Webasto ducting - type and size.

[G4ryh]

Hi,

Is there any reason why I cant use the following with and an Evo 40?

http://www.ductstore.co.uk/acatalog/DEC-Isodec-Insulated-Flexible-Ducting.html - seems cheap and well insulated and the temps / air flow specs seem fine.

Also they don't do 90mm so should I go up to 100mm or down to 80mm? I'm planning on a short 1m uninsulated run of Webasto 90mm from the heater and then stepping down/up.

Gentle please - forum newbie. I have searched but no one seems to have addressed the size issue in this way.

Many thanks.
Gary.

 

[pcatterall]

I'm all for finding cheaper alternatives to the incredibly expensive black stuff normally used. The stuff you refer to looks like it would do the job as regards temp and insulation. It looks more 'crushable' than the 'proper stuff' but used out of harms way should be fine.
The diameter will depend on your installation. I assume that there is a webastos guide to ducting installation like that supplied for eberspachers, going down a size to 80mm would be preferable, of course, in terms of ease of installation.

 

[G4ryh]

Thanks for your reply. She's a 35 foot beneteau with quite a run to the forecabin so I'm not sure whether to go up or down in the duct. If they had 90mm I would use that as recommended for the evo 40. 10 metres fully insulated for just over £20 is worth fighting for against almost the same for 1 metre uninsulated!

 

[pvb]

Is there any reason why I cant use the following with and an Evo 40?

http://www.ductstore.co.uk/acatalog/DEC-Isodec-Insulated-Flexible-Ducting.html - seems cheap and well insulated and the temps / air flow specs seem fine.

Also they don't do 90mm so should I go up to 100mm or down to 80mm? I'm planning on a short 1m uninsulated run of Webasto 90mm from the heater and then stepping down/up.

Welcome to the forums! There's no problem using 80mm ducting, the Webasto Installation Instructions Manual for the Evo 40 suggests using 80mm for the main run of ducting, and also contains a chart showing the air resistance of ducting, bends and junctions. If your installation is going to be fairly complex, you should check the resistance calculation to make sure your heater will cope. You can join 80mm duct directly to the heater outlet with a snap-on connection adaptor. Not sure why you were planning to have a metre of uninsulated duct - it should be insulated right from where it exits the heater.

My main hesitation with using the cheap ducting is that it doesn't look as if the internal wall is particularly smooth, possibly leading to higher air resistance. Also, as it comes compressed into a box, there may be bits with crushed ducting which will be difficult to spot. Additionally, the inner duct looks a bit fragile and I'm not sure how well this would work with junctions, etc. And, lastly, it doesn't look very crush-proof, so you'd need to be careful to protect it in lockers, etc. The proper ducting is pretty well bullet-proof, although much more money - but you're only going to install it once, so maybe worth using the proper stuff.

 

[G4ryh]

Thanks, thats really useful. Given the price, I'll give it a go and report back how I get on. Appreciate the tip on resistance, I'll take a look.