how do i wind a copper coil?

[emlclcy]

I'm fitting a back boiler to a morso and I was thinking it would look nice to have 15mm copper pipe wrapped around the flu 5 or 6 times to further heat the water.

so looking at ideas how to fabricate this, my thinking so far is to fill a pipe with sand or salt, solder closed both ends then somehow wrap it around the right sized mandrel. I'm not sure if a bendy spring pipe bender would get stuck forming a 4 1/4" diameter coil.

will it cause the flue to tar up to much I wonder?

[Flyboy]

I'm fitting a back boiler to a morso and I was thinking it would look nice to have 15mm copper pipe wrapped around the flu 5 or 6 times to further heat the water.

so looking at ideas how to fabricate this, my thinking so far is to fill a pipe with sand or salt, solder closed both ends then somehow wrap it around the right sized mandrel. I'm not sure if a bendy spring pipe bender would get stuck forming a 4 1/4" diameter coil.

will it cause the flue to tar up to much I wonder?

Ordinary 15mm (0.7mm wall) copper pipe from the local DIY shop is too thin a wall to bend this tightly. Go to your local metal stockist & get some thick walled annealed copper tube.

 

I seem to remember that there is a thicker 15mm (1.00mm wall) copper tube for underground use that came in coils. You may be able to get this from a proper plumbing supplier.

 

In either case I doubt if you would get a bending spring out even if you could find a spring long enough.

Edited October 15, 2015 by Flyboy

[David Mack]

If this is going to heat water the coil will need to be in intimate contact with the flue pipe. That implies winding the coil to a size slightly smaller than the flue pipe and forcing it on.

[Victor Vectis]

But remember copper work hardens so you will need to keep annealing the tube.

 

ie, When it starts to stop bending (if you see what I mean!) heat up to dull red, or just below, and quench in water.

[bottle]

This has been discussed before and the outcome was forget it, I seem to remember, the flue doesn't get hot enough.

 

Now this did not come up but maybe a 'water jacket' would be better, over to those that can work it out.

[magnetman]

I think there was some concern that cooling the flue too much might reduce the draw and make the fire misbehave.

[emlclcy]

Ordinary 15mm (0.7mm wall) copper pipe from the local DIY shop is too thin a wall to bend this tightly. Go to your local metal stockist & get some thick walled annealed copper tube.

good call, thanks.

was going to use regular straight tube but now I see there is a difference

[ditchcrawler]

good call, thanks.

was going to use regular straight tube but now I see there is a difference

http://www.asap-supplies.com/search/copper/copper-tube-10m-coil-302750I dont know if this would do the job

[emlclcy]

This has been discussed before and the outcome was forget it, I seem to remember, the flue doesn't get hot enough.

can you remember if it has actually been tried or is it speculation?

[ChimneyChain]

Here are.

 

Darren

[peterboat]

they used to call them trojan collars some working boats up here had them according to keith an ex working boatman

[Arthur Brown]

First have you checked how much heat you have available at the chimney!, is it actually worth the cost of the work and the copper? Remember that a chimney needs heat to function, if it's too cool then tar accumulates and it's hard to get a good airflow through the firebox.

 

There was once a "working hypothesis" that a litre of liquid fuel contained 11KWhours but 1KWh is needed to make the chimney work right so you can use 10KWh, this does indicate how much heat is needed to make a chimney work right.

[jake_crew]

You need newly made (drawn) annealed copper tube which is still soft.

 

Copper age hardens so a piece 6 months old will be much more difficult to form.

[DHutch]

I'll be honest, other then when running it stupidly hard (say, to keep it warm with the windows open while working on the boat) our flu is little above warm and I would not really worth it. We have a cast iron drainpipe as the flue, and the gasses are basically cold by the time the come out.

 

 

 

Daniel

[MtB]

You need newly made (drawn) annealed copper tube which is still soft.

 

Copper age hardens so a piece 6 months old will be much more difficult to form.

 

 

I don't think this is right.

 

'Standard' copper tube is 'half hard' and is designed to be bent in a tube bender, but not by hand. This remains true whatever its age.

 

'Soft' copper is fully annealed and can be formed by hand. 'Half hard' copper can be fully annealed by heating it to cherry red then quenching (or allowing it to cool naturally) then formed by hand.

 

'Underground' copper tube is fully annealed and very suitable for hand forming but difficult to find these days.

 

But as others have said, the heat available from the flue is minimal so the whole exercise will be a waste of time, money and effort. If it worked, everyone would be doing it already.

