Air Conditioning & Watermaker on a no-Gen cat - AC vs DC

[NaClyDog]

Originally Posted by Alistair242

If you want on demand AC power 24/7 like one has in a normal home or apartment then maybe living aboard is not for you or plan to stay the majority of nights in marinas.

It's always lovely to see people making rules for people they know nothing about, where they will be going, what they will be doing and how they plan on doing it.

[Alistair242]

Originally Posted by NaClyDog

It's always lovely to see people making rules for people they know nothing about, where they will be going, what they will be doing and how they plan on doing it.

I meant no offence. I’m genuinely interested in how many boats generally run their AC all night long on the hook.
The OP suggests they are referring to a Seawind so we can make the assumption that they plan to be part time or full time cruisers.
As said, no offence intended.

[jbinbi]

Mooring ball is 30 to 50 a night. Dock is 150. So running AC all night on a generator when not at a dock. Dock charge for AC is 25, so possibly less to run generator as well.

Frequently is the answer.

[Dtm67]

My 2 cents on running AC at anchor.. we are currently in Greece and have had several days in a row of high heat warnings. My wife is at the age where “hot flashes” make the night time heat even worse for her. She had taken to ice packs and wet towels to sleep (or up top on the tramp).

But since we have 600ah of lifepo we can run our lagoon 400 owners cabin AC for 7-8 hours before hitting our self imposed threshold of 20 percent SOC.
We do need to run our genset the next day for an hour and a half to make up the lost ground (we have a 220 amp battery charger). Our 1200 watts of solar takes it from there

This is roughly 3 dollars a day in diesel and is a fair trade to me (marinas cost over a $130 per night...no thanks) to keep the admiral happy on the hook for the hottest few weeks here in the Med. We don’t run it every night but it’s nice to know we can when she wants it.

Ironically I don’t sleep as well because the noise of the AC under the bunk has me worried I won’t hear an unexpected wind shift....

But we have the setup to do it so why not?

[mako]

DTM it sounds like you have a nice system in place.

I think regarding this subject, that whether you go AC or DC aircon, it's a plus to be able to live off batteries for one evening in your stateroom only, which is practical considering they work at a reduced duty cycle during the evening. Genset is mandatory of course and is a really nice convenience, and is probably cheaper than buying an extremely upgraded and huge capacity Li system.

[SV THIRD DAY]

We have a Seawind Cat client with an 800AH LiFePO4 battery bank named "Jolly Dogs" (look them up online and they can give you details) that have been running our 30GPH AC water maker through their inverter for years.

The advantage of AC over DC is the large output and non-proprietary water maker parts.

Once you have a LiFePO4 battery bank so many of the old Axioms fall away and it opens up many more possibilities.

[Zzmeyer]

I reached out to the Facebook Saona 47 group of about 110 owners. Only one said he was regularly running air conditioning off 12 volt. Another said he intended to. A couple said they were interested in learning more. Amazingly the one who is running ac has 2000 watts of solar AT 48 Volts which generates the equivalent of 2400 ah at 12 volts. I don't know where he gets the real estate. The other has 2400 watts of 12 volt solar. Others might run AC off of Lithium, but didn't respond
SV Third Day raises an excellent point. I've always been a fan of 12 volt water makers. I will willingly give up the higher production rates to avoid the risk that the generator doesn't work. However, with lithium you don't need to. One big disadvantage of 12 volt I've learned over the years is that no matter how big your generator is it only charges the house batteries at the rate of the battery charger.

[a64pilot]

Originally Posted by Alistair242

I meant no offence. I’m genuinely interested in how many boats generally run their AC all night long on the hook.
The OP suggests they are referring to a Seawind so we can make the assumption that they plan to be part time or full time cruisers.
As said, no offence intended.

Only time I have ever seen it done is Charters, and usually then it’s large Motor yachts that are Chartered. No actual cruiser I have met runs AC except when there are at a Marina, instead they move to stay in comfortable weather, anchor where there is always a breeze and if your in the weather as it begins to warm up, you acclimate. We are more often than not closing hatches to cut down some on the breeze as we are cold at night, now this is Winter in the Bahamas, but who would want to spend Summer there? Between the heat and the Hurricanes?

You can run an AC watermaker off of a large bank or better just replace its AC motor for a DC one if that’s what you want to do, but you spending big $$$ in Lithium and Solar capacity to do it when you can make the same amount of water with a Spectra on a tiny fraction of the power.

