2.5 KW Diesel gen too small?

I have a 32 Island Gypsy, single screw. The inverter is no working and I want to be able to run air and lights while anchored.

There used to be a generator on the boat as there is an extra sea cock in the hull. I'm not a limited budget and am wondering if a 2.5 KW DIESEL generator would be a good fit for my Ford Lehman diesel powered trawler.

My AC runs 12,000 BTUs. I want to be able to run a few lights and the AC with the 2.5 KW generator. Do you think it will produce enough power?
It's priced right at $3k and is relatively small.

I would assume I would want diesel rather than gasoline to run off my two main diesel tanks, right?

Any thoughts?
Thanks,
Rick

It depends partly on your ac unit. Older models used a piston compressor that draws more running amps and has a significantly higher starting amp requirement. Rotary compressors draw less amps and the start up load can be significantly smaller. Starting the compressor will be the issue. There should be enough amps to run it. If you can post the amperage requirement from the manufacturers label on the unit, that would be very helpful.

Ted

Well, 12000 btu is 3.2kW. So you're not gonna make it with 2.5KW genny. If the ac has 'soft start' then you might get away with a 4 kW unit, but better would be a 5kW. Even then, I would borrow or rent a genny on wheels of that size, walk it along the dock and plug in your ac. Test it will start the ac before buying and plumbing one into your boat. And yes, diesel is best. Boat gennies are not cheap though.

Our phasor 3.5Kw in our camano would run our 16k BTU and nothing else.

You might need to add a SmartStart soft starter or something like it to the A/C unit to reduce the start up load.

Insequent said:

Well, 12000 btu is 3.2kW. So you're not gonna make it with 2.5KW genny. If the ac has 'soft start' then you might get away with a 4 kW unit, but better would be a 5kW. Even then, I would borrow or rent a genny on wheels of that size, walk it along the dock and plug in your ac. Test it will start the ac before buying and plumbing one into your boat. And yes, diesel is best. Boat gennies are not cheap though.

Click to expand...

Your using the wrong formula. A Webasto 12K btu ac unit draws 8.5 amps at 115 volts. 115 x 8.5 = 977.5 watts (slightly less than 1 KW). There is more than enough power to run it, the question is does the genset have enough muscle to start it.

Ted

Ted
Yes, I was converting to cooling capacity. It seems that input power is a lot less. So based on your calc and Oliver's actual numbers then the OP might be OK with his 2.5kW unit if the ac is soft start. Personally I'd still test it out first before buying....

Can you tell us a little more about this 2.5 KW genset. If it is that small then it probably has a Farymann diesel. Even though they are used on the small Fishcher-Panda gensets, I consider them a toy.

Whether a generator will start a 12,000 but A/C depends on the starting current of the A/C and the generator's ability to supply it. Some small gensets like the NextGen 3.5 KW unit and maybe the Phasor 3.5 KW mentioned above have 5 KW generator ends. These will supply enough starting current for a 12 or even 16,000 btu A/C unit.

And as others have said, you can install a soft start kit on the A/C compressor. Supco makes one and Dometic makes a better one.

David

Rick,

It will be tight, but a modern Cruiseair 12K BTU AC unit draws 8.7A cooling and 10.9A heating. It draws 58A locked rotor on startup.

Dometec makes a SmartStart Soft Starter which reduces the start amperage by up to 65%, or in the case of the above unit, a little over 20A or 2.3KW. Theoretically, it should work.

I've heard of other TF members that have successfully run some 16K BTU marine air conditioners using Honda EU2000 portable generators.

Good luck with your project.

Start amps = 1.8 X run amps. So according to Ted's numbers 8.5 x 1.8 = 15.3 amps for start up. Or 1.836k watts. All this in theory, you have additional resistance in the wiring. Then there is the RPM factor, high RPM gensets will drive Ya nuts.

My 12000btu Mermaid draws about 8-10A depending on temps. A 2.5kW might or might not start it.

What gennie brand/model is the 2.5?

A better question might be why NOT the Honda?

It will run the AC , is almost silent , cheap, and can be used at home at times.

With no install time the only hassle is the rotten gas required to be sold today.

A steel old style 6 gal OB tank would make a good easy to fill tank .

IF you operate infrequently , simply run the unit out of gas , and dump the gas into your car.

FF said:

A better question might be why NOT the Honda?

It will run the AC , is almost silent , cheap, and can be used at home at times.

With no install time the only hassle is the rotten gas required to be sold today.

A steel old 6 gal OB tank would make a good easy to fill tank .

IF you operate infrequently , simply run the unit out of gas , and dump the gas into your car.

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This is what I was thinking. Way cheaper and they have been known to start good size AC units with the help of a start capacitor.

Again I find myself in complete agreement with FF. Honda has a heck of a warranty also as an upsize.

Good article here on running a 16K BTU unit off a Honda EU2000.... Using various soft start methods (Supco and Dometic).
The Supco start capacitors are only $12 on Amazon, so simple and cheap enough to try out. I'm going to and test with my 2K watt portable gen. It should be all I need to run the 12K BTU Mermaid on my boat..

Honda eu2000i and air conditioning - Page 3 - SailNet Community

Buy at least a 3 1/2 kw gen. You never know what you may add. It would be expensive to upgrade.

The Honda generator might be a viable option for infrequent use. OP lives in FL and may plan on using it a fair amount. The honda is quiet under modest loads, but gets noisier at half or more capacity. There have been a couple of theads on the forum about building sound shields for them. Not sure I would feel comfortable going to bed at night at anchor with one running in the cockpit or up on the cabin roof. Think a properly installed and maintained diesel marine generator has a significantly lower risk factor. Don't forget about the carbon monoxide exhaust which is extremely dangerous.

