Newb to AC

[Noclutch]

Please excuse my ignorance, but it’s what it is as I have no experience with air conditioners on boats.
I’m early in the process of deciding which boat/brand to order, but one of their differences is one offers a water cooled built in AC with reverse heat cycle, and the other offers a roof top AC unit.
I’m familiar with roof tops in some previous RV applications in the past, but the whole fresh water cooled thing is new to me.
From what I’ve gathered here, the pros to built in are aesthetics, maybe more likely to run underway(not a big concern but cool) with an inverter, and maybe easier start up amperage draw if on generator. Cons are potential water flow obstruction, less than ideal vent placement ( ie at shin height vs overhead) and limited access for maintenance.
Pros for overhead are access and cool air distribution, cost about half of built in. Cons may be noisier and certainly ugly up there.

What else am I missing? I’m all ears/eyes and thank you

 

[Gdavid]

The water cooled units that are mounted within the boat and use ductwork to distribute the air throughout the boat or the zone they support are only limited by the room to install them and the quality of the installation when it comes to air distribution. There is probably more work involved in most cases. The water cooled units are quieter, or at least all of the modern ones with rotary compressors.

The roof mount ones, similar to an RV are pretty straightforward to install but not everyone wants a large hole in the deck or cabin and the appearance of them. It really depends on the configuration of the cabin and your preferences. A roof mounted unit does have the ability to run when the boat is out of the water which could allow you to use use a trailerable boat as a camper of sorts or just make life easier when working on it at your house.

 

[rwidman]

Boat manufacturers almost always install water cooled AC in boats.

While some people might use an RV AC unit, it's usually a DIY installation and usually on an older boat that someone is trying to cool "on the cheap".

If you are buying a new boat, by all means, have the water cooled AC installed.

 

[DavidM]

The points made above are certainly valid, but I would make another: Rooftop A/Cs are not designed for salt air exposure and will corrode over time. You might get 5-10 years life out of one.

David

 

[mvweebles]

Most reverse cycle ACs have heat in addition to cooling. Yes, if water temps get too cold, it doesn't work well, but that's rare.

Reverse cycle AC is pretty dang reliable. Many have been quietly cooling working for 20+ years. Although initial install is fairly expensive due to ducting, pumps and thru-hulls, replacement costs are pretty reasonable - under $1500 and can often be done in a couple hours.

I don't think reverse-cycle is appreciably more efficient once the 120VAC pump is included so would not necessarily be more of an inverter-candidate than rooftop.

In the end, unless the rooftop unit is atop the pilothouse of a Shrimper in Louisiana, tough to make them look 'appropriate.'

Peter

 

[Noclutch]

Thanks for the great perspectives guys.
Yea aside from roadside camping and lower cost, it’s hard to get excited about rooftop. The builder who offers this does so on a quite old school high quality build boat that does look a little Bubba Gump-ish even new, but still…
The other manufacturer is at the other end of the spectrum style wise ( and possibly build quality wise as well, ironically), and a roof top would look totally out of place, like a deer guard on a Cadillac -seen it in my home state of Texas

Thanks again and now on to pondering battery type number and inverters. Fair amount of learning curve for this soon to be cruiser newb.

 

[sailormike]

Go with water cooled marine built a/c units. If your adding a/c to a vessel that doesnt have it your gonna run into different issues with both systems. I work on and install a/c units on both rvs rooftop and boats water cooled. Water cooled is the way to go. The cons. RV a/c are not meant for the pounding and marine environment. they are made of a lot of mild steel and aluminum that will deteriorate in no time at all. The Largest capacity rv units are 15k. Most 40 foot campers now have atleast 2 of these and still struggle when it is super hot. An rv ac you have to cut a 14 by 14 hole in ceiling that can leak and are very supportable to freezing up in high humidity. They are extremely loud both inside and outside. and as stated before the compressors arnt ment to be run going down the road but plugged in once you reach your destination. One last thoughts are they are a sealed unit and cant be refilled and only the fan motor can be changed out. they draw between 14 and 20 amps on startup. If unit is a heat pump it will shut down once temp outside reaches 40 degrees that's why on rvs they are backed up with gas or diesel fired furnaces.



Marine water cooled units yes have there limitations and pros and cons too. They are built for boats with more robust materials and metals. Nice thing about them too is you can get them in split units where evaporators are located in locations you cant get whole unit or the noise of whole unit. Yes you have to have a cooling system that uses water to cool the unit down. With proper maintenance this really isn't that big of an issue as long as you take care of the system. typically the marine units draw less power as they have to move less air with less fans. you can get soft start kits for both but once again i would get the unit made for the marine environment. Nice thing about marina airs is there are lots of user replaceable parts and they are refillable if they lose their Freon. Plus almost any HVAC tech can at-least diagnose and check and fill a marine unit. Hope this helps you make a decision.

 

[syjos]

Dometic and others do manufacturer a roof top AC unit for marine application.

