

                          Re: Manual transfer switch from generator to inverter

                          Re: Manual transfer switch from generator to inverter

                          To vtmaps: The inverter is not designed for use with systems that have a neutral-ground connection, but there is an external grounding screw on the inverter chasis.

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                          • #14

                            Re: Manual transfer switch from generator to inverter

                            Re: Manual transfer switch from generator to inverter

                            to mikeo and vtmaps: After much pondering, I had come to the same conclusions about the wiring. However I'm definitely a novice, and your comments have the ring of knowledge and experience. Thanks for the feedback.

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                            • #15

                              Re: Manual transfer switch from generator to inverter

                              Re: Manual transfer switch from generator to inverter

                              Grounding suggestions:

                              Obviously you already know (the hard way) not to have any neutral-ground bond anywhere!

                              Connect the safety grounds as normal and to one (and only one) Earth grounding point.

                              Do not run a ground wire from the generator's grounding lug (if equipped) just use the AC connection ground through the wiring.

                              If there are concerns about the current across what you are using for a transfer switch being unable to cope with the full current from the generator and/or inverter, fuse the line(s) to protect the switch. You don't want 20 Amps available from the generator to cross a switch only capable of 15 Amps. If you need the full current rating you must get a heavier switch.

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