Hello all, I'm searching for advice on my new system being fitted into a very old stone house in France.
We have purchased a thermflow 300L thermal store with a built-in expansion tank to work with multiple heating inputs (solar, electric and wood burning stove boiler). We are running 7 rads and underfloor heater from a 14 KW wood boiler, along with underfloor heating and domestic hot water coil. There is an electric immersion back up (which will be supplemented by solar thermal next year). I've attached a diagram of the levels everything is on.
The tank company have told me it's fine to pump the water to the wood boiler but my understanding from local heating engineers (and from my extensive internet reading!) is that this is not advisable due to it being an uncontrolled heat source and the lack of gravity creating a risk of the WBS boiler exploding if the pumps fail (power cut, mechanical failure, etc).
We have an excellent journeyman plumber but he's not overly experienced in heating systems of this kind - and he is very uncomfortable with the installation suggested by the thermalstore company.
It will be extremely difficult to put this tank in our loft due to access issues (and will greatly decrease the efficiency of the system due to increasing the distance from all the inputs and outputs). However if it's the only way to make the system safe, we will have to do it.
If we continue with this installation as is, our plan is to use 2 pumps, one solar and one electric both with a battery back-up. So we would need both pumps to fail simultaneously to have a problem. We would also have a pressure relief valve for the wood boiler (any recommendations on brand here would be welcome!). There is also a quench coil which came with the thermal store, but I'm not sure that would be effective in the case of a power cut / pump failure, except to protect the thermalstore itself from boiling - the wood burning stove boiler located higher than the store wouldn't receive any of that cold water.
My understanding with the above plan is that we will risk boiling the wood burning stove boiler dry (and thereby probably destroying it) but that is a risk I would take given the unlikely set of circumstances required for it to occur, (i.e. a power cut occurring at the almost exact moment we have banked up the fire; left the house for hours and all our pumps fail too). And also the cost of a new stove versus the cost of siting the thermal store in the loft is actually about 1:5.
We are 100% committed to avoiding a catastrophic boiler failure i.e. an explosion. We have a young son and can't bear the thought of a dangerous installation. So are we taking a risk that this might occur with the system we have in mind?
If yes is there any way of removing this risk with additional fail-safes? Perhaps another pressure relief valve on the boiler? Or is the thermal store going in the loft the only reliable way?
Thanks in advance for any thoughts / experiences / recommendations here.
Yours, a worried Mum
We have purchased a thermflow 300L thermal store with a built-in expansion tank to work with multiple heating inputs (solar, electric and wood burning stove boiler). We are running 7 rads and underfloor heater from a 14 KW wood boiler, along with underfloor heating and domestic hot water coil. There is an electric immersion back up (which will be supplemented by solar thermal next year). I've attached a diagram of the levels everything is on.
The tank company have told me it's fine to pump the water to the wood boiler but my understanding from local heating engineers (and from my extensive internet reading!) is that this is not advisable due to it being an uncontrolled heat source and the lack of gravity creating a risk of the WBS boiler exploding if the pumps fail (power cut, mechanical failure, etc).
We have an excellent journeyman plumber but he's not overly experienced in heating systems of this kind - and he is very uncomfortable with the installation suggested by the thermalstore company.
It will be extremely difficult to put this tank in our loft due to access issues (and will greatly decrease the efficiency of the system due to increasing the distance from all the inputs and outputs). However if it's the only way to make the system safe, we will have to do it.
If we continue with this installation as is, our plan is to use 2 pumps, one solar and one electric both with a battery back-up. So we would need both pumps to fail simultaneously to have a problem. We would also have a pressure relief valve for the wood boiler (any recommendations on brand here would be welcome!). There is also a quench coil which came with the thermal store, but I'm not sure that would be effective in the case of a power cut / pump failure, except to protect the thermalstore itself from boiling - the wood burning stove boiler located higher than the store wouldn't receive any of that cold water.
My understanding with the above plan is that we will risk boiling the wood burning stove boiler dry (and thereby probably destroying it) but that is a risk I would take given the unlikely set of circumstances required for it to occur, (i.e. a power cut occurring at the almost exact moment we have banked up the fire; left the house for hours and all our pumps fail too). And also the cost of a new stove versus the cost of siting the thermal store in the loft is actually about 1:5.
We are 100% committed to avoiding a catastrophic boiler failure i.e. an explosion. We have a young son and can't bear the thought of a dangerous installation. So are we taking a risk that this might occur with the system we have in mind?
If yes is there any way of removing this risk with additional fail-safes? Perhaps another pressure relief valve on the boiler? Or is the thermal store going in the loft the only reliable way?
Thanks in advance for any thoughts / experiences / recommendations here.
Yours, a worried Mum