Air Conditioner Magnetic Pump Priming

[BillZe]

I am having an issue when I clean out my air conditioning strainer. I fill the strainer and use a hose on a tee to push water through. I also have the sea cock open at this point. When I close the tee the water stops flowing. Last time it burnt out my pump and I had to replace it (3rd one in 3 years). This time there is water intermittently coming out but not steady. It keeps trying and my compressors are off because the safety is tripping. The water is still coming out intermittently but not constantly. Any advice?

 

[caltexflanc]

A picture of the strainer setup would help but it sounds like you have an airlock upstream from the pump. Also you should have a relay that shuts the pump off when the system is shut down.

 

[BillZe]

A picture of the strainer setup would help but it sounds like you have an airlock upstream from the pump. Also you should have a relay that shuts the pump off when the system is shut down.

How do I remove that airlock? The pump is shut off on a panel when i shut the system down. It’s after the restart I am having the issue.

 

[caltexflanc]

First thing to do is make sure the hose from the pump to the compressor(s) is one smooth up hill climb with no dips. That is inevitably the reason for chronic air locks. Clearing the air lock is simple. Close the seacock. Gradually remove the hose from the outlet of the pump. If airlocked, you will typically hear the air oozing out. Sometimes you don't have to take the hose all the way off; just working it off the pump outlet will let the air out. Then water will come down hill to the pump and you put the hose back on all the way.

I'm really curious what your strainer setup looks like; does it not have a removable strainer basket?

 

[BillZe]

First thing to do is make sure the hose from the pump to the compressor(s) is one smooth up hill climb with no dips. That is inevitably the reason for chronic air locks. Clearing the air lock is simple. Close the seacock. Gradually remove the hose from the outlet of the pump. If airlocked, you will typically hear the air oozing out. Sometimes you don't have to take the hose all the way off; just working it off the pump outlet will let the air out. Then water will come down hill to the pump and you put the hose back on all the way.

I'm really curious what your strainer setup looks like; does it not have a removable strainer basket?

I do have a strainer and removable basket. I put bromine tablets in for the first time today. Attached are pictures of the set up. It is a slight rise to the pump. I have tried a bunch of things but not have a continuous but weak stream that gets stronger from time to time.

 

[BillZe]

i do have a strainer and removable basket. I put bromine tablets in for the first time today. Attached are pictures of the set up. It is a slight rise to the pump. I have tried a bunch of things but not have a continuous but weak stream that gets stronger from time to time.View attachment 104543

 

[O C Diver]

If easily accessible, take a dock hose and put it up against the discharge port for maybe 30 seconds. The dock water should push the air backwards through the system and out through the seacock.

Ted

 

[HiDHo]

I would start at the sea cock. Take the pump suction hose off and open the sea cock to check for flow. If flow is good change out the braided vinyl suction hoses for Trident green stripe wire inserted suction hoses or hose with a spiral wire in it designed not to collapse. Then check the suction hose at the pump inlet for good flow. The pump most have a positive head of water flow to work. It is not designed to draw water into its impeller.

 

[Solly]

I would think 3 pumps in 3 years you have a design problem. Probably the pump isn't getting enough water. With the strainer basket lid off slowly open the seacock so it fills up. Make sure the water is getting from there to the pump. The pump should be 'downhill' from the strainer so the water flows to the pump. It won't suck the water as others have said. There needs to be a solid source of water to the pump.
On mine after lay up I have to do it this way to get water to the pump the first time. After that it's fine.

 

[mvweebles]

Looks like there are two small plastic strainers in the first picture. At some point OP might consider replacing these with a single larger bronze strainer (see attached pic courtesy of Steve D'Antonio). Will cost a few bucks but it should allow the A/C pumps to last much longer. Also much easier to service and less likely to clog-up.

Good luck!

Peter
(also in St Pete - boat is in MX)

 

[mvweebles]

I would think 3 pumps in 3 years you have a design problem. Probably the pump isn't getting enough water. With the strainer basket lid off slowly open the seacock so it fills up. Make sure the water is getting from there to the pump. The pump should be 'downhill' from the strainer so the water flows to the pump. It won't suck the water as others have said. There needs to be a solid source of water to the pump.
On mine after lay up I have to do it this way to get water to the pump the first time. After that it's fine.

I would think that as long as the pump is well below waterline and the supply hose is fair and clear it would not make a difference if the pump is above or below the strainer. While I agree lower is better, getting below the sea strainer isn't practical on most installations.

It's conversations like this that make me lust after the sea-chests installed on Defever's.....heart-be-still!

Peter

 

[OldDan1943]

Looks like there are two small plastic strainers in the first picture. At some point OP might consider replacing these with a single larger bronze strainer (see attached pic courtesy of Steve D'Antonio). Will cost a few bucks but it should allow the A/C pumps to last much longer. Also much easier to service and less likely to clog-up.

Good luck!

Peter
(also in St Pete - boat is in MX)

View attachment 104554

Nice lay out. I suspect Bill could learn from yours. Where possible, a bronze run if far better. Trying to replace or modify the 'run', use 45s instead of 90s.

 

[foggysail]

I would think that as long as the pump is well below waterline and the supply hose is fair and clear it would not make a difference if the pump is above or below the strainer. While I agree lower is better, getting below the sea strainer isn't practical on most installations.