Ted

You seem to have enough info on the required size of the gen set, I would add you need to check into the sound levels as well, have a friend with small 3.5 diesel gen and boy does that put out a racket, no way you would be leaving it running for AC needs.

The Nestgen is powered with a Kubota engine, belt drive geared to 60 cycles, and runs at 2800 rpm. Not a screamer or terrible vibration. I had a 5kw and was very happy with it. Built in Jacksonville. They are very helpful.

NEXT-GEN - Marine Power Units

I had a mastervolt 3kw generator (Kubota motor). Ran my 16000 btu air conditioner ok, but surged when the compressor started. I added the dometic smart start and it worked much better. Downside to a lot of small single cylinder gensets is the high rpm (3600 for the one I had). A lot of noise and vibration. One suggestion, install the exhaust water separator option if available, it makes it quieter.

The Honda is a great generator, CO is a killer. I would go with the diesel.

If money is not the issue a 3.5- 4KW unit with two or more cylinders in a sound box with exhaust separator would be best unless you have need for more power on a fairly regular basis while air is on.

Will this do the trick?

I was told by the marina I bought the boat from to replace my current no working Inverter with this model:

AIMS Power PWRINV8KW12V New 8000 Watt Modified Sine Inverter - See more at: AIMS Power PWRINV8KW12V New 8000 Watt Modified Sine Inverter
AIMS 800 Power Inverter 8000 watt sine modified inverter for 12volt

The batteries are already on board.
Need this to power my AC, Refrig and a few lights when anchored.
Any thoughts?
Thanks
Rick
PWRINV8KW12V New 8000 Watt Modified Sine Inverter

islandgypsy said:

I was told by the marina I bought the boat from to replace my current no working Inverter with this model:

AIMS Power PWRINV8KW12V New 8000 Watt Modified Sine Inverter - See more at: AIMS Power PWRINV8KW12V New 8000 Watt Modified Sine Inverter
AIMS 800 Power Inverter 8000 watt sine modified inverter for 12volt

The batteries are already on board.
Need this to power my AC, Refrig and a few lights when anchored.
Any thoughts?
Thanks
Rick
PWRINV8KW12V New 8000 Watt Modified Sine Inverter

Click to expand...

8000 watts is huge!

How big is you battery bank and what do have for recharging?

How much battery power do you have? It's pretty hard to run an air conditioner all night with an inverter. Some electric motors (compressors) can have problems with a modified sine wave.

Your marina is nuts to recommend that inverter.

Most of what you said in your post was wrong or nearly impossible. Lights and refrigerators don't run on alternating current. They run on DC (well mostly maybe you have a home refrigerator). AC which I suspect you mean air conditioning requires at least 1,000 amphours of battery capacity to run a 16,000 btu A/C unit overnight, not to mention how you are going to recharge those batteries for the next night. And where are you going to connect your A/C unit that draws more than the 15 amp rating of each of those four outlets?

That AIMS inverter is Chinese and doesn't meet UL or ABYC marine specs. Where is the chassis ground that ABYC requires be wired back to the boat's DC ground bus.

It will be lucky to make it through the warranty period before it fails. It will fail in a few hours if you try to run it any where near its 8,000 watt rated output. Can you imagine how much heat will build up inside it at 90% efficiency- eight 100 watt lightbulbs worth. And can you imagine how much DC current it could draw at that rate- 750 amps. It takes two pairs of 4/0 conductors to handle that much current safely. Where do you attach four 4/0 conductors to that inverter.

I could go on and on.

Again, whoever told you to install that inverter doesn't know the first thing about marine electrical systems.

And why is this post in a generator thread?

David

The original poster was asking about a small generator because his inverter has died. I think his marina has given him some unrealistic expectations regarding a new inverter and running an air conditioner. Not only would an ac require a battery capacity of around 1000ah to run overnight (especially in Florida), but it would take hours of engine running to recharge the batteries.

I wonder where his marina has proposed installing this 8000 watt inverter? It better be close to the batteries if they are going to use the recommended dual 4awg cable connections.

purchasing a MT 40 with Honda EU 3000i hung on transom wired directly into the ac panel on board. Handles electric under way... quite and cheap to operate.. stove, fridge etc. HVAC is reverse cycle on boat circuit. Not long distance cruiser but works for us when traveling. Cheap to fix or replace when necessary compared to Onan or like down below

I have a NextGen 3.5kw model w/out a sound enclosure. An awesome unit that simply works. Besides generating electricity, it also does a good job at making noise too. I wouldn't buy one unless it is in an enclosure, especially since you want to run A/C with it. I'd assume that is while you are inside the boat trying to read, watch tv, or sleep. Non of which you can do with a diesel genset in that size boat IMO unless you have some stellar engine room sound deadening. It goes against everything I like because having a higher output genset that runs on diesel fuel is great, I'd make a Honda EU2000i work.

I actually plan on bringing mine out on the mooring because I will need some supplemental electric space heat and battery charging for a few weeks till the weather changes up north. I would rather run the little Honda all night than have the Kubota rattle my fillings out trying to sleep.

Of course my boat is all electric so I really am not going to change anything up, need the NextGen to make hot water, cook on the electric stove, and charge batteries with 2,000 watts.

Sounds like you answered my question

RED DOT and others do make DC air cond units for truck sleepers.

About 8000BTU , enough for a cabin but not for an entire boat with large glass areas.

An inverter to run air cond from batts is not realistic , Your batts will fail in minuets.