Advice On Hot Air Outlets Required

[BlowingOldBoots]

My Mukini Hot Air heater was placed on teh back burner during the refit of my boat. I am not going to reinstate it. During the refit all the ducting was removed as it was crushed and also useless when it came to heating the boat.

The heater unit is in the aft cabin and I would like to heat the aft cabin, saloon and fore cabin, hence 3 x outlets. How should I arrange the ducting sizes? The heater outlet is 90mm diameter. Should I have 1 x 90mm ducting running from aft cabin to the bow, with 3 x 90 mm outlet ducts, or should I step down each outlet duct diameter (comes in 80-50mm sizes)?

Any advice offered is appreciated.

Alastair

[Gardenshed]

Happy to show you how my webasto is installed and how it works
If you’ve got the space, keep the diameter as large as possible. More important is to insulate the duct and reduce the heat loss between the outlets

[BlowingOldBoots]

Okay that would be good, thanks for the offer. I agree that insulation to reduce heat losses and size to reduce back pressure losses are likely what should be driving the design.

[Burst Boiler]

Not considering heating the bog? Do you have a shower and hanging locker in there? An additional vent in there helps dry out the bog and your oilies quickly. I would go for closeable vents in the cabins to drive heat to the most important rooms (saloon usually) first. You need to have one non-closable vent of course, again usually the saloon. Mellor online weren't the cheapest but had good range of stock and good service. Thermostatic control is vital to save diesel and volts, also now you can get Bluetooth controllers so can turn on the heat from the comfort of your bunk in the morning using your phone.

[BlowingOldBoots]

The bog area was going to be heated with uninsulated pipe, where it passes through the lockers to the fore cabin. The fore cabin outlet would in all likely hood heat the head as well, unless that door was closed. Might look at a reducer outlets, say 50mm for the heads as the shower (to be reinstated) is in the foreheads.

[claymore]

Our Sainted Eberspacher is located in a locker in the wheelhouse - nice and dry!
The piping runs forward - about 2 -3m and comes out in the saloon under the dining table
Hot and happy feet as a result.
The other outlet is in the aft cabin.
It runs into the first locker where we have installed the raymarine 'brains' for the autopilot so that locker is nicely aired and then into the second locker where Dear Heart keeps her clothing. Again - nicely aired - nothing worse than damp drawers apparently
Both lockers are underneath her Bunk so again - happy wifie.
The outlet gushes heat into the cabin and is wonderful for drying towels and airing sleeping bags etc
The pipes are not lagged or insulated because I thought it would be better to have some heat radiating from them as described.

[sahona]

Useful info noted John, I've been pondering a planar lately and you may have helped with the options. Thanks for posting.

[Aja]

Bill

Let me know how you get on with going down the Planar route as my Eberspacher D3L is not playing ball, after 30+ years.

Donald

[aquaplane]

On Seminole the Unit 1.8 Kw is in the cockpit locker.
The run to the first outlet in the saloon is 2 or 3 meters and is OK.
The outlet in the side cabin is maybe 6m but to be fair, going to bed I don't want heat. In the morning different.
The third outlet in the bog/shower is a waste of time. We wouldn't consider a shower if it was cold enough to warrant having the heater on.
No outlet in the fore cabin, but who has visitors when the weather is crap, and won't go for a 240v hookup to run a fan heater?