Marine A/C - please educate me

[ssobol]

[

It has always bugged me that a car AC has so many more BTU's than a boat.
A Boat is bigger has just as much or more sunload since it bigger, and well its bigger and it has lots more potential air leaks than any car.
And a car is so much smaller space.
And yet the AC capability is inferior in all boats by comparison.
People demanded fast cool downs in cars and got them.

I wold like to be able to cool my boat down fast too.

No one wants to drive their car (and be miserable) for an hour just so the interior temp gets to a comfortable level. Most car trips are way under an hour. Nothing is stopping you from sizing your boat AC system so that it cools your boat down as fast as you want it too.

Advantage of an RV type AC unit on a boat is that it will operate just fine when the boat is not in the water and it costs a whole lot less too.

I've seen lots of boats in Asia that use mini-split or ductless AC units instead of marine units.

 

[OldDan1943]

More text didn't help. Still wrong.

Home units can certainly change modes. It's the thermostat doing the work, calling for one mode or the other, not the heat pump. Likewise bringing e-heat into play when necessary. Now, whether an install is properly configured, well, home HVAC installs are often done wrong...

I guess I will talk to a heat pump tech when I get back home. I will get a heat pump thermostat that will change from AC to heat automatically.

I have heard a rumor, there are heat strips available for marine plants. I am not sure if it is true or worth the expense.

I have been wrong before. SHRUG

 

[FF]

There are other important differences between an RV style rooftop AC and the usual boat unit.

The RV roof unit is located high so warm interior air requires no space for return ducts or power to suck hot air back to the unit.

Rotten power is not uncommon in some RV parks so units can be ordered with improved low voltage operation and easier starting.

The RV units fit a std 14x14 inch , so can be R&R very easily every decade or so.

With no sea water supply , digging jelly fish out of the sea water intake is not required .

For folks that need heat , and pay for the electric , the modern Mini Split is probably the best choice of all.Many will heat at below 0 F

 

[toocoys]

I have heard a rumor, there are heat strips available for marine plants. I am not sure if it is true or worth the expense.

I'm not sure what you are referring to when you say "heat strips", but Flagship Marine units are not reverse cycle. They are actually built with a heat coil inside the fan. It's basically an electric oven element wound in a tight coil.

https://www.flagshipmarine.com/heat.html

 

[ranger58sb]

I have heard a rumor, there are heat strips available for marine plants. I am not sure if it is true or worth the expense.

There are resistance heating units -- conceptually similar to a toaster -- that can be added to existing systems.

OTOH a reverse cycle AC system already does heat well enough, so usually resistance heating is only added to a reverse cycle system in order to deal with much colder weather... and as when a liveaboard's boat is mostly winterized (no raw water flow available) and heat is still a requirement.

The "yes" in your post #12 was wrong.

-Chris

 

[twistedtree]

Got it, guys. So, here in the southeast US, where the water temps are often 80+F this time of the year, a marine A/C would be practically useless, huh?

No, not at all. It will still work great. The Freon runs much hotter, so 80 or 90F water still provides plenty of cooling.

 

[sdowney717]

https://www.sylvane.com/portable-ac-faq.html

I knew someone used a portable AC unit on his boat with the air hose. It worked fine cooling his boat. I have a split Heat pump 16k, and if it was not sufficient, and mine was working normally, I would consider getting one to supplement, it certainly would be a lot cheaper to setup and run as a DIY project than calling an HVAC tech and buying a new marine system. I do everything myself including HVAC work. I did have my home system replaced professionally years ago, but today as long as I am not gotten too old, I would do it all myself since I have learned how .

Some of them use a single air hose. I think his did. He actually cut the wood door panel with a round hole to expel the hot air, But i would maybe send it out the hull somewhere If I did it.

 

[ForceMultiplier]

[

Advantage of an RV type AC unit on a boat is that it will operate just fine when the boat is not in the water and it costs a whole lot less too.

Oh foschizzle! That's right. Well, I will definitely be putting an RV type in my next trailerable cruiser, then.

 

[syjos]

I wanted to put a RV roof type AC on Sandpiper but my wife said we would look like the Clampetts.

 

[toocoys]

I wanted to put a RV roof type AC on Sandpiper but my wife said we would look like the Clampetts.

Not to mention salty spray would rust the bearings in about 2.5 minutes if sitting idle.

 

[HopCar]

As long as the condenser coils are hotter than the water, the air conditioner will work fine.
Same with air cooled air conditioners. They work fine when the outside air temperature is pushing a hundred.

Sdowney, no evaporative cooling effect in a marine AC unit. It’s a closed system. None of the water has a chance to evaporate.

