Diesel heater ducting insulation

Just installed a new 4kW system to replace old system. I found a branch of Woolsey pipeline supply (others are available) who have an commercial air conditioning section and that air conditioning is still an imperial trade. So... 15mm (nominally 1/2 inch) wall, 67mm (2 1/2 inch) ID heat proof Armaflex bendy foam insulation and two metres long for less than a tenner. For even less it can come unslit and a Stanly blade will oblige. The also sell the goo for sticking it back together which is easy to use. 67mm is ideal for shoving 60mm ID/62mmO/D ducting down. Huge difference to toasty factor.
 
I am in the middle of installing a diesel air heater and I might investigate this product myself. Temperature range is good. It looks bulky but price seems reasonable.
I got 2 pieces of Thermoduct to try it and am impressed with how it looks at least - I found melloronline the cheapest.
 
I've been looking at armaflex but I think it's rated to 105 degrees C and the outlet temperature is up to 110. I'm sure it's fine once you're a couple of feet from the outlet but would prefer more of a safety factor
 
Where did you see an id of 50mm? The insulation thickness is either 25mm or 50mm depending on the size but I don't think that relates to the id
 
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Chaktoura said:
What are your thoughts on the following for insulating 5 metres of 60mm ducting. Unfortunately I haven't been able to find a closer fitting alternative and don't want to pay for the expensive webasto / eberspacher variety
https://www.has-store.co.uk/flexibl...ium/insulated-flexible-ducting-size-80-detail
Click to expand...

This looks identical to the stuff I got with my ventilation system. It is rated to 70degC and if you put a bit of the silvery material it up to a lit match, it almost instantly flashes into flame. It's not actually aluminium, but rather something along the miles of mylar and made of plastic with a very thin metallic coating.

Even though I had a 10m section left over from my house, I chose not use it for lagging the boat heater ducts as I don't think it's a safe option.

EDIT: I followed the link to the tech specs and it is apparently rated to 140degC... so not the same as my stuff... would be interesting to test its characteristics at high temperature as it might well be a suitable option after all.
 
We fitted the webasto stuff after fitting the heater. The difference was; without you could hold your hand infront of the grill. With insulation; you could only manage a couple of seconds before it was too hot. This was on a 4m run from heater to cabin outlet grill. So definitely worth using something.

Pete
 
I used 100mm version of this ducting (bought on ebay) for my chinesium workshop heater. Took ages to heat the place as the ducting got very warm whereas with no ducting fitted it heated the space up alot quicker.
 
I used two layers of thermal foil(The diy stuff that's bubble wrap)and it made a huge difference to the heat output. Possibly the cheapest most effective job I've done on my boat in 12 years of tinkering and fettling.
 
OP here. In the end I decided that the aluminium foil insulation I linked to was a bit bulky so have gone for 4m of self seal 67mm armaflex (under £7 for 2m from JTM Plumbing) which is rated to 110c and a length of the proper Webasto stuff rated to 140c which Mellor are selling on eBay for £12.99 including postage. It seemed like a good compromise as I could only find the high temperature armaflex with a 60mm id which I thought might be a bit tight. It was also no cheaper than what I've gone for. Incidentally B&Q have a clearance deal on thermawrap for 60p a roll but I couldn't see what it's rated to and seemed a bit of a faff for less insulation
 
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