It's conversations like this that make me lust after the sea-chests installed on Defever's.....heart-be-still!

Peter

That is my thought also. And those pumps are not self priming at least those I am familiar with. The pump must be below the waterline to work properly.

 

[FF]

IS the pump mounted below the water line?

If not lower it, hose is cheap.

 

[Solly]

I would think that as long as the pump is well below waterline and the supply hose is fair and clear it would not make a difference if the pump is above or below the strainer. While I agree lower is better, getting below the sea strainer isn't practical on most installations.

It's conversations like this that make me lust after the sea-chests installed on Defever's.....heart-be-still!

Peter

I was thinking more of an air lock in the strainer not allowing full flow to the pump. Still it's easy to check and try. Filling my strainer to the top with water using the seacock, and making sure water is flowing to the pump, then screwing the top on, seems to work on my system.

 

[BillZe]

If easily accessible, take a dock hose and put it up against the discharge port for maybe 30 seconds. The dock water should push the air backwards through the system and out through the seacock.

Ted

Thank you!

 

[BillZe]

IS the pump mounted below the water line?

If not lower it, hose is cheap.

Yes, it is below waterline

 

[BillZe]

Looks like there are two small plastic strainers in the first picture. At some point OP might consider replacing these with a single larger bronze strainer (see attached pic courtesy of Steve D'Antonio). Will cost a few bucks but it should allow the A/C pumps to last much longer. Also much easier to service and less likely to clog-up.



Good luck!



Peter

(also in St Pete - boat is in MX)



View attachment 104554

That is a great setup! I will look into that.

 

[caltexflanc]

I've been to this movie a few times, on mine and other boats. The key is the hose from the pump to the compressor assembly. If that is not a continuous up hill climb with the pump at the bottom of the hill, you will get airlock issues. You can either correct them as they happen as I described, or you can fix the root cause. On the suction side, I'd rather have a straight shot from the strainer to the pump intake, but as long as both are under the water line, probably not a big deal. You do want to make sure the strainer has a fresh gasket and the top seals to prevent air intrusion there; you will see bubbles in there when the pump is running. Personally I'd get rid of that flushing system, it only adds complications IMO.

 

[Comodave]

Actually you want a continuous rise from the strainer to the pump so that air will not be trapped before the pump. That can prevent the pump from priming. After the pump it doesn’t really matter if there are dips in the hose because the water will be under pressure from the pump. The key is from the strainer to the pump. The pump does need to be below the waterline.

 

[Comodave]

This is from Mermaid Air Conditioning installation manual. Note that it refers to an incline from the strainer to the pump.

Water will flow from the sea cock through the strainer into the inlet of the pump. Ide- ally, the strainer and pump will be mounted so the water flow is at a slight upward grade to help eliminate air locks. Once you have settled on the mounting locations of the strainer and pump, attach each of their mounting brackets with (2) 1/2 inch s/s pan head screws. Note that the strainer is directional. Take notice of the stamped arrow on the top of the strainer when installing and insure the arrow is pointed toward the flow of water to the air conditioner unit

 

[Pmcsurf1]

Check raw water intake/clamshell. Clogged with plastic bag is my bet.
Had same problem on my boat. After buying new pump and still poor flow I drove under and pulled saran wrap out of clamshell.

I am having an issue when I clean out my air conditioning strainer. I fill the strainer and use a hose on a tee to push water through. I also have the sea cock open at this point. When I close the tee the water stops flowing. Last time it burnt out my pump and I had to replace it (3rd one in 3 years). This time there is water intermittently coming out but not steady. It keeps trying and my compressors are off because the safety is tripping. The water is still coming out intermittently but not constantly. Any advice?

 

[BillZe]

I have a diver coming this week. Hopefully that is exactly what the issue is...

 

[caltexflanc]

Actually you want a continuous rise from the strainer to the pump so that air will not be trapped before the pump. That can prevent the pump from priming. After the pump it doesn’t really matter if there are dips in the hose because the water will be under pressure from the pump. The key is from the strainer to the pump. The pump does need to be below the waterline.

That is not entirely true, the upstream airlocks are formed when the pump is off. Really, I have witnessed and dealt with this first hand.

 

[LongJohn]

I had air lock problems every time that I cleaned the strainer, no matter how careful I was about filling the strainer before closing it back up. I teed into the system between the strainer and the pump with a hose from the raw water pump discharge. A burst of pressure will typically clear the airlock, as well as the clearing the thru hull of any obstruction.

 

[HiDHo]

BillZe, I took some photos of my heat pump circulating water system, I have never had air locks or pump problems. The pump is a March model AC 5-C MD with a Groco strainer. This pump service two 16,000 heat and a/c units.
What did the diver find ?

 

[Swfla]

Make sure all the hose is clear of buildup. Is this original system? Did it work fine for many years and then start giving you trouble in recent years? Being in FL, barnacle buildup in the hose is a real possibility. A piece of rebar, cut cleanly makes a great scraper. It may be simpler to replace the hose instead of cleaning it out. This way you're certain it's clear.

 

[Exsailor2018]

I put a T in the line just before the pump with on off valve just below it and a long clear hose that I could lead to a bucket. After cleaning the strainer and putting a new 3/4 inch copper T loose into the strainer I would start the pump and open my bleed line till solid water came lout. Never had another problem with air.