Air conditioning - aft cabin or saloon?

[Wckoek]

Say there is a 40+ sailboat with a lot of glass in the saloon and a single larger aft cabin that the owner got to use.
Boat is in the tropics

If you can only install a single marine air conditioning unit, where would you install it?


Saloon:
+ Get to use most of the time
+ In need because of the amount of glass and sunlight
- More powerful unit is needed because of the larger area.
- Owner didn't get to enjoy


Cabin:
+ Lower power requirements since there isn't as much porthole and smaller space.
+ Owner get to enjoy for his own sleep and shielding himself for the few dreadful hours.
- Didn't get as much use as having it in the saloon for guests.

[acunningham]

Personally I'd go for the aft cabin. Air conditioning isn't so important during the day if you're acclimatised to the conditions, even in the tropics. On the other hand, it is nice to run for an hour or two before going to bed to help you get to sleep.

[Chotu]

Not disagreeing with the last post, but I would do the opposite.

And I did.

Get lots of air conditioning power for the salon and then you can use fans to blow it into the aft cabin if necessary. I assume with a lot of glass in the salon it is a deck salon? If that’s the case the cool air will naturally fall downward to the aft cabin as well.

[Wckoek]

Originally Posted by Chotu

Not disagreeing with the last post, but I would do the opposite.

And I did.

Get lots of air conditioning power for the salon and then you can use fans to blow it into the aft cabin if necessary. I assume with a lot of glass in the salon it is a deck salon? If that’s the case the cool air will naturally fall downward to the aft cabin as well.

Yes it is indeed a Sun Odyssey DS.
I don't understand how you can use the fan to blow the cold air to aft cabin, do you mean you have the air conditioning pointing aft in the saloon?

[Chotu]

Originally Posted by Wckoek

Yes it is indeed a Sun Odyssey DS.
I don't understand how you can use the fan to blow the cold air to aft cabin, do you mean you have the air conditioning pointing aft in the saloon?

Assuming you don’t get a ducted system and you only cool down the salon, you can aid the convection currents with a fan. These are a great example of the type I’m thinking of:




Air conditioning needs to be high up (and heat down low) for proper circulation.

Warm air will naturally rise up from the aft cabin to the salon, while cold air sinks down to it.

If you have a beast of an air conditioner that can cope with all those windows on a record high temperature day, it will also be enough to cool off the aft cabin after the sun sets and all that thermal loading from the windows goes down.

Ideally, you run ducts from a ducted AC unit and don’t need a little helper fan, but if you don’t want to do that, the helper fan can assist in exchanging air between the very cold deck salon in the evening and the aft stateroom.

You’d locate it near the doorway to either push hot air out of the stateroom or push cold air in.

[Pizzazz]

I would say it depends how you use the boat. If you are mostly in a marina, I would cool the main saloon. You have plenty of power and you may want to work from the boat, which becomes impossible without AC. If you are mostly cruising then you move in and out, there is a breeze, and usually you don't use the AC much during the day but it would be nice to cool down the aft cabin to get a good nights sleep.

[Jolly Roger]

I have been able to do both with my aft AC, by mounting it in the middle and ducting the air fore and aft, so it blows both ways. If we need more cool air, (or hot in the winter) in either the aft sleeping cabin or the saloon, I just reduce the outlet vents on one side or the other. Whether you can do this rather depends on the power of your AC.

[Wckoek]

Originally Posted by Chotu

Ideally, you run ducts from a ducted AC unit and don’t need a little helper fan, but if you don’t want to do that, the helper fan can assist in exchanging air between the very cold deck salon in the evening and the aft stateroom.

You’d locate it near the doorway to either push hot air out of the stateroom or push cold air in.

Near doorway, that is a good idea, but I see how it can implemented in the layout.

Originally Posted by Pizzazz

I would say it depends how you use the boat. If you are mostly in a marina, I would cool the main saloon. You have plenty of power and you may want to work from the boat, which becomes impossible without AC. If you are mostly cruising then you move in and out, there is a breeze, and usually you don't use the AC much during the day but it would be nice to cool down the aft cabin to get a good nights sleep.

It gets a bit of fair use in the marina, but I am struggling whether it is more useful in the saloon even while underway, since the saloon gets used more during daytime where it is warmer.

Originally Posted by Jolly Roger

I have been able to do both with my aft AC, by mounting it in the middle and ducting the air fore and aft, so it blows both ways. If we need more cool air, (or hot in the winter) in either the aft sleeping cabin or the saloon, I just reduce the outlet vents on one side or the other. Whether you can do this rather depends on the power of your AC.

I'll look into whether ducting it would be a complicated matter.
Thanks.

[S/V Illusion]

Originally Posted by Wckoek

Say there is a 40+ sailboat with a lot of glass in


.

If you insist - there is a 40+ sailboat with a lot of glass…

It’s all about volume, temperature and circulation. And how you manage circulation.

[Wckoek]

Originally Posted by S/V Illusion

If you insist - there is a 40+ sailboat with a lot of glass…

It’s all about volume, temperature and circulation. And how you manage circulation.

There is a lot of humidity, like 90+
I hope that fan and circulation would be sufficient but that is not the case.

[Shanachie]

I have a Catalina 320 (34 feet with 11'9" beam) and run a 12,000 BTU unit into the main cabin. With doors open, the AC cools the entire boat relatively quickly. This boat has a large aft cabin.



I would buy shades, though. Lots of sunlight with AC running is a losing proposition.

[sailorboy1]

I have both a salon AC unit and an aft cabin AC unit

I run the main one 20+ time more.

Like the OP I also have lots of window, I covered them. For the big ones I even put some insulation between the cover and window.

[wrwakefield]

The previous owners of our 43 ft ketch put 3 independently controlled air conditioners in it. (Forward; midship; aft cabin) They only used the one(s) needed based upon need and occupancy. (They are also heat pumps so they get used by us if at a dock in winter...)

They also installed a very slightly tinted IR blocking film on the inside of the glass windows of the main salon (pilothouse) that greatly reduced the solar gain.

They shared that although they were well acclimated, there were times when the A/C was welcome- especially for good sleep.

Just a bit of perspective from a very active retired couple who spent 15 years in the tropics on what became our boat...

Cheers, Bill

[Wckoek]

Originally Posted by sailorboy1

I have both a salon AC unit and an aft cabin AC unit

I run the main one 20+ time more.

Like the OP I also have lots of window, I covered them. For the big ones I even put some insulation between the cover and window.

Do you mean you use the saloon one more?

[OS2Dude]

Look online for websites that allow you to size the A/C for the task. Too small is better than too big. We made the mistake of putting in a 24k BTU unit in our boat. (30' Catalina) It would cool the entire boat from 92 to 72 degrees in 15 minutes. Sounds good, but it had a minimum run time, so after reaching the set temperature it would cool/heat so fast that it would go well beyond the set temp (in the other direction) during its minimum run time. It cycled constantly which is not good for it. After a year, we replaced it with a 16K BTU unit. It takes two hours to cool the boat 20 degrees, but once there it is much more stable.