 

[ForceMultiplier]

Not to mention salty spray would rust the bearings in about 2.5 minutes if sitting idle.

Nah, there's lots of folks that run the Coleman RV units on the roof of their C-Dorys and get several years out of them.

 

[wkearney99]

Oh foschizzle! That's right. Well, I will definitely be putting an RV type in my next trailerable cruiser, then.

Sure, go for it.

 

[ssobol]

Nah, there's lots of folks that run the Coleman RV units on the roof of their C-Dorys and get several years out of them.

Apparently the ACOE see RV type AC units as the preferred AC method on their work boats.

Also a RV AC unit is a whole lot cheaper than a marine unit and easier to replace too. Lift off/lift on.

 

[sdowney717]

Apparently the ACOE see RV type AC units as the preferred AC method on their work boats.

Also a RV AC unit is a whole lot cheaper than a marine unit and easier to replace too. Lift off/lift on.

Its a good idea that can save money. I prefer to put it into the roof and not a hatch though.

 

[ssobol]

Its a good idea that can save money. I prefer to put it into the roof and not a hatch though.

It'll still be lift on/lift off. I was talking about the ease of installation, not actually using it that way.

 

[sdowney717]

It'll still be lift on/lift off. I was talking about the ease of installation, not actually using it that way.

If I need something, I would get a portable AC if they are cheaper, drill an exhaust hole in the cabin side and it would sit on the cabin floor. The prices around 350 to 500.

 

[toocoys]

Nah, there's lots of folks that run the Coleman RV units on the roof of their C-Dorys and get several years out of them.

We live on the coast and lost our bearings during Harvey. Like three days and it was done. It was a brand new Coleman Mach III that was on our brand new RV.

Based on *MY* experience, *I* wouldn't put one on my boat. But again, thats based on my experience only.

 

[ssobol]

If I need something, I would get a portable AC if they are cheaper, drill an exhaust hole in the cabin side and it would sit on the cabin floor. The prices around 350 to 500.

I actually use a window AC unit from Walmart. Slip it in the window when I need it. Cost about $110 and so far has lasted over 6 years.

 

[BerettaRacer]

Got it, guys. So, here in the southeast US, where the water temps are often 80+F this time of the year, a marine A/C would be practically useless, huh?

Here in Ft Lauderdale, my experience is that units will work fine until water temp hits high 80's to low 90's. By mid 90's water temp, when you really need A/C, efficiency goes way down.




And before anyone makes note of 90+ degree water temp, yes it does happen, and happen regularly during summer around here with local water flowing out of the 'glades heading to ocean. Don't believe me, park your boat at any of the shipyards along the upper portion of Ft Lauderdale's New River. I've recorded consistent mid 90's and a high of 97 degree river water temp.

 

[sdowney717]

Here in Ft Lauderdale, my experience is that units will work fine until water temp hits high 80's to low 90's. By mid 90's water temp, when you really need A/C, efficiency goes way down.

And before anyone makes note of 90+ degree water temp, yes it does happen, and happen regularly during summer around here with local water flowing out of the 'glades heading to ocean. Don't believe me, park your boat at any of the shipyards along the upper portion of Ft Lauderdale's New River. I've recorded consistent mid 90's and a high of 97 degree river water temp.

An honest appraisal!

In summer, we can also get some super warm slip water into the mid 90's which does affect how well the cruisair cools. It wont last long water being that hot. Right now all this week we are having super hot days, Air temps 95 to 100 *F. Every day for days, about 6 days left of this super heat, and were a few days into this wave. It is so hot, I go to the boat early AM, but I cant stay outside there too long with the sun beating down, leaves me gasping for breath. I recently was working on the gen, and few other projects, and I am limited to a couple hours in the AM. Bad thing boat is in full sun on aft deck in the AM, afternoon aft deck in the shade, of course by time I get there if going in afternoon, boat cabin has been heating up all day. Feel like would be nice to turn on ac remotely ahead of time! And got to be careful walking on the wood docks, hot enough to burn bare feet.

 

[MYTraveler]

Got it, guys. So, here in the southeast US, where the water temps are often 80+F this time of the year, a marine A/C would be practically useless, huh?

No. The refrigerant is compressed and becomes very hot -- hypothetically 160 degrees. Then it is cooled off with seawater (or air, in the case of home / auto AC) to something above ambient temperature -- perhaps 100 degrees. then it is expanded and cools down radically, perhaps to 50 degrees, and internal air is blown across that.

 

[stubones99]

So you think air will cool a condenser faster than submerging it in water?

No, water has 13 times the thermal coefficient as air at the same temperature.

