I
immerse
I have just got my system going with a home-built controller to use 'excess' PV generated electricity to heat my indirect hot water cylinder. This has a top entry 3kW Steeple 80027BT immersion heater (which I imagine is 27 inches long, I cannot find any technical data) and a Diamond WT18 thermostat, which I believe is 18 inches long and appropriate to the immersion heater. I use a step down transformer to deliver 1.5 kW into the immersion heater when there is sufficient 'spare' PV power available.
This all works as expected except that at the end of a long sunny day the water temperature is highly stratified, very hot at the top and only mildly warm half way down the 90 cm x 45 cm cylinder, where I would have expected the thermostat sensor to be positioned. There is plenty of energy available, about 12 kWh, enough to raise the whole cylinder from room temperature to boiling point. Conceivably this could arise because the immersion heater is not being driven to its design operating power - can anyone comment on this, please? (A number of other people, using either transformers or Triac load switching, comment that they get a full cylinder of hot water).
Alternatively, there could be some sort of fault with the heater or thermostat (although the max. temp. of the water is about the 70 deg C I set on the thermostat). Or maybe this arises because the heater is a long thin thing delivering heat over its whole length? If so, why do others not experience the same problem? Is it possible to purchase a 27 inch immersion heater wherein the whole power is delivered at or near the bottom end rather than along the whole length? This would lead no doubt to better convective stirring and less stratification.
Any advice would be gratefully received!
This all works as expected except that at the end of a long sunny day the water temperature is highly stratified, very hot at the top and only mildly warm half way down the 90 cm x 45 cm cylinder, where I would have expected the thermostat sensor to be positioned. There is plenty of energy available, about 12 kWh, enough to raise the whole cylinder from room temperature to boiling point. Conceivably this could arise because the immersion heater is not being driven to its design operating power - can anyone comment on this, please? (A number of other people, using either transformers or Triac load switching, comment that they get a full cylinder of hot water).
Alternatively, there could be some sort of fault with the heater or thermostat (although the max. temp. of the water is about the 70 deg C I set on the thermostat). Or maybe this arises because the heater is a long thin thing delivering heat over its whole length? If so, why do others not experience the same problem? Is it possible to purchase a 27 inch immersion heater wherein the whole power is delivered at or near the bottom end rather than along the whole length? This would lead no doubt to better convective stirring and less stratification.
Any advice would be gratefully received!