It really comes down to the numbers.
Say your hows is heated to 20°C by bed time and it needs 5 kWh to keep it at 16°C over night, and then another 3 kWh to get it up to 18° in an hour. All you need is a thermal store large enough for that.
The rest of the times is down to the burner being slightly over sized for the space heating needs.

It seems a bit odd to 'have' a tonne of water to say 75° just to supply a couple of kWh of thermal energy to a radiator or similar for an hour in the morning.

This is why knowing the thermal properties of the house are so important.
If you do not know these, then you have no choice but to over size and supper the efficiency loss.

I had a Heating Engineer here today that said I need a gravity feed system to at least 3 Radiators to take the excess heat from the Stove. I had my doubts about this. Any thoughts please.

You do need somewhere for the heat of the boiler stove to go in an emergency e.g. power cut so no pumps, or store is too hot to provide cool water to the stove. But it does not have to be radiators, but it does depend on the design of the stove. We just have a separate cold water feed to the stove, an outlet pipe (15mm) and a valve that in an emergency the can flush cold water into a skin of the stove to cool it and then to outside. It would waste the heat, but it only happens in an emergency not normal opperation.

Best to have a loading pump (a "laddomat") to control how the water from the boiler on the stove is delivered to the thermal store. Not sure if that has been mentioned yet.

It also could be useful to have a display near the WBS that shows the thermal store temps. You don't want to he loading more wood when the store is already plenty hot. Initially I was popping into our plant room where the thermal store is checking temps, it is nice now to make an emponpi setup that I can monitor remotely. Do think about monitoring so you can build in both sensors and any wiring.

Posted By: Peter_in_Hungary

Posted By: GreenfishWe just have a separate cold water feed to the stove, an outlet pipe (15mm) and a valve that in an emergency the can flush cold water into a skin of the stove to cool it and then to outside. It would waste the heat, but it only happens in an emergency not normal opperation.

The cold dumps work but the manufactures design them in for emergency use. My boiler has a built in coil for this purpose.
Completely useless for me as I am off the water grid and the borehole only works when the pump has power - you need reliable mains water for these to work.
If the valve dumped into the boiler directly I would be concerned that the cold water entering an over heated stove then some damage might result from the sudden cooling. Perhaps the lesser of 2 evils.

I'm not entirely sure where the cold water goes in the wood boiler stove, but It is designed not to break anything.
We even tested it during commissioning the system.

I am also on a borehole, but we have pressure vessel, so even in a power cut we can supply water to do this. But to be honest since the stove is in the living room with us tending it I doubt we would ever get to that situation. We know we can't burn safely without power for the pumps. That is a downside, then again with grid connected PV and pumps for everything I gave up on my ideas of off grid living some time ago.

(Sorry for my Laddomat error, what I have is a loading pump).

Hi,
Yes have had wood burners in most of the houses I have lived in, now I have a small parcel of Woodland that hasn't been touched for years I have access to more wood than I will need. I understand the work that goes into it and still wouldn't want to use oil gas or electric. Haven't bought anything yet, still reading advice on here. Can the means to get rid of excess heat be through towel rails? No I don't fancy lighting a fire in the summer to heat the DHW hence the PV Panels and the size of the TS is as Peter says not wanting to get up to a cold house. I want to keep the PV away from the Grid here in France too.

Posted By: Michael1Can the means to get rid of excess heat be through towel rails?

The heat leak should be not less than 10% of the stove output, so you have to do the calculations based on your chosen stove. The stoves you have mentioned above if I remember correctly have about 10kW to water so that would be a 1kW towel rail minimum - but don't forget if the towel rail is covered in towels then you won't get the heat output due to the insulation effect of the towels.

Posted By: Michael1I have had a couple of quotes for the equipment and would appreciate it if someone would take a look at the for me, not for the prices but to give the kit a once over to see if I have had decent advice.

You could post the list of equipment here, but apart from obvious omissions like say no pressure relief valve mentioned it will be more about how the kit of parts are put together that will make more difference that what is on the list.
e.g. If you are going for a pumped system than a Laddomat or alike should be included, but if you are going for a gravity system then a Laddomat is not needed. Similarly unless the unless the heat leak rad is specified as such then who knows which is what - and even then if it is not installed properly so doesn't work then it is of little value.

What people have done previously is to post a schematic diagram of the proposal to be picked over. This is perhaps better than a list of parts.

From what you have said so far I would still have a concern that if your house is well insulated then the space heating function of your stove will be too much for you to be able to heat the TS. Up to 4.5 kW to a room is a lot whilst you are trying to get the TS up to temp. and the over heating of the room is a real concern.

Hi Peter,
What does a Laddomat do?

Posted By: Michael1What does a Laddomat do?

Watch the video - however short answer is that it keeps the temperature of the water in the stove above 72deg. (depending upon the thermostat cartridge) to prevent the over cooling of the stove an thereby spoiling combustion efficiency and cleanliness.