B & S 12KW generator engine start error

[user 159780]

Normally active in the heavy equipment forum, if necessary please move this to the proper forum.

We installed a 12kw whole house Briggs and Stratton generator, about 12 years ago. To date it was necessary to replace the voltage regulator capacitors five times, including today, at $65 for the pair.

The generator will run briefly, but since there is no voltage it flags an engine start error. The controller does not detect output from the head so it thinks the engine is not running, when it is.

Typically this happens with outages in excess of 12 hours. Since the capacitors are strapped to the generator head could it be that heat is cooking the capacitors or ? Anyway I always have a spare set of capacitors for events like today.

The unit is programmed to exercise (without a load) 20min./wk.

I tried to solicit a response from the B&S Q&A site, but they replied that my question does not comply with their rules. ‍

 

[cedarhollow]

i'm not sure what type head they used but it could need to be flashed if not used in a long time.
do google search on flashing generator
i've had that happen to gen before, engine runs but gen does not produce power
or could be connection terminals are corroded.
i'm not an expert just a hobbiest

 

[user 159780]

This B&S has an Italian made generator head, the capacitors are made by Ducati.

 

[cedarhollow]

the thing is that some of the small generators can become demagnetised, by lack of regular use and can be flashed with a 6 volt lantern battery to get them to produce power again, by small i mean one like yours, big standby generators like baldor, cat, cummins/onan, the stuff used by hospitals. municipalities and such are made different. this according to the tech that showed me how to flash my genny.

 

[user 159780]

Reviewed a number of YouTube videos about flashing a generator.

All of those were portable generators with no output. My unit has ample output until the regulator capacitors give up.

 

[uniballer]

You know the generator does not need to be flashed, because it initially works.

Do the components in the voltage regulator (capacitors and other components) actually get hot in use? An IR thermometer might be safer than touching them.

If you cool the components after the genny stops putting out voltage does it recover? A fan might be enough to see if it is heat related, but it used to be pretty common that electronics guys could identify a bad component by cooling it with a spray (e.g. something like this); if the unit started working when you cooled Q109 then you knew to replace that component.

Of course, it could also be effective to artificially heat up the regulator and see if that makes it fail quicker, but be careful not to overcook it.

 

[user 159780]

The regulator on this consists of two 35uf 500V capacitors, wired in parallel. Both are strapped to side of the alternator housing and covered with a protective metal shield.
If one capacitor fails there is no generator output. Measuring the recent pulls with a DVM, one reads 35uf the other zilch.

Never bothered to look at the temp. specs on these until now. A bit difficult to decipher (made in Romania) the caps are temp protected. Converting from C to F the specified temp range is -13F to 115F. The caps were hot to the touch, after shutting down for about 15min.

Runs with about a 25% load, higher when the well pump kicks on, after 12 hours is 115F a possibility? Outdoor temp was around 40 degrees when this failure occurred.

I don't see an obvious way to change the mounting location. Maybe try running without the shield in place? It's as designed so I assumed heat should not be an issue.

 

[uniballer]

Are these the caps you have?

Curious about whether your cap is failing shorted or open, but it doesn't really matter.

Notice that the cap is rated for 30000 hours at 425VAC, but only 3000 at 500VAC. Hard to tell if it is really rated for 70C (158F) or only 46C (114F).

I would try to find a better capacitor, i.e. higher voltage and temperature ratings. This is not likely to be easy; a simple google search didn't find anything better. Maybe a friendly older (aka much experience) generator repair guy would be your best bet.

Of course, it is also possible that something else is wrong with your generator that is making it eat capacitors, but I don't have enough information to tell you how to figure that out.

 

[user 159780]

All replacements have been the OEM B&S Ducati caps. One is failing open the other reads OK.
Researched what B&S is using on present day units, no luck so far.

An online generator specialist claims that extreme cold will take these out otherwise the caps are very reliable.

I'm considering using an isolation material between the caps and head, to minimize heat transfer. Any suggestions?

 

[uniballer]

I'm considering using an isolation material between the caps and head, to minimize heat transfer. Any suggestions?

One problem is that if the capacitor begins failing by exhibiting an increased equivalent series resistance (ESR), which many do, then the capacitor will itself heat up in use and cook any electrolyte solution in the capacitor. In that case trying to get heat to radiate away from the capacitor would be much more important than blocking heat from the head from reaching the capacitor.

 

[user 159780]

The caps could be mounted on the inside wall of the generator enclosure. And extend the wires from there to the head.

Seems extreme but worth a try. The next step is replacing this with a new unit.

 

[LegDeLimber]

How do you load test this unit? Have the service guys ever done it?
Digital test gear usually dosnt put a real load on things, You need something like a space heater across the output to see if the voltage sags unusually when you load it.
I've had power supplies that would show close to correct (phantom) voltage to a digital meter, but putting a load across them would just knock the reading down enough to show a bad winding.

Seems like with residual magnetism, you should be able to draw a minimal speced voltage and current from it without the caps installed.

Reason for asking is:
My first thought is an intermittent winding or insulation break down that might cause an inductive spike of the voltage and killing the caps?
Check every connection and follow all the wires to look for chaffing, rodent damage, ants etc.
Lose stuff and arcing makes nasty spikes in power supplies.

How is the grounding throughout all of the unit?
Any thing that uses chassis instead of wires gets rusty and be electrically noisy.
Got a dog peeing on it?

The heat rating is the other thought.
Don't forget simple vibration.
Could be a funny surprise from missing screws, a cracked panel, cover or bad mounting buffers etc, But only shows when running under load.

Just some things that come to mind, But I might be total idiot too.

 

[user 159780]

All legit questions...thanks!!

From date of install the unit exercises for 20min./wk,without a load. Maybe this extends the life of the transfer switch, I never asked. 800+ hours on the clock.

The generator is mounted in a weather resistant cabinet. No signs of rodent activity, looks like new inside.

I will take a closer look at the connections around the head. The mains wiring is, protected from weather, but I will double check this as well.

Over the years the capacitor failures occur during utility power outages, anywhere from 8 to 48 hrs. Never experienced an issue with shorter outages.

BTW I am the service Tech. When the engine was replaced under warranty, by a B&S authorized contractor, it was not load tested. The next outage it was a paper weight.
Turns out the generator circuit breaker was toast. I can do much better.

 

[user 159780]

Update...

Today I received a new set of capacitors. Unlike the previous replacements of Ducati capacitors these are US mfg. Aerovox capacitors. A notice was supplied which mentions the size and connection difference. Maybe B&S has found a substitute part with more life to it..

 

[mbrick]

Did the new capacitors solve the issue, temporarily or for a longer period of time?

 

[user 159780]

The last set of Ducati capacitors are still operational. The Aerovox capacitors are on standby.

 

[user 159780]

UPDATE
The Ducati capacitors installed on 10/19 failed yesterday 9/21, during an actual power outage. As before one capacitor tested good the other was open.
It was operating for about 3 hours before it quit, flagging a low voltage error.
This time both capacitors were replaced with the Aerovox brand.
The generator is back on line.