Sorry to intrude here, but I have a problem that I hope some of you can help me out with.
My wife and I are building a small, remote cabin in a swamp in south Alabama. We're about .75 miles from the nearest dirt-road and the power company wants a 30' swatch cut in the trees to run power. Without a lot of discussion, we're going to be off-the-grid, relying on battery-bank, inverter, a couple of pv-panels to help things along (not much solar sky in the trees), and a generator. The problem I have is with the generator.
We purchased a new Kubota diesel/7.5kw Mecce Alte generator-head gen-set. Supposedly good for around 30amps per 120v leg. The problem that we're having is one 120v leg of the single-phase setup appears to be weak. Here's the scenario:
One leg shows 120.5v at 61.7hz while the other one shows 117.1v at61.7hz. No fancy meter equipment, just a "Watts-Up" plug-in meter along with a Radio Shack meter.
The circuit connected uses only one leg of the generator which I understand creates an unbalanced situation. The circuit is comprised of 3 feet of romax going to a receptacle. This circuit is intended to power saws, drills, etc.,.,
The first thing we loaded the generator with was a 13amp skil-saw. Upon energizing the saw the generator made a very loud, continuous noise which I've since been told was actually the rotors hitting the stators inside the genny. We quickly stopped the saw and shut the engine down. Just to check things out we hooked up a 75w light bulb and it worked fine...much smaller load. I checked the wiring and all is well. We tried it several more times with different sized loads, but nothing over 15amps. We had the same result...loud noise and apparent weak power.
I next switched the circuit to the other generator leg. This leg reacted very differently from the other leg. When we loaded it with the skil-saw and later a small compressor it would "bark" briefly upon being loading, smooth out quickly and, from what I could tell, power the equipment fine.
We switched legs back and forth a couple of more times to be sure of what was going on and the above results were obtained each time.
Upon talking with the seller, GeneratorQuotes/GeneratorSales/Central Maine Diesel, they had me recheck my wiring with the data they gave me...all checked ok. Bill Perry, Sr., the owner of Central Maine Diesel, called Mecce Alte and they stated that what I'm seeing isn't unheard of in the generator-head that I've got. There recommendation was to rewire it to 120v only and that that should balance the generator and solve the problem. I'm hoping to hear from some of you before I do this.
Even if this works, I'll still need two 120v legs later along with the240v for the well pump. My idea with the generator was to power the battery charger on the Trace 4024 along with the pass-thru circuits on one leg and to run a small window A/C unit on the other leg. At times, though, the A/C unit won't be running and I'm wondering if even though the "wired to 120v only" fix will cure things for now, will I have a problem later on when I wire back to 120/240?
I can't understand why if it's a balance problem why one leg works fine unbalanced while the other one makes the genny sound like it wants to come apart at the seams. Also, the fact that the "problem leg" shows 117v while the "good leg" shows 120.5v makes me wonder a bit, too.
I guess it comes down to wanting your opinion on whether you think it's an "out of balance problem" that is normal, or if something is screwy with the generator. It was a large investment for my wife and I which we hope to use for many years to come. But, for now we're scared to use it to work on the cabin with. As a side-note, we've been using a little 3000w Coleman for the last couple of months to power the equipment that we loaded the Kubota up with...though strained at times it runs everything we've thrown at it.
Thanks for your help and feedback, Ed Welch South Alabama KF4KRV