# Paralleling a non-paralleled generator?



## pie (Aug 21, 2015)

Hi everyone new here. I just purchased two Predator 2000w inverter generators (Harbor Freight). I decided to try paralleling them since one will not always start my 13,500 btu rv ac unit. I ran 12/2 wires out of each from the side of the receptacle (the only one) into a 30 amp rv receptacle. Then a ground from the 30 amp receptacle to the ground lug on each generator.
With each end hooked up to a generator I start one. It runs fine. Then start the other. One will overload and die. Sometimes one sometimes the other. Doesn't matter which one I start. And that's without a load. I've looked at the Honda wiring diagrams for the parallel jacks and they look simple. Is there something on these factory parallel capable machines that keeps one from overloading? Thanks in advance.


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## aandpdan (Oct 8, 2012)

It is simple on the Honda. The jacks allow the two inverters to synchronize so that the a/c waveforms are identical.

You won't be able to do it any other way. If you're not perfectly synchronized, and you won't be able to synchronize them, you'll overload one or the other.


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## exmar (Jun 29, 2015)

aandpdan Nailed it. Simplisticly stated, if the waveforms aren't exactly in sync, one machine will "generate" and the other will "motor" bet you heard some interesting noises as they went into oscillation. If you had ammeters installed, you'd have seen some unbelievable current swings. Smaller, inexpensive gensets are difficult if not impossible to sync. 

Your AC unit is probably about 15-16 amps. That's about 3500 Watts with nothing else running. Assuming your RV has a standard 30 Amp connection, get a 5500W unit and no more worries. I just picked up that size Generac for my house at Lowe's and it was about $600.

Good luck,


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## KRE (Nov 29, 2011)

aandpdan said:


> You won't be able to do it any other way. I


That is incorrect. You can parallel them with the proper adjustments, a tie breaker and a voltmeter. You will not get 100% from both (but w/o voltage matching technology no system will) but you would be able to get 80-85% of both. I've done it many times over the years, but on such small units it's not worth it. 
Wave forms have to match that is correct, but one has to be the lead and the other lag. This can be done in many ways, but paralleling in droop is the preferred method with re-sips or turbines that are not tying to the mains. I've tied re-sips with different prime mover speeds together, as well as turbines to re-sips. When tying to the mains (Utility Power) with either re-sips or turbines other factors come into play, such as power factor control. There will be circulating currents no matter the method, to what extent is in the hands of the power generation tech setting everything up. Some control systems take most of the currents out of the equation w/o issue but a good tech can tweak the system to get a higher percentage of both units. If that person is very good, reverse current CT's will be/have to be changed to allow the higher percentage gain. The average adjustments with proper protective gear allows 95% of the total cap of all units tied up. A good tech will get 99-99.5%. Voltage matching allows 99.9% of total, but only with utility grade controls an switch gear. Electrical Power generation (EPG)is a field that will be here forever and if your in the top 10% pays very, very well. That said, it changes faster than most other fields, so staying at the top is a challenge most don't/won't keep up with. 
Hope this helps,


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