Hi to all, i've been reading this forum for ages whilst getting round to installing my log burner and store. Finally it's in and working pretty well but i'm not really getting more than a day's worth of heating per charge and i had hoped for maybe two days when the weather is mild. I have ordered a tech 431 'steering' to control the CH mixer valve and in the meantime i have adjusted it right down which gives us a fairly low temp on the rads, not hot enough for a cold day. If i adjust the mixing valve back up, the tank destratifies. One solution i think would be some ufh circuits to cool the radiator return temperature but they would have to be fed from the radiator return to have this effect.
The question is simply: Will this work?

The thing is the rads are already installed as i have changed over from an oil fired system. I am going to add one or two more rads where i have space but the upstairs floors are not finished yet and i've seen these aluminium reflectors that can be installed across the joists to allow UFH. I was hoping i could then get more low level heat, at least upstairs, and help keep the tank stratified on colder days when i need to turn the flow up a bit, which at the moment destroys the statifiction.
It's seems like a win-win situation as long as there are no reasons why the CH return cannot be used as UFH flow. Please feel free to correct or enlighten me!

That's a good question! All i can assume is that it's too hot when the mixer is more than just barely open. The tank then drops from 85 at the top to 70 and beyond quite quickly.

Posted By: johnnyhI have ordered a tech 431 'steering' to control the CH mixer valve and in the meantime i have adjusted it right down which gives us a fairly low temp on the rads, not hot enough for a cold day. If i adjust the mixing valve back up, the tank destratifies.

A 4 port mixer valve can help to minimise destratification by maximising the return temperature to the tank, but it may require you to use different take offs.

Posted By: johnnyhOne solution i think would be some ufh circuits to cool the radiator return temperature but they would have to be fed from the radiator return to have this effect.
The question is simply: Will this work?

It depends. The flow rates, flow temperatures and thermal time constants are very different for radiators and UFH. If you're looking to dump huge amounts of heat into a building that is unlikely to over-heat then it will work. If you're looking for precise control of room temperatures in a well insulated building then it doesn't sound like the right way forward.

David

If it de-stratifies in the mornings then if you have TRV everywhere and they are open (to get the temp up to daytime temp. then perhaps at that time you have a high flow around the system which will be shoving a lot of return water into the TS and so causing turbulance - just a thought.
I had a concern about my TS (also 2000lts) about disturbing the stratification either from the CH or the DHW that is a separate tank along side the TS. To avoid the possibility I put a return manifold on the outside of the TS to allow the return water to enter at its own temperature - tests after installation showed it works, but it would be difficult to retrofit. see here http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13082&page=1#Item_8

Rather then controlling the mixer based on the flow temperature to the redactors, what about controlling it based on the return temperature?

When the building is colder, the return temperature will be lower, so more heat will then be given to the building.

You may also do better letting the heating run all night, so it does not need lots of water to heat up in the morning.

Posted By: johnnyhThe thing is the rads are already installed as i have changed over from an oil fired system. I am going to add one or two more rads where i have space but the upstairs floors are not finished yet and i've seen these aluminium reflectors that can be installed across the joists to allow UFH. I was hoping i could then get more low level heat, at least upstairs, and help keep the tank stratified on colder days when i need to turn the flow up a bit, which at the moment destroys the statifiction.
It's seems like a win-win situation as long as there are no reasons why the CH return cannot be used as UFH flow. Please feel free to correct or enlighten me!

Is it new or a refurb ?

No expert but AIUI
UFH upstairs is not normally necessary if you have the ground floor cosy.
Can you try for 1 winter as see how it works out ?

Its a refurb, a long, slow refurb...

It's an old stone building with no south-facing windows, (but no north-facing either) and high ceilings. It's not an easy task to heat this place. The ground floor is not that cosy and if the UFH upstairs might mean i could turn off one or two rads upstairs then that may also help the stratifcation in the store.

Radiant wall? The same set up as the floor? ( but in the wall of course).

I could wait til after the winter for the UFH and it might well happen that way anyway. What i'm searching for really is a way to make the store last 2 days in the milder weather.

