[RE-wrenches] Generator Overvoltage Troubleshoot

Fri Jan 3 12:34:06 PST 2025

Reading that the problem started AFTER the gen set was rebuilt, seems to 
point to adjusting generator voltage and frequency set points, or a 
faulty voltage regulator.  My guess is something went wrong with the 
rebuild.  Unless it was factory rebuilt, I've found local generator 
service companies to be overall fair to bad.  All the knowledgeable old 
timers are retiring, replaced with younger folks that mostly are there 
to just collect a paycheck.  My experience with gen sets that start 
having trouble, is they have to be replaced.  I just haven't seen them 
ever be reliable again, once they start needing work.

As soon as the gen set service company hears "Solar", they pin the blame 
on us, and to be fair, Inverter battery charging is a tricky load.

Ray Walters
Remote Solar

On 1/3/2025 1:21 PM, Blair May via RE-wrenches wrote:
> What IS the AC output prior to connecting to the Inverters? Hzs? Is 
> the generator an older unit w/ mechanical speed controls? 55kW gen set 
> should have no problem that load and the OV will usually occur during 
> the disconnection phase not once loaded. On a generator, the "Gain" 
> setting controls the sensitivity of the voltage regulator, essentially 
> determining how quickly the generator responds to changes in load by 
> adjusting the excitation current to maintain a stable output voltage; 
> a higher gain means a faster response to load fluctuations, while a 
> lower gain results in a slower response, potentially leading to larger 
> voltage swings under changing load conditions. TUMP
>
>> On Jan 3, 2025, at 3:01 PM, Jerry Shafer via RE-wrenches 
>> <re-wrenches at lists.re-wrenches.org> wrote:
>>
>> I work with gen set and inverter integration all the time, unless you 
>> have an inverter beginning to fail, it has to be the gen set, when l 
>> run load banks it for 2, 4 hr. or even longer and the voltage may 
>> only be checked at intervals and not continues. Use a fluke or other 
>> high quality meter set to min max and test all the integration, now 
>> the inverter may be pushing back spikes. You should also be able to 
>> tune in voltage at the gen set regulator, it can set volts and freq.
>> Fun times
>>
>>
>> On Fri, Jan 3, 2025, 6:17 AM Jim Gowdy via RE-wrenches 
>> <re-wrenches at lists.re-wrenches.org> wrote:
>>
>>     Hi all,
>>          I need some help with a generator overvoltage troubleshoot. 
>>     I'm working on an outback offgrid system that consists of 2 x
>>     Radian GS8048a, 1 x MATE3S controller, 1 x FM 80 charge
>>     controller, 1 x 55kw single phase propane AC cummins generator,
>>     about 4kw of solar *not sufficient enough to keep up with the
>>     load, and 24 x 4v Rolls batteries series/paralleled to make 48v. 
>>     The generator was rebuilt and the batteries replaced about a year
>>     ago and since then, the generator has been faulting due to
>>     overvoltage.  I had help and first found that the MATE needed
>>     calibrating so that was done, but the generator still was
>>     faulting. I found changing the AC Input Charging from 30a to 20a
>>     seemed to work.  I put a power monitor on the generator output
>>     and found that, with the AC Input Charging set at 30a, noticed
>>     that there was a voltage spike up to 300+V at about a 70a draw. 
>>     The generator company put a load bank on and verified the
>>     generator may not be at fault and the problem is after the
>>     generator.  Has anyone encountered a problem like this and have
>>     suggestions?  I've attached a PDF with a timeline of what I've
>>     done for troubleshooting so far.
>>
>>     -- 
>>     Jim with Gowdy Electric
>>     Cambria, Ca 93428
>>     business  805 927 2630
>>     cell  805 975 5279
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> "We must all learn to live together as brothers,
>  or we all will perish as fools."
> MLK
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