As usual, click an image for a larger view.

What have I got? This is a relatively standard domestic indirect hot water tank with a 28mm indirect coil.
(The full spec is shown on a label lower down)

I'm planning on having several heat generating sources in the future. At the moment the hot water tank is only heated by electric. I 'used' to have a LPG boiler running off a bulk tank in the garden, but that was ridiculously expensive to run, so the LPG system was removed. I've always wanted the HWT to be heated off the wood burning stove, but I'd have to take the house to bits to install the pipework and the HWT and WBS were at opposite ends of the house, so the two were never connected. Time has now moved on and I am room by room gutting them to install thick layers of insulation which has made a massive difference to the warmth of the property, let alone cutting our use of wood fuel by around two thirds. I have covered the pipework between the WBS and the HWT in the Wood Burning Stove - Flue Heat Recovery pages.

Coming back to this tank... Present and future heat sources will be wood burning stove, thermal solar panels, air source heat pump and obviously the emersion heater. Looking around there are many fancy ways to connect various heat sources with loads of different control systems, but no one seemed to have any definitive ways to connect all sources, especially as I would need different solutions/liquids in each system (anti-freeze, Fernox), so I got thinking and came up with the idea of modifying my HWT to have several direct heat exchangers built in to and on the tank. Many have suggested using external plate heat exchangers, but I felt I'd have a lot of un-necessary pipework and pumps that way, plus some loss of heat transfer efficiency, hence my experiment of modifying the tank to have a number of separate indirect heat transfer systems.


First I cut off a section of the insulation.

Rather than openening up the coil, only to have to re-wrap it around the tank, I carefully opened up the coil enough to pass it over the end of the tank, thus little dressing was required.

When in position I liberally brushed on some Laco flux.

The tank is sat in an up-side down work-mate type thing to make it easier to work on.

When I had soldered the pipe in place, I then ran another run of solder on the other side of the pipe.

BTW I brushed extra flux on for every section.

It was a shame it was not possible to easily fit the nice uniform coil in through the emersion heater port, as it looks quite neat. To get the coil in through the port, I had to expand it slightly to enable me to wind (screw) the coil down through the port, then it was the tricky bit of getting the bottom of the coil to come out of the bottom hole which was finally achieved by first adding a bit of wire to use as a fish to the bottom of the coil, then out through the bottom port. Got there in the end!