Best way to Winterize marine Air conditioners

All agreed, but while Mysteri mentioned 5 units running on one pump, he also spoke of a "front drain", in his OP.
This makes me think that those 5 units are spread somewhere around the boat, rather than all in the same location.
So, assuming for instance that 3 chillers are astern (together with the raw water pump) and 2 at the bow, by the time the AF flows out of the front drain, he could have already wasted a lot of it from the drain of the stern units, which are obviously reached faster.
This was the reasoning behind my previous suggestion to close the valve (if present) on the first outlet which starts spitting AF, and then go on with the rest.

The marina guys here all all about efficiency & have a contraption that is like a suction cup and a hand pump.
After the boat is blocked.
They put the A/C raw water pump suction hose into a bucket of anti freeze, duct tape over the discharge ports on the outside of the hull, put the suction cup over one hole at a time and draw the antifreeze through the system at one hull through hull at a time. Un-taping the hole in use of course and re taping each hole as they go.

I never really scrutinized the contraption up close though as I never needed it.

In theory it could be a 1 man job if the bucket were big enough.

It is possible that their contraption is home made.

Interesting, but are you sure?
I never came across any AC system working without a refrigerant GAS, on top of the refrigerant LIQUID.
Mind, the latter in some systems is confusingly labelled in the same way as the gas, but the gas is self-contained inside each chiller unit, and it's not supposed to be handled by the boat operator.

There are actually AC systems that only have sea water and refrigerant GAS, like the so-called "turbo" series from Dometic, but they are fully self-contained machines, meant to directly blow cold air, with no air handlers. These are the exceptions I mentioned in my post #15, which I've only seen in small boats, with just one or two areas to be cooled (typically, saloon+one cabin).

That's because there isn't a valve attached on the internal side of those discharge ports, I suppose.
Out of curiosity, is it so rare in the US to have shutting valves also on ports above the w/line?
I appreciate that they are not as essential as in fully submerged seacocks, but it's still good practice to have them, just in case.

I'm reasonably sure. Our systems are self-contained Dometic Turbo reverse cycle units, gives AC and/or heat depending on system and thermostat setting, each has its own has onboard blower.

I've assumed OP's systems are all self-contained units, too, partly since they're about as common as dirt.

-Chris

Fair enough, that's exactly the exception I previously mentioned, where indeed you don't have any fresh water circulating inside the air handlers, since, well, technically you don't actually have any air handler, but "only" grilles blowing out cold/warm air!

When I hear of more than 2 units, I tend to think of systems with chiller(s) separate from air handlers, which is what I've usually found on boats above 45 feet or thereabout.

Mapism. Most cooling units in the USA on boats of the size we have been discussing are self-contained reverse/cycle units which only require an open salt water circuit to operate. You may be familiar with different units.

The stand alone units generally used here can have their own salt water pump for circulation of salt water or can use one pump for multiple units. The OP apparently has 5 reverse cycle units serviced by one pump. The units are probably spread around the boat (salon, bedrooms, bridge,etc). For instance my units are located in the front berth, the master berth and beneath the salon. Each is suitably ducted to at least 2 locations per unit to distribute the cold/heated air generated at the unit. The discharge line will probably not have interior shut offs at the thru hull because they are probably 6 - 12" above the waterline.

Why don't you ask the yard to do it this year. Watch how they do it, then you're all set for the future years? Cracked hardware is not cheap.

Thanks Beau for enlightening me. Every day is a school day, as they say.
I can't remember to have ever seen boats built by any European yard, above 50 feet or so, whose AC system was based on self-contained units.
Doesn't the compressor noise bother you, particularly in the cabins while sleeping?
In my own boat (a 56 footer, so not exactly a superyacht!), the two chiller-only units with their compressors are in a lazarette astern of the engine room, and anywhere inside the boat you are unable to tell whether they are running or not!

On the other hand, with regard to shut off valves on any discharge lines above the waterline, yes, I'm aware that not all builders fit them - but some indeed do.
So, I thought to mention them because, if existing, they could be useful in this case.

Dunno if called "air handlers" or not, but there's a built in 6-speed blower on each unit pushing hot/cold air through all the ducting.

Our set-up is one unit in the saloon for saloon (lots of windows)and one unit under the master berth for master and guest stateroom, head, and galley.

In another post you asked about noise; yes, we can hear the compressors when they kick on. Not particularly overbearing. The Turbo units can have an optional sound shield installed, and I may look in to that sometime... But it happens our Turbos are very new to us, only installed this season, and they're quieter than the previous Marine Airrrr Vector Compact units.

-Chris

I think it doesn't matter which AC unit you turn on... I think any of the 5 will cause the pump to come on, and then the pump will be servicing all routes at the same time. You can test to confirm that...

-Chris

They don't, in your self-contained equipment.
Actually, since I'm not English mother tongue, this thread made me wondering if I was using the correct terminology, so I made a quick search, with the results below.
And definitions aside, the drawings should also clarify the misunderstanding ref. the number of water circuits.
In fact, it's easy to see that self-contained systems, which as I understand is what most of you folks had in mind, only need sea water for cooling the condenser inside each self-contained unit.
On the other hand, the second diagram clarifies that in systems with separate chillers there is also a closed circuit, with its own pump, that circulates cold or warm fresh water, that flows inside the air handlers, which eventually cool/warm up all the areas where they are placed.


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It's really quite easy, any AC unit will get the water pump running. Just need a bucket and for your boat maybe two or three gallons of antifreeze and it will come out all AC thru-hulls. I have two 16000 BTU compressors only in the engine room double stacked to which one has one big air handler on it and the other unit has three air handler on it. No water goes to the air handlers. Only to the compressor loop around the compressor and back out to cool things down. Or make heat in reverse cycle. Our units are not self contained.

You probably have five AC units in your engine room stacked and side by side to which your one water pump feeds all five. Not sure why you have so many discharge thru-hulls. I would think it's just one big one. But you said it's not. I guess you have a thru-hull for each compressor.. Anyway you have a big AC pump moving a lot of water, it takes a lot of water pressure to feed five units with one pump. Hence it take a lot of antifreeze pressure to feed five units....

Yep. The top diagram illustrates our system well, aside from actual placement and discharge routing. OP's Carver setup is likely similar, although with 5x compressors instead of 2x.

Normal ops, raw water enters pump and then routes to all compressors and then overboard. Winterizing, antifreeze goes to pump and then routes to all compressors and then overboard. In ours, any one compressor will activate the pump, and fluid routes to/thru all compressors, then overboard. Likely the same in OP's Carver.

-Chris

I have a carver 396 with 3 ac units (reverse cycle). We struggled to find a good way to winterize ac units also. Just some background on this unit. We have a single water pump that supplies sea water to a water manifold that in turn ,sends water to all 3 units at the same time. So when trying to winterize these units using the pump to push antifreeze thru the lines. The antifreeze or any liquid would follow the path of least resistance. So it would winterize the shortest water line run very well ,but would not make it to the others. So the first year we had it ,we disconnected each line and pushed antifreeze thru them 1 at a time with a small pump. Year 2,I put 3 shut off valves at the water manifold. Now we use the ac water pump and just open 1 valve at a time to flush with antifreeze.