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Old 12-10-2013, 03:10 PM   #1
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Roof top rv type AirConditioners

Ok it's cold here today (in oklahoma, 21 degrees) and I'm doing some plumbing in the boat in my yard, a 50 foot trawler, biggest boat in Comanche county. I needed to move a couple of ac units out of the way to get to the areas that I needed to run the PEX. That got me to thinking about the marine ac units. They are a PITA. no way around it. They are , I'm sure, more efficient than air to air units but I wonder where the pay out is. I can buy a 13,500 btu rv unit for less than $750. A similar marine unit would be at least $2500. The marine unit needs a pump and associated plumbing. This boat has 5 ac units ranging from 5000 btu to 22,500 btu. One for each space. I could replace these with 3 15,000 btu roof mounted units and not have the plumbing. On the flip side, the current units are fairly new, the 22.5 has never been used. But, I really dont like the watercooled units, mostly because I cannot make myself leave the boat unattended with them running. Dometic is making a "marine" roof top unit that is supposed to be more corrosion resistant but I have seen the work boats in the gulf that run just standard rv units for years with very few problems. When this boat goes back in the water it will be cruising and I would like not to be messin around with ac pumps and such. But, if watercooled units are enough better and enough more efficient I would be willing to put up with it. As always, your thoughts are appreciated.
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Old 12-10-2013, 03:17 PM   #2
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I would keep the marine ac units, personally I would not be able to bare with those bulky ugly things sticking out of cabin top. That's just me though. Also the marine ac units last, I had a friend that finally had to replace one of his units, an 1980.
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Old 12-10-2013, 03:55 PM   #3
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I had the roof top units on a previous trawler. Nothing wrong with them except the extra fan making noise and the coils not lasting because they are made of aluminum.

My present trawler has the marine units with sea water condensing. quiet and efficient. No corrosion problems. Much smaller package than the roof tops. The March sea water pumps last forever.

I say go with the marine units.
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Old 12-10-2013, 04:10 PM   #4
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We have one on the roof of the pilot house. Works great!
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Old 12-10-2013, 04:23 PM   #5
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It seems like when we move from the "yachty" side to the "this works" side simple trumps. But, if it can be prooven, either economically or reliability wize, that marine units are better I would go with what I have.
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Old 12-10-2013, 04:25 PM   #6
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Wow, 5 units. Where are you going to be boating? We have 2-16K marine AC, ducted, units on our boat that kept us cool in the Sea of Cortez and now in FL with no issues.

On a 50 footer, I'm not sure you'll be able to effectively cool the boat with just "RV" style AC unit's. The helm and salon are pretty easy and maybe the forward area but on the deck it might look a little "different". With the "RV" type, how do you handle the condensate?

Maybe consider a compromise. A couple of the "RV" plus a couple of the marine units. When you aren't on the boat, run the RV units to at least handle the humidity and at the same time you'll keep things a little cooler since leaving them (marine units) unattended is one of your concerns.
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Old 12-10-2013, 04:39 PM   #7
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I have an rv unit on my boat. It works for us. but, i could park several of my boats on yours. i am only 28', 10' beam. In a boat of 50' you may be hard pressed to get the air to flow around enough to be comfortable...they dump the air where ever they are. Mine is 6 years old and still works so they are reliable in the marine environment. You can make an argument that they look odd on a boat but i keep mine covered with a canvas cover when not in use...which may help account for longevity too.

all that being said. i wouldn't rip out a marine system to replace it with an RV style one. but if i had an enclosed FB with a hard top or a hatch in an hard to heat/cool (mine has a heat strip too) area it i'd look seriously at an rv unit.
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Old 12-10-2013, 05:47 PM   #8
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I was looking at the rooftop marine units at the last couple of boat shows, but the only practical application I can think of on our boat is for Pilothouse only usage. There's plus and minus features to all the alternatives.

1. Marine unit, compact, efficient, plumbing required, another hole in the boat, ducting necessary.

2. Rooftop Marine unit, a bit more noise, no plumbing, very heavy and usually mounted high up, requires hole in roof or deck, expensive, no word on how long it would last.

3. R/V unit, same as above but can be used with engine mounted compressor requiring long refrigerant lines, holes, etc.. Cheap, limited life in salt.

4. Rolling floor unit up to 10K BTU like sold at home stores, could be gutted and installed in smaller spaces like under helm, requires 5" duct to and from outside, plug in requires generator use, less efficient but cheap.

These are just some of the many things to consider.
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Old 12-10-2013, 05:54 PM   #9
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There was a roof monted un on my 39 Allied ketch when I bought it. It cooled very well. the down side was the noise andthat it was difficult to see over when I was steering the boat and thye downdraft was very cold if you sat below it. You have a much larger boat so it might work for you. I personally would not get another one.
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Old 12-10-2013, 06:02 PM   #10
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4. Rolling floor unit up to 10K BTU like sold at home stores, could be gutted and installed in smaller spaces like under helm, requires 5" duct to and from outside, plug in requires generator use, less efficient but cheap. These are just some of the many things to consider.
Thats seems the most logical to me.
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Old 12-10-2013, 07:26 PM   #11
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Our 1977 Tolly has its original "Coleman" AC unitís motor and cover under fly bridge dash (looks same as an RVunit... maybe itís marineized??). In the several years we've owned our Tolly we've not really needed to use any AC due to relatively temperate climate in SF Bay and Delta... good thing though as it has never been electrically hooked up since some time before we owned the boat (at least power has not been available to it and I have not tried repair - yet). Unitís motor and cover are out of way on bridge while still relatively accessible for recharging/repair. Its airflow operations are also in a good location of salon ceiling at entry to forward stateroom. Of the few hours a couple times during last few years it may have been nice to have AC available we simply went swimming more! Not sure if the several hundred dollars to get this one operational (if it can even be made to work again) is worth it for a once or twice a year couple hour use. Also, seeing as weíre nearly always on the water when on the boat we would have to have gen set running Ė something we try to limit much as possible. New unit I priced looks exactly same as out 1977 original including the operating panel on salon ceiling. Cost would amount to $1000 plus, plus. Installation of new replacement would take some in-depth doings modifying the bridge console for R&R.

