Lagoon 380 w/AC Min Generator Size

[Byrdman]

Did a search and couldn't find the answer, so does anyone know amp usage running AC on a lagoon 380?

Looking at one with no AC or generator and yes, Admiral retirement! So looking for the smallest generator needed to do the job.

I get it, we may not need it and solar lithium is the way to go but just want to look at all options.

I have a very quiet 4200 kw portable with 30A. Will that do the job?

[SailingHarmonie]

When it comes to generators, "really quiet" and "portable" are mutually exclusive. Even most below decks fixed models are bad neighbors in a quiet anchorage for people sleeping with hatches open (Which is almost everybody, btw.) Running one all night to power your AC is a great way to make anti-friends while you sleep in a storm of white noice with closed hatches.

If you REALLY believe that boat 100 yards away can't hear your generator, you are deluding yourself. If you know they can, but don't care, well... nothing I can say will fix that.

But...

How big a generator do you need? How can we tell?? How big are your air conditioners??? do they have soft start circuits? How many will you run at once?

[malbert73]

All I’ll say is if you have a genset, the install makes a big difference. Please install a water/exhaust separator and have the water drain below waterline. That and decent sound insulation and your neighbor 50 yards away will only hear the trickle of your AC. Install just a water lift muffler and we all have to hear the sound of the exhaust water splashing being pushed by exhaust air yards away into the water.
Now, do we run ours overnight often? Almost never. The sticky hot breezeless nights we do, we are very thankful to have AC and genset.

[Tin Tin]

OK a starting point. A Lagoon 380 air-con of say 12,000 BTU will cool the salon with stairwells closed off. A 6000-8000 will do a cabin+bathroom. The 12k btu unit will have a start up amperage of 28Amps at 230V = 6.4KVA. A 6k BTU is around 17A at 230V = 3.9KVA. The 12k BTU running amps is 5.1 + say 2 for the pump - say 7A to run at 230V = 1.6KVA. This is all pretty rough. Amps will double for the 115 V system but KVA will be the same approx. This data is for Cruisair/Dometic there may be other brands with different specs.



The Start up (Locked rotor) amps can be lessened with a soft start capacitor, extra $, so you may get away with a 3 - 4 KVA generator for a 12K btu unit and 1/2 that for a 6k btu unit. If you want to run 2 or more units off say a 6KVA generator you will need to make sure they do not start at the same time.


This is all to give you a rough idea, there will be plenty of fine tunes that may improve things. If you want to run it on Lithiums you will need a hefty inverter and if you run it for 8 hours a 12btu unit will need 8 * 230 * 7 = 13,000 watts / 12 = say 1000 AH in the battery system which will need to be recharged the next day - so a bunch of solar panels say 1500W, cos you need to run everything else as well.



Running a portable generator at night whilst sleeping is not only anti-social it is dangerous from a CO point of view especially if it is gas powered.

[Cheyne]

We use a Honda 2200 for now in the winter on our 380 to help charge the batteries when solar can’t keep up. We only need to run it around 1 or 2 days a week depending on weather. This has been enough that we ordered a NexGen 5.5kW genset. We have yet to run our AC overnight if we are not in a marina. Our Honda will get shunted to being the backup to backups for power.

Cheyne

[malbert73]

Originally Posted by Cheyne

We use a Honda 2200 for now in the winter on our 380 to help charge the batteries when solar can’t keep up. We only need to run it around 1 or 2 days a week depending on weather. This has been enough that we ordered a NexGen 5.5kW genset. We have yet to run our AC overnight if we are not in a marina. Our Honda will get shunted to being the backup to backups for power.

Cheyne

Good choice- love my NextGen 5.5

[Madehn]

I have a 6000 btu and a 12000 btu units on my boat the 12 k might actually be 15 k. Can’t remember for sure. They pull around 22 to 24 amps at113 volts AC. More briefly at startup. I don’t start them both at the same time.

[SailingHarmonie]

Originally Posted by malbert73

All I’ll say is if you have a genset, the install makes a big difference. Please install a water/exhaust separator and have the water drain below waterline. That and decent sound insulation and your neighbor 50 yards away will only hear the trickle of your AC. Install just a water lift muffler and we all have to hear the sound of the exhaust water splashing being pushed by exhaust air yards away into the water.
Now, do we run ours overnight often? Almost never. The sticky hot breezeless nights we do, we are very thankful to have AC and genset.

Yeah, this exactly. Our generator is installed like this, and in a sound shell, AND in a very well sound isolated engine room. We have had people tied to the side of our boat in their dinghy who did not know our generator was running.

And, likewise ont he running over night. In 6 years of cruising we have run an AC at night at anchor exactly ONCE. And we have spent summers in the southern Caribbean. I understand that a catamaran with black heat absorbing solar panels glues to the deck might be different.

[Nor]

My 12k btu cruisair draw around 1150W with the pump. I have a soft start so no problem starting and running from batteries for some hours. It doesn't have to run all the time, depending on how low you set the thermostat.

[team karst]

Originally Posted by Cheyne

We use a Honda 2200 for now in the winter on our 380 to help charge the batteries when solar can’t keep up. We only need to run it around 1 or 2 days a week depending on weather. This has been enough that we ordered a NexGen 5.5kW genset. We have yet to run our AC overnight if we are not in a marina. Our Honda will get shunted to being the backup to backups for power.

Cheyne

that's exactly how we did our system. started with the 2200i, ended up with nexgen 5.5 wired to do either 120 or 240v for our 3500psi nitrox compressor. Neither ac unit needs softstart, the compressor does. Lots of noise filling tanks. Rarely are we anchored around others. Last year at Georgetown summer/early fall there were less than 10 transient cruisers in that area.
we have outgrown sweaty and salty sheets and run the air con when we feel like it.

[Cheyne]

Originally Posted by team karst

that's exactly how we did our system. started with the 2200i, ended up with nexgen 5.5 wired to do either 120 or 240v for our 3500psi nitrox compressor. Neither ac unit needs softstart, the compressor does. Lots of noise filling tanks. Rarely are we anchored around others. Last year at Georgetown summer/early fall there were less than 10 transient cruisers in that area.
we have outgrown sweaty and salty sheets and run the air con when we feel like it.

Our current setup is a Victron Quattro 5000 and a 1596 amp/hour lithium battery bank with about 2500w of solar. In the summer we rarely go below 70% SOC, but in the winter we rarely get above 75% SOC and usually have to run the Honda once a week for 4 hours to catch up. We are a heavy use electricity boat and that won’t change. The NexGen 5.5 best use for us it to top off the batteries in the winter and run the AC in Virginia when we are on anchor.

Cheyne