Small (Quiet) GenSet recommendation

Hi,
I have an older 20kw genset which needs to be replaced but in the meantime I was thinking about getting something smaller (5kw range) in addition to a larger set. The larger is only needed to power the 3 AC units which rarely will get used so wondering if folks had done something similar. I heard NextGen units are good, compact and quiet?

Any thoughts or advice would be appreciated. I have a yard evaluating the space requirements, etc so its more a question of which units are best should they say we can do the auxiliary unit.

Thanks
Arthur

Do you spend many days/hours per day on the hook without running the propulsion engine?

If not, retrofitting an Alt setup designed for high-amp charging of a large quality high-acceptance deep cycle bank gives the luxury of sitting in silence when not motoring. You still may want some solar to get maximum lifespan out of the bank.

If yes, then solar alone may be enough if you have enough surface area and sunshine relative to your average AH usage per day.

Finally, many can make do with the very quiet 2kW inverter suitcase gennies, like Honda or Yamaha.

To me buying, carrying and maintaining two bigger ones seems wasteful, but that's me.

You likely don't need 20 kW. On our vessel we have 3 ACs, water heater, inverter, washer and dryer, electric range, additional 50 amp charger, microwave and hair dryers as big loads. We have a 12.5 Westerbeke that with a little load management does fine.

Suggest you consider carefully what your ultimate needs are now, get that unit and forget the small and not inexpensive 5kW install.

The newer generators are extremely quiet, my Onan 11kw I don't even know it is running.

I had a 3.5kW NexGen on my sailboat. It was a single cylinder 3,600 rpm unit. Noisy as all get out and lots of vibration. I have 16kW Northern Lights on the big boat. Much quieter and smoother. Been thinking of a 6-8kW as a backup. I have room in the machinery space. The Fischer Panda's were very quiet. But I dont know much about their reliability. I do not want a gas engine so that rules out the little Hondas.

Good feedback, I honestly don't know the exact draw yet as I just got her and she is in the yard (where they found several parts for the 20kw would be hard to get and expensive so hence this thread). She isn't small so I need to plan on the following.
AC fridge, AC washing machine (combo unit), AC dishwasher, hot water heater, plus running all her systems. Heat/cooling is currently designed Florida so likely never to stress it that much.

Im feeling a bit rushed into the decision since I haven't cruised on her yet and already need to make a call so may just see if the genset can make it through a summer then choose the right unit.

Anyone running two units? advice came from a very experienced boater but I guess in fairness I think he has a pretty large yacht where it might make sense.

AC

Get a Northern Lights that is properly sized for your electrical load. We have three AC units, two 12K and a 16K, water heater and 80 amp three battery charger and an 8KW Northern Lights generator is hard to keep a proper load on it.
For reliability, economical parts, easy to work on and QUIET, get the Northern Lights.

Our 12kw Northern lights runs our five ACs and everything else. If we are running only two ACs,. We use the 6 kw northern lights.

Gordon J said:

Our 12kw Northern lights runs our five ACs and everything else. If we are running only two ACs,. We use the 6 kw northern lights.

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So you have dual gensets? Im hearing conflicting thoughts on two versus one generator.

The PO put a 6 kw in the boat when she was 7 years old. The smaller generator has 500 more hours than the 14 year old 12 kw. Ib find the smaller one enough for most things and it is cheaper to run.

Gordon J said:

The PO put a 6 kw in the boat when she was 7 years old. The smaller generator has 500 more hours than the 14 year old 12 kw. Ib find the smaller one enough for most things and it is cheaper to run.

Click to expand...

Thanks,
the yard is going to try and get a decent read on draw, but in the NW in the summer our heat/ac systems are not stressed at all so may have to go off of spec. I know that 20kw is way too big as the boat originally had an electric range.
AC

Ideally I would get the 20kw running and get some time on the boat to see what your real needs are before dropping $$ on a second generator. Right now it would be an expensive guess.

Dual generators - one small and one large - are common on bigger boats. On most I'm aware of, the smaller gen gets much more use than the big gen. The small unit is typically sized to carry AC and other house loads over night. For bigger loads, the larger generator is run.

