Generator Frequency Issues

[egaito]

On our last trip, a recurring issue with our generator became annoying enough that we actually started studying it and experimenting.

Background:

Occasionally, which over time has become more frequently, our newer AC blowers and new galley appliances would begin to act up. In the past, we would change the small filter on the genset (Westerbeke 15k) and all would be well for awhile.

After we put a 2micron filter in the Racor, and replaced the 7 micron on the genset, within an hour we were back where we started. Our first experiment was to shut down the genset for 20 minutes and restart without changing any filters (which always looked clean). It worked for a while, which started me looking at other things. Voltage was stable, so we started monitoring frequency. With a small to moderate load, it's putting out up to 64 hz, which is when things go wonky.

Studying the manual, I noticed that the spec for full load hz was a bit lower than no load, so the next experiment was to fire up all of the ac units, setting the thermostats so that they could not possibly "satisfy". Everything ran find for two days, and we slept well under blankets.

The simple answer is to adjust the governor to get the hz back in spec, which I plan to do, but the whole exercise of getting here raised some questions in my mind, if anyone has some wisdom (no lack of that here, right?) they might be willing to share.

First, the genset apparently does not run through the isolation transformers, which seems common. Why is this? Would the transformers not correct the voltage and frequency as they do with shore power?

Second, there is an optional voltage regulator mentioned in the Westerbeke documentation. It does not mention frequency regulation, but I'm wondering if this is a worthwhile addition to the unit.

I've read through the procedures for adjusting the governor, but would appreciate any real life experience tips on doing so.

Thanks,

 

[MikeP]

What you are describing is quite common - the Genny will vary RPM slightly based on load. The variation is within the limits of the governor but means that the frequency will vary a bit. We have a dishwasher that will run perfectly at 60 HZ but will not run at 61. I doubt if any mechanical governor can maintain the RPM/freq within 1 HZ. SO... all you can do is set the Genny RPM for 60HZ at a common load setting and hope for the best. Some appliances are extremely sensitive to frequency differences; others are less so. The only item we have on the boat that is that sensitive is the FisherPaykel dishwasher. We love the unit but it will only work when the Genny is powering a couple of AC units at the same time. Otherwise, the freq is at 61 and no-go!

 

[SKYCHENEY]

The isolation transformers will not correct frequency. There would be no purpose of using them with generator power as there is nothing to isolate. You are not connected to an external source. The transformer also creates some heat and is less efficient than a direct connection to the generator.

 

[kflod]

I have a Northern Lights genset that I adjusted from 60 to 50hz. The tech consultant from NL told me that I should aim for a no load rpm of no higher than 52, which would correlate to 50 fully loaded. My thoughts are that your no load rpm is too high. Have you measured the Hertz with normal and full load? Perhaps you're better off adjusting the engine speed to give 62 Hertz with no load? An electronic controlled speed device I was told is at best very expensive to retrofit, and most likely impossible for my unit. Good luck

 

[doc g]

Not sure if this will help but some loads are more sensitive to voltage and others are more sensitive to voltage . I have Dual stacked inverters and they are much more sensitive to voltage than frequency. I think most appliances are the same. You really need to check voltage and frequency when you are having isssues. We also have the external voltage regulators and I have found I can get past most issues by adjusting the voltage only. Get the HZ where it should be by adjusting the rpm and then look at voltage ...... I guess what I'm saying you can't compensate for low voltage by boosting hz..............Pat

 

[Pascal]

First of all, why do have a finer fiter in the racor than in the secondary? Doesnt make much sense. I ve always had 20 microns in the racor and whatever the manufacturer recommends as th secondary, usually 2 or 5 micron. Basically your 2 micron racor is goin to clog faster and the 7 micron secondary is never going to do anything

As to freq, 64hz under light load is way too much. What was it under heavy load? Try to bring it down to 61/62 no load which shoudo get you 58/59 under load.

As we ve talked about before, we ve had issues with charmer dishwasher for years (fisher paykel drawer). Until recently when i read one of mike's post i thought the failures were random whereas they were in fact caused by a freq issue.