An air conditioner compresses the refrigerant liquid to concentrate the heat, and it gets HOT! With the refrigerate at 150+ degrees, cooling it with 80-degree water will work. It would work better with 40-degree water, but the delta between the refrigerant (freon, etc.) and the cooling water will take on the heat from the refrigerant and let it cool the interior. The efficiency varies with that temperature delta, but it will work.

If you were stationary, you could pick up the cooling water from deeper depths and get higher efficiency, but that adds another layer of problems.

 

[Capecodder]

Marina AC

I’m in SW Florida, today the canal water was 88.2° my Webasto marine AC was pumping out 44° Outside it was about 94°
Good water flow, need to keep the raw water system clean, slit, slimy and hard marine life grow fast.

 

[Steve91T]

This post is perfect. I have a mermaid reverse cycle AC unit that stopped working. The pump works but the compressor won’t kick on. I came here to research how they work to help me troubleshoot.

So what kind of refrigerant do they use? Can you use one of those auto parts store AC recharge kits to top it off if it needs it?

Our ac’s struggle to cool the boat during but day. I thought there was something wrong but after reading this post I now know that it’s most likely just warm water. And once I get the 3rd ac unit working, it’ll help the other two.

Any thoughts on why a compressor won’t kick on?

 

[FF]

"Its a good idea that can save money. I prefer to put it into the roof and not a hatch though."

Any rooftop unit requires a hole in the roof to blow thru.

The 14x14 hole is a std size for AC and also for some fine DC vent fans.

The vent fans can be has with thermostats and automatic rain closure devices .

Just the flange for an AC hole can be had 4 or 6 inches deep for under $20.

Those that night prefer their rooftop "marinised" can find them easily.

The RV units last so long , I have never seen the Sea Going Version , but they exist at about double the RV versions price.

https://www.pplmotorhomes.com/parts...MIlvmH9KW-4wIVj4bACh05nQG6EAQYAyABEgLwi_D_BwE

https://www.walmart.com/ip/Fan-Tast...MIid6Xrqa-4wIVUtbACh2cUA0DEAQYBCABEgLXUfD_BwE

 

[O C Diver]

This post is perfect. I have a mermaid reverse cycle AC unit that stopped working. The pump works but the compressor won’t kick on. I came here to research how they work to help me troubleshoot.

So what kind of refrigerant do they use? Can you use one of those auto parts store AC recharge kits to top it off if it needs it?

Our ac’s struggle to cool the boat during but day. I thought there was something wrong but after reading this post I now know that it’s most likely just warm water. And once I get the 3rd ac unit working, it’ll help the other two.

Any thoughts on why a compressor won’t kick on?

While I'm not an HVAC mechanic, nor have I played one on TV, I may be able to help you as I have a mermaid AC unit on my charter boat. If you experience a high freon pressure from either low cooling water flow or a fouled heat exchanger, there is an overload trip that requires pushing a manual reset button. The button is on the device that senses pressure or temperature. It is in the path of the freon tubing and has an electrical wire running to it. The button is red. I think the location is shown in the owner's manual.

Ted

 

[sdowney717]

This post is perfect. I have a mermaid reverse cycle AC unit that stopped working. The pump works but the compressor won’t kick on. I came here to research how they work to help me troubleshoot.

So what kind of refrigerant do they use? Can you use one of those auto parts store AC recharge kits to top it off if it needs it?

Our ac’s struggle to cool the boat during but day. I thought there was something wrong but after reading this post I now know that it’s most likely just warm water. And once I get the 3rd ac unit working, it’ll help the other two.

Any thoughts on why a compressor won’t kick on?

Probably R22, especially if older, you can only use auto refrigerants if it uses r134, and its unlikely.
If it has a start capacitor and a start potential relay, either might be bad.
If it has a run capacitor it could be bad.
Some meters let you check them, and you can do some basic tests on them with ohm meters. Many times such capacitors will be visibly damaged, like their tops popped up.

Open the control box on the unit itself and take a picture.
Does it try to start with a lot of amps and you hear an overload click off, or does it make no sound at all?

 

[FF]

Many of the auto refill systems are about 90% propane and 10% butane.

This is a more efficient refrigerant than the old F-12 , but it can be ignited.

There are numerous propane sniffers for folks that cook, heat or refrigerate with propane that could be used as a safety.

The Brits attempted to use it in house reefers to gain efficiency , but with the usual level of British labor , a few house fires soon stopped it.

 

[wkearney99]

It's going to be a scorcher up here this weekend. I've got a wireless camera in the engine room and it's already reporting 89F down in there at 8am. This after 5 days without the engines running, so that's just ambient air and water. Looks like it's going to be a pretty sweaty start/check routine for the sea strainers...