When power is limited, it doesn’t make sense to go to a lot of trouble and expense to increase power production so that you can operate an inefficient machine, it makes far more sense to operate an efficient machine and either save the excess power or don’t have to buy it all to begin with.

An AC watermaker is just too easy to operate from a Honda generator, and charge the bank at 30 amps too, or to operate off of a largish alternator when motoring

[a64pilot]

Originally Posted by Zzmeyer

I reached out to the Facebook Saona 47 group of about 110 owners. Only one said he was regularly running air conditioning off 12 volt. Another said he intended to. A couple said they were interested in learning more. Amazingly the one who is running ac has 2000 watts of solar AT 48 Volts which generates the equivalent of 2400 ah at 12 volts. I don't know where he gets the real estate. The other has 2400 watts of 12 volt solar. Others might run AC off of Lithium, but didn't respond
SV Third Day raises an excellent point. I've always been a fan of 12 volt water makers. I will willingly give up the higher production rates to avoid the risk that the generator doesn't work. However, with lithium you don't need to. One big disadvantage of 12 volt I've learned over the years is that no matter how big your generator is it only charges the house batteries at the rate of the battery charger.

We have a member who runs AC off of Solar and I believe he has over 2KW of panels, and based on his actual experience, to run AC 24/7 would take of course a huge bank, but 5 kw of panels as well.

I had a discussion last year with a man who I know was straight out lying, he said he ran his AC off of batteries, when I called him on it, he said “I have two 400W wind generators and 500W of panels, so I make 1300W of power and that will run one AC.
I didn’t even bother to say he never, ever sees 1300W of power output.

[RickG]

Our energy budget is 280 amp hours at ~12.5V, about 3500 watts. Our old 12K BTU Cruisair with EasyStart pulls 11.5 amps at 115V, about 1300 watts at 50% duty cycle. But, it would pull about 100 amps through the Inverter while running. Our Victron Multiplus 3KVA and 800ah of Fireflys can handle that. But... that is a big load. I decided not to setup that way. We have the a/c off of our Victron Multiplus at AC-out-2 which is only active when there is shore power. Our Honda 2000 runs the a/c well with leftover power for charging batteries. We run the a/c only occasionally at anchor.

One thing I did not consider when going with a combined charger inverter is that the Mulitplus will not change the frequency of power from 50Hz to 60Hz when connected to shore power. Our Cruisair is an old 50/60Hz unit so it still works on Grenada power. With separate inverter and charger I could charge the batteries using 50Hz power and run all 115V AC/60Hz off of a separate inverter. As it is, none of our AC devices complain about 50Hz. If we upgrade/replace our air conditioner I would probably add a separate high amperage charger. The more likely solution would be to pull the air conditioner and gain back storage space.

Cheers, RickG

[pbmaise]

I calculated this before for my vessel and found I needed about $15,000 worth of solar panels and support to generate enough solar power to run 2.5 tons of 48v AC and a large 48v freezer. I planned on transfer of ice packs from freezer to fridge and decommissioning the water cooled fridge. Max output of solar was going to be 9kw.

I am now set to dock tie an AC line and will go AC cooling and plan on converting a cabin to house large chest freezer.

[Gerrit Coetzee]

Originally Posted by wathey

Great thread. Some quick research yields a DC Mabru unit at 12k btu is about 5500 US. A similar dometic AC, AC unit is 3500 so there's a few $k difference but relative to a new Seawind this is a nominal expense. Bigger question is whether Seawind will take on another manufacturer relationship if their current AC supplier doesn't have a similar product. I don't agree with the statement you must have a genset. I do agree that you must have a monster sized Lipo pack. The Mabru states it draws 40 amps. If you have three you may be limited to running specific hulls or 1 hull and the saloon to achieve the desired runtime. The largest lipo pack on a cat of that size I have seen in person was (6) 280ah lipo units to achieve 1680ah. That boat did have a smaller genset to charge the pack on rainy days when they were at anchor when the 2800 watt solar array could not do the trick. But seriously that battery bank was likely around 22,000 US and the solar setup another 20k, at least , I don't have specifics but that was aftermarket installed the factory pricing could be significantly higher. My guess is that your plans will bump the purchase price by at least ten percent. I think the videos they have posted are great for understanding the math involved. Also check out sailing Uma and their elctrobeak series. It's about using a forklift battery as a main engine but they do a great job explaining amp heures, watts, DC controllers and the difference between AC and DC electric motors.
Important is where you are cruising. In many areas we only run our AC just when we are cooking at anchor and it gets over 80 in the saloon. Further south like Panama you will run it much more.
It will also be interesting to see how this effects resale value but only time will tell how the market responds to these DC based boats. I think there are others heading in that direction. There have been a few threads about DC gensets over the past few years which is ultimately where this is going.

