Modifying a mini split A/C with marine condenser?

[s/v Jedi]

Why is nobody doing this? Buy a water cooled condenser to replace the OEM condenser and huge fan, use the condenser fan power to start the water pump">raw water pump.

You get VSD, nice air handlers, near silent operation and very good efficiency.

Before I go down this path, I’m sure someone must have tried?

[Sailmonkey]

I’ve never owned a boat large enough to mount the evaporator, but have thought about doing it just for giggles.

[NPCampbell]

I'm not an A/C expert by any means but I thought there was a limitation to the amount of tilt that you could expose your compressor to before the oil would start running down the refrigerant lines?. Can a normal compressor handle the degree of heel that is experienced on a sailboat?

[Sailmonkey]

Originally Posted by NPCampbell

I'm not an A/C expert by any means but I thought there was a limitation to the amount of tilt that you could expose your compressor to before the oil would start running down the refrigerant lines?. Can a normal compressor handle the degree of heel that is experienced on a sailboat?

The compressors on marine HVAC systems are the same compressors found at your house. The only thing that makes a marine AC different than a window unit is the coaxial condenser, and the packaging.

[s/v Jedi]

I see many problems already:

- indoor units are 30+ inches wide and bulky/ugly.
- they have feedback sensors on the condensor like temperature, fan rpm etc.

I think I’ll go back to planning for ducted and wait for new products that were announced. But I see boats using these, putting the big outdoor units on deck houses etc.

[Singularity]

I can't make out all going on here, but apparently the thing at least turned on in colder weather:
https://www.reddit.com/r/DIY/comment...ater_for_boat/.

One way or another this is technology that needs adapting.

[s/v Jedi]

Originally Posted by Singularity

I can't make out all going on here, but apparently the thing at least turned on in colder weather:
https://www.reddit.com/r/DIY/comment...ater_for_boat/.

One way or another this is technology that needs adapting.

Good find… some remarks:

- he made his own water cooled condenser using lots of fittings, but you can buy them ready to go.

- the sensors are not a problem, he just left them.

- he used the condenser fan power line to run a pump of equal wattage.

- it works very good.

- the bulky wall unit is too large for a pretty fit in his cabin.

[ItDepends]

Originally Posted by s/v Jedi

Why is nobody doing this? Buy a water cooled condenser to replace the OEM condenser and huge fan, use the condenser fan power to start the raw water pump.

You get VSD, nice air handlers, near silent operation and very good efficiency.

Before I go down this path, I’m sure someone must have tried?

If you work for free, yes, sure you can cut apart a household AC unit and remake it into a water cooled system--if you really know what you are doing. It is not the kind of kludge I'd expect to find on a Sundeer 64, but whatever floats your boat.

The nice thing about the purpose built marine units is they are very compact and fit in small spaces. Our main saloon AC unit cost us $2k, but there was no cost of an added condenser, or a blower to connect to duct work, and no fabrication time taken away from more important projects. And the unit runs on 50 OR 60 Hz so we can use it no matter where in the world we are plugged in.

You CAN do it. But it's a hobby project, not a good use of resources.

To be fair, I take on a good number of hobby projects that I enjoy doing, so this isn't meant to be discouraging...

[s/v Jedi]

Originally Posted by ItDepends

If you work for free, yes, sure you can cut apart a household AC unit and remake it into a water cooled system--if you really know what you are doing. It is not the kind of kludge I'd expect to find on a Sundeer 64, but whatever floats your boat.

The nice thing about the purpose built marine units is they are very compact and fit in small spaces. Our main saloon AC unit cost us $2k, but there was no cost of an added condenser, or a blower to connect to duct work, and no fabrication time taken away from more important projects. And the unit runs on 50 OR 60 Hz so we can use it no matter where in the world we are plugged in.

You CAN do it. But it's a hobby project, not a good use of resources.

To be fair, I take on a good number of hobby projects that I enjoy doing, so this isn't meant to be discouraging...

You have a VSD (variable rpm) marine unit for $2k that does not require ducting and has no fan? I can’t believe it, please tell me what brand/model etc. or do you have old tech?

When you marinize the outdoor unit you can make it as compact and nice as you like and it will have the same components than any marine version.

I really don’t know what my boat has to do with choice. I now have a lame noisy power hungry CruiseAir unit… does that go along with a Sundeer better?

[NPCampbell]

Originally Posted by Sailmonkey

The compressors on marine HVAC systems are the same compressors found at your house. The only thing that makes a marine AC different than a window unit is the coaxial condenser, and the packaging.

I have a Copeland dual speed scroll compressor in my home unit. The specified maximum tilt angle while the compressor is on is 15 degrees. How do you get around that limitation on a sailboat?

[Sailmonkey]

Originally Posted by NPCampbell

I have a Copeland dual speed scroll compressor in my home unit. The specified maximum tilt angle while the compressor is on is 15 degrees. How do you get around that limitation on a sailboat?

I think you’ll find that the generator to power the AC also isn’t intended to operate at angles greater than 15-20 degrees. On top of that the condensate is likely to not drain properly at those sort of angles.

I don’t have a specific model in front of me to look at, but you can pull the compressor model from a marine AC and purchase the compressor from grainger. Nothing special here.

[sinnerman]

I would question whether the house unit would stand up to a contstant salt air environment, and not be eaten alive in a season or two.

This is what happens when people install RV units on their cabin roofs.

[Ninedotsix]

Originally Posted by s/v Jedi

I see many problems already:

- indoor units are 30+ inches wide and bulky/ugly.
- they have feedback sensors on the condensor like temperature, fan rpm etc.

I think I’ll go back to planning for ducted and wait for new products that were announced. But I see boats using these, putting the big outdoor units on deck houses etc.

I’ve worked my thinking all around the same subject, and with my background in HVACR, surprise myself that I didn’t try it already.
The reasons against in view in the thread are all valid.
I’m not sure that avoiding ductwork makes it worthwhile, but agree it’s a pain to fit in, and takes up precious space.
PO of my boat fitted a water cooled a/c, used PVC pipe for duct, and only change I made was to relocate the unit footprint, since it sat square in the middle of the port quarterberth, and was walled behind a chintzy makeshift “bulkhead”, though not structural at all.
I’m ready to replace it with a compact R-410a unit, possibly Dometic, not completely decided.
Not sure what size required for your boat, but it’s possible to put separate “heads” (evaporator units) in two or more cabins, connected to common condensing unit, in parallel, or two-circuit condenser.
I could build it, but not cost effectively.
Since you contemplated modifying a costly new mini-split with water-cooled condenser (voiding warranty btw), maybe think about a purpose built marine split, or even a chiller with chilled water fan coil units.
Alright, I’ll get this one out of my system: a distributed low-temp piping system that hugs the underside of the coachroof, and spaces above each sleeping berth. Similar to Valent brand Direct Expansion chilled tube system; the cold air flows by gravity off of the tubing, and settles over the occupants, or is redirected by small, quiet air circulators.
Got a headache, yet?
One fix we have for heat stress is to pack a bag of ice between your femoral arteries. Saves all the guess work, lol
Cheers ~ 9.6

[ThereAndBack]

Jedi, have you looked at this:
https://www.forestair.ca/en/serie-mini-anglais

The air handler side is quite compact.

[s/v Jedi]

Originally Posted by ThereAndBack

Jedi, have you looked at this:
https://www.forestair.ca/en/serie-mini-anglais

The air handler side is quite compact.

They are all the same, around 32” minimum.