Generator KW required

[soggy]

We have been looking at trawlers as our next boat for long range cruising. We have pretty much settled on the 44 Defever as the one we want. I have found one that is a 2001 but it only has an 8 KW on it. I currently have a 10 on a smaller boat. I am thinking a 44 would be more suited with a 12 kw. Question is, is the 8 enough or would power management become a full time job?

 

[swampu]

Does the boat have any gas appliances? If it was bult with a 8kw and all that does is run water pumps, ac's and lights than that would be enough. If it has to run a electric oven/range/fridge/heater.ect than it would probably not be enough.

 

[Moonstruck]

An 8 kw will run a lot of stuff. If you have 3 A/Cs and electric cooking, you could have to do a little load management. I would look into adding a 3.5 to 5kw generator to bring on line when needed. Also, if doing island cruising it could serve as backup if the big one goes down. Battery charging and refrigeration are the essentials. A spare battery charger and/or inverter are also good ideas. Don't ask me how I know.

Plus you would have to be careful to keep about a 70% load on a 12kw. Much easier on an 8.

 

[Larry M]

Total everything up on the boat you have now. How many amps full on? What does the 44 have over your current boat that would take an additional 3-3.5KW?

We have an 8KW now and we don't load it correctly. Our 2-16KW ACs draw 19 amps, add the charger, hot-water heater and we're less than 50 amps total. Add a toaster or microwave we're getting close, but only for a few minutes. We cook with propane.

 

[Phil Fill]

A 8 KW# will produce 60 amps (8,000/120). Most boats are wired for 50 amps, so the 8 KW is sized the boat. The Eagle is wired for 50 amps, so what we did was load share, put timers on high demand items and convert things to DC, propane and diesel to reduce the total amp draw.

 

[ksanders]

We have a 47' boat with all electric appliances including a clothes washer.

Since we are in the PACNW we do not have AC though.

We're running a 9 kw generator and never have to power manage.

consider this...

A 30 amp 120 volt dock connection is only 3.6KW

A 50 amp 120 volt dock connection is only 6KW

 

[soggy]

Thank you all for he insight. I think we will go look at the 44 we found. We locked through this weekend next to a 44. They docked next to us and we got to meet them and see the boat. Great people and a really nice 44, she was a 1990.

 

[DavidM]

Most boats have a generator that is too big to keep loaded properly.

If you just add up all of your AC loads and size your generator accordingly you will have a tough time keeping that generator loaded to 25% and at night when the A/C load drops off, it may be as low as 10%. That won't be very good for the genset's engine.

So size your generator to run those loads that absolutely have to run simultaneously and do some power management to keep it loaded like don't run the microwave and the hot water heater at the same time, etc.

David

 

[Baker]

8kw should be just fine!!!

 

[Codger2]

8kw should be just fine!!

Couldn't agree more! You always have a management situation aboard, relative to your electrical needs, and if you don't, you have too big a boat!

 

[Aquabelle]

If you find that the genset is a little small for peak loads (eg running multiple air-con units simultaneously) you might find the best strategy is to invest in a load-sharing inverter/charger of the type made by Victron and MasterVolt. These are capable of adding to genset capacity for peak/surge loads & allow for a smaller genset to do the job. Also means the smaller genset is running better-loaded most of the time...as noted above by others, this is a good thing in its own right.

 

[IslandEagle]

If you find that the genset is a little small for peak loads (eg running multiple air-con units simultaneously) you might find the best strategy is to invest in a load-sharing inverter/charger of the type made by Victron and MasterVolt. These are capable of adding to genset capacity for peak/surge loads & allow for a smaller genset to do the job. Also means the smaller genset is running better-loaded most of the time...as noted above by others, this is a good thing in its own right.

I could not agree more. I have a 6KW and I run it through a Xantrex 4024MC, which has load sharing. It works like a charm.

Scott Welch
Island Eagle

 

[psneeld]

wow...what understatements...8kw isn't nearly enough if you need it and WAYYYY too much if you don't.

