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As installed report, 4788 furnace system (with photos)-gctid341634

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    As installed report, 4788 furnace system (with photos)-gctid341634

    After much debate, discussion, and work not only on my part, but the part of the techs over at North Harbor Diesel we finally have a fully operational heating system in our 4788.

    The technology we chose was forced air with a fresh air component. We went with this because we wanted to have the furnace draw fresh air from outside the boat, heating and ventilating at the same time.

    The brand of units we chose was Wallas. We went with Wallas primatially for two reasons. First, the Wallas units are dead quiet. Much quieter than any other furnace on the market. Another reason is that on most furnaces the furnace cycles on and off all night long. I actually timed it on our 2859 and about every 15 minutes in 45 degree weather outside the furnace would cycle back on.

    The Wallas units have a thermostat that varies the BTU output of the unit between 1K btu on low and 10K btu on high, with several intermediate steps. This means that on a normal evening, the furnace will "figure out" the correct heat setting and keep the temperature constant.

    The 4788 is a big boat with three living levels. Heating it is a challenge. We decided that all total we needed between 25 and 30K BTU to meet our goal of keeping the interior at 70 with a 25 degree outside air temp. Having too large of a furnace is almost as bad as too small. The challenge is to properly size the system so that the "low" output of the furnace will not create too much heat for the space on a semi warm day, and that the "high" output keeps the space at the desired temp on a very cold day.

    We installed one 7K btu furnace behind the pilothouse dash. This furnace heats the pilothouse and provides defrost. Return air is pulled from both inside the pilothouse and outside for fresh air ventilation.

    The salon is heated using a 10K btu furnace installed behind the setee. This has two vents on the setee, with fresh air being drawn from inside the cabin and from outside.

    The staterooms are heated using a 10 kbtu furnace installed underneath the pilothouse setee. There are vents in each stateroom.

    Here's a bunch of photos. I'll post photos of the stateroom heater when I round them up.

    Attached files [img]/media/kunena/attachments/vb/644200=23411-pilothousedefrost.jpg[/img] [img]/media/kunena/attachments/vb/644200=23412-pilothousefurnace.jpg[/img] [img]/media/kunena/attachments/vb/644200=23413-pilothousethermostat.jpg[/img] [img]/media/kunena/attachments/vb/644200=23414-pilothousevents.jpg[/img]

    KEVIN SANDERS
    4788 LISAS WAY - SEWARD ALASKA
    www.transferswitch4less.com

    where are we right now?

    https://maps.findmespot.com/s/36S4

    #3
    Kevin,

    Just curious on what percentage outside air verses cabin air are you using on the return air? Is it fixed or do you have a way to control it so you can use more outside air if having a moisture problem verses less to conserve fuel? I assume you are using only outside air for the makeup air for the burner.

    Once again the work being done by North Harbor Diesel appears to be top notch.
    John Rupp
    1989 2455 Ciera Sunbridge
    5.8 OMC Cobra

    1989 3288
    Starshine
    Hino 135

    Comment


      #4
      johnrupp wrote:
      Kevin,

      Just curious on what percentage outside air verses cabin air are you using on the return air? Is it fixed or do you have a way to control it so you can use more outside air if having a moisture problem verses less to conserve fuel? I assume you are using only outside air for the makeup air for the burner.

      Once again the work being done by North Harbor Diesel appears to be top notch.
      The Wallas furnaces have two return air ducts.

      One is pulling outside air, one is cabin air.

      KEVIN SANDERS
      4788 LISAS WAY - SEWARD ALASKA
      www.transferswitch4less.com

      where are we right now?

      https://maps.findmespot.com/s/36S4

      Comment


        #5
        johnrupp wrote:


        Just curious on what percentage outside air verses cabin air are you using on the return air? Is it fixed or do you have a way to control it so you can use more outside air if having a moisture problem verses less to conserve fuel?
        John, our forced air system is a Wabasto installed by Olympic Boats in Seattle way back when. They only used inside air for heating with no outside air. It worked well for a number of years, since we only cruise in the summer, until one trip to Alaska when it rained 99% of the time we had our own mold & fungus garden inside. I added a wye on the intake tube and a closeable grille in the cockpit. Problem solved. Go to the Sure Marine site and on their catalog page 10 & 11 you will see a number of options. I was told that a 40/60 split is what you should try for.

        http://www.suremarineservice.com/cat...talogMAY11.pdf
        Bill
        1993 3888 with Hino 210s
        2005 Selene 55

        Comment


          #6
          Thanks for the info Bill and Kevin.
          John Rupp
          1989 2455 Ciera Sunbridge
          5.8 OMC Cobra

          1989 3288
          Starshine
          Hino 135

          Comment


            #7
            Where are you pulling your outside air from? We thought we were smart and set a grill on side of port side two steps in the cockpit of our 47 for our Espar air intake. We do have to be careful if we also have gen set running and wind is coming from behind us. In that case we close up rear canvas and cover the three cockpit drains with those flat sink drain covers. Those are handy to just leave installed to keep any smoke from entering the back deck while underway. Bayliner did not leave enough air access for the engines and when they are running they want to suck in more air through all the hatches both in the cockpit and in the salon. Keeps salon a lot cleaner.
            Started boating 1965
            Bayliners owned: 26 Victoria, 28 Bounty, 32, 38, and 47 since 1996

            Comment


              #8
              Kevin

              Great Post

              Will be interested in the additonal Photos of the stateroom installations.

              The Wallas units really seem to have some great advantages.

              You noted two advantages of guiet operation and adjusting to a constant burn rate. The other significant one is the exhaust temp is considerably lower - 400 degrees compared to 800-850 degrees.

              Thanks

              Ron
              Ron O'Blenis
              B 38 175 Hinos 1989
              Completed Great Loop
              https://ronandfaye.blogspot.com/

              Comment

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