Generator size

“Worn out water jacket?”

What? Tell us more?

When we bought our boat it had a non-working 15K 4 cyl Westerbeke - took up half of the ER. Purchase price reflected. Boat originally had elec stove - replaced long ago with propane. Did a load calculation for two 16k a/c, water heater, frig, ice maker, microwave, coffee maker....Installed a 2017 9k Kohler in sound box and have been very pleased while at anchor in 95 degree Southern heat Did not want to have to fool around with load management.

gknoepfler said:

I have an’06 IG 32 with a 5kw split genny. I have to manage the loads to keep from tripping. I wish I had a 6-7 kw. Below is a load test I did with most of my heavy draw stuff:

Sea Neff 110V Amp Loads

House Bank
• Water Heater - 12 Amps
• Microwave Oven - 10.5 Amps
• Kuerig Coffee - 11.7 Amps
• Hair Dryer - 13 Amps

A/C Bank
• A/C Water Pump - 2 Amps
• Both Air Handlers - 3 Amps
• Forward A/C Compressor - 5 Amps
• Salon A/C Compressor - 7 Amps
• Peak Amperage with both A/C's - 31 Amps

Hope this helps.

Click to expand...

Split - Does this mean your genny is setup 125/250 with 2.5 kw available per side? Or is it 125 VAC only feeding 2 panels?

5kw produces about 42amps. I have a 2 pole circuit breaker on the genny, 20 amp each side.
So, I can’t run both ac's under genny, too much amps. Have to manage other heavy load stuff also,

HiDHo said:

You might check out Dometic Smart Start unit. My boat has two 16,000 btu heat pumps run by a single 5 kw NL generator. The Smart Start takes 65% out of load start spikes. No problems with generator overloads and my generatorj load is probable 75% or more making for a happy generator.

Click to expand...

These smart start, or similar units can reduce the needed load coverage. Fellas that I have heard used them said the same, they work good. Although it is one more thing.

The size genny, as said is relative to the load you wish to manage.

Unclematt said:

What size diesel generator is needed to power a 32' trawler with reverse cycle heat / ac, electric stove, lights and other basics while anchored? Has anyone heard of Nexgen they make a 4K genset. I am working on figuring out how much the boat will cost above sale price before making an offer. Thanks Unclematt

Click to expand...

Hi. I'd add two key considerations.

1) Whatever max load you think you'll need, add a margin. Why? You may buy more kit. You might use your electric kettle for a cuppa but won't want to turn off the a/c while the kettle boils.

2) Make sure you have a genny which auto-regulates your 60Hz frequency. Why? Some items you may have on board are very frequency critical. For example, a modern hob for the galley (I think you call them burners).

GPB

Ski in NC said:

Not necessarily good advice. If you add up everything and add 10%, you may end up with a really big machine that ends up spending most of its time running at 20-30% load 90% of the time and that is not good for the engines.

Best to size it modestly and tolerate some load management.

If you absolutely do not want to manage load, then size it as you suggest. Just understand there are downsides to doing that.

This applies especially to a smaller boat (like OP's 32). Not so much to a large boat, as that will usually have plenty of load and the physical size and weight of the machine is a non-issue.

Click to expand...

You might also consider a different approach: a smaller genny that is supported by a lager inverter;
The disadvantage of a larger generator that is sized to meet your peak demands is that 99% of the time it will work at only a small percentage of its total power; not good for the diesel engine which will probably die prematurely and also not very efficient in terms of fuel usage.
If you size the generator to meet your basic continuous needs (like the AC running 24 h and whatever continuous loads you might have) at around 70% of generator power and you add a large inverter with a top-up function to meet your peak demands (like when cooking while running AC) it is more cost effective. The inverter will top up the power using the house bank for the peak demands (which will normally only be a few minutes, like until the water boils etc) and after the peak, the small power reserve of the generator will be used to reload the house bank. During the whole time the diesel will work in a very efficient range (also good for its live expectancy).
The overall costs of the system (small genny & larger inverter) are similar to a larger genny and a small inverter; the follow up costs are lower.

