Distance from engine to calorifier/water heater

Discussion in 'OnBoard Electronics & Controls' started by mbowser, Oct 16, 2023.

  1. mbowser
    Joined: Nov 2015
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    Location: Canterbury NH

    mbowser Junior Member

    The new isotemp spa water heater showed up over the weekend and after some test fittings in various locations aft of the engine, I'm coming to the realization that I'm just too tall for boats (6'5"). Yes, I can mount the tank in several locations aft of the engine (or where the engine will be installed). However, if I do, it will effectively eliminate my ability to service the back of the engine or steering gear should I need to so I'm looking at alternate locations. I'd rather have a less efficient water heater than have a steering or engine failure that I can't fix because I can't access it. I should note that in the Niagara 35, the engine uses a v-drive and it is mounted backwards in the hull, with the belts at the aft end, so it's important that I can get to it. The closest logical location would be under the starboard settee which would require 2-3 meters of hose in each direction from engine.

    So I guess the question is: Can the engine coolant pump (Westerbeke W27) handle moving the extra volume of coolant to and from the tank? Based on volume of cylinder calculations, a 5/8" ID hose would need an additional 12 ounces of coolant for every meter of run. So if the total length to and from engine were 6 meters, then I would need an additional 72 ounces of coolant. Thoughts?
     

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  2. comfisherman
    Joined: Apr 2009
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    Location: Alaska

    comfisherman Senior Member

    There are several low volume high temp coolant pumps, they draw very little last for several thousand hours and make heaters so much better.
     
  3. mbowser
    Joined: Nov 2015
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    Location: Canterbury NH

    mbowser Junior Member

    Thanks for the reply. So do you think that length of run warrants a circulation pump? I've never used or even seen one, do you have any examples? I assume it would be wired into the engine harness to start when the engine does?
     
  4. comfisherman
    Joined: Apr 2009
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    Location: Alaska

    comfisherman Senior Member

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  5. wet feet
    Joined: Nov 2004
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    Location: East Anglia,England

    wet feet Senior Member

    My sympathy goes out to you for your size challenge.I don't think you have too much reason to be concerned about the pump because in any time span it will be shifting the same amount of coolant as before.What it will have to do is overcome the drag imposed on the circulating coolant by the pipe runs to and from the calorifier and the internal coils of the calorifier.Just avoid sharp bends and don't kink the pipes.If the engine is a bit tired,then it would be down to the condition of the pump components.
    For the most effective heat transfer you may need to consider wrapping the pipe carrying engine coolant to the calorifier with some kind of insulation,although warm,dry lockers can be nice things if the beer isn't stowed in them.
     
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  6. mbowser
    Joined: Nov 2015
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    Location: Canterbury NH

    mbowser Junior Member

    I've been getting similar responses all over the place, some recommend a circulation pump, others think I'll be fine. I doing an engine rebuild over the winter (engine is out and in my shop) and with that there will be a brand new OEM cooling system so I don't think the 'tired' engine will come into play. I'm thinking now that under the settee is the right place for it despite the distance from the engine, and when I do get to the installation after the engine rebuild, I'm going to plumb in a water heater bypass so that if there are issues, I can re-route the coolant so it doesn't impact the engine. Then I can decide if the issues warrant a circulation pump and install that. At least I'll have an easily accessible location to mount and install something like that should I need it.
     
  7. comfisherman
    Joined: Apr 2009
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    Location: Alaska

    comfisherman Senior Member

    Last boat we didn't have insulation on the silicone rubber heater hose, this time we used a foam rubber insulation we got from a grainger like store. Only insulated spaces where heat was a problem got insulated. Keep in mind I'm using my boats north of the 57th parallel so keeping spaces cool is easy.

    Back in 2005 we did our first big water heater/heater install and used the engine pump. It worked fine but had short runs. Didn't want an extra system so it didn't put a coolant pump in. Next boat got a pump because we had nearly a 40 foot total single circuit side and wanted heat up in the top house. It was perceptible how much faster the water tank worked specifically at idle with the coolant pump. Initially it was plummed on three way valves so it could be isolated and swapped or bypassed all together. After about three or four seasons (about 1000 to 1500 hrs long) realized the pumps were long loved enough the valving wasn't necessary. Current boat has engine circuit isolation valves but no pump isolation.

    Also used a generic heater rated 5/8 hose, last install got silicone rubber hose. It's nice stuff, but the cost per foot has gotten out of hand. So far thr current stuff seems just fine, it lasted many years on my first boat.
     

  8. mbowser
    Joined: Nov 2015
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    Location: Canterbury NH

    mbowser Junior Member

    Wow, 40 feet. That's a long run and that silicon hose pricing is nuts right now. I just bought a 2" x 3' exhaust hose (Trident #252V2000-36) and it was $120 (FOR THREE FEET)....
     
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