I am second guessing the prices. $22,000 for 1680ah lipo's ???

*www.mhn.co.za Mecer LiFePO4 2.4 Kw 12v 180AH battery $380 - To make 1680ah that will equate 9 of these batteries (bigger/fewer battery options too) at $380 = some $3600. A far cry from $22k.

Same with the solar pricing- $20k for solar ???

[Gerrit Coetzee]

Originally Posted by Augi

As you suggest going with DC air conditioners and DC watermaker is more efficient. My understanding that going with AC air conditioners and AC water maker the losses are 30-40% versus DC.

Other things to consider are even though what Seawind is specing for you will likely cost more there are advantages to have everything come for the factory in terms of less hassle, running wiring, running ducting, all the components ought to be complementary, potential warranty issues maybe can be avoided if a manufacturer of one comment will not honor their warranty because they say their component is not compatible with a componet you installed.

I think Seawind will run the ducting, wiring, prep the electrrical panel, etc for a generator or air conditioning. If you are sure you want air conditioning have them run the ducting, wiring at least at the factory.

I think Seawind will install larger Master Volt alternators on the engines. Depending on your climate, how much you motor, how much capacity lithium and solar you are going with that set up may provide enough juice to satisfy your need for air conditioning when not connected to shore power. Air conditioning is the big power drain. Before spending the money on being able to run air conditioning including maintenance when not connected to shore power consider going with more 12 V fans, wind scoops, hatch fans, etc

Another option instead of a generator is to go with a new alternator / generator( run by a special CPU that Nigel Calder helped develop that you can put on one or both engines( see links below). At max RPM Calder says the alternator / generator will generate 8KW to 9KW and at a high idle will generate approx. 4KW. At low idle Calder says enough load is put on the engine to not cause the problems/ inefficiency associated with running engine with low load to charge the batteries. If it does what Calder claims it is more efficient, weighs less and requires less maintenance/hassles of having an independent generator. The installation does not look like it is a lot different than installing a new alternator. The company says they will do all the engineering for whatever the specific engine, solar capacity, batteries chemistry / capacity for whoever does the installation. It is a new product so check it out carefully, get an in person demo. From what I know Nigel Calder is not apt to sell out and put his name on a product that can't do what he says it can do.

https://integrelsolutions.com/

If you have not already seen it, checkout the video below about setting up a Seawind for long term cruising.

Thank you.
Good advice.
Great to learn of this new technology!
I dislike generators, if only for me, 1½hrs of engine/generator running is too much for me. 20min of that new device off Nigel is great solution. I can bear 20min.

[valhalla360]

Originally Posted by 3cdad

We plan to take delivery of a Seawind catamaran in 2022. It will have a robust solar and lithium system, and no generator. The manufacturer is currently spec'ing out AC air conditioning and AC watermakers. But that means that the inverter will have to get involved, which also means a significant loss of energy from converting the lithium's DC to AC. In boats without generators, but with ample lithium and solar, doesn't it make more sense (as in energy efficiency) to install DC air conditioning and a DC watermaker?

A quality inverter doesn't waste much power. (Picking a high quality model is a cheap solution to minimizing the issue)

Standard air/con units will be easier to get serviced. If you buy some off brand DC unit, finding qualified techs to troubleshoot and repair will be more difficult and they likely won't have the commonly replaced parts.

So what exactly is your "robust" solar and lithium system? Is 1 robust = 1000w of solar or 2000w of solar? The fact that you didn't lead with numbers suggests you haven't ran the numbers for what it takes to feed air/con away from the dock/generator.

Watermaker...usually not so critical and DC ones are more common.

[valhalla360]

Originally Posted by makobuilders

Just to fine tune your statement, I would assume a 50% duty cycle, or perhaps as high as 75% if you are here in Florida in the middle of August (80-90% humidity, 90 degrees F). Better yet is just program your aircon to run one hour every three in your stateroom.

Did you see they were referencing a 3,500btu air/con unit...I would expect in most cruising destinations to cool even a modest size cabin would have that running close to 100% duty cycle.