Originally Posted by christhefish
I was wondering if anyone had thought about making a heat exchange unit to heat the calorifier
and towel rail . Using soft copper pipe coiled around the flue of a heater
because there is such a waste of heat . I realise I would need an expansion tank and some careful planning but it must be possible or shall I carry on dreaming while this gale is blowing !
Yes, I've been planning it for use on my Sig heater, very similar to the Refleks. I had a soft copper coil in my old boat
, in which I also had a Sig. In that installation
I had the coil in the firebox and always worried about corrosion
of the copper from fuel
On this one I'm thinking of doing what you described making a coil that wraps around the flue. I will enclose the coil wrapped flue with a larger diameter flue pipe so that it concentrates the heat. I'm pretty sure it'll work
. My chimney flue is 3" so I'm going to use 3/4" copper and a 6" SS flue pipe to enclose the assembly.
The picture is of the heater with the fin radiators I made, which cool the flue pipe by at least 100 degrees F, the heat at the deck head
was reduced by 100 + degrees the rest still goes out the chimney. I expect that I'll harvest most of that heat using the water
jacketed flue. The trade
off is maybe that I'll have run the draft
assist fan a bit longer, and, that I'll not have quite so much heat from the chimney fin radiators. But the head
compartment and forward compartment will be warmer. I'm not yet sure if there will be enough transfer from the heater coil to heat the water
With the coil in the firebox it took a while to to get the convective water flow going or it would boil the water and create a steam lock up, I finally put in a small aquarium water circulator pump
that only needed to run for a little while to ensure that the convective flow started properly and then it could be shut down. And yes you will need an expansion tank and a water venting valve at each end of the water piping.
On my old boat
I was harvesting enough heat to distribute to radiators I'd installed under the cabin
soles and still had plenty going up through the flue. I enclosed that flue pipe with a 12" diameter fiberglass insulation
pipe with a 4" diameter tee top and bottom and harvested a huge amount of heat that way. The heat sharing of the insulated flue pipe was so great that it melted the muffin fan I had installed incorrectly on the heat outlet rather then the inlet and almost caught the overhead on fire at the deck
As I write about the old installation
I suspect that there would be enough waste heat for the water heater if the coil was long enough and enclosed correctly.
I've also installed a truly excellent down draft
cap called the Vacuvent. I can't praise it highly enough since I installed it I've experienced no blow backs and no fire box explosions. (photos below)
Enjoy the dreaming, I've often enjoyed the winter gales snug below with the heater running.