Edited October 15, 2015 by Mike the Boilerman

[emlclcy]

But as others have said, the heat available from the flue is minimal so the whole exercise will be a waste of time, money and effort. If it worked, everyone would be doing it already.

are you sure?

fitting a back boiler (inside the fire) by nature will make you run the fire harder to heat the ever cooling back boiler with exhaust going up the flu.

when I measure the stove temp the bottom of the flu is hot, the sides are hot

so has anyone actually tried this?

[emlclcy]

the concept of this idea is the boat has central heating powered by a erberspacher which when I got the boat about 4 months ago had not been used for years, the system has been drained and it is noisey. so I'm thinking a back boiler hooked upto the central heating pipes and a water pump to circulate. I don't like running the engine which warms the airing cupboard so this will do the same to a lesser degree but hopefully stopping damp forming at the back of the boat.

the flu coil would be 4 or 5 loops, sort of more visual than functional, a bit like the Vulcan sterling engine spinny thing

[magnetman]

the concept of this idea is the boat has central heating powered by a erberspacher which when I got the boat about 4 months ago had not been used for years, the system has been drained and it is noisey. so I'm thinking a back boiler hooked upto the central heating pipes and a water pump to circulate. I don't like running the engine which warms the airing cupboard so this will do the same to a lesser degree but hopefully stopping damp forming at the back of the boat.

the flu coil would be 4 or 5 loops, sort of more visual than functional, a bit like the Vulcan sterling engine spinny thing

Would the intention be to feed the water into the same circuit as the back boiler? If you were intending to have a seperate circuit then an extra pump would be needed = more electric consumption.

 

I don't really see what advantage it would give if you have the back boiler fitted anyway. I suppose it may have an effect of some sort and would look nice if done well

 

Not sure you will be sending enough heat to the back of the boat to solve a damp problem. Depending on length of boat a second (small) stove may be worth considering. Nothing like a coal fire to dry the place up.

[nb Innisfree]

As an experiment I made a heat exchanger from 22mm copper tube and mounted it against the back of our Villager Puffin. Result- next to useless! Surface contact on the tubing was too little, maybe square tubing might have worked!

[MtB]

are you sure?

fitting a back boiler (inside the fire) by nature will make you run the fire harder to heat the ever cooling back boiler with exhaust going up the flu.

when I measure the stove temp the bottom of the flu is hot, the sides are hot

so has anyone actually tried this?

 

 

For clarity, no I'm not sure and I haven't tried it. I'm only saying it won't work having thought through the theory.

 

A back boiler works because it is fitted directly over the firebox so picks up huge amounts of radiant heat from the glowing coals.

 

A copper pipe (of any cross sectional shape) can only draw heat energy from the flue pipe which is shielded from the high energy heat source by the baffle. So although the flue pipe gets hot from conducted heat from the stove top and from the smoke/products of combustion passing through it, the amount of heat energy heating the flue pipe is tiny in comparison to the heat radiating from the coals.

 

Those who retro-fit a back boiler often comment on how much less well the stove heats the room and how much more fuel they have to feed it. This is because the back boiler is nicking perhaps 25% of the combustion output. Pipes wrapped around the flue will just cool down the flue tube a bit, collecting (at a guess) perhaps 1% of the heat the firebox is producing.

[magnetman]

One of my favourite French expressions comes to mind.

 

"C'est comme pisser dans in violon"

 

Its like pissing in a violin

(Similar to "raking water uphill")

Edited October 16, 2015 by magnetman

[FadeToScarlet]

they used to call them trojan collars some working boats up here had them according to keith an ex working boatman

Similarly, I know of a converted ex-working boat with a good deal of the exhaust from the air-cooled Lister wrapped in copper tube, to give "free" hot water.

[BEngo]

The Lister exhaust is passing about as much heat as the engine is delivering to the shaft and alternator, (and lots more than the fire flue) and it is generally a lot hotter than a stove flue is in normal conditions. A water jacket will be more effective than a coiled copper tube.

 

N

[magnetman]

The Lister exhaust is passing about as much heat as the engine is delivering to the shaft and alternator, (and lots more than the fire flue) and it is generally a lot hotter than a stove flue is in normal conditions. A water jacket will be more effective than a coiled copper tube.

 

N

And the Lister does not rely on the exhaust pipe temperature to operate correctly and safely like a fire does.

 

Out of interest - is the water from the Lister exhaust system coil mentioned tapped off directly as hot water or is it circulated through a calorifier coil ?

[emlclcy]

Would the intention be to feed the water into the same circuit as the back boiler?

yes. the erberspacher is at the back of the boat, replace this with a circulating pump then T into central heating pipes which pass close to the stove at the front so it should be a simple modification.

I have to run the stove at its absolute minimum at the moment otherwise the cabin get to hot so spreading the heat should help to reduce dampness, which will involve driving the stove a little harder (should make the airwash work - its a 1430) well that's the thinking