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  1. #1
    Join Date
    May 2019
    Location
    The Clyde, Scotland
    Posts
    28

    Default Air Heater installation motor boat MF805

    Two of this winters major jobs are going to be the installation of a calorifier and also an air heater on our Merry Fisher 805.

    I think I'm ok with the installation of the calorifier and I'm planning to put it under the floor below the sink where the water tank, pump etc is located(assuming I can remove enough flooring to get it in there easily enough... failing that its going in the lazarrette)

    The question I have is in regard to the air heater-

    My initial plan was to use the already installed window blower ducting that I believe comes from the engine compartment and install the air heater in there, however when using the air blowers at the moment the smell in the cabin is terrible and headache inducing(I'm surprised about this and haven't gotten to the bottom of why this is happening?).

    So, I'm now planning on installing the air heater in the lazarrette and run the fuel line from the main tank and ducting the warm air into the main cabin and fore cabin under the floor on the port side.

    Is it better to duct the fresh air inlet(not combustion air) from the lazzarrette(other potential noxious smells/wet stale air), the cabin(no fresh air circulation) or from outside(cold air)???

    I'm leaning towards outside air at the moment but I would appreciate any other opinions.

    Thanks

  2. #2
    Join Date
    May 2001
    Location
    UK East Coast
    Posts
    36,519

    Default Re: Air Heater installation motor boat MF805

    It's best to take the air intake for the heater from outside; this will help to reduce build-up of condensation in the boat.

    You need to investigate the smell from the window blowers, it sounds like exhaust fumes are getting in to the air supply.

  3. #3
    Join Date
    May 2019
    Location
    The Clyde, Scotland
    Posts
    28

    Default Re: Air Heater installation motor boat MF805

    Quote Originally Posted by pvb View Post
    It's best to take the air intake for the heater from outside; this will help to reduce build-up of condensation in the boat.
    Thanks, I was leaning this way but wanted other opinions as I believe the factory installed option takes its air from the engine bay which I suppose could be classified as outside air due to the large air vents on either side of the boat?

    Quote Originally Posted by pvb View Post
    You need to investigate the smell from the window blowers, it sounds like exhaust fumes are getting in to the air supply.
    Its on the to-do list, I only had them on once and turned them off and then duly forgot about them...

  4. #4
    Join Date
    May 2001
    Location
    UK East Coast
    Posts
    36,519

    Default Re: Air Heater installation motor boat MF805

    Quote Originally Posted by alex_m24 View Post
    Thanks, I was leaning this way but wanted other opinions as I believe the factory installed option takes its air from the engine bay which I suppose could be classified as outside air due to the large air vents on either side of the boat?
    Don't take the air from the engine bay, you'll just get (at best) diesel and oily smells in the cabin and (at worst) exhaust fumes which could harm you.

  5. #5
    Join Date
    May 2016
    Location
    Suffolk
    Posts
    7,962

    Default Re: Air Heater installation motor boat MF805

    Quote Originally Posted by alex_m24 View Post
    The question I have is in regard to the air heater-

    My initial plan was to use the already installed window blower ducting that I believe comes from the engine compartment and install the air heater in there, however when using the air blowers at the moment the smell in the cabin is terrible and headache inducing(I'm surprised about this and haven't gotten to the bottom of why this is happening?).
    The window demisters are connected to a small heater matrix, that is heated by what would normally be the cabin heater, were the engine in a car/truck. Can't remember if that's fitted at the very back of the wardrobe in the forward cabin, aft of the battery charger, or it it's in the space beneath the saloon table, just forward of the batteries. I'm leaning towards the wardrobe. It's not in the engine room (at least not on the ones i've owned/seen).

    So, I'm now planning on installing the air heater in the lazarrette and run the fuel line from the main tank and ducting the warm air into the main cabin and fore cabin under the floor on the port side.
    Sounds like the best place to me

    Is it better to duct the fresh air inlet(not combustion air) from the lazzarrette(other potential noxious smells/wet stale air), the cabin(no fresh air circulation) or from outside(cold air)???
    Just let it draw air in from the lazarette, it's not well sealed and will work fine.
    Last edited by PaulRainbow; 08-08-19 at 00:15.
    Rainbow Marine.
    www.rainbowmarine.co.uk

  6. #6
    Join Date
    Aug 2004
    Location
    Home East Lancashire boat Spain
    Posts
    4,670

    Default Re: Air Heater installation motor boat MF805

    Quote Originally Posted by pvb View Post
    It's best to take the air intake for the heater from outside; this will help to reduce build-up of condensation in the boat.
    This is the standard advice that is given on the forum. I repair and sell heaters and only rarely will I install them.
    My instinct is that the heater is most efficient when used in recirculation mode ( ie re-warming the cabin air as In a car) but I recognise the condensation issue.
    When testing heaters in my small insulated workshop I sometimes find that I have to use recirculation mode if the heater is to start warming the space, I can then swap the ducting round to bring in outside air and the heater then manages to maintain the temperature.

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