When my old 25 kw generator died 8 years ago, I replaced it with a small 10 kw panda and added an inverter/charger that can deliver a synchronized 20+A/230V in addition to either the shore power (which is between 4 and most of the time 15 A/230V in the local marinas) or the generator.
In the old situation, I had to start the generator even when having shore power for cooking larger meals (with several pots on the stove and the oven running); in that situation my average energy consumption on the A-meter in the kitchen was around 6-8 A but the peak sometimes around 30 A/230V 50Hz – only for a few minutes but too much for the max 15 A shore power; now the inverter kicks in during the peak moments and my total generator time is down to the time at anchor where I run the genny like 2 h a day (during dinner cooking and to refill the house bank) and the inverter powers the 230 V appliances for the rest of the time. I safe around 100 h of generator time a year compared to the previous situation. The overall investment in a smaller genny plus larger inverter are almost the same as a larger generator, however the running coast are much lower and I freed up a lot of space in the engine room. I hindsight, I would take an even larger inverter or combine two of them, just for peace of mind because I had a few situations when running AC plus cooking plus washing machine where I had to watch the ampere meter again in order not to overload the system.

gknoepfler said:

5kw produces about 42amps. I have a 2 pole circuit breaker on the genny, 20 amp each side.
So, I can’t run both ac's under genny, too much amps. Have to manage other heavy load stuff also,

Click to expand...

You may want to look at how the gennie breaker and the rest of the boat is wired. If a 120v boat both poles of the output breaker should be tied together giving a total of 40A. If a 240V boat, load is not balanced between legs if it trips.

Needs a closer look if tripping with the two ac's on.

Last year I replaced the 9kw Kohler on our 40' Mainship with a 4.5kw Phasor, and couldn't be happier. Much quieter, and less weight to haul around.
It will run any three of the seven major devices, two a/c's, hwh, electric range, microwave, hairdryer, inverter/charger charging depleted batteries at the same time without straining.

Folks refer to Load Shedding like it is a big deal. It is quite simple to automate..

A single wire is run from the more important load to a relay on the secondary load.

The relay is" NC "(normally closed) and will open when the controlling item is powered.

The range could be the control for say the HW heater.

Air cond 1 the control for air cond 2.

4KW is plenty for a 30ish ft boat.

syjos said:

The 5.5 Kw generator is perfect in the winter running electric heaters and hot water tank.

In the summer at anchor, the 120 VAC holding plate freezer compressor and the battery charger are the only loads after the 15 amp hot water tank reaches temp. The compressor uses about 5 amps and charger consumption declines as the battery gets charged but starts at around 20 amps when the batteries are down 50%.

So in order to keep the generator loaded after the water heater turns off, I have to run an electric heate outside the boat. When I had the 4.5 Kw generator, did not need to run a heater but sometimes had to manage loads.

Reason to correctly size the generator.

Click to expand...

Syjos,
I thought I might be the only one running an electric heater out on deck in the summer (to help load up the generator)
My boat came with a 9KW generator that is way too big for our needs. The boat was originally going to have AC installed (so I am told), but does not have AC. So, I try to load it up to at about 40 to 45 amps, with the odd time having 2 heaters on deck. I do get some strange looks and/or comments from passing kayakers

I've been known to have an A/C unit running with windows open to keep more load on the generator when I have it running only for something fairly small, like warming the hot water tank.

firehoser75 said:

Syjos,
I thought I might be the only one running an electric heater out on deck in the summer (to help load up the generator)
My boat came with a 9KW generator that is way too big for our needs. The boat was originally going to have AC installed (so I am told), but does not have AC. So, I try to load it up to at about 40 to 45 amps, with the odd time having 2 heaters on deck. I do get some strange looks and/or comments from passing kayakers

Click to expand...

I put the heaters right outside the PH doors and they are hidden by the portuguese bridge.

9Kw is a lot of power without AC

rslifkin said:

I've been known to have an A/C unit running with windows open to keep more load on the generator when I have it running only for something fairly small, like warming the hot water tank.

Click to expand...

You guys need to come on down to the South - no need to open windows in our heat and humidity . We run our two 16k a/c units full blast when at anchor. Our 9k Kohler is fairly new, and I'm not too worried about under-loading.

Our boat, purchased six years ago, came, apparently an original installation, with two generators, a 12kw Perkins powered Kohler and a 7.7kw Westerbeke. We use the Westerbeke more than the Kohler as it is much quieter. I considered having one of them removed to gain some engine room space but was talked out of that idea by the good folks on this forum. If one of them craps out, I will remove it then and not replace it. The Perkins-Kohler, however, is indeed a monster. Doesn't help much to address the original question but I will say that I would go with a larger unit if I had the space. Sure, with diligent load management one can get along but if one is already going to pay for the installation the incremmental cost of stepping up to the next larger size is not thaat much. No regrets later.

Play d'eau has two Onans. 13.5 & 7.5. The larger is far quieter. Hence, we tend to use this far more when at anchor, regardless of load. Both at 14 years old and both are in tip top condition.