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Air in aircon seawater system

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kipwrite View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kipwrite Quote  Post ReplyReply Direct Link To This Post Posted: 05 August 2022 at 13:37
Thanks! That's a worthwhile improvement. On the list.  
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SimonGH View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SimonGH Quote  Post ReplyReply Direct Link To This Post Posted: 10 August 2022 at 14:55
Originally posted by SVZara SVZara wrote:

I must be lucky.  I have NEVER closed my A/C seawater intake.  The system stays primed and ready and runs without issue even after sailing 100s of miles while offshore.  I am surprised this an issue for you guys.


I think it depends on where the intake is on your particular boat.  My prior boat didn't have this issue because i put the intake on the centerline and near the engine, so it would be underwater in almost all conditions.  Another big contributor was the fact that the outlets of the AC cooling water on that boat were above the waterline, so it naturally self "primed".

My 415 has the intake far enough off the centerline so when you heel over about 10 degrees the water drains out.  I think more importantly, the outlets of the cooling water on this boat are below the waterline, so there is "backpressure" that prevents self priming.  The air gets trapped in the pump until you vent it somehow.

I love the idea of a tube and valve.  very clever.

I will say that I'll deal with this hassle over having the cooling water vent above the waterline.  That resulted in slime on the hull and that constant noise of flowing water...

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Post Options Post Options   Thanks (0) Thanks(0)   Quote SimonGH Quote  Post ReplyReply Direct Link To This Post Posted: 10 August 2022 at 15:00
Originally posted by Arcadia Arcadia wrote:

Bleeding air at the pump is the best way since that is where the water is being pushed from. I replaced the small nylon NPS stopper with a same size barb fitting. I then added a 2 foot length of 3/8 clear tubing with a small shut off valve at the end. This makes it a lot simpler to bleed. I fish out the tube, raise it above the waterline and open the valve. The air is quickly forced out by the incoming sea water, but the water will not come up past the height of the hose. I then close the valve and drop the tube back down. This is all done without turning on the pump or messing with the thru hull or strainer. 30 seconds, no tools ! 



One little comment - you've now made this little tube part of "below the waterline" plumbing.  If it fails for some reason and you're not there, it will eventually cause a real issue if your bilge pump dies or can't keep up with the flow.

I love this idea, my only modification would be to put the shutoff valve on the pump side, then a barb with the hose.  Raise the hose up and open the valve near the pump.  Same result, but you're no longer relying on that clear tube to stop your boat from sinking...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Arcadia Quote  Post ReplyReply Direct Link To This Post Posted: 11 August 2022 at 13:07
Yes Simon that would be better, but unless we close all 20 of our seacocks, then we will have plenty of plastic hose below the waterline all over the boat! And, if closing all seacocks is something you choose to do, then closing the Aircon seacock will suffice to protect the bleeder hose. Besides, it may be tricky to mount a valve directly on the pump body. Let me know if you manage it. Thanks.
Leon / ARCADIA
2018 Hanse 588
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SimonGH Quote  Post ReplyReply Direct Link To This Post Posted: 11 August 2022 at 15:16
Originally posted by Arcadia Arcadia wrote:

Yes Simon that would be better, but unless we close all 20 of our seacocks, then we will have plenty of plastic hose below the waterline all over the boat! And, if closing all seacocks is something you choose to do, then closing the Aircon seacock will suffice to protect the bleeder hose. Besides, it may be tricky to mount a valve directly on the pump body. Let me know if you manage it. Thanks.


Yes, I always smirk at the guidance that says "close all seacocks when you leave the boat".  I'd be there for ages...

What size thread was the NPS to barb fitting?  My pump is some italian thing, so i'm not sure what size the plug threads are - they look metric to me.

ABYC has standards for below the waterline hose, as well as things like double hose clamps etc.  Hopefully the stuff keeping water out of the boat meets those requirements.  I've been generally comfortable with the build quality of my 415 and everything I can see seems to be done properly (more so than my 2019 Beneteau!)

This isn't cheap, but adheres to the below waterline standards (although the pic only has one clamp per connection, which i would double):

They sell it to vent air from the jet thruster pump, but no reason it couldn't be adapted for the AC pump.  Interesting to note that they want you to vent it overboard...



Edited by SimonGH - 11 August 2022 at 15:17
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SVZara Quote  Post ReplyReply Direct Link To This Post Posted: 12 August 2022 at 16:25
Originally posted by SimonGH SimonGH wrote:

Originally posted by SVZara SVZara wrote:

I must be lucky.  I have NEVER closed my A/C seawater intake.  The system stays primed and ready and runs without issue even after sailing 100s of miles while offshore.  I am surprised this an issue for you guys.


I think it depends on where the intake is on your particular boat.  My prior boat didn't have this issue because i put the intake on the centerline and near the engine, so it would be underwater in almost all conditions.  Another big contributor was the fact that the outlets of the AC cooling water on that boat were above the waterline, so it naturally self "primed".

My 415 has the intake far enough off the centerline so when you heel over about 10 degrees the water drains out.  I think more importantly, the outlets of the cooling water on this boat are below the waterline, so there is "backpressure" that prevents self priming.  The air gets trapped in the pump until you vent it somehow.

I love the idea of a tube and valve.  very clever.

I will say that I'll deal with this hassle over having the cooling water vent above the waterline.  That resulted in slime on the hull and that constant noise of flowing water...


Yes, my thruhull is dead center in front of the engine.  I thought all 505 and 508 had the AC raw water input in the same location.  Interesting.
Marc
S/V Zara
2016 Hanse 505, Hull #129
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SVZara Quote  Post ReplyReply Direct Link To This Post Posted: 17 August 2022 at 18:48
While we are on this topic.  Where can I get new screen for the raw water strainer for the A/C unit?
Marc
S/V Zara
2016 Hanse 505, Hull #129
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Johny Quote  Post ReplyReply Direct Link To This Post Posted: 18 August 2022 at 09:35
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kipwrite Quote  Post ReplyReply Direct Link To This Post Posted: 20 November 2022 at 21:33
The fitting on the AC pump is 1/4" NPT. 
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