No Hot Water after draining down system

[flutterbye]

Oh I see! Thanks for the explanation - makes sense.

Still not sure why the immersion method wouldn't have worked though? Would I have blown up the cylinder?

 

[bab]

It wouldnt of blown up but would of turned itself into a kettle boiling the water in the cylinder & left alone would probably damaged the coil seals boiled up in to the header tank which if plastic would loose shape until it collapsed. seen it done once. BIG MESS.

 

[Softus]

Would I have blown up the cylinder?

Probably not.

The effect of removing the immersion thermostat is to cause localised boiling within the cylinder, next to the element but not particularly close to the coil. The result would be to create a bunch of bubbles and scale - thanks to convection, it wouldn't boil the water within the coil; even if it did (which it wouldn't), the energy expended by the element (3kW) is hugely less than that produced by a gas boiler without a thermostat (24 kW, typically).

The effect of removing the boiler thermostat is to cause pockets of steam in the pipework - pipework within which water can circulate. The creation of the steam has a tendency (some would say a 100% tendency ) to 'shove' water (and air) along the circuit and kick-start the circulation.

BTW, an undetected run-away immersion heater has been known to have fatal consequences, hence the recent European standard for IH thermostats with a built-in non-auto resetting overheat thermostat.