Cabin heater vent tube construction

C

Ctarmigan

Member
Hello all,

We have a Toyo NS2800 cabin heater on our 22. It's wonderful; lots of heat and low fuel consumption. With a two-year-old on board, this really extends our season (which in the Yukon can otherwise be rather short).

I've been doing some maintenance on it (dealt with a small exhaust leak at the fuel nozzle), and would like to replace the vent tubing. It's currently made of 2" ABS. This has held up remarkably well, only a little deformation near the heater output, but I'd rather use something better suited to moving hot air. Presumably, breathing aerosol ABS derivatives isn't good for us.

What have you used for vent pipe material for cabin heaters? Do I need to go with something specific, or is there a widely available material that can be repurposed? I'd prefer something rigid, based on the configuration I'd need, and would need to incorporate both a 90° bend and a t-junction. Heater output is 65mm diameter.

Cheers,

Oliver
 
I have the smallest Espar heater, so the exhaust is only 3/4 inch. There is commercially available stainless flex tubing in that size. I only used a small section of that (for alignment allowing the rest to be straight pipe) before changing to 3/4 inch copper plumbing pipe. The copper (and the corrugated stainless) is then insulated with fiberglass tape, often sold as "header tape" for car exhaust.

You may need is some flexible 2 inch metal pipe. It is available in plumbing shops, but most is chrome plated and it is the threaded fitting that is 2" (the tubing being smaller). The chrome plating, if inside the flex pipe, would make soldering difficult/impossible. An exhaust could also be done with all soldered 2" coper pipe and fittings, but the last time I priced 2" copper fittings it was shocking. Well, so is the straight pipe. I checked the melting temp of my solder and am confident that my exhaust temp won't be an issue. I also used high-temp silicone at all clamp-on connections. I didn't want any possibility of exhaust leakage in my little cabin.

Corrugated pipe is much more resistant to flow. Espar publishes a table showing the exhaust length and number of bends allowed. My guess is most of the trouble with small heaters is caused by heat and exhaust systems being too restrictive/long.


https://www.supplyhouse.com/Holdrite-QF ... JkEALw_wcB
 
replace the vent tubing. It's currently made of 2" ABS. This has held up remarkably well, only a little deformation near the heater output, but I'd rather use something better suited to moving hot air.
Click to expand...

My interpretation of this is that he is referring to the hot air output duct tubing, not an exhaust hose (which is 1" and ABS plastic would melt). The duct tubing is 2 3/6" (?) vs 2"..

There are any number of flexible "vent" hoses which are used as various hot air ducts/vents on Amazon--and in plumbing supply houses which are made of metal (aluminum?). There are multiple ways to "splint" the flexible hose to keep it from sagging between bulkheads or other support points--I have used PVC pipe cut in half or 1/3" and wire tied to the ducts.
 
Thanks thataway - yes, I should have better clarified, I'm looking to direct heated air, rather than exhaust (my exhaust pipe system's stock, and works just fine).

I'll check out some of the flexible hose you mentioned, and see if I can get it in hand to get a feel for rigidity; though I prefer the rigid construction I have right now (if not the material), there may be room to use flexible tubing if it's durable and rigid enough.

Oliver
 
For the heating duct, I bought a kit like linked below (after checking it was the right size). When shopping, I thought that some of the "big name" heaters used a weird proprietary size, so be careful or get a bushing that changes size. For my big boat, I bought a venting kit that included a couple connector sleeves, a Y, and two Els. After I was about 5 feet from the heater, I changed to large foam pipe insulation (linked below) and white PVC fittings. That was because I was going through a long unconditioned space (the bilge) that didn't need heating. May not apply to the C Dory, but just for info it puts up with the heat.

https://www.ebay.com/itm/353334951655?h ... fresh=true

https://www.zoro.com/aeroflex-2-x-6-ft- ... 8gEALw_wcB

Although the heat doesn't seem dangerously hot, I left my Crocs sitting in front of the shortest heater run and the heat shrunk one of them to the point that it didn't fit anymore. Crocs can't take the heat.
 
Ctarmigan":1ktegjj7 said:
Hello all,

We have a Toyo NS2800 cabin heater on our 22. It's wonderful; lots of heat and low fuel consumption. With a two-year-old on board, this really extends our season (which in the Yukon can otherwise be rather short).

I've been doing some maintenance on it (dealt with a small exhaust leak at the fuel nozzle), and would like to replace the vent tubing. It's currently made of 2" ABS. This has held up remarkably well, only a little deformation near the heater output, but I'd rather use something better suited to moving hot air. Presumably, breathing aerosol ABS derivatives isn't good for us.

What have you used for vent pipe material for cabin heaters? Do I need to go with something specific, or is there a widely available material that can be repurposed? I'd prefer something rigid, based on the configuration I'd need, and would need to incorporate both a 90° bend and a t-junction. Heater output is 65mm diameter.

Cheers,

Oliver
Click to expand...

I use Hi temp heater /AC duct tubing purchased at
https://www.fisheriessupply.com/ I also use galv. stove pipe of various sizes & insulate as nec. :thup
 
Thanks, all - I'll see about getting my hands on the appropriate vent tubing material for a long-term fix.

In the interim, I've made a hybrid solution. The old ABS had some of the aluminum-lined vent tubing taped to the outside, presumably to protect users against touching the hot ABS. I built a new vent system from ABS, but had sufficient old aluminum-lined vent tubing to be able to cut it down to reduce diameter and line the inside of the ABS tubing. Now there's rigidity I'm looking for from the ABS 'plumbing', but presumably some insulation of the ABS from full-blast heat provided by the internal vent tube lining.

As yet untested - we'll see how this works over the coming weekend.
 
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