 

[sailormike]

Dometic and others do manufacturer a roof top AC unit for marine application.

I am am a Dometic certified dealer and installer and have been since 2006 and this is news to me. They do have a commercial line but its the sae product with a higher price tag

 

[Noclutch]

Extra thanks to sailormike for the front lines/been there done that perspective!

 

[sailormike]

Extra thanks to sailormike for the front lines/been there done that perspective!

Thank you I will do do diligence and call dometic tomorrow just to make sure I am accurate because things do change and are not fully passed down

 

[syjos]

Dometic Brisk II Evolution Commercial Rooftop AC
Installed on many commercial smallcraft, LE and Military vessels.





.

 

[OldDan1943]

Per using power from an inverter for either type of A/C, in my feeble mind, just ain't gonna happen. You will need LOTS of healthy batteries and a couple of good size inverter. Then you need a real work horse to recharge all the batteries.
I do not see this happening on boats 25-40 ft. So basically, you need a generator to support the AC plants.

I have 2 reverse cycle A/C plants on board my boat. A 16K and a 12K, they were both new after I bought the boat. They ran flawlessly for about 3-4 years. One AC plant went belly up about 6 weeks ago and the 16K kept the boat habitable while waiting on a replacement for the 12K.
Within a week, the 16K started going down on HP. Tech came out, I pointed out the 'almost' no overboard discharge water. He blew out the gunk out of the line and presto, LOTS of overboard discharge water. Things are almost back to normal with the AC plants. The only thing to address is the condensate overboard lines. One condensate pan was overflowing so he blew the line out. I was down in the ER yesterday, no problem. Today the condensate overboard line. LOL Tech addressed everything. I will see what tomorrow brings. LOL

Side note: I was going to hook an air line to one of my SCUBA tanks and blow out the line but, I decided to let the tech check out his new installation work.

The old plants had a metal tray, the new plants have plastic condensate trays. Nothing the flake off and plug up the pan drains other than the gunk in the overboard line.

Also, there seems to be a scarcity of AC plants. Ready for the reason?? Covid19.
I called the shop, ordered the plant then drove into town and prepaid..... (I got a veterans discount because I asked.) The lady was nice, I was nice and didn't grumble..... She called me once a week to report the progress. Now that's good customer service!!

 

[HTurner]

Per using power from an inverter for either type of A/C, in my feeble mind, just ain't gonna happen. You will need LOTS of healthy batteries and a couple of good size inverter. Then you need a real work horse to recharge all the batteries.
I do not see this happening on boats 25-40 ft. So basically, you need a generator to support the AC plants.

I have 2 reverse cycle A/C plants on board my boat. A 16K and a 12K, they were both new after I bought the boat. They ran flawlessly for about 3-4 years. One AC plant went belly up about 6 weeks ago and the 16K kept the boat habitable while waiting on a replacement for the 12K.
Within a week, the 16K started going down on HP. Tech came out, I pointed out the 'almost' no overboard discharge water. He blew out the gunk out of the line and presto, LOTS of overboard discharge water. Things are almost back to normal with the AC plants. The only thing to address is the condensate overboard lines. One condensate pan was overflowing so he blew the line out. I was down in the ER yesterday, no problem. Today the condensate overboard line. LOL Tech addressed everything. I will see what tomorrow brings. LOL

Side note: I was going to hook an air line to one of my SCUBA tanks and blow out the line but, I decided to let the tech check out his new installation work.

The old plants had a metal tray, the new plants have plastic condensate trays. Nothing the flake off and plug up the pan drains other than the gunk in the overboard line.

Also, there seems to be a scarcity of AC plants. Ready for the reason?? Covid19.
I called the shop, ordered the plant then drove into town and prepaid..... (I got a veterans discount because I asked.) The lady was nice, I was nice and didn't grumble..... She called me once a week to report the progress. Now that's good customer service!!

Descaling the system is important to do along with keeping the strainer clean. Glad you got it going, keeping cool.


Don't forget:


https://www.homedepot.com/p/AC-Safe-Pan-Tablet-30-ct-AC-913/203216149

 

[OldDan1943]

Descaling the system is important to do along with keeping the strainer clean. Glad you got it going, keeping cool.


Don't forget:


https://www.homedepot.com/p/AC-Safe-Pan-Tablet-30-ct-AC-913/203216149

Oh yea, cleaning the strainer is always first on the list.
Per tablets..... there are many options.
Descaling is preventative maintenance.

 

[Noclutch]

Dometic Brisk II Evolution Commercial Rooftop AC
Installed on many commercial smallcraft, LE and Military vessels.


Good to know syjos. Couldn’t find the start up amperage on the Dometic website. Anyone have an idea what it may be?

 

[sailormike]

Dometic Brisk II Evolution Commercial Rooftop AC
Installed on many commercial smallcraft, LE and Military vessels.


Good to know syjos. Couldn’t find the start up amperage on the Dometic website. Anyone have an idea what it may be?

