Silicone ducting for Diesel air Heater

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JimSea

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Hi there, has anyone used high temp silcone ducting with a Diesel air heater? I am looking for something stronger and less prone to crush damage than the standard APK type ducting.

I had been considering using neoprene ducting with a wire helix, but recently read a blog where the chap said that he's had lots of problem with rubber smells when the heater was on despite it being rated up to 150degC.

This silione ducting (HIGH TEMPERATURE SILICONE DUCTING - FLEXIBLE DUCTING RANGE - Shop) is rated up to around 250dgC but I wanted to know if anyone has used anything similar and whether there was any issues with smell.

Many thanks.
 
Ive used it but only to protect the APK and insulation where is was vulnerable to being crushed. If I was installing another heater Id probably use it inside as well as outside the insulation
 
Thanks for your replies.

Slipstream 34, did you encounter any issues with any ducting smells when the heater was first used or on any subequent uses?

Ammonite, that's another possibility - thanks.
 
I used silicon ducting on an Eberspacher installation. The ducting looks similar to that in the link. I think it was single ply. It has been very successful. … there was a smell when the system was first used. I assumed that there may be a release agent on the inside of the ducting? … smell disappeared after the heater had been used for a few hours.
 
JimSea said:
Hi there, has anyone used high temp silcone ducting with a Diesel air heater? I am looking for something stronger and less prone to crush damage than the standard APK type ducting.

I had been considering using neoprene ducting with a wire helix, but recently read a blog where the chap said that he's had lots of problem with rubber smells when the heater was on despite it being rated up to 150degC.

This silione ducting (HIGH TEMPERATURE SILICONE DUCTING - FLEXIBLE DUCTING RANGE - Shop) is rated up to around 250dgC but I wanted to know if anyone has used anything similar and whether there was any issues with smell.

Many thanks.
Click to expand...
Nothing wrong with the APK-Type ducting, Boris is proposing to it use as the basis for a tunnel between Scotland and Northern Ireland which may turn out to be a pipe-dream:). See the link below
Ireland-Scotland Rail & Road Link Across North Channel is on the Agenda Again
 
JimSea said:
Thanks for your replies.

Slipstream 34, did you encounter any issues with any ducting smells when the heater was first used or on any subequent uses?

Ammonite, that's another possibility - thanks.
Click to expand...
There was a smell for a couple of hours. It was a new heater so can't say if it was the hose or the heater.
 
Thanks everyone for your relies, very useful info. I have to run the ducting into some very hard to get at places so I didn't want to go ahead and install it without being pretty confident it would be ok. Great forum !

Spirit (of Glenans) - why the doubt? ... Boris always tells us the truth ..... ?
 
@JimSea, hi, I'm about to try solve the same problem and was thinking silicon. How did you get on? I'm running 10m forward to the saloon from a diesel heater on the port side well aft, and 10m forward to the saloon from another one on the starboard side well aft, with a T halfway along each one to vent hot air into the bathroom (port) and main cabin (stbd). My concerns are the longer run and associated airflow resistance compounded by the corrugation of the typical diesel heater ducting, and the loss of heat along such a run (though it's not really wasted as the whole internal volume of the vessel will be heated, not a bad thing). Saloon is 5m wide so two vents into that space will help heat it quicker -- I could do it with one heater of course but I'm also thinking of redundancy at sea.
 
By the way, hello to all -- new member here -- based out of Wellington NZ on a 75 gaff-rigged Chesapeake Bay (copy) staysail schooner, triple skin diagonal macrocarpa and kwila (locally built). Adding two of everything for redundancy in the Southern Ocean! Here to learn :)
 
Welcome - DanBishop

Just out of interest - what is the name of the schooner?

I'd have thought with heating in southern NZ its not redundancy but warmth that would dictate the choice :)

Jonathan
 
Formerly Maggie, aka The Maggie, or Maggie o’er Whitford. Now Maya. And I chose one heater that would supply enough warmth, then doubled up anyway!
 