We have a 20kw as well and I don't think I've ever been able to get the loading up over 60-70%. I think a 16kw, or perhaps even 12kw with some load management would be plenty for a single generator if you wanted to replace the 20kw completely.

If you want to add a second smaller generator, I'd just make sure it can carry your base heating/cooling load. 5KW might be a bit low. 9kw might get you some more head room.

Before considering a Panda, google around and read about people's experience with them. It's not pretty.

BTW, how old is the 20kw and what brand? I'm surprised you are finding parts hard to get.

It's an Onan 20 mdl4-3cr, guessing 1988

Arthur

In Seattle, if Sure or Gallery Marine can't find the parts then I'd agree they are hard to find.

If a yard can't find the parts maybe it's because they'd like to do a genset install.

I have a question for the generator experts......

How much more does a big generator work to provide XXX load vs a smaller generator carrying the exact same XXX load?

Kinda like a big and small engine propelling a boat the same speed.

Seevee said:

I have a question for the generator experts......

How much more does a big generator work to provide XXX load vs a smaller generator carrying the exact same XXX load?

Kinda like a big and small engine propelling a boat the same speed.

Click to expand...

About the same in roughly the 20%-100% load range. Figure on 0.1 gph per kw of generated power. And that's actual generated power, NOT the capacity of the generator.

But a small generator running at 50% load will be more fuel efficient than a bigger set running at 10% load.

But is this even what you are asking? Maybe not as I re-read the question.

We owned a Panda. Much of the negative chatter is not worth the time it takes to read. Like any system, so much depends upon a number of factors including installation and use. We all have seen the range of possibilities for either category.
Early Panda's had seawater cooled generator sections that were problematic so people had legitimate complaints there. Beyond that, they remind me of the European autos I spent my life maintaining. They are quiet, capable machines and are capable of very long life.
Bruce

twistedtree said:

About the same in roughly the 20%-100% load range. Figure on 0.1 gph per kw of generated power. And that's actual generated power, NOT the capacity of the generator.

But a small generator running at 50% load will be more fuel efficient than a bigger set running at 10% load.

But is this even what you are asking? Maybe not as I re-read the question.

Click to expand...

Twisted,
I'd bet the additional fuel burn for a bigger one would be relatively small overall. And even if it were double, it wouldn't make much economic sense unless Arthurc was full time, long term with the boat.

Arthurc: What are your goals with the boat?

Regarding fuel burn Vs engine loading...

My Northern Lights 9KW generator is rated at...

.93GPH at full load of 9KW

.51GPH at 1/2 load or 4.5KW

What that means is that you'll burn a little less than 10% more fuel per KW produced if you load the generator to 1/2 load Vs if you load it to full load.

Not bad...

One thing to remember its that generators like to be loaded. Running a 12kw worth one AC and a charger could result in glazed cylinders.

Regarding panda....I had one on last boat. I was generally happy with it. It was a 6 kw. I had no real issues, other than an intermittent issue of it shutting down for now reason that I could discover. I would start it right back up and she would run for hours. The 6kw panda appears to me to be smaller than our 6 kw northern lights. Both equally quiet.

Gordon

Seevee said:

Arthurc: What are your goals with the boat?

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Long term ownership and trips to Alaska as well as a Hawaii crossing at some point. I plan on re-powering her this winter (the sp225 has many design issues and hard to get parts - likely will go with a JD). So bottom line looking for long term solutions that will last over short term savings/etc.
planning on also installing a water maker but may try and have it engine driven when I repower.

Bruce B said:

We owned a Panda. Much of the negative chatter is not worth the time it takes to read. Like any system, so much depends upon a number of factors including installation and use. We all have seen the range of possibilities for either category.
Early Panda's had seawater cooled generator sections that were problematic so people had legitimate complaints there. Beyond that, they remind me of the European autos I spent my life maintaining. They are quiet, capable machines and are capable of very long life.
Bruce

Click to expand...

Two questions

--Did you install a Panda in your new boat?
--Aren't the Panda's 3600 RPM?

The MDL4 is a good machine, but true that some parts are unobtanium. Since you are planning a repower, that would be the time to replace it. See if you can get it running long enough to last til the repower. That will also give you time to figure out what your cruising electrical loads really are.

