New a/c install

Hello All,

My wife and I recently purchased a 1996 Shannon Voyager in CT and have brought it to NC, It Never had A/C.
The Shannon factory said 16,000 to 18,000 btu's should be good but different online sites have guidelines and it seems that I need two units around 25,000 btu's for 230 sq. ft. of interior space approximately.

Anyone with a similar boat ? They only made 16 of these so not many around.

Thanks,
Bill R.

Bill R. said:

The Shannon factory said 16,000 to 18,000 btu's should be good but different online sites have guidelines and it seems that I need two units around 25,000 btu's for 230 sq. ft. of interior space approximately. Thanks, Bill R.

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Bill, Shannon's (nice boat) numbers sound about right. But, it depends upon your cruising style. If a lot of time under cover vs in the hard sun it will make a big difference in cooling requirements. As will where you set the thermostat. Then if you use the genset to power it, starting load and genset capacity comes into play. Then do you have exhaust fans to cool the ER (after a hard run) while running your AC. Then space for multiple units, the list goes on.

On our bigger boat, we have 3 ACs (1 - 16 and 2 - 12 Ks) and rarely need more than the salon 16K running unless temperatures climb above 90, a rarity in PNW.

You can always start with one and see how it does. Size the water pump for 2 units though.

Bill, Was the boat at Gwenmor for a bit this summer?

Bill.....I thought that was you in Washington the other week at the pig fest but wasn't sure as I hadn't seen any info on your purchase....Nice looking boat.
For what it's worth, my 12K BTU unit on my little Cape dory is barely adequate when the heat cranks up in our area and you've got a LOT more interior volume...I'd lean towards the bigger option....

If we are talking about the Shannon Voyager 36, that boat can be cooled adequately with one A/C unit only if you accept that it won't be 70 degrees inside on a 95 degree, full sun day. But one A/C unit can keep the boat at below 80 during a hot, sunny day and will keep it at 70 at night. And if you put a sun shade tarp over most of the cabin length, then a single 16,000 but unit will keep it below 75.


I did it with one on my boat and it worked.

But I would look for the biggest 120V A/C that I could find and install that. I think Cruiseair makes a 20,000 btu unit. But if you want to be cool during the middle of a hot day, go with two 16,000 btu units.


But do look at your power situation and generator capacity. Two 16,000 btu units will be marginal on a single 30 amp 120V service.


David

Think about using the next generation of HVAC.

Where you are winter cold still can be a hassle.

The Mitsubishi mini splits solve the heat problem and you will not have the hassle of pulling jellys out of the sea strainer at midnight ,as the ancient style units suffer.

Guys,

Heron,
yes that was me at the Washington waterfront and sorry I did not stop by to say hello, it was busy and I did not even get a chance for BBQ !

jleonard,
Could have been, I did not take possession until almost October.

Thanks to all for the comments and advice and here in Eastern NC I have got to deal with 90 plus and high humidity so it may be prudent not to take any chances.

Bill R.

FF said:

Think about using the next generation of HVAC.

Where you are winter cold still can be a hassle.

The Mitsubishi mini splits solve the heat problem and you will not have the hassle of pulling jellys out of the sea strainer at midnight ,as the ancient style units suffer.

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Can you provide a link for a boat application?

I may have to replace one of my AC units next summer.

Always looking for new ideas.

"Can you provide a link for a boat application?'

Not really but in the med and Istanbool you will see them on loads of boats.

As they are a local purchase it might be really hard to spec US electric in most of Euroland.

Mitsubishi has plenty of competition , so check out Panasonic and the rest.

Bill; from a quick Google search it would appear that your boat is of roughly sportfisher configuration: Cockpit, saloon, fwd cabin(s) and flybridge. My feeling is that two split-system a/c's would be the way to go if space in your engine room permits. Maybe 1x12k and 1x16k? Much more flexibility. Good quality a/c's should last a long time if used regularly; so cost is not so significant in the big picture. Dedicated thru-hull, Perko strainer, adequate raw water pump. Suggest you consider Cruisair. Let us know what you decide.

The nice thing about self contained units versus split units unless they are equipped with quick connects...is you can take off a couple wires and hoses and take the unit to a local AC&R shop.

The largest divergence in marine costs over land costs to me seem to be in repairing AC&R.

Thanks Guys,

I'M familiar with split units but never thought about them for the boat.

Thanks !

One caution , too big is very bad when selecting units.

The hassle is the cabin space will het cool very fast , and the unit will shut pff quickly.

To quickly to remove moisture from the air , so you end up with a cool clammy boat.

In normal summer you need the units to opertate for hours , not minuets to properly de humidify the boat.

The builder probably knows this so specified 1/3 of what others think should work.

16,000 btu vs 50,000 btu.

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Although mostly for larger boats the easiest to maintain setup seems to be the water circulation models.

Here each cabin has a heat exchanger with thermostat, when cooling the water is about 40F , and when heating 180 , weather from a boiler , the engine or noisemaker coolant.

The usually 3 or 4 cooling units simply cool water, as many as needed at that moment.

. An advantage is an errant screw in the wall only requires a water line fix , not a Freon fix with a skilled person.

Each cooler can be removed and be replaced with a spare , and later serviced ashore.

This is also a solution for vessels that operate on US and at times Euro current.

The ones that use the local power can be selected

Bill R. said:

Thanks Guys,

I'M familiar with split units but never thought about them for the boat.

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I was referring to the marine split-units made by Cruisair etc with the compressor part in the engine room, copper pipes leading upstairs and the evaporator/blower bit in the cabins. I have no experience in using domestic split units on boats. Would prefer to learn by other people's mistakes!

I completely agree with Psneeld on the convenience of self-contained units. I have three on my boat. The amount of space you have available in saloon and cabin lockers may well be the deciding factor on which type you go with.

Being is South Florida I am a firm believer in an abundance of A/C. There are quite a few things you can do to improve performance, window coverings/films/blinds being #1. Stopping the sun before it gets in is best, so an outside window treatment works best. You can have all the ventilation you want in the ER but it is still going to radiate to accommodations, so if you want A/C underway consider a few BTU for that.


If you look at me olde Mainship those are outside screens on the side and front windows, and there are sunbrella inside snap on covers for the front windows that have a sewn in pocket for a thermal insulation board. Those few window treatments took a marginal unit and made it work really well.

Take into consideration noise when you do the install. I see way too many units installed under a setee or a berth pushed right up to a return grille. Push the unit back or over a couple of feet and break the line of sight with a baffle. Noise always comes out of the return, and it can be reduced very easily and usually at no cost on installation by taking a few simple steps.

Talking of learning by other people's mistakes, this may help!

http://www.trawlerforum.com/forums/s31/doing-your-own-air-conditioning-6741.html