Diesel cabin heater piping

[goboatingnow]

I’m fitting a diesel heater this autumn , I was wondering if anyone has used 75mm PVC flexible ducting as an option to the more common aluminium which I always finds hets crushed

I’d use a 3 foot aluminium initially on the heater output.

The pvc pipe is also considerably cheaper to boot

[silvercreek]

PVC would be fine on the air intake side, but could melt if used on the output (heated) side. I would bite the bullet and stick with the multilayer paper/aluminum conduit.

[goboatingnow]

Originally Posted by silvercreek

PVC would be fine on the air intake side, but could melt if used on the output (heated) side. I would bite the bullet and stick with the multilayer paper/aluminum conduit.

Given the output temperature is around 55-70 degrees C , why would it melt , my old system was down at 50 within 2 metres of the heater.

I have no air intake plumbing anyway as it just draws internal boat air ( the heater will be the transom space )

[Jammer]

If you have any straight runs you can use rigid ductwork. It will deliver more airflow because the diameter is consistent and the frictional losses are less. I don't know about the situation where you are but in the USA you can get aluminum and galvanized ductwork in 75mm at any home center. You can bend it into an oval shape and it will still work better than flex. It is easier to work with than PVC. You can seal joints with foil tape, rivets, screws, or a combination.


I have also used the insulated plastic ducting which works OK. It's the stuff sold as heating duct, not just flexible PVC pipe for plumbing.

[ItDepends]

Most flexible PVC ducting has a max temperature rating of 50 to 75 C. Are you SURE your heater can’t output anything hotter? Are you comfortable working that close to the limit? You’ll need to be pretty rigorous with your support. Even the higher rated pvc will be very soft at that temperature..

You boat, your choice. But do check the max temperature rating of the exact product you plan to use….

[Oeanda]

Judging by how things were a bit smelly for the first few days after I fired up our heater for the first time (using aluminium ducting), I’d be worried about off-gassing. Not sure what caused the smell specifically, but you know how it is with new stuff - generally carries a whiff of chemical badness from the factory. A little surface gloss or residue. And there was some foil tape on seams, along with whatever off-gasses from the new heater itself.

But it went away. I tend to assume that the aluminum duct is pretty inert after the initial cooking.
With PVC, perhaps not so much, since it’s basically a toxic material at heart.

Just a thought though, not science.

Maybe you could try the heater with a length or two of pvc and see how you feel about it.

Edit- Thinking about it for a couple seconds more -I realized that the vent outlets and a couple joins in our ducting are pvc. Through they’re pretty far from the heater. It’s the first few feet close to the heater that get crazy hot.

So -hmmmm…..

[goboatingnow]

Originally Posted by Oeanda

Judging by how things were a bit smelly for the first few days after I fired up our heater for the first time (using aluminium ducting), I’d be worried about off-gassing. Not sure what caused the smell specifically, but you know how it is with new stuff - generally carries a whiff of chemical badness from the factory. A little surface gloss or residue. And there was some foil tape on seams, along with whatever off-gasses from the new heater itself.

But it went away. I tend to assume that the aluminum duct is pretty inert after the initial cooking.
With PVC, perhaps not so much, since it’s basically a toxic material at heart.

Just a thought though, not science.

Maybe you could try the heater with a length or two of pvc and see how you feel about it.

Edit- Thinking about it for a couple seconds more -I realized that the vent outlets and a couple joins in our ducting are pvc. Through they’re pretty far from the heater. It’s the first few feet close to the heater that get crazy hot.

So -hmmmm…..

The first 6 feet will be aluminium.

But thanks everyone , food for thought

[wrwakefield]

For flexible heating duct you need a material that can handle higher temperatures than PVC can [160°F].

Aside from the aluminized ducting you mentioned, there are polypropylene [225°F], polyurethane [225°F], and silicone [450°F] flex ducting materials available.

I have used all 3 over time on different vessels. All work well and have better longevity compared to the typical aluminized paper ducts when used in damp environments.

In case this is useful.

Cheers! Bill

[silvercreek]

Originally Posted by wrwakefield

For flexible heating duct you need a material that can handle higher temperatures than PVC can [160°F].

Aside from the aluminized ducting you mentioned, there are polypropylene [225°F], polyurethane [225°F], and silicone [450°F] flex ducting materials available.

I have used all 3 over time on different vessels. All work well and have better longevity compared to the typical aluminized paper ducts when used in damp environments.

In case this is useful.

Cheers! Bill

Wow these are great. Both look superior to the paper/aluminum sandwich version. The polypropylene Especially.

[c.K.]

Originally Posted by goboatingnow

I’m fitting a diesel heater this autumn , I was wondering if anyone has used 75mm PVC flexible ducting as an option to the more common aluminium which I always finds hets crushed

I’d use a 3 foot aluminium initially on the heater output.

The pvc pipe is also considerably cheaper to boot

Better safe then sorry the heat from forced air diesel heaters can be too much for a pvc flex tube expecially close to the unit

[goboatingnow]

Originally Posted by c.K.

Better safe then sorry the heat from forced air diesel heaters can be too much for a pvc flex tube expecially close to the unit

Thanks. I’ll stay with the usual all aluminium ducting