People in this forum thought I was crazy for upgrading 2-30 amp services to a 50 amp 120/240 which produces 12,000 watts or 12 KW...and living aboard you can easily exceed that amount like the average house nowadays needs more than a 100 amp service.

Until you know what kind of "hotel services" you will be demanding at anchor or at no electric docks...you have no idea what king of genset you really need. Many boats with propane cooking can get by with a very small genset...mainly to heat water and run the batt charger. But if you like all electric (cooking included) and run a space heater or two during chilly weather...8KW is gonna run out fast.

The real trick is to find out what you need MOST of the time and size the genset to that. If you need more...maybe augment with an inverter or switch some appliances to other energy sources.

You don't want too big or too small..and what are your other options...

Kinda difficult to answer in a forum paragraph or two.

 

[koliver]

Also note what the wiring in the boat will handle. If it comes with an 8KW and you want to upsize to 12, you may need to rewire to handle the extra amperage. Now THAT is a big job.

 

[Portuguese]

MY boat is 46' and we have a 7 KVA genset. By the way, we are in a tropical country where AC is paramount. We have total 24000 BTU in the boat, MW, charger, one domestic refrigerator and several lamps.
No need for bigger genset

 

[psneeld]

MY boat is 46' and we have a 7 KVA genset. By the way, we are in a tropical country where AC is paramount. We have total 24000 BTU in the boat, MW, charger, one domestic refrigerator and several lamps.
No need for bigger genset

Wow...good deal on the Air Conditoning...

I'm in a relatively cool zone with 32000 BTUs of Air Conditioning on a relatively small 40 footer.

Either way I'm still only at 30 amps for the a ACs and would have enough (either with my 8kw or your 7kw) to run enough other stuff...especially with a propane range.

Most of the time at anchor...unless cooking , running electric heat or air conditioning....much above 5kw is hard to really work hard enough for it to be good for the genset.

 

[FF]

Question is, is the 8 enough or would power management become a full time job?

8KW is plenty , and at a very modest cost automatic LOAD SHEDDING is easy to install.

Once worked out life is very simple

 

[CaptTom]

...and at a very modest cost automatic LOAD SHEDDING is easy to install.

I looked at this for my house genset once. The theory is very simple, and I'm sure it's easy to install. I'd like to hear more about the "very modest cost" part. As I recall, that's not what I found.

 

[ksanders]

Question is, is the 8 enough or would power management become a full time job?

8KW is plenty , and at a very modest cost automatic LOAD SHEDDING is easy to install.

Once worked out life is very simple

Actually I'm in the wholesale power switching business and I have not and cannot find a commercially available automatic load shedding device.

The units that are being deployed are one off devices built from a protective relay and contactors by the electrician. Nobody is happy with this but again nothing is available that works.

There are a couple of units that work in their specific brands of generators, but nobody elses, but there is nothing that I can find that does not utilize propritary signaling.

The concept is simple, but there is nothing is commercially available yet.
If you know of somethingthat is available, and is UL listed, please either post it or PM me, because I can and will add it to our product portfolio.

 

[RickB]

Also note what the wiring in the boat will handle. If it comes with an 8KW and you want to upsize to 12, you may need to rewire to handle the extra amperage. Now THAT is a big job.

Unless you increase the consumers (load) you can put a 500kW generator in and not have any problems with the wiring.

Amperage is not pushed down the wires, it is dragged.

With regard to load shedding, I have never used one of their products but Panbo makes a programmable load shedding controller for small boats that might serve the purpose very well.

 

[CaptTom]

As far as I can tell, Panbo is the name of a blog, not a manufacturer of load shedding controllers. But it's a generic enough name that it could be I missed them.

I did stumble onto this one from Paneltronics that might do the job. At $584 I guess it's not too bad, but I've got quite a few other upgrades ahead of that on my list.

I also found a few commercial ones like this from ABB, but I'm pretty sure I'm not going to like the price any better.

 

[RickB]

As far as I can tell, Panbo is the name of a blog, not a manufacturer of load shedding controllers. But it's a generic enough name that it could be I missed them.
QUOTE]

You are absolutely correct, sorry for the mixup ... I saw it on a site and thought Panbo was the manufacturer.