You likely can size the unit down. But even though the PNW means little aircon load, you might venture south or sell the boat to a southerner. So don't go too small. Do the homework and decide if load management is tolerable or not. A 54' could probably do fine with a 12kW or even a 9, maybe.

sunchaser said:

Two questions

--Did you install a Panda in your new boat?
--Aren't the Panda's 3600 RPM?

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Our new boat has a Northern Lights generator. It had issues right out of the box!
Of course there is no support like Northern Lights and it was fixed up in no time. Yes, Panda's are 3600 rpm generators but they are very quiet.
Bruce

Another thing to check, it is only an Onan because of the generator section, its probably a Kubota or similar small diesel and you will want to go to a tractor repair place not a marina to fix it. '88 is not that old.

I think it is a Kubota but the parts needed are specific to marine (Coolant Pump
And Raw Water pump), they are available but need to be ordered from the factory and just this service looks like it would cost 4-5k... at that point why not get a right sized genset as I know the 20kw is overkill even with full load.
I'm new to larger boats so am making two assumptions 1) 30 year newer gensets and gotten quieter 2) high quality sets with industrial engines will still last 30+ years if bought new today.

Arthurc said:

I think it is a Kubota but the parts needed are specific to marine (Coolant Pump
And Raw Water pump), they are available but need to be ordered from the factory and just this service looks like it would cost 4-5k... at that point why not get a right sized genset as I know the 20kw is overkill even with full load.
I'm new to larger boats so am making two assumptions 1) 30 year newer gensets and gotten quieter 2) high quality sets with industrial engines will still last 30+ years if bought new today.

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That seems high, to me. Maybe get a cost break-down for parts versus labor. Labor is usually impacted by access, too... so if you look at your unit and can tell the coolant pump is way behind, completely inaccessible... than maybe lack of access would be loading more labor hours into the project.

OTOH, if both pumps are reasonably accessible, replacing those with new could maybe turn out to be no big deal.

For example, I could probably change our genset's raw water pump in a couple hours or so... and one of the techs here can usually cut my time in at least half, sometimes thirds (since they have a clue, and I have to learn as I go). But even if it turned out to be 3 hours of tech's labor, that'd only be about $300.

I suspect your assumptions about newer units are OK, but OTOH, I'd expect your current system to still be good for lots o' years too, if the parts issue is not insurmountable.

Is yours in a sound shield? If not, could maybe be that a box could tame noise levels... (at some expense to access, of course).

Don't think it's a bad idea to right-size your genset. Think I'd lean toward that instead of adding another smaller one (another system to maintain). But I also think maybe neither of those is absolutely necessary, pending parts and potentially other methods of sound abatement.

-Chris

There is an ongoing debate over whether to have two identical generators or one larger and one smaller. Both sides have their sound arguments. The argument of one large and one small is that you can match to the requirements at the time. You can run the larger when running A/C or the watermaker and working in the galley and the smaller one when you have minimal use.

We chose to go in all cases with two identical generators. When we'd start sizing the smaller unit we always concluded we could reasonably go down to about 50-60% the size of the larger one. However, we gained very little in terms of less weight or a smaller footprint, and saved far less in cost than we would have thought. We also then had to find a pattern of usage to go to one or the other. We did not want to have to cut the A/C off to use a smaller one as we want it to come on if needed overnight. Similarly we didn't want to have to go switch generators for other reasons during the day. The big advantages to us of two identical were total redundancy, one set of parts, and since we run the generator all the time we're running, spreading the usage equally over two generators.

One thing we observed on boats with two very different sized generators was that one gets used 90% of the time. In our observations on larger boats, it was the large one that got used and the small one became nothing but an emergency backup. I know on some boats it is the other way around, we just found few examples.

We have experience with three brands of generators and we'd recommend those three over other brands. We have used Northern Lights from 25 kw to 99 kw, Kohler from 5 kw to 8 kw and Onan 21.5 kw.

Our experiences. Northern Lights level of service pushes them to the top of the generators in larger sizes. Kohler in the size range we have pleasantly surprised us with quietness and with lack of problems. Then we used Onan for our loop and were very impressed. Often I think people compare generators of different vintages and there are more differences than currently produced generators where all have made improvements. In all cases, our brand of generators was based on the builder who only used that brand, but we find that a good method as the builder and generator manufacturer have experience together and solid working relationships.

