AC on a 28

[DougSea]

Hi Guys,

I've been considering putting AC into my 28 this season and I was wondering about the experiences any of you may have had. My biggest questions are around size (BTUs) and outlets. I'm thinking a 5,000 BTU unit would be sufficient - I don't need it "cold" but I want to take the edge off both the heat and humidity during the hotter Connecticut summer days. I was also considering putting vents in both the cabin and the pilothouse.

Defender has a reverse cycle 5,000 BTU unit from Webasto at a reasonable price and, since I don't use my livewell for anything but storage I already have a raw water feed source. I've already done a through-hull transducer install so I don't see much challenge installing the drain.

Thoughts? Pics, as always, are greatly appreciated!

Thanks!

[Carl]

Go here:http://www.dometic.com/enus/Americas/US ... ditioning/ and poke around. There is a formula for calculating your needs. I have one of these units in my 28 and am very happy. It is reverse cycle and I use them both about equally during the course of the season. I too thought about puting a vent in the cabin but after using it for the first season I dont see the need. Unless you have a generator you will only be using it at the dock. Most times at night you can zip up your canvas and leave one of the hatch covers cracked a couple inches and when you get up in the morning it will be either warm or cool in the cockpit. In early spring this is great as it keeps the windshields nice and clear. I dont know what size mine is but will look over the weekend. Be sure to get the electronic control, as it has a lot of nice features. This really adds a lot of comfort and extends the season for my uses. When it gets cold and I know im going fishing, I will go by the boat on my way home on friday and turn the heat on and crack that hatch cover about 1 inch. When you get there at o-dark thirty and zip up the canvas its very comfy. I use a small propane heater while under way which does the job well also. Hope this helps and I will look at the BTU rating over the weekend. Splashed her today!! One other thing, be sure to plumb your condensate pan into the shower pump box, just remember to turn that pump on while running the A/C.

[DougSea]

Carl,

Just realized I never said "thank you" for your post! So...thanks!

Do you happen to have any photos of your cabin showing the vents? I'm sure th return is centered under the table but I find myself scratching my head as to where to put the outlets. I'm thinking a 5000 BTU unit would work for me, take the edge off of the heat and dry things out. And thanks for the mention of the sump pump. Have to give that some thought.

Best,

Doug

[DougSea]

Hey guys,

Don't want to beat this to death BUT would really appreciate any photos/descriptions of current AC installations in a 28. Now that we're in a slip and the Admiral is pretty certain we'll never go back to a mooring I think the installation will happen sooner rather than later.

I have two challenges:

- What size (BTUs) unit. If too small, not enough cooling, if too large doesn't dehumidfy as well. I'm pretty sure something in the 5000-9000 BTU range but actual experiences would be a help.
- How to route a duct to the pilot house (assuming installation under the v-berth). Could just leave the hatch partly open as Carl suggests but I have an issue with that if Kat's sleeping down below and I'm up in the pilot house surfing on the iPad. Only path I can think of is through the hanging locker, along the hullside in the head and up behind the helm seat.

Thoughts?

Thanks!

Doug

[Carl]

Try to pm Rob S. He is, or by now is done installing A/C on his boat and another members at the same time. I am sure he can answer your questions. I apalogize for not getting back to you. I forgot to look at mine to see the size, but I am sure it is 5000btu.

[mhanna]

Rob S and I finished putting reverse cycle AC on our boats just this spring. We picked up Webasco 9000 btu FCF units http://marine.webasto.us/products/webas ... s/fcf.html. I only used the unit twice so far and can say that all is working the way it is supposed to. The unit itself is quiet (under the v-berth) but when running there is some noise from the air coming out of the vent. Not terrible but when sleeping in a small area it could be annoying. (reads... did I build the vents wrong ?)...

I understand your concern with the BTU, when choosing the unit I came very close to buying a 5000 BTU unit but there was little difference in the price from 5000 to 9000 (amps draw was similar, size, ect...) The online calculators show that for a 28te a 5000 is fine for the cabin (and I believe it would be) but I was hoping to get some air into the pilothouse to (somewhat cool it) and to keep it dry. I have not figured out how to vent to the pilothouse yet and not sure if I will, I just have a fan in the cabin blowing it up for now. We did however install a small vent into the bathroom to make sure it gets some cool dry air ( I saw that in Essex last year and though it was a good idea).

