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Old 05-01-2014, 18:23   #16
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Re: Quietest Diesel Gen set?

Oh, and I have the optional upgraded sound shield on the thing.
Once I installed the water separator, nobody outside the boat know, that the gen is running
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Old 06-01-2014, 03:09   #17
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Re: Quietest Diesel Gen set?

Our Fischer Panda is a 12 volt genny so it runs at the speed it needs to to supply the load demanded. So in general it will always be quieter. You get AC via an inverter.

At the heart is the inverter/charger and a large battery bank, but the charge source now becomes a DC generator.

A 12 volt diesel genset is quieter and more efficient because it runs at a variable speed to deliver only the load that is needed. It uses less fuel and requires less maintenance than an AC genset, which must run at a constant speed, no matter what the load, just to supply AC at 50/60 cycles/sec.

Large inverters are up to 95% efficient in converting to AC, so together with an efficient DC generator, the DC option is a better and more compact all-round solution for both DC and AC. Another major advantage is a DC genset can charge batteries at a very high current, up to 120 A from Mastervolt, 280 A from Fischer Panda. With AGMs this is a very good option.

The other great advantage of this "DC Option" is that you can go for a smaller DC genny than you would need if you went the AC route. With a Mastervolt or Victron "Power Assist" inverter it takes extra AC power from the batteries when needed for start up of air con etc.

For a much more detailed and in-depth look at “electricity on board”, see this 74 page booklet from Victron – especially sections 7 and 8:

http://www.victronenergy.com/upload/...yUnlimited.pdf
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Old 06-01-2014, 04:55   #18
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Re: Quietest Diesel Gen set?

You didn't really say what kind of boat you have and what kind of space you have available? If you have the space Northern Lights would be my first choice. As for sound you can make almost any generator quiet if you are willing to spend the money on good insulation, mounts and a water separator exhaust. Look at the Vetus web page, they call them gas water separator exhausts. No splashing noise. As for insulation, you want the factory sound shield if you have room. In addition 2 inch sound down, a rubber mat under the generator and isolation mounts for the enclosure all add to lowering the noise level. Check out sound down products for the insulation. Last but not least baffling and insulating the fresh air blower pulls it down another notch. I have done installs where the blower was louder than the generator.
Things I wouldn't do unless there was no other option, don't buy a single cylinder genset made by anyone. They are loud, poorly balanced and a general pain in the rump. I have a lot of experience with Fischer Panda, they would not be my first choice although under private use a lot of the issues that I have seen in charter wouldn't apply. You simply won't be putting 1000 to 1500 hours a season on it. The maintenance schedule and wear and tear on the FP is not well suited to charter use. The ones that we have had in the fleet have been much more expensive than Northern Lights to operate and maintain.
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Old 06-01-2014, 05:14   #19
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Re: Quietest Diesel Gen set?

I don't have a boat yet, but have now added a Gen to the list of the wife's "must haves", so this boat I'm going to buy now among other things has to have room for a Gen set. DC gens seem to make a lot of sense, except where do you get a 5KW or so inverter and assuming there is one that large, what does it cost? I assume you would connect it to the house bank and use the house bank for a sort of accumulator?
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Old 06-01-2014, 05:45   #20
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Re: Quietest Diesel Gen set?

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Originally Posted by a64pilot View Post
OK, hadn't thought about the generator being at a different RPM than the engine, I had assumed direct drive, but short of going to a boat show, no recommendations on gen sets in the 4 to 6 KW range? How about adding ease of service, reliability and longevity and availability of parts to the matrix? Price is relevant, but not as relevant as quality

Location in the boat -- and service access!! -- should also be factors to consider. Some locations (under a cockpit, for example) may be perceived to be quieter than others (under a V-berth).

But location, and presence of a sound shield, can also severely impact your ability to service the thing.

FWIW, ours (8kW Kohler, 1800 RPM, powered by a 3-cyl Yanmar diesel) is located underneath the saloon sole, in a sound shield, and the water discharge is aft underneath our swim platform. We can hear it, on the boat, but can't hear it from about 10 yards away (as from a dinghy, etc.).

Our sound shield sorta-kinda comes apart for service, in that the front, two sides, and top panels (doors) can be removed to reach the service points (only need to remove front door to change oil, check/fill coolant, etc.). OTOH, we can't easily get to the back side, should that become necessary.

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Old 06-01-2014, 05:49   #21
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Quote:
Originally Posted by a64pilot View Post
I don't have a boat yet, but have now added a Gen to the list of the wife's "must haves", so this boat I'm going to buy now among other things has to have room for a Gen set. DC gens seem to make a lot of sense, except where do you get a 5KW or so inverter and assuming there is one that large, what does it cost? I assume you would connect it to the house bank and use the house bank for a sort of accumulator?
If you're only running a 16k a/c unit then you don't need 5 kW. Also if you plan on sailing a lot with this running you need to look at maximum permissible operating angles of the gensets.
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Old 06-01-2014, 06:53   #22
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Re: Quietest Diesel Gen set?

