Manual transfer switch from generator to inverter

Lifetide · May 2012

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.

waynefromnscanada · May 2012

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/servlet/JiveServlet/downloadBody/1890-102-1-2785/Ins%201281%201282%201285%201286%201287%201288%201256%201257%201260%201262.pdf

mikeo · May 2012

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.

vtmaps · May 2012

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

vtmaps · May 2012

Re: Manual transfer switch from generator to inverter

Lifetide wrote: »

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

mike95490 · May 2012

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.

Cariboocoot · May 2012

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 ...

CATraveler · May 2012

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.

Shadowcatcher · May 2012

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.

Lifetide · May 2012

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..

Lifetide · May 2012

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.

Lifetide · May 2012

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?

Lifetide · May 2012

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.

Lifetide · May 2012

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.

Cariboocoot · May 2012

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.

Lifetide · May 2012

Re: Manual transfer switch from generator to inverter

To cariboocoot: Thanks for your quick reply regarding my grounding problems.

Before asking a few more questions, I'd just like to say what a great forum this is. It's an invaluable resource for anyone living off the grid, and my posted questions get answered within hours (if not sooner) instead of days or weeks or never. And I want to especially thank those who know a thing or two for taking the time to help educate those of us who are not so knowledgeable.

As for the 15 amp switch. I am sure that the cabin will never draw more than 3 or 4 amps across the switch (no inductive motors that might cause a start-up surge). There are some other loads on the generator--noteably a battery charger, some florescent lights, and a laptop--but those are all on a separate line from the generator. If those loads on a separate line cannot impact the 15 amp DPDT switch I want to install at the cabin, then I'm sure I'm okay. I am still considering sending the 15 amp model back to trade up to a 20 amp, but I'm 100% sure the switch will never have to handle anything near 15 amps.

As for the grounding: I understand that I shouldn't ground the generator. And I also understand that I should have only one grounding point--which I assume is to prevent the possibility of a ground loop. (I don't entirely understand what a ground loop is, but I have a vague idea; and from what I have read, it's not a good thing.) So here's my situation. I have my solar panels and the inverter chasis grounded to a grounding rod beside my solar shed about 100 feet from the cabin where I'm installing the transfer switch. That's obviously too far to run a ground wire from anywhere near the switch I'm putting in the cabin, and I can't put another grounding rod at the cabin. Will the ground wire on the inverter suffice? Any other suggestions?

Cariboocoot · May 2012

Re: Manual transfer switch from generator to inverter

Loads that don't run through the switch won't affect it.

A "ground loop" is a wide-range description for an alternate current path in the grounding system that can cause other parts of the system to become energized in the even of a failure rather than sinking the current to ground. Energy always takes the path of least resistance. With grounding you want to limit its choices to one path only.

The AC wiring that connects the loads to either the generator or the inverter will have a ground wire with it. This will not be switched by the transfer switch. Therefor the ground wires between components will always be connected to the grounding point. You don't need to run a separate wire for grounding.

Lifetide · May 2012

Re: Manual transfer switch from generator to inverter

To cariboocoot: Thanks, once again, for your attention to my questions. I think I'm ready to cautiously approach this installation. I'm going to hook up an older and cheaper inverter first to see how things go. I'll report back to this thread with the results after I've wired it up and tested it for a few days.

vtmaps · May 2012

Re: Manual transfer switch from generator to inverter

Lifetide wrote: »

but I'm 100% sure the switch will never have to handle anything near 15 amps.

I am 100% sure that my 14 gauge house wiring will never have to handle more than 15 amps. But I still have 15 amp circuit breakers (just in case I am wrong).

My point is that your generator could exceed the rating of the switch. Therefore you should put a 15 amp fuse or breaker on the generator output to protect the switch. It would probably be cheaper to just use a 20 amp switch. If the output from the switch goes through any wires or outlets or fixtures that are rated less than 20 amps then you should have them protected by a fuse/breaker of the appropriate size.

--vtMaps

Lifetide · May 2012

Re: Manual transfer switch from generator to inverter

To vtmaps: Point taken. I live in the boonies of the Big Island in Hawaii, and their is not much in the way of retail resources on the island. I have to order most everything from the mainland and the shipping to Hawaii is generally quite expensive. I think it was my mistake to order the 15 amp switch in the first place as the 20 amp would have only been about $5.00 more; but at this point, it would be a real hassle to send it back for a 20 amp replacement. Putting in a 15 amp fuse is not a big deal. What kind of fuse would you suggest. Maybe an Edison type. I've seen a 15 amp circuit breaker that screws into an Edison base, and also an affordable box cover designed for a single fuse. Any other suggestions as to what kind of fuse would be good?

vtmaps · May 2012

Re: Manual transfer switch from generator to inverter

Lifetide wrote: »

Putting in a 15 amp fuse is not a big deal. What kind of fuse would you suggest. Maybe an Edison type. I've seen a 15 amp circuit breaker that screws into an Edison base, and also an affordable box cover designed for a single fuse. Any other suggestions as to what kind of fuse would be good?

I don't have special insight into fuses. A year ago I went to Home Depot and bought a small siemens breaker box for $12 and a couple of 15 amp breakers for less than $4 each. Another thought: I've seen power strips with 15 amp breakers in them. You could plug one into your honda eu2000.

--vtMaps

Cariboocoot · May 2012

Re: Manual transfer switch from generator to inverter

The Honda EU2000i has its own breaker (15A). The output is rated at 13 Amps. If that's the gen being used it can not supply more than 15 Amps; there is no need for additional circuit protection.

vtmaps · May 2012

Re: Manual transfer switch from generator to inverter

Cariboocoot wrote: »

The Honda EU2000i has its own breaker (15A). The output is rated at 13 Amps. If that's the gen being used it can not supply more than 15 Amps; there is no need for additional circuit protection.

Good point. As an eu2000 owner, I should know that

It can, however, put out 2000 watts for a while and that is more than 15 amps. --vtMaps

Cariboocoot · May 2012

Re: Manual transfer switch from generator to inverter

You do realize 15 Amp breakers don't trip the instant current exceeds 15 Amps? Otherwise they'd be nuisance tripping.

If you have a circuit protected by a fuse or breaker of 'X' Amps, adding another in-line of the same value gains you nothing.

vtmaps · May 2012

Re: Manual transfer switch from generator to inverter

Cariboocoot wrote: »

You do realize 15 Amp breakers don't trip the instant current exceeds 15 Amps? Otherwise they'd be nuisance tripping.

If you have a circuit protected by a fuse or breaker of 'X' Amps, adding another in-line of the same value gains you nothing.

Yes, I realize.
I agree.
I wasn't thinking. I wish honda had named the generator 'eu1600'. then I wouldn't have to think about its capacity.
--vtMaps

Cariboocoot · May 2012

Re: Manual transfer switch from generator to inverter

vtmaps wrote: »

Yes, I realize.
I agree.
I wasn't thinking. I wish honda had named the generator 'eu1600'. then I wouldn't have to think about its capacity.
--vtMaps

I totally agree! :grr

Using a number like that which is close to the capacity is confusing.

And Honda is not the only one guilty of such chicanery. :roll:

westbranch · May 2012

Re: Manual transfer switch from generator to inverter

Just think of how happy;);) we are to have a "2000W" generator and not a "1600W"

, makes the 'boys' jealous eh?

2manytoyz · May 2012

Re: Manual transfer switch from generator to inverter

If ya wanted a 2000W generator, you should have bought a Yamaha EF2400iS generator... Yamaha doesn't confuse people with the model name vs. the rated capacity, um, scratch that.

Manual transfer switch from generator to inverter

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