Marine Air Conditioning System Maintenance


November 5, 2010 Facebook Twitter LinkedIn Google+ About,AC/Systems,Cruisair,Maintence Tips,Marine AC,Marine Air





Greetings All,

Let's start with the basics...

Seawater flow thru your A/C system is primary...

Without water flow....You have NO cooling !

Service people on the docks (at least the better ones) can walk down the dock during the summer and tell which boats they are likely to be getting a call from next just by the flow of water (or lack of) going overboard on each boat....Lack of seawater flow can cause other problems besides loss of cooling...

  • Lack of seawater flow causes high system operating pressures
  • This, in turn increases the amperage draw from the A/C unit
  • Possibly leading to: Burnt up wiring at switches or shore cord ends

Many of these symptoms can stem back to the cause of low water flow. If the flow is allowed to remain restricted,  compressor failure can also occur in some older systems.

Different than land based systems, Marine systems installed below decks have no fan to remove the heat from the refrigerant...They use water to carry away the heat for many reasons...

  • Water is more efficient than air as a heat exchange medium
  • Size of a unit with air cooling is much larger, thus making air cooling impractical on boats
  • Air cooled units require a exit path for the heat so that the space they are in does not continue to heat up as they run, thus reducing their efficiency further

As you see from the picture above....It's an example of a seawater strainer to a system that has seen little love, and this system of course did not cool.

Every boat owner should become familiar with their boats overboard flow rate when the system is clean, and become accustomed to glancing at it every chance they get...Once you have established what is normal for your boat, a simple glance may be enough to recognize a mounting problem, and thus head off a ruined trip due to the loss of A/C...

The first question a tech may/should ask when he gets a call Is..."How is the seawater flow ?"

More frequently than not...The owners answer is he thinks it ok, or Yes it's flowing...Only for us to arrive to find not much more than a trickle....All this is ok for us as techs...but if you would like to save that expensive service call...Keeping your strainer from looking like the picture is a great start !

Seawater strainer maintenance is not hard to do...But of course every boat or installation is different. You should also know that the more the system/s run...The more frequently you will need to clean the strainer. During the winter months here in central Florida we find that due to cooler water (marine organisms seem to grow more slowly in cooler water) and obviously less usage you may not need to clean the strainer but once a month....Summer is a different story !

Depending on where your boat is moored, Tidal flow, Water Temp, and Running the system/s 24/7 can require cleaning the strainer as often as every week...I have even seen worst case situations where a boat may be moored in a pass with much tidal flow (and grass flats nearby) causing the grass to "Tumble" in the water down to where the thru hull is located, thus requiring the strainer basket to be emptied in a matter of hours...

Steve~