Can I link a Honda eu2000 and a 2000 watt inverter

This is an old thread, but I figured I'd leave my experience for those searching for this later (as a friend of mine did find this via Google while searching for it).

After some research I have tried connecting a generator/inverter to different AC sources. Mostly I tried with a Kipor IG2600, but those have a similar, if not exactly the same, sync circuit as the Honda EU2000. I also have a bunch of Honda generator/inverters, both EU2000's and  EU22i's (which superseded the EU2000) and have also connected Hondas and Kipors together with no problems.

The parallel kit from Honda (or Kipor) is nothing more than paralleling the outputs of two generator/inverters. The banana plugs present for the parallel kit are connected directly parallel to one of the plug outputs of the generator/inverter (See the wiring diagram available from Honda. Though, do note that the banana plugs are paralleled with the AC output BEFORE the breaker!).

So it's actually possible to just take two male mains plugs and connect them in parallel to a single female socket. The official kits do the same thing, but add a breaker and use the banana plugs (mainly so there's not a hot mains plug laying on the ground if one is accidentally pulled, since the banana plugs have a shield). The "signal" being sent between the paralleled generator/inverters is nothing more than the frequency of the voltage provided which obviously is transmitted over the power lines.

The "Master/Slave" sync configuration is not complex. The first generator/inverter you turn on, if it does not detect an already present voltage/waveform in the first few seconds, it will just completely turn off its sync circuit and will simply try to keep 50Hz (or 60Hz in the US) on its own. This is the "Master" mode.

If, however, it *does* detect a voltage/waveform in the first few seconds, it will try to follow the present waveform the best it can. The source of this waveform doesn't matter, and it won't try to correct the frequency or anything, it will just try to follow what's already present. And if it wanders too much (outside the range it will sync to, <45Hz or >65Hz) it will simply decouple from the source until you turn it off and on again. This is the "Slave" mode.

This is also why you can safely parallel almost infinite generator/inverters (I've used up to 10 in parallel, 6 being Kipor 4 being Honda) with zero problems. The first one (turned on first) will determine the frequency, and any other generator parallelled to it (turned on later) will sync with it. Should the "Master" be turned off, trip or otherwise be disconnected, one of the other ones will turn its sync circuit off and become "Master". This happens automatically.

Anyway, the Honda/Kipor generator/inverters will sync to anything resembling a sine wave between 45 and 65 Hz. I have had no problems connecting one to mains (power grid) as stand-by (when expecting brown- or black-outs). In this use-case it will just run in low rpm mode if eco mode is on, and rev up when the grid fails. If the grid is completely dead, the generator/inverter will switch its sync circuit off for "Master" mode after a minute or so. When the grid returns it will detect that the grid is not syncing to it and switches its sync circuit back on (goes back to "Slave" mode). The larger the phase shift when the grid comes back on, the faster the generator/inverter will decide it will have to sync, as it is not being synced to.

I have had no problems either connecting the Honda/Kipor generator/inverters in parallel to a proper 12VDC to 230VAC (non-syncing) sine wave inverter in my RV, and this has also worked fine with el-cheapo inverters outputting a sawtooth or even a square waveform (Note: The resulting waveform will resemble an average of the two when the load is 50/50. If the load isn't shared 50/50, the resulting waveform will resemble more of one or the other depending on the ratio of load sharing). Besides that, paralleling to a standard diesel generator (non-inverter) with wandering frequency also works fine. The generator/inverter will happily wander along with it.

So simply put, the Honda and Kipor (and other generator/inverters designed for parallel operation) will sync to any AC source they are connected to. And they are protected against problems that would let the magic smoke out; if for some reason it can't keep the sync, it will automatically decouple. So you can safely parallel one (or more) of these generator/inverters to any AC source of roughly the same voltage.

Yes, thank you Raphidae. Very interesting.

It has been asked elsewhere if two eu2000i inverters could possibly be synced up to produce 120/240 split phase by hooking them to opposite legs of an autotransformer. It *should* work of course to hook them to the same leg, but well, ... I like the symmetry/balance of having one generator per leg.

What do you folks think?

Raphidae, your post suggests that the master does not provide some special in-band synchronization signal (pulses?) to which the slave generator syncs to. I fear that such a signal might be lost across the magnetics.

It has also been discussed on this forum somewhere that an eu2000i didn't have enough surge capacity to magnetize the core of an SPX-240 (4 kW to 6 kW autotransformer from Outback power). Much ado about soft-start circuits, but I thought the best idea was to just use a smaller, cheaper autotransformer (2 kW are available for < $200). I'm thinking of trying that out first, but obviously that's too small to handle 2 generators. My thought was to parallel two identical 2kW transformers interconnected via a 3-pole switch (or better: circuit breaker). So with the switch open, get the core of 1 transformer fired up with 1 generator, then close the switch to get the 2nd transformer going (with the 1st genny), and finally start the 2nd generator.

Uhmm, will the two transformers share the load equally? If not, is it stable, or does the overloaded one grab more of the load until it bursts into flames?

I like this because two eu2000i's are cheaper than even an eu3000 and certainly an eu7000 and one could run 1 generator until you really needed both, and save on fuel vs a larger generator all the time.

Caveat emptor of course. I have no idea how load balancing between the two parallel generators works except perhaps as BB described above, or if this idea would disrupt that?

Oh, and I should have said that from various posts and from a look at the eu2000i schematics, there is nothing fancy about the sync cables. They are physically tied to the neutral and line output wires except with the breakers bypassed.  It appears that you can just tie the outputs of two generators together to exactly the same effect as using the sync cables.

Thanks. Ouch that's a big beast, but maybe that is what it takes?