Boiler design ideas

[baffle]

Morning Baffle, nice project.

Just a couple of points, will you be adding an inhibitor and antifreeze to the indirect circuit ?

Hello Ducati - thanks for interest. Yes will add inhibitor/antifreeze once I 'm happy with the installation. Have had boiler up and running and it heats up fine and quick, and also lets the hob get most of the flames so we can still cook our toast on it I have a problem though with getting the thermosyphon to work through the water cylinder, although the radiator/s heat up fine and they are at the far extent of the thermosyphon circuit. Have discovered that coil in the cylinder was very squat, convoluted and narrow bore - i.e. not at all good for a gravity system, so am having coils in cylinder replaced with bigger bore deep coil. Hope to get cylinder back tomorrow, and fingers crossed this will do the trick.

Have been troubling folks on a canal boat forum with the thermosyphon issue - see http://www.canalworld.net/forums/index.php?showtopic=41586 Was planning to give a full update here once I had got it all up and running to my satisfaction (not forgetting to let Fintray know about tarring up etc!)

cheers

Baffle

 

[baffle]

Bit late here, but, if your tank is a little higher than the coil,then back syphoning will not happen. And the bigger the height difference, the better the flow.
KF

(done a few similar things and some solar work)

Hello Kemppi Frog. I guess you mean tank higher than boiler, not tank higher than coil? Height differences difficult to achieve on a narrow boat, and I think I have to break normal plumbing rules and have the heated appliances at a lower real level than the boiler. But as long as there is enough pipework going straight up from the boiler, this potential is enough (hopefully) to get the syphon flowing. It did on my old boat, and it is on the new circuit too - although I aint sorted the cylinder out just yet.

 

[rtbcomp]

As long as the outlet from the boiler is level or lower than the top of the heating coil or rads and the return back to the boiler is lower or level to the bottom connections of the heating coil and rads you will get thermo-syphon. The bigger the difference the greater the thermo-syphon. I'm assuming that you won't be sailing on any sloping canals.

Heat will always flow from the hottest part (boiler) to the cooler parts (rads &c).

I don't think a non-return valve will be necessary, in fact it could impede the convection currents in the system.

 

[KemppiFrog]

Baffle, yes, I was calling your heating half pipe a coil and your storage the tank. Non-return valves not a good idea, esp if the height difference is minimal. I saw an open top circuit in a solar magazine that used a form of oil trap to stop back siphoning. It relighed on the oil floating on the top of the header tank and different height entry and exit pipes to work. IIRR the heated water arrived in a taller vertical pipe and displaced the oil and then exited at a level below the oil. If it tried to back siphon, it was trying to draw light oil down the inlet pipe and the difference in specific gravities negated the small difference between hot and cold water. Hope that makes sense

I was asked to look at two solar systems that were loosing heat overnight. Both were panels on roof and storage two stories down with pumps to circulate.. The installers had negelected tp put in non-returns (OK with pumps) and the whole of the days gain back siphoned out to the night sky. The electric back-up then came on and wasted several kwh heating the sky untill the sun came up again.
KF