How thermal store boiler works?

[davidw]

How a thermal store boiler works!
I’ve got an old thermal store boiler and I’m trying to work out how it works. From what I understand the boiler keeps hot water at a steady temperature in the boiler whilst cold water enters into a coil which is held inside the hot water and this heats the cold water up so that it comes out hot. is this correct? Does this heated cold water feed into the central heating system to the radiators et cetera?

 

[Basher]

There are various ways this could be arranged - I'm assuming you are asking about an electric only system, not a gas boiler?
Taking an example I used to have:
The thermal store (ie cylinder) was heated by multiple immersion heaters from off-peak electricity, topped up by switching on if necessary during the day.
The bulk of water in the tank was pumped around the heating system, controlled by timer, thermostat, valves.
There was a heat exchanger inside the cylinder, positioned near the top, and water for the hot taps entered the bottom of that heat exchanger (eg coil) and exited at the top to the tap circuit. So it was like a combi gas boiler, heating water on demand From the retained heat in the cylinder.
The water you ran from the hot tap was not held in the tank, it was from the mains heated as required.

These days it's more usual to heat the cylinder by a coil fed from a gas or oil boiler, or solar, or heat pump, with an immersion heater for backup.

 

[davidw]

many thanks, I should have said I have a gas boiler connected to my thermal store. I'm trying to get my old head around which part feeds the rads and which part feeds the taps. I have an evohome setup 'controlling' the entire system. I'm not sure if the individual rad thermostats trigger the boiler or whether the boiler needs ot be kept on and te individual valaves then trigger the pupm? Sorry if this sounds confused, but I am! (<:
:

 

[Basher]

many thanks, I should have said I have a gas boiler connected to my thermal store. I'm trying to get my old head around which part feeds the rads and which part feeds the taps. I have an evohome setup 'controlling' the entire system. I'm not sure if the individual rad thermostats trigger the boiler or whether the boiler needs ot be kept on and te individual valaves then trigger the pupm? Sorry if this sounds confused, but I am! (<:
:

Sorry I made the wrong assumption!
The gas boiler is most likely plumbed to the coil in your cylinder, and also to the heating circuit(s), by one or two motorised valves. The water in your cylinder is probably the water that is fed to the hot taps.
Evohome either gets temperature info from each radiator valve head, or thermostats in the room(s), depending how it was set up. Whenever a thermostat detects room temp lower than set point I would expect it to energise the boiler, and the boiler will typically manage the pump (for example there might be pump over-run so the pump runs for a bit to remove residual heat after the boiler stops running).
Evohome 'learns' the heating and cooling characteristics for each thermostat, and is supposed to manage the steady state boiler switching to avoid overshoot or undershoot of temperature. Well it worked well for my last house!

There's an Evohome forum, also the Resideo website which sells all the Honeywell kit and can provide technical support.