Air Conditioning - Go Big, Small or Skip it Altogether?

[Agility]

I'm struggling with a design decision regarding air conditioning and heating on a new build Atlantic 57.

Here's the scenario. My wife and I like the tropics and hope to sail around the world some day. We like to mostly swing on the hook but for provisioning, picking up guests and doing repairs it's nice to be in a marina at times. We want a very simple Euro/US capable power setup and are using a Victron battery charger that will allow us to get power to the boat and an 2500 inverter for basic 110 needs. No generator, too heavy and we don't want/need aircon on the hook. We like the 16,500btu reverse cycle mermaid aircon because it supports a 208/230V 50/60htz voltage option but we also like a two Espar diesel heaters setup that use almost no electrical power and can be used anywhere anytime. If we don't go with the Espar's we will need something to heat the boat in the winter and it's nice to be able to get some of the moisture out. The Chris White design is a very fast and light cruising cat - weight is the enemy. However, this is a big boat and should be able to accommodate another 100 lbs here and there.

If if were your boat, what would you do for heat/aircon?

Possibilities include:
2 diesel heaters, 2 big aircon units (with or without reverse cycle)
2 diesel heaters, 1 big aircon unit
1 diesel heater for forward staterooms and head, 1 small aircon for stateroom
2 diesel heaters no aircon
1 diesel heater no aircon
1 big aircon no diesel heater
1 big aircon (reverse cycle), 1 smail aircon for stateroom inverter based, no diesel heater

Previous owners have gone with the 2 diesel heaters only more often than not.

[millsource]

On Rocketeer we removed the 8kw generator and the 2 ac units. We have not missed either. We spend almost no time at the dock where it can be hot due to not facing into the breeze. We have 2 webasto diesel heaters which work quite well for us.

[estarzinger]

Skip the aircons - it sounds like you will not be at the dock that much and reverse cycle is not very efficient.

How many Espars you need is a pure btu issue - how cold is it going to be outside and how well insulated is the boat? All the way around on a 'normal' tropical RTW you only need heat for perhaps 2 weeks in NZ. But of course if you venture off the normal route or timing you needs could be quite different.

[Maren]

Originally Posted by Agility

I'm struggling with a design decision regarding air conditioning and heating on a new build Atlantic 57.

Here's the scenario. My wife and I like the tropics and hope to sail around the world some day.
....
Previous owners have gone with the 2 diesel heaters only more often than not.

I would say don't worry about the other owners because you don't know where they sail(ed). On the other hand, I would ask Chris White since he likely has been involved in a lot more builds than you have. But you do need to be able to clearly define our needs/wants.

Going off what you wrote before, I would say 1 diesel heater (in case you end up where it’s cold and 2 big aircon units (with or without reverse cycle) since you like the tropics. But really this depends on how much you like to run your power systems and how much you like a/c. If you like the tropics b/c you think Bolder, CO is too cold and the weather in the tropics if pleasant, you'll end up with a different choice.

[Intentional Drifter]

You might also want to consider a hydronic heater like the Hurricane ITR Hurricane Marine Heating System

That gets you your zone heat plus your hot water heating, all in one system. Some friends on a MaineCat have one and love it.

There are also some interesting looking DC heatpump A/C's coming out that look pretty efficient: DC Air Conditioner: 12 Volt 24 volt 48 Volt DC Air Conditioners DC Solar Air Conditioning

Not light at about 165 lbs, though you would be saving the weight of a genset, but they are still over twice the weight of a comparable AC based, reverse cycle unit (a Marine Air reverse cycle 16K BTU is about 70 lbs) and you're adding a dedicated battery bank for it. Your weight savings over a genset and AC units is gone.

For 48K BTU with a genset and AC reverse cycle units, you're looking at 210 lbs in the A/C units alone. A Fischer Panda Mini 8 is 350 lbs. for a total of 560 lbs. But, you do get the convenience of an A/C genset and the supplemental charging.

If you really want to keep the weight off, then I agree with Evans -- skip the A/C entirely (maybe get one of those small window units and stash it for when you just have to be on a dock). The Hurricane system would probably give you the most heat and hot water, while saving a bit of weight.

