Hot air ducting?

[aquaplane]

After strugling bending myself in unnatural positions fitting the new Wallas I was gob smacked to find that 60mm ducting for it is £18 per meter. Bespoke lagging is £11 per meter, I only need 7 meters but I don't like dealing with Dick Turpin unless forced to at pistol point.

Now me being a carefull Yorkshire man thought I would do a bit of research to see if I could trim a bit off that, a philosophy you Scots will simpathise with I would think.

Sure enough on fleabay it's as near as makes no difference to the same price, once you add postage. I have found a local car place that does just what I want at £16:50 for 2 meters, but it comes in 2 meter lengths which is OK for the closest outlet but not for going to the fore cabin.

So, does anyone know how hot the air is coming out of an Eber/Webasto/Wallas, I would think they are all similar?

Does it have to be aluminium ducting? There are alternatives which are rated to anywhere from cold to 350°C, all at various prices of course.

What have you used? If it's not the "official" stuff what is it and is it OK? I can cope with plastic ducting if it goes a bit floppy, but not if it ends up in a puddle or on fire.

[marisca]

Having found similar prices a few years ago, I sympathise. My solution was black plastic drain pipe from B&Q for straight runs through lockers, the proper stuff for the bendy bits + the application of duct tape. It solved the squashing the pipe problem, is still to be lagged, but after about 4 years there is a sort of burnt plasticky smell that I suspect is from the pipe but I haven't fully investigated - the CO monitor doesn't get excited by it.

[SteveN]

This is the stuff used with the Truma gas heaters in motorhomes:

http://www.leisureshopdirect.com/carava ... ystem.aspx" onclick="window.open(this.href);return false;

It's 65mm, but perhaps it would be OK. Fair bit cheaper anyway..

[aquaplane]

Steve, it's a shame it's not 60mm. It just shows that the Eber/Webasto/Wallas folk are charging what the market will take, that's a bit bigger and £5:40 a meter. I have seen adaptors from 75 to 100 mm but non for 60 to 65mm, I wonder what I can do with a bean tin and a pair of snips? I have some silicone based sealant good for 180°C, I could blather up gaps with that.

One smarty pants on fleabay is charging £9:99 for 60mm which is good untill you see it's per half meter!

The drain pipe sounded good until the "burnt plasticy" smell reared it's ugly head, that's what I was affraid of, it's got to be pretty bullet proof, I know it's a cheapish boat but I don't want to burn it down and die.

[Clyde_Wanderer]

Aye Bob, I certainly would not advice using any plastic as on my eber the temp at the heater output is 100deg plus.
I bought the correct duct from the marine electrical place at Kip marina, that was winter 08/09 and it was aprox £12 pm for 75mm then and about the same for 60mm.
That caravan duct on the link is the same stuff only a different outside colour.
you could use cut off sleeves of it to make up the difference in dia's.
Whatever you use I suggest you fit the 3M Wabasto insulation as it eleminates a 30% heat loss from the ducting and reduces the risk of condensation on the hull if running through lockers under bumks etc, it is dear but certainly worth it.
I get almost the same heat from the vent in the heads as from the vent at aft end of main cabin which is only 3-4 ft from heater.
Dont buy the plastic vents from an ebay company called Eberbasto as they fall apart when they heat up to temp.
Incidently when I place a hand on the duct insulation it is barely luck warm, couldent do that with the bare duct!
I would check the spec on that Truma ducting, should be rated for at least 130 degree c, and I wouldent use any silicones as sealer the fumes could be poisen. use exaust putty/gum gum.
Eamonn.

[bosun higgs]

I installed a gas powered Propex hot air heater on my prout cat and the only way I could get the hot air from the engine bay where I wanted to put the heater into the cabin was to make use of a plastic (abs) drainpipe that Prout had glassed in as a cable duct. Worked fine. Bit of a smell of hot plastic at first but that went away quickly. Didnt melt the pipe. Didnt set fire to it either.

The air cant be too hot or you would burn yourself. Suggest you ask Wallas what the outlet temp is. ABS pipes can be made to withstand domestic hot water - the pipe maker will have a max operating temp. Compare them.

[aquaplane]

I got the beast fired up over Easter, and very nice it was too. It needed to be, cold and wet and miserable with dry bits would best describe the weather.

We did see Mercury during a clear spell on Saturday evening which was a first and a highlight of the w/e.

I only fitted ducting to the bottom, hotter, outlet to the saloon.
The top outlet will go to the forecabin when I have enough ducting and a new pilot hole drill for the hole cutter! At the mo it's just blowing into the ¼ berth (so that's to the saloon too).
The ducting I have fitted feels a bit more than hand hot, more than a second or two and it's time to let go. I'm going to measure the temp more scientificaly as I'm sure that it's not as hot as I imagined it would be, it'll help decide what lagging to use.

Thanks for the thoughts.

[aquaplane]

I measured the temp of the warm air coming out of the heater.
It was 60-65°C out of the bottom duct and 55-60°C out of the top one, so expensive stuff rated to 250°C is a bit OTT.

[Gordonmc]

If it is of any help I got ducting from a company in Milngavie, Flexible Ducting Ltd. They make ducting in a variety of diameters with high temperature tolerance.
I turned up at the factory and left with a couple of off-cut lengths the same day. It was a lot cheaper than ebay Eberspacher stuff.
I lagged it with rockwool and covered that with cheapo plastic air ducting out of B&Q.

[claymore]

Have you thought of buying a few thermos flasks and bottling the hot air as it comes out for release later?