Thermostat swithching

[Gavin Horton]

I've fitted a 300ltr thermal store a year ago and have just recently added solar water heating evacuated tubes. What I'm wanting you do next is get the stats to turn on the rads when the water achieves 65c. As the water from the rads returns it lowers the temp to around 45c while the fire is running. When I let the fire go out at the end of the night I need the stat to turn off at 35c. Is there away of achieving this with a single or duel stat? And what would be the wiring diagram be?

 

[Leesparkykent]

I've fitted a 300ltr thermal store a year ago and have just recently added solar water heating evacuated tubes. What I'm wanting you do next is get the stats to turn on the rads when the water achieves 65c. As the water from the rads returns it lowers the temp to around 45c while the fire is running. When I let the fire go out at the end of the night I need the stat to turn off at 35c. Is there away of achieving this with a single or duel stat? And what would be the wiring diagram be?

why do you need it to switch off at 35C? is this due to condensation and the fire/burner?

 

[Dave OCD]

You'd be looking at a couple of pipe 'stats to achieve this I think.

 

[Leesparkykent]

You'd be looking at a couple of pipe 'stats to achieve this I think.

I was thinking of a low limit pipe thermostat on the return set to 35C and the thermal store thermostat set to 65C. The low limit pipe thermostat closes on temp rise which is wired in series with the thermal store thermostat and pump/valve for the heating.

 

[Dave OCD]

Yes that's it Lee, I was wrong with the 2 pipe thermostat thing, it's been a hard week ! This is a similar set up to one that I've done a few times with a frost stat in series with a pipe stat on the heating return to shut down again as soon as the system warms through.

 

[dansk]

I've done this a few times but can never remember how to wire it, I've done via the tank stats and a relay. once the top stat opens it engages the relay until the bottom stat closes and cuts the electric feeding the relay. which then operates the two port valve.

 

[SparkyChick]

I've done this a few times but can never remember how to wire it, I've done via the tank stats and a relay. once the top stat opens it engages the relay until the bottom stat closes and cuts the electric feeding the relay. which then operates the two port valve.

Never done it personally, but this is how I concluded I'd do it when I read the OP.

 

[freddo]

Here is my attempt!

View attachment 35218

 

[dansk]

it's similar to this relay set up

View attachment 35219

 

[Gavin Horton]

why do you need it to switch off at 35C? is this due to condensation and the fire/burner?

No. The rads run at 40c and are designed to run as a back ground heat. If the middle portion of the thermal store drops below 35c the rads become infective and the thermal store losses most of its heat and would take longer to reach 65c the following day once the wood burning fire is lit.