On this past trip to the exumas, i did some testing by monitoring the freq of the generators while using the dishwasher, turned anything over 61.5 would trigger a fault. So loading the genny with both water heaters, both big engine room blowers, etc... was the only way to get it to work. Ironically i initially ASSumed the oroblem was voltwge or freq dips when air cons woudl come on so i had try running th air cons on the second genset while using the dishwasher which only made things worst

 

[Pete]

I also have a Westerbeke 15kw generator, mine being a 1996 vintage. It was ordered with electronic frequency/speed control that works great. I later added the voltage electronic module because the output voltage would rise as load was added. Was a simple task with the wiring harness and mounting position ready to go. Adjusted the voltage to 240 volts and now have more stable power on generator than any marina. My take is adding the electronic speed/frequency controls would be a big deal both in complexity and $$. The voltage control was simple and less $. I am not sure if you must have the electronic frequency/speed control as a prerequisite to adding the voltage electronic control.

Assuming you stay with both mechanical voltage and frequency controls, I highly recommend that you focus on getting the frequency on 60 Hz and see what results as a voltage. Electrical devices are generally much more particular about frequency. A couple of Hz off 60 will drive especially electronic controls nuts, where as you can easily live with a 5% voltage variation, even approaching 10%. Above 10% you are asking for trouble, and even close to 10% will impact the life of most items.

Pete

 

[SKYCHENEY]

First of all, why do have a finer fiter in the racor than in the secondary? Doesnt make much sense. I ve always had 20 microns in the racor and whatever the manufacturer recommends as th secondary, usually 2 or 5 micron. Basically your 2 micron racor is goin to clog faster and the 7 micron

It makes perfect sense. I always do that on the mains. I have run 2 micron in the Racors for years. With a dual Racor system, you can switch to the spare unit and keep running while you change the filter that is clogged (or wait until it is convenient to change it while you're not out in 10 footers). The secondary is there on the pressure side after the pump just to protect the injection system should the pump shed anything.

 

[Angela]

It makes perfect sense. I always do that on the mains. I have run 2 micron in the Racors for years. With a dual Racor system, you can switch to the spare unit and keep running while you change the filter that is clogged (or wait until it is convenient to change it while you're not out in 10 footers). The secondary is there on the pressure side after the pump just to protect the injection system should the pump shed anything.

Exactly. The Racor is way easier to change when needed than that itty bitty filter on the engine. Turns out, fuel wasn't our issue. The Racor is was recently refurbished and cleaned completely and our fuel was fresh and new. I could live with a fickle dishwasher (although my dishwasher doesn't seem to mind), but all of the air conditioner blowers stop running and that is a major, evil problem in South Florida.

 

[Pascal]

Well we re putting about 2000 hours a year on a pair on NL20 and both the 20 microns primaries and the OEM secondaries (2 or 5 microns i believe) get changed every 400 hours. Never had an issue, never had to change a filter or switch over. On a typical trip to the exumas we re on genset 20 to 25 days a month...

Anyeay back to the freq issue, how about clocks? When on gensethe clock on our GE micro/convextion runs a little fast, also a sign of higher freq. Never had an issue with th Ac blowers or electronic controls.

 

[SKYCHENEY]

Well we re putting about 2000 hours a year on a pair on NL20 and both the 20 microns primaries and the OEM secondaries (2 or 5 microns i believe) get changed every 400 hours. Never had an issue, never had to change a filter or switch over. On a typical trip to the exumas we re on genset 20 to 25 days a month...

Anyeay back to the freq issue, how about clocks? When on gensethe clock on our GE micro/convextion runs a little fast, also a sign of higher freq. Never had an issue with th Ac blowers or electronic controls.

It may not really be an issue with a generator, but how would you like to be crossing the stream on a nasty day and plug up both secondaries on your mains? What would you do then? I would still have clean secondaries and only have plugged up Racors. I'd switch to the second Racor and get keep running. You'd be bobbing around while trying to change secondaries and reprime.

 

[Pascal]

Well I can only tell you I ve put about 3000 hours on the mains in the past 7 years changing the secondaries At every oil change along with one of the two 20 microns primaries. Never had an issue. The primaries catch the bigger stuff, the secondaries get the finer and all is well.

Never had to switch on the fly. This is the way Cat and the builder set it all up.

 

[SKYCHENEY]

Well I can only tell you I ve put about 3000 hours on the mains in the past 7 years changing the secondaries At every oil change along with one of the two 20 microns primaries. Never had an issue. The primaries catch the bigger stuff, the secondaries get the finer and all is well.

Never had to switch on the fly. This is the way Cat and the builder set it all up.

I have put on half those hours and I have never had an issue underway either. But, what if? What if you get a bad load of fuel and then get caught in heavy seas? Do you want to be messing around with filters underway? Not me.

If you just cruise the ICW, then no big deal, but I'm in open water 90% of the time and seas can kick up quicker than I can get out of them.