Air conditioning install

[Pat]

Our Mermaid would not fit well in any space other than under the v-berth insert....we found pads to go under all the areas where the compressor would fit....left the compressor itself on the 3/4 inch thick wooden mount that it was shipped with from
Florida....so all areas where the compressor would come in contact with the fiberglass are very well padded and this is not a source of noise in our boat.....The compressor noise itself does make a little noise in the middle of the night as it cycles on and off.....but I would not say it bothers us to any extent..we of course have the v-berth insert in place so that does reduce the noise, I made a plexiglas cut out to cover the vertical opening and mounted the in-take vent in the plexiglass...works well...
As noted above, our water pump is also very quiet....We have a Mermaid condensator to remove the water from the pan under
the compressor...this works flawlessly...thereby eliminating the need to use the bilge which I guess some people do..The condensator pumps up from the pan to a point approx. 2 ft. higher than the water line. It is not audible from inside the boat and the folks next to us do not spend nights on their boat. .Hearing our bilge pump come on in the middle of the night makes far more noise than the entire AC system...If I had it to do over I think I would use more smooth duct rather than so much flex duct....thereby increasing the air-flow....The owner of Mermaid convinced me to install a 12,000 btu system vs. a 16,000 btu..so we don't use the system too often during the day....we have such a monstrous quarterberth that it really increases the area being cooled and the unit will freeze up if left on beyond say 10-11 a.m....at night it is a blessing.

 

[Benny17441]

The owner of Mermaid convinced me to install a 12,000 btu system vs. a 16,000 btu..so we don't use the system too often during the day....we have such a monstrous quarterberth that it really increases the area being cooled and the unit will freeze up if left on beyond say 10-11 a.m....at night it is a blessing.

I like the choice of a 12K unit as it is very adequate for a 27' boat and can be ran from a Honda 2000 portable gas generator. It is not normal for a unit to freeze up, it points to being low on Freon or having a restricted air flow. Make sure the air return filter is kept clean and the grill or intake duct has a direct access to the cabin.

 

[Jeff]

Our install has a duct above the return vent but there doesn't seem to be any short cycling. I've had this unit for 12-13 years. See the attached thumbnail pic.

 

[AndreNJ11]

I installed a Webasto FCF 12,000 A/C reverse heat unit in my O'day 322 last summer. Since I did not want to give up either water tank, and both my settees have water tanks under, that left me with the aft hanging locker as the best spot (see picture). I ducted 90% of the supply flow forward through the bulkhead into the main cabin and 10% of the flow aft through a 4" round vent into the aft berth. Since I have almost no duct run, the blower airflow is very strong. I find the 12K is adequate cooling in the day for NJ for my 32 footer. Of course if I had canvas over the boat in the heat of the day, it would be even more effective but without shade it still makes it comfortable. At night the cooling capacity is way in excess of what is needed, and cycles very briefly to cool. The heat mode is amazing at 115 degrees at the supply port, very comfortable in October nights. I find my Westabo quieter than the Mermaid 9000k I had in the 27' I had previously. The prior comment on the temp sensor being a copper tube in the return flow is correct for the FCF models The digital control is just to set the mode and temp and fan speed (3 speeds + auto speed), not to sense temperature, so it can really be placed anywhere convenient. So far after one year, I am happy with the Webasto FCF. I put my out-water through hull about 2 feet high off the waterline due to not wanting to drill through the inner hull liner, but I am sorry I did not put it lower to the water line. It is quite inside for me, but a bit noisy for the neighbor on that side. It took me 20 hours over four days to install the whole thing: shelf, plumbing, strainer, electric, through hull, sawing duct holes, duct work, and about four trips to the store, plus three mail-order A/C suppliers for the various pieces-parts. It was a very tight fit in the cabinet. I enjoy projects like this. Not everyone would. Saves about $2000 installation costs.

 

[Pat]

In 2014 we installed a in-duct fan the provides a much higher cfm of conditioned air from the ducts....I had no way to install ducts to the quarter berth without cutting holes thru the athwartship stringers that form the foundation for nearly everything in the cabin.. so the two 6 inch ducts in the main salon are as far aft as I could go with duct work....The quarter berth is approx. 9 ft. long, and as long as we don't have a bimini, the sun on a 105 degree day really heats that space up. This huge area is open to the main cabin....I keep a fan on a counter which helps to ventilate the air in the quarterberth....the area back there is approx. 5 ft. x 9 ft...minus the engine compartment so it is a sizable space....Prior to installing the induct fan I considered closing off the quarter berth with some sort of solid bulkhead, but I don't need to do that now as it doesn't freeze up anymore. I have a friend who is a mechanical engineer and he has taught me a lot about air motion and how the flex duct lowers the cfm, also the 90 degree turns, etc...the mermaid just has a little tough time on 105 degree days and such...I also hose off the boat on the hottest days before going on board...I also have this little phobia about going to the lake on a very hot day only to stay in the
AC down below with the boat all closed up....I'd rather open it up and go sailing....or anchor and swim...and play.... Pat

 

[Benny17441]

It is comforting to realize that at least some people understand that the usefulness of A/C in a boat varies with the geographical areas. In the Gulf of Mexico with temperatures of 95F approaching 100% humidity can feel like 105F so without A/C and a generator to run it anchor it is quite uncomfortable to sleep at night while away from shorepower. No unit seems to adequately cool while the sun is beating on the deck but they cool at night. We have a 12.5K btu unit so that we can run it with a Honda 2000 portable generator, for us a 16K unit would be useless. Choose what may work for you in your style of sailing.

 

[SailingGestalt]

I'm nearing the end of my install now, I'll get some photos up when I'm done. I do have a question about the sea water discharge. I understand that the thru-hull needs to be 4-8 inches above waterline.... however, waterline on a sailboat changes based on heeling. Should I install a vented loop on this discharge? I've not found much information anywhere on this subject. A lot of folks are saying no but wont that be a siphon hazard without a loop? Anything higher than 8 inches above the water will cause excessive water noise I'm reading. Any ideas?

 

[Gunni]

I don't have a vented loop. If your plumbing drains back through to your intake the concept is when you shut down your system and go sailing the seawater plumbing drains down from the loop and breaks the siphon. If your loop is above the maximum level of heel then you can't start a siphon.

 

[SailingGestalt]

Gunni,

You confused me. You said you don't have a loop but then go on to talk about having a loop above the maximum level of heel thus preventing a siphon. If my discharge is 4-8 inches above the water at level heel it will definitely be below water at times of maximum heel. In that scenario, would you recommend a vented loop?

 

[Ed Caldwell]

It's a closed system from intake thru hull to the outlet. Water can't get into the boat unless there is a leak.

 

[Davidasailor26]

What Ed said. You need a vented loop for things like toilets and engine exhausts, because they're not closed systems. If a siphon starts there it will fill the boat through the toilet, or fill the engine block. Since the AC pump has no openings, there's no risk there.

If you use a separate pump for the condensate, that one would need a vented loop, because the condensate pan is open and could allow a siphon.

 

[Gunni]

Gunni,

You confused me. You said you don't have a loop but then go on to talk about having a loop above the maximum level of heel thus preventing a siphon. If my discharge is 4-8 inches above the water at level heel it will definitely be below water at times of maximum heel. In that scenario, would you recommend a vented loop?

Said I don't have a vented loop. The discharge loop above max angle of heel is just good practice because you have fittings, pumps and a seawater strainer in the system.