I noticed yesterday afternoon that the water flow from the aft stateroom air conditioning outflow was not flowing as it should. The cabin was comfortable but something wasn't right, the air wasn't as cold as it should be. There is dredging going on in the marina and that seemed to be a likely issue. I put it on my list to take a look at it Saturday morning. But as luck would have it, the flow was down considerably by 5 o'clock.
I got my tools together and proceeded to trouble shoot. The water coming from the outfall thru hull was abnormally warm indicating a water flow issue, not a refrigerant issue.
Now to get to the water intake thru hull required moving the mattress from the aft bunk and removing an access panel below it. The thru hull and water pump are located beneath this in the lowest part of the boat. It also requires being quite careful as the autopilot mechanical connections, trim tab hydraulics and the 300 gallon water tank connections are in the same place. And yes, I did get dirt on the sheets but they needed washing anyway.
After maneuvering into this tiny place, I proceeded to remove the hose from the intake thru hull. No water flow. I proceeded to dislodge whatever was blocking the opening using the dockside water hose pressed against the fitting. Next checking the strainer, I found lots of grass and mud. Not good! Finally, I used the dockside water hose to flush the system clean of residual sediment. End result, proper water flow and heat exchange.
Marine air conditioning systems operate similar to a typical heat pump with one exception. The heat exchange is by water rather than air. Refrigerant is pumped by a compressor through coils where the heat blown across the coils by a fan is removed from the air, resulting in cold air pumped into your boat. Water passing the coils removes the heat from the refrigerant and is discharged overboard. The number 1 cause of marine air conditioning problems is water flow, probably 98% of the time. Here's what you need to know to resolve most marine air issues.
- Make a point of knowing the proper water flow from your air conditioning outfalls so you can detect any problems before they shut you down when you least expect it.
- Always assume the problem is water flow unless you know for a fact that the water flow is adequate. If you find ice on the coils, you have a refrigerant leak, call a technician.
- Feel the water from the outfall. It should be slightly warm. Hot water signals some blockage somewhere in the system.
- Check the intake thru hull first and clear blockage by using high pressure water.
- Next, be sure the strainers are clean. Remember, as a liveaboard you will be using your equipment approximately 720 hours a month versus about 192 hours for someone that uses their boat 4 weekends a month. I check mine every 4 weeks based upon past experince. The dredging obviously has decreased that for the time being. You may find you need to check yours more often or less dependng on the water quality your boat is in.
- Lastly, flush the entire system by using the dock water hose opened all the way, inserted into the hose that you detached from the intake thru hull. Have someone watch the water flow on the side of the boat and tell you when it runs clear. This may seem unnecessary but what happens is that sediment settles in the lines over time, preventing proper heat transfer. Flushing will dramatically improve the performance.
- Lastly, drop about two Bromine tablets into the strainer basket before sealing everything up. Barnacles and other clinging critters can not survive in this water.
If a man must be obsessed by something, a boat is as good as anything, perhaps better than most E.B. White
In addition, check the hoses. I did and found a surprise.
The salon hose was the worst. Picture a doughnut for illustration purposes. The inside diameter of the hose is the diameter of the doughnut. The grass growing inside the hose reduced the opening to the size of the doughnut hole, roughly 1/2 the original opening. The hoses on the upstream side of the pump were clear.
As the hose was on the suction side of the pump, I needed reinforced hose for a replacement. A quick trip to West Marine and about 1/2 hour later brought water flow that was incredible. The air conditioning was cooling now much better than before.
So, be sure to visually check your intake hoses for partial blockage if you suspect a water flow issue. Purging with the water hose will not remove the grass that may be there.
