Pros & Cons of A/C Systems

I'll be looking for an A/C system for a 2 stateroom, 2 head 45' pilothouse trawler. I'm needing some help deciding if a split gas system or chilled water system is best. What are the advantages of one over the other?

It is my understanding that all in one units are the most energy efficient of the raw water cooled AC/ heat systems. Split units are a close second. Chilled water units are a distant third. This is with regard to watts of power consumed versus BTUs of cooling realized.

If you're installing AC for the first time or replacing a split or all in one system, routing the heavily insulated chill water lines can become space challenging.

When I did my refit on my 45' trawler, I briefly considered chill water units to replace my 3 all in one units. In addition to being more expensive and more difficult with regard to running the chill water lines, there was a significant likelyhood that I would be undersized on the generator as a result of the required increased capacity do to lower efficiency.

Ted

I have one self-contained unit and one split unit. When the split unit dies I will be replacing it with a self-contained unit to save space.

Comodave said:

I have one self-contained unit and one split unit. When the split unit dies I will be replacing it with a self-contained unit to save space.

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The self contained units have gotten better and better and more compact. Much easier to install and deal with than a split unit. If one of my splits fails I will replace with a self contained unit.



Ken

Just added a self contained unit for the bedroom. Very quiet, uses very little power and easy to install.

I will put in a vote for the alternative.

My boat has Marineairr chilled water A/C system (which I think is now a Dometic Group company?).

In Brisbane, Australia, it gets pretty humid and warm at the peak of our summer. Compared with similar GB 46s and GB 42s I have been on that have split gas systems (I believe the brand is called Cruiseair?), my boat is noticeably cooler at any given time of the day and I never have to run my a/c system below 23 degrees celsius (73.4 farenheight) whereas the cruiseair equipped boats are running at 19 degrees and they are still warmer.

Of course there are lots of variable to this and I am not an engineer - maybe my boat just has a bigger system? However my own experience is that chilled water systems perform better in heavy heat/humidity load situations.

I am told that chilled water systems (a) cost more to buy (b) have larger hoses and so forth to install (c) are usually used on larger boats. In marketing material for new boats, installation of chilled water a/c is often highlighted as a 'special extra' or a reason to choose that boat.

Just my experience.

Hamish.

If you have hydronic heat, you can use the same plumbing for chilled water AC if the plumbing is insulated. I don't have AC in my current boat, but set up the hydronic with forced air units instead of radiators so it would be ready for AC.

Pros & Cons of A/C Systems

It’s tough to justify a chiller system unless you have complete access to the boat during construction. Though you can eliminate several through hulls on a larger system, you do need to add an additional circ pump and a big set of loop lines which will need to be properly insulated( extra difficult to find leaks under the insulation).The new self contained units are almost plug and play and relatively cheap. Our current boat has two 3 ton chillers, but only one is needed to cool the boat. The two circ pumps pull about 2 amps each at max and the compressor pulls 15 at full locked rotor. We can cool or heat the whole boat with our 6 kw genset. We tend to relocate seasonally so that we need neither at anchor, but we do like to run a climate controlled ship when we are underway. If you are going spend most of your time on the yellow cord in a marina I’d just go with the cheapest solution and oversize your intake through hulls and hoses.

More votes for the self contained units than I expected. I wasn't even going to consider them due to the higher noise levels than the other two alternatives. Can anyone confirm or deny the noise level concern?

The compressors are so quiet, it's the fans and airflow you hear.

The same from air handlers from splits or chilled water.

I have one of each and do not notice any difference in noise.

Regarding noise, there is a wear in period on many things with electric motors. Some actually get quieter after a wear in period. The Webasto AC units I have are nice, but I wouldn't call them quiet when I installed them. After a year of modest use, they are significantly quieter. You have to listen carefully to hear the compressor running.

Ted

My all-in-one in my salon is very loud. I was considering a split system mostly for noise reduction. I am surprised by the answers in this thread too. Seems like moving the compressor from under the settee to the engine room would have to be quieter.

My units are very old marine air units. Are the new unit substantially quieter than the old units?

We really don’t hear the compressor noise much, mostly is the fan and air noise. Not that my units are really new but the noise isn’t objectionable.

What is meant by an "all in one" a/c? A window rattler, a rooftop RV unit,maybe even a portable one which pumps air out a tube via a window. I`m guessing it`s more sophisticated, but what is it?

IF an excellent modern RV rooftop unit were too small, I would look at a mini split style unit.

These have none of the losses of the old split units that require large duct work for feed and return .And no water lines and pumps to operate.

The slow down of the compressor cuts electric consumption , useful at a pay for juice power pole , or in keeping noisemaker loads reduced

What is meant by an "all in one" a/c?

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Also commonly called "self contained," the units have all of the air conditioning components in one package, including an air handler/cooler/blower. The split systems cool the coolant medium at one location (the engine room?) and then pipe it to an air handler that uses the cooled medium to cool air that it collects, blows through a transfer device, and then returns it to the area to be cooled. I assume they have their own water pumps for cooling (not sure), and they'll still exhaust condensate that you'll have to get rid of. (The description based on my rudimentary understanding of how these things work.)

But if you google "marine air self contained" you'll get many examples.

Another benefit of all in one units.......