Think weíll probably just keep swimming to cool down during the seldom occurring really hot days!
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Old 12-11-2013, 12:11 AM   #12
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Instead buy a quality brand stand alone self evaporating AC unit that has only one exhaust vent. Put in a closet-vent it out a portlight and be done with it. They're light, and are ice cold. Cost $350.00 or less. Heck, they even have remote controls. They're not very big either. They've made RV roof top type AC's obsolete. Don't eat much electricity either.
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Old 12-11-2013, 06:08 AM   #13
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Size matters and the rooftops can be had in large BTU sizes wit special soft start options so the power demand on start up is mild.

Most RV have 120V 30A power hoses so its similar to a boat , and in most cases only ONE will operate from a 30A cord. Mostly depends on the supply CB.

If the boat is fairly open a PH mount allows the cool air to sink to the cabins and float much of the hot air up for recycling.
The downfall of many built in marine systems is the installer didnt take the return air section of the install instructions to heart.

The rooftop does get the return air automatically , so many are more efficient than the 5X more expensive boat units.

Yes on high blower , high output , the fan can be noisy , but once the boat cools a bit , the output of cold is the same with low fan setting. After sun set low works even in FL.

Happily the cost is so low , compared to marine, repairs are,,, toss it out.

The 14x14 required hole is a std RV size , so if the unit is stored a std RV fan vent can be used.

They are available with reverse cycle heat for places where the air temp is modest 40-45F or toaster wire resistance heat for freezing operation.

WE love ours.
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Old 12-11-2013, 10:43 AM   #14
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The roof top is 20+ years old and still working plus it has a heat for the pilot house, and many times we use it on fan only. The pilot house is not heated with the Webasto as heat rises. During the warn summer months we do not heat with the Webasto.

As for the rest of the boat the AC is 4 domestic window mount 8,000 btu units, 250 bucks each, that I built enclosures for and butted up against salon and stateroom ports. In the winter we use them on fan mode to clean/move air around.

If additonal AC capacity is required I would by a portable unit.
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Old 12-11-2013, 01:36 PM   #15
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I agree with Pilothouse - the vented ones are effective and cheaper. I have two marine units in mine. I had a marina neighbour with a roof top almost under his seat on the bridge. They all work but I have often wished I had either the roof top or the vented as backup because sometimes when we put the boat in or have it out for service the marine units are unusable and because we are liveaboards all summer we have no where cool to go.
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Old 12-11-2013, 03:07 PM   #16
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Greetings,
Mr. bob. "...all summer we have no where cool to go." It gets warm in Winterpeg????? Don't the igloos melt?
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Old 12-11-2013, 04:08 PM   #17
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Quote:
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The roof top is 20+ years old and still working plus it has a heat for the pilot house, and many times we use it on fan only. The pilot house is not heated with the Webasto as heat rises. During the warn summer months we do not heat with the Webasto.

As for the rest of the boat the AC is 4 domestic window mount 8,000 btu units, 250 bucks each, that I built enclosures for and butted up against salon and stateroom ports. In the winter we use them on fan mode to clean/move air around.

If additonal AC capacity is required I would by a portable unit.
so you have 5 ac units on a boat in Washington???
I am contemplating AC on the O.A. but that is for Mexico!

I never have needed AC for a day in the past 20 years here in Washington..
but then I did grow up in the desert in Cal and miss " the dry heat"

HOLLYWOOD
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Old 12-11-2013, 04:45 PM   #18
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Here's what I mentioned above in example # 4. It's an LG 9000 BTU plug in unit that needs a 5" exit for hot air. The unit serves me well as-is, but I've had it apart and the interior will fit easily under the helm with the 5" duct right through a hooded vent in the pilothouse wall, like maybe a dryer duct flapper type. But the trick is that in order to get efficiency, you need to duct the intake up high in the pilothouse to get the hot air, or just vent the hot air out a roof hatch or solar vent in the roof....and be satisfied with re-cooling the cool air that comes in at the base of the unit. This unit outperformed the Haier 10K BTU unit of similar design I bought later. Of course, these units also de-humidify and do best by connecting a drain hose from the spout included at the base of the units condensation pan. I got it at Home Depot for 199 on sale....ebay is 219.
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Old 12-11-2013, 06:07 PM   #19
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Thanks Larry, Phill, Hollywood and all others...

Heck, I'll not spend hundreds to get our Tolly's orig 1977 Coleman AC working again simply to use for few hours each season - if at all!

But rather... I'm a gonna purchase one of dem dere 9K btu portable LG AC units.

Simple is as simple does!

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Old 12-12-2013, 10:06 AM   #20
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igloos?

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You are sharp today aren't you?
Winterpeg is darn cold right now and the igloos have no chance of melting but I keep the boat on Lake St Clair which is a long ways south of here.

Just so you know, even Winnipeg restaurants are igloos

Pop-up restaurant on ice set for January 2014 run - Manitoba - CBC News
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