Do RV rooftop Air Conditioners work well on boats?

[a64pilot]

I see a whole lot of commercial boats with them, shrimp boats, tugs etc.
They work fine for a few years, everything wears out, but these are a lot cheaper to replace.
They do drip water continuously of course, the condensate has to go somewhere.

[Sailmonkey]

Originally Posted by a64pilot

I see a whole lot of commercial boats with them, shrimp boats, tugs etc.
They work fine for a few years, everything wears out, but these are a lot cheaper to replace.
They do drip water continuously of course, the condensate has to go somewhere.

As well as the accompanying rust stains.

[Colin A]

They actually make marine versions common on a lot of small workboats. Local contractor with a tug had one. Coleman marketed them under Sea Mach and Marine Mach. They seem to work well.

https://www.airxcel.com/coleman-mach...ne/marine-mach

[Group9]

I notice a lot of the commercial boats, and our state marine police, using them on their enclosed boats down here.

[smj]

Domestic also makes a marine model.
https://www.dometic.com/en-us/us/pro...0-btuh-_-20696

[rwidman]

Originally Posted by smj

Yes they absolutely work. We had a single RV rooftop 15 or 16,000 btu on our old 36' catamaran and you could hang meat in there on a hot humid Galveston summer day. The 16,000 btu marine unit wouldn't even remove the humidity. ......

A BTU is a BTU. You had some other issues or you're making a bad comparison.

[smj]

Originally Posted by rwidman

A BTU is a BTU. You had some other issues or you're making a bad comparison.

We have gone through this before. Once the water reaches a certain temperature the water cooled units aren't very efficient. Water temps in the 90's? Forget about it.

[a64pilot]

Originally Posted by smj

We have gone through this before. Once the water reaches a certain temperature the water cooled units aren't very efficient. Water temps in the 90's? Forget about it.

I agree with what your saying on principle, however both my AC’s output air in in the 50’s with internal Boat temp in the high 80’s or 90’s. And water temp in the 90’s. A 40 degree drop is about all you can hope for.
I’d suspect that maybe your water flow is lower than optimum.

However aircooled airconditioners can work just as well as water cooled ones or better, if properly designed.
I’m sure the regular Marine AC is water cooled more because it is easier, and there is a inexhaustible supply of water available, not because water cooling is more efficient or better, cause it isn’t.

[smj]

Originally Posted by a64pilot

I agree with what your saying on principle, however both my AC’s output air in in the 50’s with internal Boat temp in the high 80’s or 90’s. And water temp in the 90’s. A 40 degree drop is about all you can hope for.
I’d suspect that maybe your water flow is lower than optimum.

However aircooled airconditioners can work just as well as water cooled ones or better, if properly designed.
I’m sure the regular Marine AC is water cooled more because it is easier, and there is a inexhaustible supply of water available, not because water cooling is more efficient or better, cause it isn’t.

My opinion wasn't taken from experience with one unit on one boat but quite a few different units in different boats. I found I could get a 8000 btu window unit to produce as much cooling as a 16000 btu marine ac in the dead of summer. And the RV rooftop ac was far superior to anything we had owned. This includes over 18 years full time liveaboard on 5 different catamarans. From what I've read, the cooling of the reverse cycle ac starts to lose efficiency when the waters reach 85 degrees, and the heating when the waters reach 45-50 degrees. The water temperature in the summer time where we kept our boat would reach the mid 90, and in those water temperatures the air cooled ac's were far superior in my opinion. One must stick to and enjoy what they find to be the best option for them!

[newhaul]

Originally Posted by a64pilot

I agree with what your saying on principle, however both my AC’s output air in in the 50’s with internal Boat temp in the high 80’s or 90’s. And water temp in the 90’s. A 40 degree drop is about all you can hope for.
I’d suspect that maybe your water flow is lower than optimum.

However aircooled airconditioners can work just as well as water cooled ones or better, if properly designed.
I’m sure the regular Marine AC is water cooled more because it is easier, and there is a inexhaustible supply of water available, not because water cooling is more efficient or better, cause it isn’t.

a little advantage for air cooled units . The good ones doing the condensate into the condenser coils to assist with the air cooling .

[a64pilot]

Originally Posted by newhaul

a little advantage for air cooled units . The good ones doing the condensate into the condenser coils to assist with the air cooling .

Even the cheap box store window units usually have a slinger ring on the condenser fans that slings the water around and of course through the condenser.

[a64pilot]

Originally Posted by smj

My opinion wasn't taken from experience with one unit on one boat but quite a few different units in different boats. I found I could get a 8000 btu window unit to produce as much cooling as a 16000 btu marine ac in the dead of summer. And the RV rooftop ac was far superior to anything we had owned. This includes over 18 years full time liveaboard on 5 different catamarans. From what I've read, the cooling of the reverse cycle ac starts to lose efficiency when the waters reach 85 degrees, and the heating when the waters reach 45-50 degrees. The water temperature in the summer time where we kept our boat would reach the mid 90, and in those water temperatures the air cooled ac's were far superior in my opinion. One must stick to and enjoy what they find to be the best option for them!

Your right at the correct numbers where the water cooled and or heated units lose efficiency, however excessive water flow will to some extent help make up for it, of course there is a point where it won’t. I doubt I have ever been in mid 90 temp water, maybe that’s it.
Mine worked fine in Key West in July and August last year, not sure of the water temp then.

[smj]

Originally Posted by a64pilot

Your right at the correct numbers where the water cooled and or heated units lose efficiency, however excessive water flow will to some extent help make up for it, of course there is a point where it won’t. I doubt I have ever been in mid 90 temp water, maybe that’s it.
Mine worked fine in Key West in July and August last year, not sure of the water temp then.

How many units and what btu are they? The Keys can be hot that time of year!
We were in Pine Island Florida this past October with highs in the upper 80's to low 90's. First time we have run AC on this 38' cat, but a 8000 BTU window unit kept us comfortable during the day and under a comforter at night. I was happy and impressed! We are now in the Keys and doing well with an open hatch and breeze, much my preference [emoji1303]

[Idylles15.5]

Originally Posted by Colin A

They actually make marine versions common on a lot of small workboats. Local contractor with a tug had one. Coleman marketed them under Sea Mach and Marine Mach. They seem to work well.

https://www.airxcel.com/coleman-mach...ne/marine-mach

I had one of the marine grade Coleman units on my 15.5 idylle. I made a fiberglass cover to fit right over the lexan cabin house sun lens, etc. All of the parts of the motor were made of stainless or powder coated. It was reverse cycle too, but couldn't heat up my saloon when it was really cold. As for the a/c. Holy crap it was freezing in the whole boat. As someone else mentioned I could of hung meat in there. I had to turn it down constantly. It's only about 10 inches high off the deck. I had no problem with lines, and I don't think anyone's boom sits right off the deck. I actually still have the unit and if anyone wants it, its for sale. I only used it one season. I made a butterfly hatch and installed that in it's place.

[a64pilot]

Originally Posted by smj

How many units and what btu are they? The Keys can be hot that time of year!
[emoji1303]

One Webasto 16K and a Webasto 6K