12-14amps depending on temp leveling out to around 7-9

 

[FF]

The std mount hole for most rooftops is 14 inches square.

 

[sailormike]

The std mount hole for most rooftops is 14 inches square.

Absolutely correct the unit is sandwiched over the 14by 14 square hole utilizing a 1 inch thick foam gasket. wiring passes through the air box.

 

[rgano]

12-14amps depending on temp leveling out to around 7-9

My Dometic Penguin II 13.5 KBtu unit had one heck of a lot more startup AMPS than that before I added a Micro-Air Easy Start - something like 60 Amps if I recall correctly.

 

[rgano]

Just to add some affirmations to the discussion, my Mainship Pilot came to me with BOTH rooftop and marine water-cooled units, both made by Dometic. The rooftop is enormously noisy and seldom used. One advantage is that I can cool the area under the bridge deck's hardtop for summertime engine maintenance with the boat hanging in its lift, something not possible with the marine water-cooled unit. I climb up there once every other year or so to cure corrosion issues with the steel grill work on the rooftop unit. Not much I can do about the aluminum condenser fins/coil but rinse with freshwater. The unit is at least ten years old and works fine. I would certainly NOT have added it had the boat come without it. The original 7 KBTu Dometic marine unit rotted out and was replaced with a splendid Dometic 10K DTU unit (at a premium price I might add). Both units have had the Micro-Air Easy Start added by me for near noiseless transition of generator and ac compressor from just running the fan to full up compressing and cooling. Dometic now offers their own Smart Start as an option, and I most HIGHLY recommend it or the Micro-Air on any AC unit. Just as an aside, there are often additional things you can do to a boat to improve the effectiveness of your air conditioner. They include topside awnings, exterior white window screens or covers, insulating foam panels against the windows, and added insulation in the ceilings since some boats come with none or minimal.

 

[sailormike]

My Dometic Penguin II 13.5 KBtu unit had one heck of a lot more startup AMPS than that before I added a Micro-Air Easy Start - something like 60 Amps if I recall correctly.

ABSOLUTELY INCORRECT!



if amperage was that high you would immediately trip the recommended 20amp breaker that supplies power to the unit.



The soft starts are a pricey but exceptional product desinged and built for people who have smaller generators and the small inverter generators that can easily run it once the compressor is started. I also highly recommend the Micro-Air Easy Start. Their RV Thermostats are the best on the market too.

 

[rgano]

I checked the specs for my Penguin II. Locked rotor amps 61.0.

 

[sailormike]

I checked the specs for my Penguin II. Locked rotor amps 61.0.

Yes you are correct the That 61 amp is if the compressor is locked up and run amps on the compressor is around 12amps to 15 amp depending on wire size and ambient temps. When I attended dometic AC Training academy we were most concerned with run amps of the compressor.

 

[sailormike]

Dometic Brisk II Evolution Commercial Rooftop AC
Installed on many commercial smallcraft, LE and Military vessels.
.

So Finally getting a chance to respond back to this and we are both correct they still make a commercial version. major difference in the commercial version and the normal brisk airs are the the steel components like the tray and ducts are made from galvanized metal instead of pot metal. After talking with a friend of mine in the USCG that is an engineer the ease of replacement cost of replacement and ability of when vessel is on the trailer for the ac. noise and vibration and condensate on the decks dont matter in there application

 

[rgano]

Yes you are correct the That 61 amp is if the compressor is locked up and run amps on the compressor is around 12amps to 15 amp depending on wire size and ambient temps. When I attended dometic AC Training academy we were most concerned with run amps of the compressor.

I have a mere 3.5 KW genny to overcome the start issues with a total of 23.5 KBtu of air conditioning, and I cannot run the 13.5K and the 10K units simultaneously because with one of them running, the whole system shuts down when the second one tries to start its compressor. My clamp-on ammeter showed a peak of 4-5 times the running amps you speak of and I saw on them individually. With Micro-Airs, they both run happily on the little genny.

 

[rgano]

Here is some possibly useful information I requested from Micro-Air:

QUOTE

Typically start amperage (for a 13.5 KBtu Rooftop AC unit) is about 17-19 amps with EasyStart and about 50 without. If you are trying to select a generator, HERE (Selecting a Generator - Micro-Air, Inc.) is an article that better explains it since the starting amperage is not what you should be looking at.

If you are looking for an inverter, we have had them work on 2000 watt Xantrex units on battery power.

UNQUOTE

 

[Noclutch]

I did stumble across this online regarding the Coleman SeaMach 13.5 BTU here

https://flagshipmarine.com/roof-top-units/


“ Hard start capacitor makes starting much easier on your vessel's power supply and generator.”
But still no start up numbers. Marketing hooey or valid claim?

 

[rgano]

Don't be fooled by the hard start capacitor nonsense. It does NOT perform the softening of startup in the way the micro processors by Dometic and Micro-Air as examples.

 

[FF]

"But still no start up numbers. Marketing hooey or valid claim?"


VALID claim for the past 40-50 years.