You might be able to pull them out with minimal effort and take them to a local AC shop for repair. Rather than waiting for someone to schedule, charge you for driving to the boat, do a crappy troubleshoot, lousy repair, and send you a bill for more than a whole new unit..

You might get a great, inexpensive repair...... but most AC stories I have heard are from less than happy boaters.

Rain Dog, the newer units are surprisingly quiet compared to the old ones. They are, however, more expensive.

I replace the 20 year old CruiseAiiiir unit in the forward cabin on my boat when it burned up last year with a new Webasto self contained unit. Out of the box it was noticeably quieter than the old unit and after a year of running it, it's so quiet you really only hear the noise of the air out of the vents. You have to really pay attention to hear the compressor kick on and off. Very nice, worth every penny

So now that you all have satisfied my concern about sound, on to my next concern with self contained units - thru hulls. Each unit requires a raw water intake and overboard discharge whereas the split & chilled water system require just one. Am I correct that a vessel with three self contained units would have three separate water intakes, circulating pump and overboard discharge or do you share the intake/pump for all three units?

Well, the Bayliner setup is one thruhull intake and one supply pump with enough capacity for both units installed. When a unit energizes the pump, water flows thru both units and out separate discharges above the water line. I don't see why you couldn't size the supply side to feed 3 units from one pump.

Also, you might not need 3 units? My forward unit supplies air to the master bedroom and guest room. The duct "Y's" off the blower...and I think I have enough air flow to "T" a 3" vent into the guest bathroom. The other unit takes care of the salon and galley.

I have 2 16k BTU units running off 1 pump. They each need their own through hull for the discharge.

I have 3 units. They are all fed by one pump. My boat is setup with two 2" community collection drains (drain pipes collect water from a number of different sources and drain through 2" above water through hulls). The AC raw water drains into these pipes.

Ted

Self contained is the way to go. Dometic offered two self contained versions of a 10K Btu unit this year when I replaced my rotted out 7K Btu unit. The lower priced unit would not physically fit where I had to put it. The physically smaller unit, quieter, and more efficient unit, called a Dometic Turbo Unit (DTU) was way, way more expensive but is doing a great job. It did not come with a seawater pump which was bought separately.

On my 42-foot trawler, I had two 16,000 Btu units, one split and one self contained. The ducting for the one feeding into the aft cabin and the main cabin could be directed into both spaces or only into wither one of them while the other unit supplied the salon and the forward cabin.

Believing in redundancy, I felt the separate intake through hulls and pumps gave me the capability to continue to have cooling where I slept in the event of a pump failure. All I had to do was to put a box fan in the companionway down to the aft cabin from the main cabin if the aft system died for any reason.

Jim Cooper said:

So now that you all have satisfied my concern about sound, on to my next concern with self contained units - thru hulls. Each unit requires a raw water intake and overboard discharge whereas the split & chilled water system require just one. Am I correct that a vessel with three self contained units would have three separate water intakes, circulating pump and overboard discharge or do you share the intake/pump for all three units?

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On MOJO (www.mvmojo.com) we have two 16K BTU & one 24K BTU self-contained units running off one 30 gph "Little Giant" pump. A control box mounted near the pump has three 24v/110v relays to allow any unit to start the pump whenever it's thermostat calls for air conditioning. There is one common discharge amidships for cooling water. Whenever the pump is running, water is circulating through all three units, whether the compressor is running or not. It's my belief that this keeps the condenser lines much cleaner than allowing water to sit in the lines growing algae, etc., although the units are plumbed so that water drains from the coils when the pump isn't running. I also have a manifold that allows me to isolate any unit if needed, but generally all valves are left open. Condensate lines from all 3 units return to the engine room and are teed into the galley sink drain leading overboard. Been working well for 18 years, with normal routine maintenance.

Talk about timing.... one of my 16 btu cruise airs condenser just went south for my aft cabin. Glad it happened now instead of the Bahamas. So i will be looking at 3 options

Fix the condenser/compressor in engine room(Unit/fan in aft cabin seems ok )

Replace the condenser/ compressor with new one

Take both condenser fan unit out and install self contained Wabasto or Dometic if it will fit in the aft cabin space and I can get water to that space.

Will get pricing this week on these 3 option

Anybody have an idea on total cost to change out to 16 btu self contained?
Or cost on new condenser only?

Thanks

check out Ocean Breeze self contained units. www.oceanbreezeac.com. Give them a call for pricing, talk to Joe Baruch, the owner. You can buy direct from the manufacturer w/out the middle men distributors and retailers.

Just gave them a call For a 16,000 btu reverse cycle self contained it was $1680 at their dock. $70 freight to here and I am sure Uncle Sam wants a donation also. This for Ocean Breeze
I think the Dometic is about $2,200 plus tax

So far here are my options

Replace Cruise Air with new Cruise Air combo split $4,700
Change out condenser in ER $2,500
Cruise Air self contained $3,600
Ocean Breeze self contained $1,800 plus install so maybe save $300 + install

Cruise Air comes with 2 year warranty and installed by factory approved tech
The others I don't know as I am going through a local Cruise Air Dealer

Thoughts??

Why reverse cycle for heat? I think it's more money than a "Cal-Rod" heat set up. We have 3 Ocean Breeze units with the Cal-Rod heat and they work great. They blow warm air irrespective of the water temp, and do not run the water circulation pump. Reverse cycle runs the pump and only works until the water temp gets down to about 40F.