Get the boat first. Then you can figure out the load requirements, because I guarantee you it's more than just the ac. You'll probably run a microwave and coffee maker and battery charger, etc. based on the boat you'll determine the size and location. Sound proofing will always improve on the noise.
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Old 06-01-2014, 06:57   #23
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Re: Quietest Diesel Gen set?

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If you're only running a 16k a/c unit then you don't need 5 kW. Also if you plan on sailing a lot with this running you need to look at maximum permissible operating angles of the gensets.
I figure a 16K BTU Ac could be run with 2KW, but not started with 2 KW, but put a coffee maker or the microwave (not both simultaneously) and the water heater, I think you may need as much as 4 KW? I'm also assuming you want to size a gen so as not to exceed 80% of it's capacity? I don't even know what the duty cycle is for one either, can a 5 KW gen produce 5 KW infinitely without overheating?
Four to six KW was picked sort of arbitrarily as it seems to be about the smallest offered and very little difference between the two price wise, fuel consumption doesn't concern me too much either as we are talking about short times aboard as I still work. I will look into max permissible angles.
My previous experience was with sport fisherman, there it seemed 7.5KW was small

Pirate I was typing when you replied, but I agree if anything I'd rather have a slightly large gen than one slightly too small. Not much price difference between a 4 kw to a 6 kw.
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Old 06-01-2014, 07:00   #24
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Re: Quietest Diesel Gen set?

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Originally Posted by a64pilot View Post
....DC gens seem to make a lot of sense, except where do you get a 5KW or so inverter and assuming there is one that large, what does it cost? I assume you would connect it to the house bank and use the house bank for a sort of accumulator?
You have to decide why you really need a 5Kw inverter? The hair dryer, the curlers, the coffee maker, the air con, etc., etc.. If all of these and more don't use them all at the same time!

Victron 3 Kw inverter/chargers can all run in parallel to give you more than you'll need, but you will need a good sized battery bank - 800Ah or more if you want AC without running the DC genset too much.
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Old 06-01-2014, 07:01   #25
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Re: Quietest Diesel Gen set?

For everything you ever wanted to know about marine diesel generators, including sound levels. Marine Generator Test - Victron Energy
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Old 06-01-2014, 16:08   #26
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Re: Quietest Diesel Gen set?

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but you will need a good sized battery bank - 800Ah or more if you want AC without running the DC genset too much.

There in lies the problem as I see it.
First I need to admit I know nothing about sailing / living aboard or cruising, so often what I think is a plausible idea immediately gets shot down by some obvious fact I omitted out of ignorance.
I first thought about a dual Alt set-up driven by serpentine belts, you should be able to pull like 300 amps out of that, that's 4.2 KW at 14V, if your pulling 2 KW as an average high use and you have a large enough battery bank, then your running 50% of the time during the day and as I assume little if any AC use late at night, no diesel running at night. But you had better have one big mother of a battery bank, both to be able to absorb a high charge rate without damage and to discharge it at a high rate and for a cycle to last hours. sounds ideal for Lithium?
300 Amps would be a large enough load on the engine to keep it up to proper operating temps and prevent stacking etc. If you need more propulsion force, just turn down the alt's while under way on engine power.

Then I figured this is way too risky / controversial and there must be some reason almost everyone runs an AC gen for AC power and I didn't want to lose the money and pain discovering the reason.
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Old 06-01-2014, 16:13   #27
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Re: Quietest Diesel Gen set?

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For everything you ever wanted to know about marine diesel generators, including sound levels. Marine Generator Test - Victron Energy

Thanks Rick, unfortunately Safari won't download the test, have to wait until I'm on a real computer I'm afraid
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Old 06-01-2014, 16:25   #28
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Re: Quietest Diesel Gen set?

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For a much more detailed and in-depth look at “electricity on board”, see this 74 page booklet from Victron – especially sections 7 and 8:

http://www.victronenergy.com/upload/...yUnlimited.pdf
Great resource! thanks
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Old 06-01-2014, 17:01   #29
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Re: Quietest Diesel Gen set?

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Thanks Rick, unfortunately Safari won't download the test, have to wait until I'm on a real computer I'm afraid
Safari worked fine for me....
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Old 06-01-2014, 17:06   #30
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Re: Quietest Diesel Gen set?

Be careful to not underspec. A 16,000 BTU A/C can draw 60+ amps every time the compressor cycles on. This can pop breakers on smaller gensets especially if anything else is running (battery charger?). Also spec your genset so that it runs between 25% and 75% load. Less than 25% and you can get carbon problems. More than 75% (except for brief peaks) will reduce life.

I chose between Northern Lights and Onan(Cummins). Very similar specs, quiet, and reliability. Went with Onan because Northern Lights are rare in some areas and parts not readily available. On the other hand, every significant boatyard stocks Onan parts and has a mechanic who knows their way around Onans.

In four years, no problems or repairs on the Onan beyond routine annual oil, filter and impeller. But Northern Lights are very good too.
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