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Old 02-04-2016, 20:02   #1
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9KW Generator

I am looking at buying a 45' cat, new or 2nd hand, the boat will have a minimum of 3 AC units, a water maker (though maybe 12v) , dive compressor, etc. Is a 9KW generator sufficient?
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Old 02-04-2016, 21:29   #2
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Re: 9KW Generator

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I am looking at buying a 45' cat, new or 2nd hand, the boat will have a minimum of 3 AC units, a water maker (though maybe 12v) , dive compressor, etc. Is a 9KW generator sufficient?
===

It's probably enough if you are prepared to manage your electrical loads so that you don't have all of your high power equipment on at the same time. If you want to be able to run everything at once you'll have to study your peak load demand and then add 25% or so as a safety margin.
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Old 02-04-2016, 22:18   #3
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Re: 9KW Generator

Our old 9KVA Kohler Genset set seemed to be able to handle 2 aircons, charger, AC fridges and light loads on the electrical outlets just fine. We seem to be having some problems with our new one.

We are 220v 50hz and the maximum load should be 38amps.

I assume you are 110v 60hz so should be able to handle double the amps?? configured that way. One of the big problems is startup of the compressors. Make sure everything is wired with soft starts including the A/C fridges and this will help a lot.

Our main a/c is 50000btu, master cabin 20,000btu and the guest cabin is 15,0000btu but we never run them all at the same time.

But as advised already it is best to calculate the reasonable loads that will run simultaneously and get something a little bigger. It is nice to be able to fill the air tanks down below in the air conditioned environment.
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Old 02-04-2016, 22:29   #4
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Re: 9KW Generator

I can't imagine you'd overload a 9KVA genny with 3 ACs.

I have an Onan Emerald 5500 with 2 30A breakers on it. I've tested it with 2 15,000 BTU ACs, microwave, 1800w blow dryer, 3hp 110v air compressor, 40A battery charger (draws over 15 amps, oddly) and a vacuum cleaner. There were also 2 TVs and 2 sat. receivers on at the same time. That's all of the loads I had and it didn't miss a beat.

I imagine you'd be able to run at least 2 ACs and the scuba compressor at the same time, and still handle the microwave as well.
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Old 03-04-2016, 06:20   #5
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Re: 9KW Generator

That's about 75amps (120V) it can put out.

How many amps do you expect the air/cons to pull?

Our 16k unit draws about 11.5amps continuous, so 3 would be no issue as long as all 3 don't try to kick on at the same time. Remember startup loads getting the compressor going are typically 2-3 times the continuous load.

What you need to do is figure out all the loads (both continuous and startup) and compare that to the generator's ratings. The advantage you have over smaller boats is with multiple air/con units, the odds of your full air/con system starting simultaneously is unlikely.

PS: Is that 9k continuous or peak?
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Old 03-04-2016, 08:33   #6
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Re: 9KW Generator

I can run three a/c's off my 8kw without a problem as long as I turn the inverter/charger down to 50% output. It also runs my dive compressor as long as the a/c isn't running. We have a lot of 230v loads and you just have to watch the amp draws.

If your buying the cat in the med and need a generator, I have one for sale btw. Either a Northern Lights 12kva or 8kva. 2200 hours each and in very good condition. I don't need two which is the reason to sell one.
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Old 03-04-2016, 09:10   #7
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Re: 9KW Generator

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I can run three a/c's off my 8kw without a problem as long as I turn the inverter/charger down to 50% output. It also runs my dive compressor as long as the a/c isn't running. We have a lot of 230v loads and you just have to watch the amp draws.

If your buying the cat in the med and need a generator, I have one for sale btw. Either a Northern Lights 12kva or 8kva. 2200 hours each and in very good condition. I don't need two which is the reason to sell one.
===

I might be interested in the 8kva depending on price, specs, etc.

For example: 60 cycle, 240 volts? Sound shield? Weight? Dimensions? Present location? Remote panel? Photos?
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Old 03-04-2016, 09:41   #8
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Re: 9KW Generator

Hello Wayne,
Perfect boat application but unfortunately I'm in the Med. The generator btw can be 50 or 60 hz and has a sound shield.
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Old 03-04-2016, 10:38   #9
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Re: 9KW Generator

You really think you are going to A/C a boat sailing or at anchor? Maybe a condo would be better
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Old 03-04-2016, 10:43   #10
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Re: 9KW Generator

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You really think you are going to A/C a boat sailing or at anchor? Maybe a condo would be better
That's an odd question Gregg. Why would you not be able to run and air conditioner, dive compressor, or water maker when sailing or at anchor?
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Old 03-04-2016, 14:06   #11
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Re: 9KW Generator

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You really think you are going to A/C a boat sailing or at anchor? Maybe a condo would be better

I have, when it's the middle of August in Fl and there is a 2 Kt breeze, I've been known to crank the generator, and burn a quart of Diesel an hour for a couple of hours and cool the boat down.
I gave up being hard core when I retired from the Army, then I had to put up with sweltering desert heat, but not now.


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Old 03-04-2016, 17:02   #12
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Re: 9KW Generator

I run my generator and HVAC for both heating and cooling (and other electrical loads) all the time when not at the dock. Burns 5-6 gallons in 24 hours. I sail, my wife is comfortable down below, and at night we are always comfortable in all conditions. You don't have to chose to be uncomfortable to sail. On other boats, I've sat on watch, cold, somewhat wet and uncomfortable. Not so on my boat. I also have a full enclosure for the cockpit for those times when it's cool and lots of spray. Makes life more comfortable and enjoyable for us. If you like roughing it, go for it! I did in my youth, now in my late 60's, I have nothing to prove.


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Old 03-04-2016, 17:57   #13
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Re: 9KW Generator

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I run my generator and HVAC for both heating and cooling (and other electrical loads) all the time when not at the dock. Burns 5-6 gallons in 24 hours. I sail, my wife is comfortable down below, and at night we are always comfortable in all conditions. You don't have to chose to be uncomfortable to sail. On other boats, I've sat on watch, cold, somewhat wet and uncomfortable. Not so on my boat. I also have a full enclosure for the cockpit for those times when it's cool and lots of spray. Makes life more comfortable and enjoyable for us. If you like roughing it, go for it! I did in my youth, now in my late 60's, I have nothing to prove.


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Well said!
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Old 03-04-2016, 18:26   #14
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Re: 9KW Generator

9000 is just enough for 3, if they are setup and run by a controller to make sure the starts are staggered, and only if they are modern AC units, and not the old reciprocating compressor.;
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Old 04-04-2016, 02:40   #15
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Re: 9KW Generator

The Cat we've decided will be a Helia 44 Evolution, new build, 220v, an 11kva Onan isn't an option on FPs specs unless 60khz. I haven't got any specs on the AC units yet.
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