Having said that, though, and since you asked "if it were my boat..." -- being from the PacNW, we're far more acclimated to "cool" and have found some days in the tropics to be very difficult. We were glad to have the genset and A/C. Sure it costs some weight and complexity, but we found it to be worth the penalty. On an Atlantic 57, just how much penalty would there be? 1/3 of a knot?

Love your boat, by the way. One of those boats that really provokes "boat lust" for me.

ID

[Agility]

My temptation is to go with the two diesel heaters and skip the aircon but what I'm really trying to understand is what would other people do in case I sell the boat sooner than later. It's a ton cleaner/easier/cheaper to do it now rather than later. I've heard folks like my Dad who spent a lot of time in the Bahamas say he wouldn't buy a boat without aircon. I always hate doing anything my dad says not to do.

I think the Atlantic design minimizes the need for aircon with it's thoughtful attention to ventilation but my old Tayana with blue hulls got hot. I wonder how big a different in a marina it would be between the two.

My wife say's kill the aircon. What a great admiral...

[Intentional Drifter]

Our St. Francis has excellent ventilation, too. Those big underwing bow hatches really let the cooler air off the water flow through the hulls very nicely. When at anchor, it would really have to be a hot, windless day before things get uncomfortable and (usually) even then, a quick swim takes care of that!

On the dock, though, I agree with your dad.

You could do a compromise: Run the duct work, build in the pans for the units and run the cabling. Actually putting in one of the self-contained MarineAir, CruiseAir, etc. units is the easy part. That way, if you or a subsequent owner later decided to put them in, it would be relatively easy.

ID

[Agility]

Originally Posted by Intentional Drifter

You might also want to consider a hydronic heater like the Hurricane ITR Hurricane Marine Heating System

That gets you your zone heat plus your hot water heating, all in one system. Some friends on a MaineCat have one and love it.

Thanks, that sounds interesting. I already decided on the Precision Temp instant on hot water heater so this would eliminate/combine one system.

[kiapa]

so much depends on the boat, and its intended use... your boat, an atlantic 57, is a great platform. it's big enough to be loaded up to be a floating condo, but it's inherent design supports it being a very capable sailing cat. your stated use is "on the hook", as opposed to plugged in at the dock.

given the boat and your use objective, why load it up with 'air con' and all the supporting gear. you very well could ruin your boat. folks flying in for a few days of vacation often have a difficult time adapting to tropical conditions. on the other hand, cruisers adapt... and cruise plans usually factor in season & local weather conditions (i.e. go some place nice). there is nothing like being on the hook, with trades blowing across the deck and thru ports & hatches. there is also nothing better than getting warm, then cooling off by jumping into clear, cool tropical water. there is nothing worse than being on (or next to) a boat all closed up with genset and aircon running in a beautiful tropical setting.

we moved from monohull to cat a couple years ago. one of the major benefits of the switch is the availability of "quiet power". we have 4 x 130watt solar panels on the bridgedeck roof. they routinely produce 100-150 A-H per day. No, they won't run aircon... but they'll run everything else, day in & day out, without the need to run genset or main engines. it doesn't get better than this.

i think your heating decision is less critical. if you cruise, it is very nice to have heat... as you will want to sail to high latitude to avoid hurricane season somewhere. and, since you've "adapted" to tropical heat... you'll want a heater. over our 3 decades of racing & cruising, i've always preferred small 'forced air' heater units (espar & webasto) because of their simplicity and the great job they do drying things out. on our cat, we were persuaded to use a larger hydronic unit (webasto DBW2010)... and i think the advice was excellent. two small units does get you 'redundancy', but you also have two systems to install & maintain. the swing vote for me was that the larger hydronic systems are significantly more robust. the manufacturers will stand behind DBW2010 (or equivalent) for continuous use. They qualify 'intensity & duration' of use on their smaller units. our dbw2010 with 2 small radiators in each hull and one larger radiator in the bridgedeck does a great job keeping our 52' cat warm & toasty.

hope you decide to keep your boat light & simple. we think you'll enjoy her more. good sailing!

