Manufactured by Marsh Marine...Tank Cleaning Professionals         “Our experience is your protection since 1966”

Made with Xara

Deck Fill Protection Device

T oday’s   larger   pleasure   craft   typically   all   have   marine   air   conditioners.      We   tend   to   take   these   creature   comfort devices   for   granted…until   they   break!      In   this   article   we’ll   examine   a   particular   AC   problem   nearly   every   owner will   encounter:   stopped   up   raw   water   intake   lines.   We   will   discuss   an   amazing   product   that   can   keep   your   cool   air pumping   and   an   often   unknown   health   hazard.      Let’s   begin   with   a   simple   review   of   how   marine   air   conditioners work. T here   are   basically   three   major   components   to   any   AC   system:      The   raw   water   pump,   the   compressor,   and   the condenser   (sometimes   called   the   air   handler).      The   last   two   are   often   combined   into   what   appears   as   a   single   unit, generally   tucked   away   beneath   a   berth   or   some   other,   usually   inaccessible,   space.      Raw   cooling   water   comes   into the   boat   via   a   standard   through-hull   fitting   and   sea   cock.      A   small   electric   pump   then   circulates   the   water   through hoses   to   and   through   the   air   conditioning   unit.      From   there   it   goes   overboard   through   a   second   through-hull   fitting located above the waterline. T he   raw   water   circulates   through   a   simple   heat   exchanger   usually   attached   behind   the   condenser   and   resembles   a coil   of   pipe.      The   heat   exchanger   is   actually   two   tubes,   one   inside   the   other.      The   two   are   closed   off   from   one another.      One   tube   carries   the   raw   water;   the   other   the   compressor’s   refrigerant   gas.      As   the   cool   raw   water circulates in the coil, it absorbs the refrigerant’s heat through the neighboring tube wall. This   heat   exchanger   design   combined   with   the   laws   of   gas   physics   allows   the   unit   to   perform   an   interesting   dual function.      In   hot   weather,   heat   is   taken   from   the   air   inside   the   boat   and   dissipated   into   the   cooling   water.      In   spring or   fall   when   the   air   is   cool,   the   air   conditioner   takes   heat   out   of   the   water   and   dissipates   it   into   the   boat   to   provide warmth. This switch from cooling to heating is known as reverse cycle operation. R everse   cycle   heating   works   well   until   the   sea   water   temperature   reaches   approximately   38   degrees.      Below   that temperature   there   isn't   enough   heat   in   the   water   for   the   unit   to   work   efficiently.      Still,   reverse   cycle   heating   can   help extend the cruising season during cool spring and fall months. A s   you   might   have   guessed,   or   experienced,   the   weak   link   is   this   raw   water   flowing   through   the AC   system.      If   it   is restricted   or   worse   stops,   the   condenser   cannot   release   its   accumulated   heat.      The   air   conditioner   begins   to   work harder   to   maintain   the   selected   temperature   and   eventually   gives   the   fateful   error   message,   High   Head   Pressure , and ceases to function.  Pushing the reset button will restart the unit, but only until the heat limit is again reached. I f   you   are   experiencing   cut   off   problems,   there   is   one   simple   means   to   trouble   shoot   the   cause.      It   isn’t   very scientific,   but   it   works.      Place   your   hand   on   the   heat   exchanger   coil.      If   it   is   too   hot   to   hold,   you   are   not   getting enough   water   flow   through   the   system.      Once   this   is   determined   look   for   the   cause.      The   best   place   to   start   is   the over-the-side   through-hull,   if   your   boat   has   this.      Some   of   the   newer   boats   discharge   into   the   engine   exhaust   tube   or beneath   the   swim   platform.      If   you   can,   check   the   water   discharge   flow.      Is   the   stream   discharging   with   its   usual volume, simply dribbling, or perhaps stopped altogether?