Clogged air conditioning condenser coils make for a hot boat

Ben Stein

Ben Stein

Publisher of, passionate marine electronics enthusiast, 100-ton USCG master.

11 Responses

  1. Joe Eckenrode says:

    Hi Ben, you could just put a preset pressure safety in the discharge line to a digital input. On R-22 most people go for 325 or 350 psi. Of course you wouldn’t see the pressure creep up but you would be alerted to protect your compressors. I didn’t see you mention if the compressors were shutting off on thermal overload or discharge pressure, but if the condensing units don’t have high discharge safeties you should definitely think of adding them. The compressor’s thermal overload should be it’s last line of defense.
    As far as monitoring goes you could put a temperature probe on the dropleg (liquid refrigerant line leaving the condenser) to have an idea of the pressure. We have one Trane chiller that we take care of that only uses temperature probes to calculate refrigerant pressures in the system!

    • Ben Stein Ben Stein says:


      I think you’re exactly right that the compressor eventually shutdown on the thermal safety. I believe what happened is that it was shutting down on high pressure but, because of the different control system with effectively just a handful of relays and a time delay unit this compressor doesn’t do what standard SMX controlled units will which is shut down until manually reset after the third high or low pressure shutdown. As a result, it was just banging off the high pressure switch until the compressor got hot enough to hit the thermal limit.


  2. Gary Groves says:

    Ben, we used to live in Beaufort, SC with their hot and humid summers. With their 4 kts tidal currents, marine growth was a major issue for circulating water systems, e.g. a/c and refrigerator. We installed the water flush system design like yours and had to flush monthly to clear out the barnacles and other creatures of the deep that got sucked into the intakes. It’s good that you only need to do it every six months. BTW, how’s the Seakeeper doing? Ours is great and we use it all the time when in motion.

  3. Michael G. says:

    Ben, the first thing that jumps to my mind, for N2K monitoring, is Maretron’s FPM100. It is their six channel analog pressure transducer to N2K box. The transducers that they sell are spec’d as being compatible with refrigerant, and are available in models up to 5000psi. Now I have no hands on experience with a/c systems, so I don’t know how difficult it would be to integrate into a system. If you wanted to get real ambitious, you could use those last two channels to monitor seawater suction vacuum, or condensor back pressure.

    • Ben Ellison Ben Ellison says:

      I wondered about using the FPM100 too. Though I haven’t tried one, I know well from other Maretron sensors I use that you could set up alerts for higher than normal pressures and alarms for a seriously bad situation.

      I’m also reminded of an elaborate custom motoryacht I once toured — — that had some sort of electrodes in all the seacocks to kill zebra mussels. Apparently, the owner also had a fleet of commercial boats working the great rivers and feared the clogging they can cause.

      • Ben Stein Ben Stein says:

        I’m planning to reach out to Maretron and see if they think their sensors would be appropriate for use with refrigerant.

        It would be very nice to be able to monitor AC health at a glance from the NMEA-2000 network.

        • Brian says:

          BTW, somewhat easier is monitoring temp on the input side and output side, and then just looking at temp differential between the two, this is the approach I am planning to take. When the temp differential gets too low, it is an indication that something is off.

  4. Cyril Silberman says:

    I’ve been managing my Marine Air SMX systems for almost 20 years now and early on determined that some level of monitoring the health of the system, other than waiting for the compressor to shut down was required. I have effectively installed thermocouples to the suction line near the compressor on each of my condenser unites on not only the A/C units, but also the refrigeration throughout the vessel. Five on the A/C units and four for the various refrigerators. Some effort to locate the best and coldest spot on the suction line is required however it is generally near the service port on the low side.
    On an R-22 system this should show a temperature of around 45 to 50 degrees F if the unit is stabilized and properly charged. It doesn’t really matter exactly what the temperature is, important is that generally it stays the same over the years and changes mean it’s time to do some maintenance.
    On my boat I have installed a Maretron data collection system where I monitor 33 unique temperatures throughout the vessel including the temperature of the Trend Marine shaft seals. I have set up alarms to let me know when a device drifts to an exceedance level. I can also look back at history and see interesting correlation’s to foolish things I might done such as dragging the boat thru some mud and discovering that 30 minutes later none of my A/C units seem to be cooling properly…. Time to clean the screens!

    Thanks, Cyril

  5. Colin A says:

    I think monitoring the temp on the lines is a good idea. Flow meters on raw water intake can also be helpful, but in this situation you may have had enough flow where it wouldn’t have triggered. Also I imagine Marine AC makers could create a self diag system if they really wanted too. Some auto AC systems have a surprising amount of info in the body computers.
    On the having gauges thing, after being a broke parent and having to fix my own car AC I bought a set of R134 gauges about a decade ago. Great investment, HVAC is much less a black art then most DIY people think.

  6. Brian says:

    I just put together a similar garden-house flush set for the 2 A/C units on my Silverton 330SB. They also share a single seawater pump, and by adding shut-offs for the hoses feeding each unit, I can flush either line effectively, plus also balance the flow between them a little better.

  7. Larry Olson, Sea Life says:

    Great article. I’ve been hooking a line up from the output of the pump and loop it to the output of the condenser, but requires a small pump in my bucket to circulate the solution of Barnacle Buster. I like the idea of hooking up stream of the water pump, let it do the work and cleaning it too.

    I have two condensers that are fed from the one water pump, so if I did them individually, I’d need a simple way to shut the flow off for the unit not being cleaned. Or perhaps I could clean both units at one time.

    Here in the FL waters where the boat lives mostly (exception of doing the loop this past year), once a year seems to be adequate.

Join the conversation

Your email address will not be published.