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Post by rapide on Oct 29, 2013 1:24:50 GMT
We have a new 379, our first large boat. We completed an offshore race and once docked, we found the air conditioner would not work. We were told the problem was due to an airlock in the seawater circulation system and that we either needed to ensure the seacock was closed while sailing or have a bleed valve installed to get rid of the air in the seawater system. If this is to be a reoccurring problem, why wasn't a bleed valve installed to begin with? Have any of you had this problem? Did you have a bleed valve installed? Thanks
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Post by adoyabn on Oct 29, 2013 2:21:02 GMT
An airlock on Marine AC's is pretty commonplace after an underway. I installed the AC on my SO43 myself. In my case the AC through hull, strainer, and pump inlet are roughly on the same level and well below the water line. Instead of a bleed valve, I crack the strainer with the seacock on to bleed air.
If your strainer and pump intake line are roughly at the same level and relatively close together you should be able to do the same. |
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Post by Don Reaves on Oct 29, 2013 9:39:37 GMT
I always close the seacock on my A/C unit while I'm away from dock. Well, almost always. The few times I've forgotten, I experienced the same problem. But it always clears itself after a couple of hours.
In fact, our habit is to keep the seacock closed any time the A/C will not be used. The valve is open only when the main breaker for the unit is on.
Don
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Post by rapide on Oct 29, 2013 13:00:33 GMT
Thanks for the quick response. We are on the Gulf Coast so at least the dehumidifier is always on when docked. Guess the seacock will get a lot of use.
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Post by adoyabn on Oct 31, 2013 4:06:24 GMT
Every marine AC saltwater pump that I have seen is centrifugal which means it is not self priming. If you happen to introduce air into the intake side, you will lose suction and the pump will stop working. The pump will not work again until the great majority of the air is bled out. I'm sorry, if you truly do have an air bound centrifugal water pump, waiting a couple of hours won't solve the problem.
First good indicator that you have a problem, is no discharge. First check the strainer and make sure you haven't sucked something up. If the strainer is clear and you don't a have a bleed valve, with the intake sea cock on, crack the strainer or temporarily disconnect the hose on the intake side of your pump. If you do have air in the intake side you should hear a slight hissing sound with the strainer cracked and then some water dribbling out. If you have to temporarily disconnect the intake side of the pump, with the sea cock on loosen the clamps and pull off the hose and put it back on. You should see a fairly healthy stream of water coming out of the intake hose. If you don't, see good flow this means you have a clog somewhere in the intake side down to the thru hull.
Unfortunately, marine AC's are not an install and forget system. It's always a good idea to periodically take a look at the discharge. |
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Post by Don Reaves on Oct 31, 2013 10:06:05 GMT
The one or two hour wait works for me because the strainer and pump are below the water line. So when I open the seacock, the system will eventually fill up the pump, purging the air.
Don
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Post by adoyabn on Oct 31, 2013 10:26:43 GMT
Don, One plausible explanation is that you may have a small leak somewhere in your lines below waterline near your pump. Air slowly escaping out of a small leak would account for a two hour wait. Either that or you have successfully altered the laws of physics with a two hour wait  ! John |
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Post by Don Reaves on Nov 1, 2013 11:19:35 GMT
It's true that an air leak would assist the purging. But I've never seen any sign of water in the area.
I suspect the true reason is that the plumbing has a nice gentle uphill climb from the seacock to the A/C unit. There's no reason for air to remain in the pump if water is trying to get in. Once enough water gets to the pump, it will work.
Or maybe I'm just lucky.
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Post by adoyabn on Nov 1, 2013 22:49:51 GMT
Don,
The most important thing is that you don't have a leak below the waterline. I hope I didn't offend you with my attemp at humor. Your crew is certainly more understanding than mine. If I told my wife she had wait two hours for air contioning and did nothing......
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Post by Don Reaves on Nov 2, 2013 1:21:20 GMT
No, I wasn't offended. (I even have a graduate degree in Physics, and I let that go too...)
As it turns out, my wife is quite dependent on the A/C, which is one reason why I am very diligent about closing the seacock except when we need it to be open.
Alas, it's getting quite cold here on the great lakes. I can only hope for weather when the A/C is needed again.
Don
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!