Air conditioner pump struggles

[Cartouche]

When the water is flowing, the two air conditioner units work great and keep the boat comfortable whether heating or cooling. Getting the water flowing in the forward unit after being out of the water (for the winter here in Lake Erie) has always been a struggle. This is the first Spring I've struggled to get the salon unit flowing. Both pumps are below the water line, so it's not a priming problem. The valves are open and strainers are clean, so it's not a suction head problem. It really has the feel of an air lock problem or some other blockage in the condenser itself or maybe the piping along the way.

The air conditioner water flow I see on most boats leaves with authority; not quite garden hose flow, but way more than a lazy gurgle. Both air conditioner pumps aboard our boat produce a lazy gurgle. The through hull returns are near the waterline and large at maybe ½", so it could be the same flow I see on most other boats but running through a larger fitting makes it look slower. Again, when the pumps are moving water, neither unit ever fails to maintain its thermostat setting.

Here's my question. Starting and stopping each system a few times hoping to get lucky gets less attractive with every passing year. We have a Barnacle Buster set up, but here in freshwater I have not used it yet. That may be next, but it seems like some apparatus to force water through the system would speed the process. What do you guys do to get the pumps primed and units flowing?

On My 390 I could pour anti freeze in fall and water in spring from outlet and it would charge the system when on land with the seacock closed, it was full when liquid came out of the Salon Unit discharge, as it was lower than the forward cabin unit

 

[jfolding]

When the water is flowing, the two air conditioner units work great and keep the boat comfortable whether heating or cooling. Getting the water flowing in the forward unit after being out of the water (for the winter here in Lake Erie) has always been a struggle. This is the first Spring I've struggled to get the salon unit flowing. Both pumps are below the water line, so it's not a priming problem. The valves are open and strainers are clean, so it's not a suction head problem. It really has the feel of an air lock problem or some other blockage in the condenser itself or maybe the piping along the way.

The air conditioner water flow I see on most boats leaves with authority; not quite garden hose flow, but way more than a lazy gurgle. Both air conditioner pumps aboard our boat produce a lazy gurgle. The through hull returns are near the waterline and large at maybe ½", so it could be the same flow I see on most other boats but running through a larger fitting makes it look slower. Again, when the pumps are moving water, neither unit ever fails to maintain its thermostat setting.

Here's my question. Starting and stopping each system a few times hoping to get lucky gets less attractive with every passing year. We have a Barnacle Buster set up, but here in freshwater I have not used it yet. That may be next, but it seems like some apparatus to force water through the system would speed the process. What do you guys do to get the pumps primed and units flowing?

On my MS Pilot 34 I have a Marinaire. I have a hose with a ball valve and a female hose end connected to the input water. When needed I can attach a water hose to it and force feed the ac. It solves the problem. I think it’s an airlock and the pump just can’t get it going on its own.

 

[tagillette]

The fail proof solution is quite simple. Guaranteed.
Close the seecock.
Remove the cover for the grocco strainer. Install an grocco cover with a garden hose fitting.
Allow just a little water to flow out of the strainer by opening the seacock just for a second.
Attach a hose to it from the dock.
Turn the water on partially. You don’t want 65 psi going through your air conditioner heat exchanger.
When you see a good stream of water coming out the through hull opening, turn off the water.
Remove the grocco cover with the hose connector.
Install the original grocco cover. This works perfect for me. No waiting for things to “settle out”.
Defender sells a grocco cover with the hose fitting. I made my own. I use the same grocco cover for winterizing. But I use a 5 gallon pail with a ball valve and a hose fitting. By filling the 5 gallon bucket with antifreeze, you can see how much is going through the system. I use this same bucket with a hose to introduce antifreeze into the fresh water tanks for winterizing.

 

[tagillette]

Many ways I have threaded bleed screws such as found in a radiator found in old school hot water hydronic heating. Available at plumbing supply house. Place in high spot before pump. One of my thru hulls is sorta high near hard chime gotta check if we get waked

 

[lwarden]

Interesting to hear how many folks have this problem. Seems like a general flaw in the design. Is there a reason people don't use a self-priming pump for AC cooling? The only thing I can think of is the extra maintenance of changing a pump impeller every couple years, but if all the centrifugal pumps airlock then why not switch to a self-priming type?

On my boat, when we get up on a plane we get an airlock on the AC afterwards so I have to go through this priming each time we run the boat at speed, it's a pain.

 

[O C Diver]

Interesting to hear how many folks have this problem. Seems like a general flaw in the design. Is there a reason people don't use a self-priming pump for AC cooling? The only thing I can think of is the extra maintenance of changing a pump impeller every couple years, but if all the centrifugal pumps airlock then why not switch to a self-priming type?

On my boat, when we get up on a plane we get an airlock on the AC afterwards so I have to go through this priming each time we run the boat at speed, it's a pain.

Most self priming pumps have valves. Most require a diaphragm or piston to work, versus a non contacting impeller. This generally requires significantly higher HP (electrical consumption) for the same volume flow. Centrifugal pumps are miserly in power consumption for their volume of flow.

Ted