Thru hull location for HVAC

Jackdaw · Mar 28, 2016

4 inches or so. There is no up-side to it being higher, and it only makes more of a splashing noise in your slip when running.

kloudie1 · Mar 28, 2016

I agree.. just high enough that you can see the stream and hear it.. Since it is a closed system back to the inlet thru-hull, no loops or stuff like that is necessary.. I installed mine with the boat in the water and did my measurements carefully so that when I drilled the hole, no water came in.! Still it puckered me up a bit to do that!

Gunni · Mar 29, 2016

FYI, the ABYC specification for a seawater HVAC is that plumbing drains back from the discharge to the intake. Not sure why, but I assume it is to keep the circulation pump primed.

jlp0217 · Mar 29, 2016

Gunni said:
FYI, the ABYC specification for a seawater HVAC is that plumbing drains back from the discharge to the intake. Not sure why, but I assume it is to keep the circulation pump primed.

I hope somebody pipes in with an explanation because my first thought on that is that they require a single through hull with a T with both intake and discharge connected. But that's just stupid, Flow will just be through the loop, heating or cooling the water in the hose, but never replacing it with new sea water. So my second thought is when the pump shuts off, water should flow backwards through the input when the system drains, not forward through the discharge. But that either requires a centrifugal pump, or a bypass circuit, since most pumps contain check valves in their design.

justsomeguy · Mar 29, 2016

Ken_Smith343 said:
What sealant is recommended for this thru hull fitting above the waterline?

I recommend 4000 or 4200 from 3M.

BigEasy · Mar 29, 2016

Ken,
Don't know how far you have progressed so I will start at the beginning. The original owner of my boat installed a Cruisair emerald "split" system. So my system set up won't be any help to you.
I did charter a 343 many times that had the factory setup. It was a 12k btu self contained Cruisair. The water intake (bronze thru hull & ball valve), strainer , & March circulating pump are located under the aft berth just left of the plywood panel adjacent to the water heater. The circulating pump may have been mounted to the panel/divider. This location is somewhat inconvenient for opening/closing the ball valve & cleaning the strainer. A hose is routed to the self contained air conditioner that is located at the aft end of the port settee. The water discharge line is a short straight run from the unit out the side of the hull. Mount the bronze thru hull fitting above the water line, preferably on the wide green boot stripe so the discharge water doesn't discolor the white gel coat. Return air grills(2) are mounted at the port setee, one facing inboard & one facing forward. The flexible duct comes off the unit & into a plastic "T" manifold. The duct running aft goes thru the galley cabinets, under the oven, & up thru the port locker in the aft berth. The duct terminates into a round adjustable plastic vent on the aft surface of the locker. The forward duct attaches to a plenum with a horizontal teak vent mounted on the portside shelf midway along the setee. From the forward end of the plenum, another piece of ducting runs forward into the port locker where it terminates into a round plastic adjustable vent that is mounted on the forward surface of the locker. You will have to install a condensator or a self contained shower sump with pump to prevent the condensate from draining into the bilge. Beneteau urges that you use a completely separate power source for the air conditioner, so that means an additional shore power cord, another transom mounted Hubble power inlet (mounted below the existing inlet), double pole circuit breaker in the lazerette (mounted inboard of the power inlet), and finally a power panel with breakers mounted on the forward facing panel above the chart table. You can use a stock Blue Sea panel or you can have Beneteau order one from their original source. The digital control / thermostat is also mounted above the chart table. I think that just about wraps it up!!! Let me know if you have any questions or need more.

Gunni · Mar 30, 2016

jlp0217 said:
I hope somebody pipes in with an explanation because my first thought on that is that they require a single through hull with a T with both intake and discharge connected. But that's just stupid, Flow will just be through the loop, heating or cooling the water in the hose, but never replacing it with new sea water. So my second thought is when the pump shuts off, water should flow backwards through the input when the system drains, not forward through the discharge. But that either requires a centrifugal pump, or a bypass circuit, since most pumps contain check valves in their design.

Intake is on the ship's bottom, up through a sea water strainer, into a water-proof mag-drive centrifugal pump like this, up the the HVAC unit, up to loop above max level of heel and out the ship. And yes it all drains back when the pump shuts down.

ddrewry · Jun 20, 2017

I'm currently installing a 16K unit. To my surprise, all of the A/C manufacturers say to avoid a loop in the discharge line. The intake should rise gradually through the pump and then to the A/C unit, and the discharge should either continue to rise or discharge horizontally. Of course with shut off and strainer installed before the pump. All that said, I did install a loop above the highest heel point in the discharge line when I installed A/C in my Beneteau a few years ago. There are only two times in several years where I had to manually prime the pump even though it is mounted below the floor boards and the waterline. Looking at the mfg recommended install today could explain this as there may be enough suction from the lines draining when the system shuts down to pull an air bubble down toward the pump rather than what I would expect - a clean, water drains overboard from the top of the loop and allows the remaining water to flow backwards down the loop to the unit/pump... maybe...
Its always puzzled me both times the forward A/C lost its prime...

kloudie1 · Jun 20, 2017

Loops are typically there to prevent water from syphoning into the boat.. or engine.. no such problem with AC water since it goes overboard or back through the pump.. if the condenser is below water level and pump is as well, everything stays primed.. The only times I've had to get air out is after being on the hard or cleaning the strainer.

Gunni · Jun 20, 2017

I had problems with prime until I had the system inspected and changed by an competent tech. He handed me the ABYC specification. From thru-hull to the pump all fittings BWL. From there everything slopes upward to the A/C and through hull. I too have a discharge loop, just cause I'm old school.

Jackdaw · Jun 20, 2017

If the intake seacock is left open when sailing, heeling can burp the intake and it will lose its prime.

Mechone · Jun 20, 2017

While your at it you might want to add a venturi injector and suck the condensate. Beneteau's because of there design ( closed matrix)it's not good to dump in the bilge.
I'm just installing one.

Gunni · Jun 20, 2017

Jackdaw said:
If the intake seacock is left open when sailing, heeling can burp the intake and it will lose its prime.

...and it will refill when she is back on her lines because everything from the pump back to the intake is below the waterline.

justsomeguy · Jun 20, 2017

Mechone said:
While your at it you might want to add a venturi injector and suck the condensate. Beneteau's because of there design ( closed matrix)it's not good to dump in the bilge.
I'm just installing one.

Thinking of doing the same on my IP's Mermaid condensate pan. What kind of $ does Bene get for their venturi unit?

Mechone · Jun 20, 2017

I think the Bene one Mermaid condensate is 200.00 us .The one above is 20 bucks or less on ebay or amazon. This a copy of a Mezzei injector which a lot of people have installed on boat A/C. There is a built in check valve that won't allow water back into condensate pan

justsomeguy · Jun 20, 2017

Mechone said:
The one above is 20 bucks or less on ebay or amazon.

Yah, after a bit of research, just make your own.

Jackdaw · Jun 21, 2017

justsomeguy said:
You forgot to check for flow? Twice??

Not me.