CONTESSA 32 ASSOCIATION Homepage
Forum Home Forum Home > Technical Help > Internal Fixtures and Fittings
  New Posts New Posts RSS Feed: Hot air heater ducting
  FAQ FAQ  Forum Search   Calendar   Register Register  Login Login

Hot air heater ducting

 Post Reply Post Reply Page  123>
Author
Message
George Isted View Drop Down
Moderator Group
Moderator Group
Avatar

Joined: 08 May 2009
Location: Solent
Online Status: Offline
Posts: 374
Post Options Post Options   Quote George Isted Quote  Post ReplyReply Direct Link To This Post Topic: Hot air heater ducting
    Posted: 28 Oct 2014 at 3:25pm
When fitting a hot blown-air heater (Webasto, Eber, etc) and you want to have heating outlets in the middle and forward cabin do you run the ducting down the port side or the starboard side of the boat?

I'm assuming the heater is fitted in the larger port-side cockpit locker as that makes fuel-in and exhaust-out easy.

If running the ducting down the starboard side I guess it will either run from the heater through the engine bay or around the stern of the boat before going forward.

Running the ducting up the port side would be easier but would require cutting holes in the GRP galley locker/cool box liners and I don't really want to do that.

Thoughts?
George Isted
www.solentboatbutler.co.uk
Contessa 32 "Concerto"
Co32 Class Measurer and ex Class Captain.
Back to Top
Silver Harmony View Drop Down
CO32 Members
CO32 Members


Joined: 19 Sep 2012
Online Status: Offline
Posts: 21
Post Options Post Options   Quote Silver Harmony Quote  Post ReplyReply Direct Link To This Post Posted: 10 Nov 2014 at 9:34pm
My Eber is in the port side cockpit locker as you suggest, tucked up inside the cockpit coaming. Nicely out of the way and tricky but not impossible to get in and out. I have a small hatch in the coaming to access the glow plug.

My hot air ducting comes down the port side. There is enough space behind / below the liners for the galley lockers. I have a Y joint in the locker aft of the saloon table and the first outlet is there. The 2nd outlet is at the forward end of the heads cabin, below the sink. The main disadvantage with this routing is that the ducting gets in the way of servicing the heads seacocks.

Combustion air is drawn directly from the cockpit locker. Air for the cabin is drawn from the starboard side cockpit cubbyhole via a duct round the stern inside the lazarette. Having the heating air intake outside makes the heater very effective at drying the boat but is less efficient at actually heating than drawing from the cabin.

My exhaust runs out to the transom via the lazarette. It gets very hot and even with lots of lagging anything plastic that touches it (including fenders and ropes) will melt. Also, reaching the transom skin fitting to get the exhaust pipe on and off is a long and uncomfortable stretch.

I have a love/hate relationship with mine. It's great when it's working but it's somewhat temperamental and replacement parts are very expensive. To be fair it is probably getting on for 30 years old. If I was fitting a new one I would use the finest quality marine grade wiring I could find, and add some waterproof connectors to the loom to make getting the heater unit in and out easier. I would also oversize the main power cables as a lot of the problems with them seem to be down to voltage drop in the wiring. Eberspachers and their mounting fasteners are not stainless so grease the threads if you ever want to get it out again.

If you don't already have one a carbon monoxide detector is a good idea otherwise if the exhaust leaks or the wind is blowing it back towards the hot air intake the heater can fill the boat up with CO.
Robert Fox
Contessa 32 "Silver Harmony"
Back to Top
Alastair D Pugh View Drop Down
CO32 Members
CO32 Members


Joined: 03 Dec 2012
Online Status: Offline
Posts: 17
Post Options Post Options   Quote Alastair D Pugh Quote  Post ReplyReply Direct Link To This Post Posted: 11 Nov 2014 at 9:58am
And now for the other side .......
Mine is in the stern locker tucked up on the starboard side with the mounting bracket on the bulkhead.  Heated air duct goes down below cockpit, through longtitudinal  bulkhead, under pilot berth, through the under chart-table bin, Y-branch under saloon berth to outlet and forward through hanging locker to fo'c'sle. Combustion air is from locker, heating air is from a duct laid along the lid of the pilot berth.  Fuel is tee'd off the tank sight tube.  Getting it in and out is not too difficult once you've sussed out the angles for the hose.exhaust clip screws - one tip is to block the gap at the bottom of the bulkhead, it makes picking up dropped washers etc. so much easier.  Like Robert's mine was fitted when I got the boat.

I second the CO detector!  I got very ill when the exhaust split on mine - that was before I ducted the air intake forward. 

Alastair
Back to Top
George Isted View Drop Down
Moderator Group
Moderator Group
Avatar

Joined: 08 May 2009
Location: Solent
Online Status: Offline
Posts: 374
Post Options Post Options   Quote George Isted Quote  Post ReplyReply Direct Link To This Post Posted: 11 Nov 2014 at 11:08am
Thanks both for your messages, I already have a CO detector in the boat.

I have now managed to cut ducting holes up the port side, there is space behind both the GRP locker liners in the galley, although I have had to take a corner out of one to bring the ducting down to the under-seat berth at the aft end of the table.