Rob or others will see this post and chime in but for the 1 hot day we had, the 9000 unit cooled the cabin (but not as quick as you may think). From a hot cabin it took 1-2 hours to have the unit cycle normally (but I did have the doorway to the pilothouse open).

It helped to have Rob to go through ideas and we even did some extras including setting up a freshwater flush (assists in priming, flushing and winterizing). I will post some pictures in a bit to show the installation.

Matt

[RicM]

You have to be careful if you run the AC with the cabin doors open. My unit (and any AC) will freeze up if it doesn't cycle on and off occaisionally. Supplied with an endless amount of humid, warm air, the heat exchanger will ice up and stop cooling. You can damage the unit if it continues to run after freeze up.

[RobS]

Doug,
Matt Hanna and I have both just completed installing Webasto 9K Btu/h units in our 28's. We've had enough warm days to feel confident we made the right choice in sizing the unit. We were originally set to go with the 5K unit as the calculations told us that it would suffice but we decided to go the next size larger since the 9K would not be over-sized and with the pilothouse included the 5K unit was on the edge of being undersized. Defender gave us the Miami boat show price while the show was going on even though we orderded off the website. I think it was $1,050 for the unit. We ran a vent in the bathroom, not the pilothouse. Leaving the cabin door open is the pilothouse solution. Here are some pictures, click to enlarge:

Platform was not provided from the factory. Made a platform from 3/4M plywood. It wraps around the thruster and sits on the forward end of both stringers

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The discharge duct runs up through the bottom of the starboard sliding locker. We made a collector box out of rigid insulation board to minimize sweating etc. and it was easy to work with.

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Bathroom supplied with a 2" PVC pipe ran from collector box through hanging closet

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Here is the unit in place

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The Webasto has the "brains" remote mounted. This also fit in the forward V, to the port side of the intake

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The condensate drains into the bilge. I have a small bilge pump mounted down in the V of the hull which gets almost all of the water out. Can be plumbed into the shower sump at later date if warranted.

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Sea Water supply and return ran under the dinette

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Sea Water discharge comes up through floor under vanity, added a vented loop on the bulkhead and a new thru-hull discharge next to the one for the sink drain

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Manual Controller Mounted next to the Breaker Panels. This unit also comes with a remote control which has proven to be very convenient

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AC Pump and strainer. Stole the seacock from the head. Tapped in fresh water by adding a T on the cold water supply to the water heater. This allows flushing out the sea water loop when the AC is not being used and also allows purging air from the system if needed. Turn on the fresh water pump, close the seacock and open the fresh water valve. Unit can also run off dockside water if need. Head was tied into non-pressure side of the fresh water with a check valve.

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[RobS]

As I was writing this post I see Matt and Ric have both chimed in as well. I will have to watch for Ric's concern regarding leaving the doors open..

As Matt mentioned it was definitely key that we completed this project together for the sharing of ideas, debating pros & cons, etc. and the extra set of hands really helped with the manual labor and the shopping for all the misc parts. Matt also mentions the "air noise" and questions if it's due to the design of the collector box we built. I do not think so as Ric has mentioned to me more than once that his main complaint with the AC is the noise of the air "wooshing" out of the vent...

One hot day I went to the boat and the cabin was 97deg 47% hum and I ran the unit with the doors shut but 2 hatches left out and in an hour it was 78deg 41%hum.

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[RicM]

While not an HVAC expert, I do a lot of training videos for the industry and picked up some knowledge from hours of editing, scripting etc. The noise issue is somewhat unavoidable and probably not a function of the shape of the collector box, rather the speed and volume of the air and that air carrying fan noise along on it's journey. The answer is to slow the air flow, not stop it when you get to the setpoint temp/humidity. Most smaller, less complicated systems have only 2 fan speeds, Hi or off. A better way is a 3 or 4 speed system that will kick down to a quieter speed once the heavy cooling is done, but still recirculating the air more quietly while kicking the compressor on and off as needed.
My system control has settings for various fan speeds, but the fan motor is a single speed AC motor. AC motors are not easily speed controlled (causes heat and waste) and a more expensive fan with several speeds built in raises the initial cost of the install.

