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Old 05-08-2016, 08:07   #16
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Re: How do you choose a GENSET?

What happened to Davedoug68 , one question and he is gone.

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Old 05-08-2016, 08:09   #17
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Re: How do you choose a GENSET?

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What happened to Davedoug68 , one question and he is gone.

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Happens a lot, I don't know why.
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Old 05-08-2016, 08:15   #18
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Re: How do you choose a GENSET?

All the great information that was provided ???

His loss ,

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Old 05-08-2016, 08:16   #19
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Re: How do you choose a GENSET?

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You don't need to power the starting loads with generator capacity.

Power boost inverters will do the trick. A gang of Victron Multipluses would start anything.

You only need to power the constant load.
First, you don't need a generator rated for 6-7 times the continuous rating to get a compressor going. Usually around 2-3 times will start a compressor just fine. (We run a 12kbtu that draws around 1200-1500watts continuous off a 2400watt generator with no special consideration)

The Victron units are nice but cost quite a bit, so unless you really need to downsize the generator for space and weight savings, cost will likely come out better with a slightly larger generator.

For an air/con compressor, a cheaper option would be a hard start capacitor which is available for many of the marine air/con units.
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Old 05-08-2016, 08:27   #20
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Re: How do you choose a GENSET?

I think we are talking a high pressure Scuba compressor, and if your into diving and want to be able to fill more than one high pressure steel tank a day, you need a pretty big compressor, and those may just take a pretty big generator.
Course all this is speculation.
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Old 05-08-2016, 08:39   #21
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Re: How do you choose a GENSET?

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Generally speaking, standby and prime-rated diesel generator sets are designed to operate between 50 and 85 percent load, while continuous-rated diesel generator sets optimize between 70 and 100 percent load.
Operating diesel generator sets at loads less than 30 percent for extended periods can impact engine life.
Donít oversize your generator.
Well we can agree on that. If the AC was off I would expect a 9 kw generator on a cat of around 40 ft to be running at somewhere near 30% capacity.
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Old 05-08-2016, 09:52   #22
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Re: How do you choose a GENSET?

We are happy campers with Honda generators. Actually any motor made by Honda. Flawless engines. The old 5000w diesel is the best. Small, reasonably quiet, and reliable. Fairly easy to rig it to fit in a boat.
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Old 05-08-2016, 10:30   #23
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Re: How do you choose a GENSET?

Some other posters have said that the proposed generator would be extremely heavy so I wandered over to the Northern Lights website to check on the exact weight. A 9 kw model weighs 537 pounds.

WOW !
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Old 05-08-2016, 14:08   #24
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Re: How do you choose a GENSET?

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We are happy campers with Honda generators. Actually any motor made by Honda. Flawless engines. The old 5000w diesel is the best. Small, reasonably quiet, and reliable. Fairly easy to rig it to fit in a boat.
I agree with Hondas being the best for both durability and quiet. The Honda 6500 IS (gas) is a great choice. It only weighs 290# and is a real work horse. If you are running a dive compressor, it would be better to have a 3000 watt inverter running off your battery bank and use the Generator to charge the batteries only (of course it has plenty of power for other uses when you want to use it but you wouldn't have to rely on it for the compressor demands. It also has a built in Eco mode that provides only the power asked for and shuts down to about 1/2 power when there are no demands on it. I believe it has a 2000 watt inverter built in but I fear a dive compressor might tax the limits of the two thousand and effect its overall durability (thus the suggestion of the 3kw inverter off the battery bank).
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Old 05-08-2016, 19:06   #25
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Re: How do you choose a GENSET?

Id be careful offering info like that, 3.0kw for A/C?
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Old 05-08-2016, 20:01   #26
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How do you choose a GENSET?

My 3.5 KW if you assume 120 V is a 29 amp machine, my 16K AC pulls 11 amps, my 5KW pulls 6 amps, and my battery charger when the batteries are full, but I have a bunch of junk running pulls about 5 or 6 amps, so if I run both AC's and all my other junk, TVs and the like, I pull about 21 or 22 amps, or about 75% to 80% load.
Now if I were or run the toaster or microwave etc, something has to be turned off, I usually turn off the little AC.
So it can be done, you just have to power manage, but I'm also a 30 amp boat, so a 29 amp genset matches pretty well.

Hint, if you only have a single 30 amp shore power cord, you don't need a 9KW generator.


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Old 06-08-2016, 03:55   #27
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Re: How do you choose a GENSET?

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My 3.5 KW if you assume 120 V is a 29 amp machine, my 16K AC pulls 11 amps, my 5KW pulls 6 amps, and my battery charger when the batteries are full, but I have a bunch of junk running pulls about 5 or 6 amps, so if I run both AC's and all my other junk, TVs and the like, I pull about 21 or 22 amps, or about 75% to 80% load.
Now if I were or run the toaster or microwave etc, something has to be turned off, I usually turn off the little AC.
So it can be done, you just have to power manage, but I'm also a 30 amp boat, so a 29 amp genset matches pretty well.

Hint, if you only have a single 30 amp shore power cord, you don't need a 9KW generator.


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You have less power than the KW rating. You are running at more like 95% to 100% of capacity in your example above because you haven't corrected for the power factor. That will be something like 0.8. So your 3.5kw genset puts out about 2.8 kva or 23A.
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Old 06-08-2016, 19:52   #28
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Re: How do you choose a GENSET?

Re Dive compressors I no longer experience the cumbersome dive tanks. I never carry dive tanks anymore on board. Now I dive with a hooker unit for two people runs on 12 volts. solar power is enough to keep me from running out of air down to 18 meters. Easy also to carry an extra battery for diving off Dingy if not diving off your sailboat. ...
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Old 06-08-2016, 20:06   #29
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Re: How do you choose a GENSET?

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You have less power than the KW rating. You are running at more like 95% to 100% of capacity in your example above because you haven't corrected for the power factor. That will be something like 0.8. So your 3.5kw genset puts out about 2.8 kva or 23A.

It has actually made in excess of 30 amps for several minutes until boat CB blew, it was just a little over 30, like 32 or so.

Now I am not saying try to run a dive compressor off of a 3K, you might a Bauer Jr, if you only power it but I do not think anything bigger
However if a generator is capable of sustaining 11 KW, then at 120V that is 91 Amps, just make sure I guess that your boat can hold 90 Amps, cause if it's only a 50 Amp boat, then a 9 KW is 75, way more than a 50 Amp boat can hold, what is the 11K for?


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Old 07-08-2016, 03:35   #30
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Re: How do you choose a GENSET?

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It has actually made in excess of 30 amps for several minutes until boat CB blew, it was just a little over 30, like 32 or so.

Now I am not saying try to run a dive compressor off of a 3K, you might a Bauer Jr, if you only power it but I do not think anything bigger
However if a generator is capable of sustaining 11 KW, then at 120V that is 91 Amps, just make sure I guess that your boat can hold 90 Amps, cause if it's only a 50 Amp boat, then a 9 KW is 75, way more than a 50 Amp boat can hold, what is the 11K for?


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The 11k is for a non inductive load. Power motors with it and you need to derate it by your power factor. Most gensets are specified this way. Maybe yours has a bit of headroom or maybe you weren't all on motors, say using a good charger - you will have a decent power factor then.
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