Alastair - good tip to take a Tee off the fuel sight tube as that will save me drilling a hole in the top of the tank - not easy in situ.

I am having a custom sized wiring loom made up with oversized tinned cabling so hopefully that will reduce the likelihood of wiring issues.

I can see why many owners go for the smallest heater from webasto/Ebber as I have the medium sized one (3500w output) that is a bit physically bigger and it's a very tight fit.

Re the exhaust - how high on the transom, the higher it is the less of a goose-neck bend can be put into the exhaust so I was going to go for a middle to low position on the transom and hope the height of the goose-neck will keep any water away from the heater.

Cheers

George
George Isted
www.solentboatbutler.co.uk
Contessa 32 "Concerto"
Co32 Class Measurer and ex Class Captain.
Back to Top
waratah912 View Drop Down
CO32 Members
CO32 Members


Joined: 17 Dec 2010
Location: Lymington
Online Status: Offline
Posts: 98
Post Options Post Options   Quote waratah912 Quote  Post ReplyReply Direct Link To This Post Posted: 11 Nov 2014 at 6:47pm
A survey of Lymington Contessas by rowing dinghy showed most were low on the transom, so that's where I fitted mine. This gives you a longer gooseneck which I would imagine reduces the possibility of water ingress. Water doesn't much like flowing up narrow pipes!
Paul Smith
Waratah
Contact details available from the members only area
Back to Top
Silver Harmony View Drop Down
CO32 Members
CO32 Members


Joined: 19 Sep 2012
Online Status: Offline
Posts: 21
Post Options Post Options   Quote Silver Harmony Quote  Post ReplyReply Direct Link To This Post Posted: 11 Nov 2014 at 7:11pm
I agree a lower exhaust outlet makes sense. The inside end of the skin fitting angles up too so if the fitting is too high the exhaust hose will hit the deck. The spiral wound flexible pipe doesn't like sharp bends. Pick a site you can reach from inside because the flexible exhaust hose doesn't last forever. You can also get elbows for the heater end that have a drain point which are maybe worth considering.

Good luck with the install. The muted roar of ignition followed by the blast of hot air at your feet will make all the time spent jammed in the cockpit locker feel worthwhile!





Robert Fox
Contessa 32 "Silver Harmony"
Back to Top
George Isted View Drop Down
Moderator Group
Moderator Group
Avatar

Joined: 08 May 2009
Location: Solent
Online Status: Offline
Posts: 374
Post Options Post Options   Quote George Isted Quote  Post ReplyReply Direct Link To This Post Posted: 11 Nov 2014 at 7:18pm
Thanks gents, having done a trawl of online pictures of Co32 transoms I have concluded that low and central-ish on the transom is the best location, allowing more height inside.

Cheers
George Isted
www.solentboatbutler.co.uk
Contessa 32 "Concerto"
Co32 Class Measurer and ex Class Captain.
Back to Top
waratah912 View Drop Down
CO32 Members
CO32 Members


Joined: 17 Dec 2010
Location: Lymington
Online Status: Offline
Posts: 98
Post Options Post Options   Quote waratah912 Quote  Post ReplyReply Direct Link To This Post Posted: 11 Nov 2014 at 7:37pm
For those cold night watches you could also consider a vent in the cockpit, for a modern take on the hurricane lantern between your feet and sailbag over your knees :) 
Yes, I'm from the East Coast!
Paul Smith
Waratah
Contact details available from the members only area
Back to Top
waratah912 View Drop Down
CO32 Members
CO32 Members


Joined: 17 Dec 2010
Location: Lymington
Online Status: Offline
Posts: 98
Post Options Post Options   Quote waratah912 Quote  Post ReplyReply Direct Link To This Post Posted: 11 Nov 2014 at 8:46pm
Another consideration, oil soaked lagging is a major source of fire in refineries, so I sleeved mine in flexible aluminium ducting over the top of the lagging and sealed the ends with aluminium foil tape. You need bigger holes if you've got to go through a bulkhead, but it reduces the chance of fire significantly and of chloride induced stress cracking if you get seawater on the lagging, neither if which are ever going to happen - right???
Paul Smith
Waratah
Contact details available from the members only area
Back to Top
Silver Harmony View Drop Down
CO32 Members
CO32 Members


Joined: 19 Sep 2012
Online Status: Offline
Posts: 21
Post Options Post Options   Quote Silver Harmony Quote  Post ReplyReply Direct Link To This Post Posted: 11 Nov 2014 at 9:09pm
I used ExoWrap on mine. ASAP supplies sell it. It's basically lagging with an aluminium foil backing, specifically intended for "high temperature surfaces in vessel engine rooms."
http://www.marinetapes.com/index.php/marine-division/14-exowrap%C2%AE-insulation-system.html
http://www.asap-supplies.com/search/exowrap

I wouldn't worry about stress corrosion cracking though. I've replaced my Eber exhaust twice and both times it was plain old corrosion that caused it to fail. Maybe next time I'll try and source a titanium pipe.
Robert Fox
Contessa 32 "Silver Harmony"
Back to Top
 Post Reply Post Reply Page  123>

Forum Jump Forum Permissions View Drop Down