[RobS]

My unit does have a 3 speed fan but they should have named the speeds, HIGH, HIGHER, HIGHEST, not LOW, MED , HIGH because the delta between the 3 speeds is minimal and the lowest setting is still quite high. To look on the bright side, it's better than not having enough air flow...

[DougSea]

Wow!

Thank you so much guys! You answered all of my questions and ended up totally inspiring me to take this on. As i was reading your descriptions i felt a kindred spirit, you guys approached this in many of the ways i would and look to be just as anal as i am when it comes to your boats. (i say that as a considerable compliment!!) You even vented the head nearly the same way I was considering. My thought was to run a 3" PVC pipe from the hanging locker into the side cabinet in the head, put a reducing T and a 2" vent in the head and then continue to the pilot house with the 3" and get a vent in as high as I could.

I'm hoping to take this project on later this month and I'm sure I'll have some questions. Thank you Rob and Matt for the details and Carl and Ric as well. I really appreciate you taking the time to answer my post so completely!!

Doug

[RicM]

Yeah, the manufacturer is probably worried about freezing up the heat exchanger in AC mode so they are "over blowing" it. Are the fan speeds identical when in heat mode?

On another note....I was asked by a guy at Wickford Shipyard who just bought a BRAND NEW Back Cove 37 to help him better his close quarters manuevering. He said that last year he admired my "back and fill" technique around Daves' dock and couldn't seem to get his boat (single engine diesel, Cummins, 600HP!) to do what he wanted. Sooooo last night I spent 3 hours at the helm of a half million dollar pleasure palace. What a ride! Smooth, whisper quiet, EVERY bell and whistle, including dual screen NavNet 3D and Flir night vision camera. I was a bit let down by the Flir, although it did show lobster buoys pretty well in the dark. The Navnet 3D was a giant PITA, way too much going on for my taste, although he kept switching it from perspective to heads up, both of which I have come to hate. I'm a full time North Up guy myself now. I was pleased to find out that my close quarters skills translated quite well to a boat about twice the size of my 28 TE. I was able to spin it 360 in about 1.5 times it's length (very calm night) with no thruster (it has front & rear) and would have felt perfectly comfortable docking it, but he wanted to try out my ideas while I coached. Of course, he, like everyone else at first, was using too much power for too long, and then was having to correct for the over shoot with more power. We took a ride over to Newport and back (15kts, 8 Gal/hour, about 2 mpg) over, about 8-10 kts on the way back in the dark. Gorgeous boat, but too nice to fish I'm afraid!

[RicM]

Doug,

Talk to an HVAC guy about duct sizing. 3" to the helm isn't going to do much for a volume that size, you will probably end up opening the cabin door any way. In both the head and helm you need a return to get air flow, which means you will have to open the doors. Otherwise you are "blowing into a coke bottle". My guess is it's going to make a lot of noise, but you won't get much air exchange and you will have cut up your boat for little benefit.

[DougSea]

Doug,

Talk to an HVAC guy about duct sizing. 3" to the helm isn't going to do much for a volume that size, you will probably end up opening the cabin door any way. In both the head and helm you need a return to get air flow, which means you will have to open the doors. Otherwise you are "blowing into a coke bottle". My guess is it's going to make a lot of noise, but you won't get much air exchange and you will have cut up your boat for little benefit.

Good points Ric and I had a couple of thoughts to mitigate the potential issues. We have Central AC at home and I had thought to use some of the same techniques on the boat that work there. Our Master bedroom (pilot house) is at the far end of the AC run and didn't cool properly. I added an inline duct fan (bilge blower) and a return vent (vent in head and pilot house door) which greatly improved airflow. The noise of the bilge blower would not be a factor as it should be limited to the pilot house and controlled by a speed switch. Of course if I can do so reasonably I'll put a larger pipe/duct in. All of this is intended to allow me (the night owl) to stay up late in the pilot house while minimally disturbing my slumbering wife. I'll be doing some POC work ahead of drilling too many holes!!