[kiapa]

agility, we've used the 'precision temp' on our last two boats. i can't speak highly enough about the product. it's the perfect solution -- all the hot water you want subject only to availability of water... and virtually no wasted heat.

[Jeannius]

If you are ever going to want to sell you'd better have air con. Most people want to have it available even if they don't use it. If you have a big expensive boat like yours without air con re-sale may be difficult.

[Agility]

Originally Posted by kiapa

you very well could ruin your boat.
...
hope you decide to keep your boat light & simple. we think you'll enjoy her more. good sailing!

Originally Posted by Jeannius

If you are ever going to want to sell you'd better have air con. Most people want to have it available even if they don't use it. If you have a big expensive boat like yours without air con re-sale may be difficult.

Well said and the crux of my dilemma.

[Dockhead]

Originally Posted by Agility

My temptation is to go with the two diesel heaters and skip the aircon but what I'm really trying to understand is what would other people do in case I sell the boat sooner than later. It's a ton cleaner/easier/cheaper to do it now rather than later. I've heard folks like my Dad who spent a lot of time in the Bahamas say he wouldn't buy a boat without aircon. I always hate doing anything my dad says not to do.

I think the Atlantic design minimizes the need for aircon with it's thoughtful attention to ventilation but my old Tayana with blue hulls got hot. I wonder how big a different in a marina it would be between the two.

My wife say's kill the aircon. What a great admiral...

I don't know why you need any heat in the tropics. YOu can produce domestic hot water with a calorifier run from an engine fresh water cooling circuit, and/or electrical heating element.

A great compromise to air conditioning the entire boat is to just do the master cabin. That will take something like 1/4 of the power (and expense), depending on your boat's plan. You might be able to do it with DC power which will allow you possibly to run it without the generator (at least, without the generator running all the time). 90% of the value of air conditioning, in my book, is the value of being able to have an enclosed (to shut out sound), cooled place to sleep in. I don't know about you, but I can tolerate just about any heat while I am awake, but sleeping can be tough when it's 30C+.

An air-conditioned sleeping place can be also extremely valuable if you are moored up in a noisy port or marina.


My experience: none yet. Our old boat had reverse cycle air conditioning throughout but no generator. We didn't use it much (predominantly Florida Gulf Coast). For heat sometimes in marinas in the winter; occasionally for cooling in the summer, but again only in marinas. At anchor in Florida (where we spent 90% of our nights), even in the height of summer, it's cool enough to sleep with decent ventilation.

But I've wished desperately I had air conditioning in the Med, in noisy places in the summer. Like Bodrum marina when the Meltemi is up, the wind itself is about 40 degrees C, and the discos thump all night.

Our new boat has Eberspaecher heat but no AC. She is poorly ventilated -- one of the design flaws. We plan to move her to the Mediterranean probably year after next. Before then we will defintely air condition her throughout. She already has a 6.5kW generator.

But we are not doing a round the world, where we will be just the two of us 99% of the time -- we will generally have a boat full of people. If you're sailing just the two of you, the master cabin is enough, I think.

[kiapa]

Originally Posted by Jeannius

If you are ever going to want to sell you'd better have air con. Most people want to have it available even if they don't use it. If you have a big expensive boat like yours without air con re-sale may be difficult.

i've been a (high performance, blue water) cat buyer. i'd look hard at an atlantic 57. i'd NOT buy it if it had aircon. if you were buying a yapluka 70, i'd agree with this post. assuming you picked the right new boat... DON'T DO IT!!!

on heat, indeed you don't need it in the tropics... that's why the precision temp makes so much sense (for hot water). problem is that many cruisers cross (relatively) cold oceans and move to higher latitudes for hurricane season. cabin heat IS a requirement on a 50-footer that travels, even a light high performance cat.

[kiapa]

agility, i shared this post with my wife... she reminded me that this decisions revolves so much around 'intended use' -- parked or cruised.

we spent 3 years in the south pacific. of the 100's of boats we sailed with, not one under 50 METERS had air con. of that same group, every boat that did not have cabin heat... rushed off to buy heaters when they got to nz.