If it only costs $584 for the complete setup and does what it claims, it is a steal.

 

[ksanders]

As far as I can tell, Panbo is the name of a blog, not a manufacturer of load shedding controllers. But it's a generic enough name that it could be I missed them.

I did stumble onto this one from Paneltronics that might do the job. At $584 I guess it's not too bad, but I've got quite a few other upgrades ahead of that on my list.

I also found a few commercial ones like this from ABB, but I'm pretty sure I'm not going to like the price any better.

Tom

Thanks very much.

The unit from paneltronics looks like it would work for a boat. It appears to be self contained.

The one from ABB is just a load shed controller. This is what I was talking about. I can do this with a protective relay as well. It has outputs to go to contactors, so you need a panel with contactors in it to make this a system.

I sell the contactors, I can sell the load shed controller. I have no source for the load shed controller and contactors as an integrated unit.

 

[CaptTom]

I looked at that marine one again, and it has its limitations. The loads are shed for a pre-determined time (AC a little longer than the others) so it's not smart enough to bring the loads back on line only when there's available power. It only works with ONE 30- or 50-Amp main. So if you have two 30A feeding two main breakers, you're out of luck. It does seem to allow different "max" values depending on whether you're being fed by shore power or the on-board genset, which is a nice feature. But again, useless to me because my genset feeds two different mains.

I don't think the price is unreasonable, just not justifiable for me because I have more critical items still on my list.

 

[RickB]

I looked at that marine one again, and it has its limitations. The loads are shed for a pre-determined time (AC a little longer than the others) so it's not smart enough to bring the loads back on line only when there's available power. It only works with ONE 30- or 50-Amp main. So if you have two 30A feeding two main breakers, you're out of luck.

Are we reading different data sheets?

The one I have says "Automatically restores power to ... loads when total load current drops below 30A for 120V 30A shore cords, 50A for 120V 50A shore cords; or 30A to 75A (field adjustable) for generators."

As far as the ONE main, it refers to one unit on one cord. If you have two cords and a split buss you should be able to shed 6 loads, or 5 cords on 5 split busses you can shed 15 loads. The box doesn't know how many busses are running elsewhere, only the one it controls. If that were not the case you could only use one of the things in the whole marina.

 

[beachbum29]

People in this forum thought I was crazy for upgrading 2-30 amp services to a 50 amp 120/240 which produces 12,000 watts or 12 KW...and living aboard you can easily exceed that amount like the average house nowadays needs more than a 100 amp service.

.

The average home today requires a 200 amp service. Most larger homes have a double 200 amp service.

 

[psneeld]

The average home today requires a 200 amp service. Most larger homes have a double 200 amp service.

I know...trying to explain myself 6 months ago to some was like pulling teeth. Then again I live aboard and they didn't so trying to relate a 2-3 week annual cruise with a propane stove aboard and they had all the answers.

Even if you tried to explain to them...run your house on one or two 30 amp cords and see how many times you'll be chasing breakers was lost on them.

Again..I live days or weeks at anchor on 12volts if I have to...but when that's over...it's nice to have the conveniences probably most of us have gotten used to.

Except there is this one guy in Alaska....hmmmm....maybe he is used to it.

 

[beachbum29]

But he is now phantom...

 

[Larry M]

psneeld: I have to ask, what are you running on your boat that you need 12KW or more?

 

[psneeld]

It's very possible to be running 2 stove top burners, microwave, hot water heater, 2 ACs or 2 space heaters, freezer, fridge, electric tools, misc electronics, lights, batt charger.....

I don't need 12kw...but I sure need more than 6kw....though I have thought about waiting till after the new propane cooktop install...the electric cooking is usually the killer.

It's also the way the boat is wired...like many with 2 ACs on one 30 amp circuit...if I split that up it would help but is still complicated for the "average crew" to understand load shedding prior to the cb popping. Much of last year I had a space heater on the AC circuit but still drove the crew crazy when I would tie up to a 30 amp and nothing else...having a 50 amp would force me more times to tie into that than just a single 30.