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Thread: Manual transfer switch from generator to inverter

  1. #1

    Exclamation 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.
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  2. #2
    Join Date
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    Default 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.

  3. #3
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    Default 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
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    MikeO

  4. #4
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    Default 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

  5. #5
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    Default Re: Manual transfer switch from generator to inverter

    Quote 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

  6. #6
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    Default 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.

  7. #7

    Default 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 ...
    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

    Ohm's Law: Amps = Volts / Ohms
    Power Formula: Watts = Volts * Amps

  8. #8

    Default 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.

  9. Default 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.

  10. #10

    Default 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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