Economy 7 Water Tank - Timer Switch

[Echo the husky]

I'm still pretty lost! ....

When all taps are closed, a small amount of water heated by the Willis heater will rise up into the expansion pipe, with the displaced cooler water moving downwards into the cylinder and/or the feed from the Willis heater. Since no water is being drawn, no water will be drawn from the bottom of the cylinder. So long as the taps remain closed, I cannot see why water at the top of the cylinder should get significantly heated - which would mean that there would be no significant heating of water in the cylinder whilst the taps remain closed.

The heated water doesn't go up the expansion pipe (ok the level might rise a bit) the cool water comes from the cylinder not the cold water feed tank, there will be no flow from the cold tank unless a tap is opened. thermosyphon is surprisingly effective, and the water will have no problems circulating around the cylinder. It has been used for cooling stationary engines for decades.

It seems no pumps. I can see how therm-syphon will move the water,

I'm not sure how the system in your photo works, the outlet pipe seems to route under the inlet pipe? All the ones I've seen have been piped as your diagram.

 

[JohnW2]

It seems no pumps. I can see how therm-syphon will move the water ...

I'mnot sure that I can! "Move the water" from where to where? With all taps closed, I can't see why heated water should move anywhere, other than into the expansion pipe - remembering that water will rise through cooler (more dense) water and fall through warmer (less dense) water.

... what I can't see is how there as any control as to how much water is heated.

I presume that more-or-less all of the water in the Willis heater (however much that is) will get heated to the temp dictated by it's thermostat (I presume it must have one?). When a tap is opened, it will draw water from that in the heater (diluted by cooler water from the cylinder). That sounds to me to be similar to (but a bit 'worse than', because of the dilution) an 'instant hot water' unit with a small (1-5 litre under-sink reservoir) - in which case, as soon as all the heated water from the small supply (in reservoir or Willis heater) has been drawn, one will just be left with 'real-time' heating, which would need to be many kW to achieve a reasonable temp and flow rate.

I continue to assume that, IF the system works reasonably (are we sure it does?) I must still be missing something fairly fundamental!

 

[JohnW2]

The heated water doesn't go up the expansion pipe (ok the level might rise a bit) ...

I'm not talking about additional water moving into the expansion pipe. Rather, I'm talking about standard convection, with warmer (less dense) water rising through cooler (more dense) water, thereby displacing the cooler water which hence ends up below the warmer water - but with still roughly the same amount of water in the pipe (other than, as you say, a slight expansion).

... the cool water comes from the cylinder not the cold water feed tank...

Why? ... particularly given that (as I've also said) ...

.... there will be no flow from the cold tank unless a tap is opened

... thermosyphon is surprisingly effective, and the water will have no problems circulating around the cylinder. It has been used for cooling stationary engines for decades.

I may need some educating here, since I was under the impression that a 'thermosyphon' was all about convection. As for it "having no problem circulating [water] around the cylinder", I agree that convection would have no problem in doing that IF some heated water were introduced into the cylinder - but my problem is in understanding how heated water from the Willis heater into the cylinder (seemingly contrary to the standard mechanism of convection)

'm not sure how the system in your photo works, the outlet pipe seems to route under the inlet pipe? All the ones I've seen have been piped as your diagram.

None of my photos here