Hi DanBishop, 75ft sounds like a very big boat! even more reason to make the right ducting decisions... I still havn't completed this project yet as others have come along and have taken priority. I do need to make a decision very soon though I have to get the tanks back in and the ducting has to run behind them first. I'm either going wih 80mm APK ducting inside 90mm silicone for protection , or with 80mm silicone ducting. I still have a tiny niggling voice in my mind that says that aluminium ducting definitely won't emit any kind of smell where as the silicone type could. I guess that probably depends on the exact type of silicone ducting used and its spec. I think you're right, the APK type would have higher air resistance than the silcone type due to the corrogation - if that's a word :) , I plan on insulating the ducting in bilge areas to help avoid condensaton.
 
Hi Jim,
I got this
2 Ply Silicone - 4m Length

and very happy with it. Wrapped it with Screwfix alu/bubble foil and foil tape which was a great success. It did have a very slight smell for the first hour but gone now. Replaced old cardboard / alu eberspacher ducting that was falling apart and i'm guessing the silicon will outlast the heater!
Hope this helps
 
I'm now looking at Uraflex, which is a polyurethane 80mm clear hose with spiral steel rated to 90 deg c, can handle up to 100 deg for short periods. Silicone looked expensive whereas the Uraflex comes in at NZ$21/m plus gst. My thinking on offgassing is -- houses offgas (paint, etc), cars have plastic heating systems, etc. Can't be that bad ...
 
DanBishop said:
I'm now looking at Uraflex, which is a polyurethane 80mm clear hose with spiral steel rated to 90 deg c, can handle up to 100 deg for short periods. Silicone looked expensive whereas the Uraflex comes in at NZ$21/m plus gst. My thinking on offgassing is -- houses offgas (paint, etc), cars have plastic heating systems, etc. Can't be that bad ...
Click to expand...
OK - I'll bite ;-)
From the Eberspächer manual....
"In the event of overheating, possible local air temperatures can reach 150°C and surface temperatures up to 90°C"
 
Thanks Ammonite. That’s good input. In fact though, I visited a local ducting shop and — remarkably — they listened to my requirements with great interest and gave me (not sold, gave, I was very surprised!) three 1m lengths of 100mm extendable alu ducting that extend by a factor of x3, plus enough insulation for the whole install. The logic was, the ducting is proven plus the slightly bigger diameter to 100mm will counter the longer run. They suggested I use the short diesel-heater-supplied piece of ducting for the first 1m from unit to first bulkhead.
One of their team has just decided to go sailing around the world, I think that inspired their generosity. Company is HVAC in Petone, I’ll promote them on my Insta.
I’ll install tomorrow and report back ;)
 
I used a silicon elbow directly on the heater.. No smells and good insulation ! I came across a silicon exhaust covering and was amazed at how well it worked..
For straight runs I used 75mm aluminium tube as smooth bore and far cheaper than the corrugated proper stuff
 
LoneHort said:
Hi Jim,
I got this
2 Ply Silicone - 4m Length

and very happy with it. Wrapped it with Screwfix alu/bubble foil and foil tape which was a great success. It did have a very slight smell for the first hour but gone now. Replaced old cardboard / alu eberspacher ducting that was falling apart and i'm guessing the silicon will outlast the heater!
Hope this helps
Click to expand...
Thanks LoneHort, more thumbs up for silicone which is good. I did ring a couple of diesel heater installers but neither had used it which probably added to my hesitation. Thanks also for the link to where you bought from.
 
Fitted heater #1 on the port side today and for now, just ran 6m of cheap corrugated 100mm alu ducting forward into the saloon along the sole without any insulation. Just to check the unit can pump that far., heat at the end etc. No problem, next step is to run the insulated semi-rigid alu properly down the port side behind the fixtures, then install heater #2 on the starboard side.
 
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