Now, to address the question of load. All of our manufacturers have very similar recommendations and that is something like 25-75% load with 50% being ideal. However, the old tale of never running below 50% is refuted by all three manufacturers when it comes to today's units. None of them get concerned until below 25-30% or above 70-75%.

Now there are a lot of boats being build with slightly different sizes such as 20 kw and 28 kw and one or the other is used simply based on the season.

All this just fits our cruising but then a couple of things significant about ours. One is that we nearly always have the A/C or Heat on, they just run as needed. We also normally have a number of people aboard who will be showering at different times, doing laundry, deciding to cook something, so far more to manage than if just two aboard. Then we also have watermakers, washers and dryers, and PTO's for hydraulic thrusters on some boats which both add generator usage.

Hi Arthurc.

My previous boat was a 53' Canoe Cove, fitted with two Northern Lights generators. One at 12KW, and the second at 5KW. Both fitted in sound shields. The boat was built here in the PNW, and designed and fitted out as a high-end motor cruiser for this environment. That is, diesel heat, hot water, watermaker, washer/dryer, etc. All the amenities (for it's day, anyway) to enable us to cruise without practicing bleeding before leaving the dock. No AC, as is pretty typical up here.

If I ran the 12KW generator, I could operate the boat, either underway or at anchor, with impunity. That is, run all AC stuff at will, without having to juggle AC loads to prevent inadvertent overload. However, if I chose to run the 5KW generator, I was always manually load-shedding, which was a giant PIA. As this was an 80's vintage boat, all loads were manually controlled, without automatic anything. So load shedding was up to me.

And, I couldn't detect ANY difference in sound level for the generators, either inside the boat, or close aboard outside. Nor any difference in fuel consumption. Given the fairly low usage of my generator(s) per engine hours, fuel consumption was simply lost in the noise. I never could figure out why the boat was equipped with both generators! I'd have been very happy to ditch the 5KW, with it's attendant cost, space, service, and wiring hassles. After 12 years aboard, the 5KW was virtually unused.

My present boat (WAY smaller and simpler!) has one 6KW Northern Lights. Couldn't be happier.

Regards,

Pete

jungpeter said:

Hi Arthurc.

My previous boat was a 53' Canoe Cove, fitted with two Northern Lights generators. One at 12KW, and the second at 5KW. Both fitted in sound shields. The boat was built here in the PNW, and designed and fitted out as a high-end motor cruiser for this environment. That is, diesel heat, hot water, watermaker, washer/dryer, etc. All the amenities (for it's day, anyway) to enable us to cruise without practicing bleeding before leaving the dock. No AC, as is pretty typical up here.

If I ran the 12KW generator, I could operate the boat, either underway or at anchor, with impunity. That is, run all AC stuff at will, without having to juggle AC loads to prevent inadvertent overload. However, if I chose to run the 5KW generator, I was always manually load-shedding, which was a giant PIA. As this was an 80's vintage boat, all loads were manually controlled, without automatic anything. So load shedding was up to me.

And, I couldn't detect ANY difference in sound level for the generators, either inside the boat, or close aboard outside. Nor any difference in fuel consumption. Given the fairly low usage of my generator(s) per engine hours, fuel consumption was simply lost in the noise. I never could figure out why the boat was equipped with both generators! I'd have been very happy to ditch the 5KW, with it's attendant cost, space, service, and wiring hassles. After 12 years aboard, the 5KW was virtually unused.

My present boat (WAY smaller and simpler!) has one 6KW Northern Lights. Couldn't be happier.

Regards,

Pete

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Exactly what we faced on our latest purchase which came with an Onan 21.5 kw. We wanted a second generator and everyone said, add a 10 or 12 or so. We realized that we'd never be willing to go through the load juggling and it would sit unused unless the larger unit broke. So, it became either add a second 21.5 kw or add nothing. Still don't know the right answer. We added the second 21.5 kw and have alternated uses of the two. We have redundancy but really haven't needed it yet. However, if we ever had a generator to go down for a few days, we'd regret not having the backup unit. We keep the usage almost identical on the two units.