Have a look at "fan convectors" e.g. http://www.myson.co.uk/products/ivector.asp I think it will be easy to replace your radiators with them without doing much plumbing and they will run with lower water temperatures that will let you get more heat out of your store.

Hi again...

Posted By: johnnyhi'm not really getting more than a day's worth of heating per charge and i had hoped for maybe two days when the weather is mild

Couple of questions:
what is the heating requirement (at the moment, not when you're finally finished...)
what is the power rating of the wood stove ?
what is the power when the TS is fully charged ?
how many days' HR can fit in the TS ?
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Posted By: johnnyhIt's an old stone building with no south-facing windows, (but no north-facing either) and high ceilings. It's not an easy task to heat this place.

Great ! sounds like the perfect place for a RW...

You might find THIS interesting...
https://www.aecb.net/forum/index.php?topic=5138.0

gg

Are there not two types of 4 port values?

I think one type mixes the return, mid taping of thermal store and top taping of thermal store to get the flow. So the top of the store is only is used if the mid of the store is too cold.

I think the other type keeps a constant flow rate in a boiler, while deciding how much of that flow goes into the UFH, so that the bypass does not operate on the boiler.

I don't actually know my heating requirements. The radiators (mostly cast iron) will keep us warm as long as they are on and they are not really that big, perhaps 700mm x 1000mm or 700 x 1200mm as an average size and of the 4 column variety.
The store is 2000 litres and boiler is 40kw.

The pipework and rads have been installed for a few years now so i am willing to 'tap in' to the system where it's easy to do so but a full redesign a different story.

Posted By: johnnyhif the the idea of the batch burning/laddomat/thermal store combo was to burn hot and fast to get every last bit of energy then the pump should be switched on and off to achieve this and the fan should run all the time unless there is nowhere left for the heat to go (store full) or there is a problem and the boiler needs to shut down. This doesn't seem very complicated to me but it is too complicated for the ekoster. Maybe it's just a question of pump switching hysteresis.

The job of the Laddomat is to keep the boiler at a high enough temperature so that proper combustion can take place. It does this by recirculating the water within the boiler until there is sufficient heat to pass to the thermal store whilst maintaining the boiler temperature. The Laddomat pump must run all the time and should stay on until the boiler has run out of fuel otherwise the recirculation can not happen.

If you do stop the pump on the Laddomat the construction is such that a valve will open and allow gravity circulation to the detriment of boiler temperature. If the boiler /TS pipework does not facilitate gravity circulation then the boiler will overheat triggering what ever mechanism the boiler has to manage over heating.

The fan driving the combustion however can switch on and off and the fan will run until a pre-set maximum temp. is reached when it should switch off until the temp. falls whereupon it should start up again. The other event that should switch off the fan is 'out of fuel'. This should also switch off the Laddomat pump. The out of fuel signal is often generated by a flue thermostat although on my boiler this is sensed by the boiler dropping below a pre-set level (70deg in my case) and this low temp. signal is overridden during the start phase.

"I don't actually know my heating requirements. "

You are not alone (I suspect that many people install (expensive) heating systems without giving it a single thought...).
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You could do a rule-of-thumb HR calculation by estimating (or counting...) what installed power you actually have - is it enough to keep the place warm, Y or N... etc.
or , "what would you put on a dream-list ?" (such as 10 x 1-kW radiators, one in each room etc. etc.).

Otherwise, some smart & easy-to-use calculators online...
such as...
https://www.chromalox.com/resources-and-support/calculators/comfort-heater.aspx

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Otherwise, concerning your thermal store, a few details would be useful:
what dimensions, actually?

(to my mind, it does not sound like it is stratifying very much at all)
for optimal stratification, it needs to be T-A-L-L... and "not flat"...

gg

Posted By: johnnyhEvery time the fan stops i assume there are combustible gases escaping through the chimney without igniting. I know the laddomat is there to protect the boiler against undertemperature but it also inadvertently controls it's maximum temp as well so it is the most efficient way to control the temp. of the boiler, i.e. keep it in the 85-90 degree zone.
Thinking about it, perhaps the reason my temperature swings so much if i set the 'pump on' to 86 or 87 is because the laddomat thermostat, i'm assuing it's a wax type thing, takes a minute or two to open and close. So when the boiler control turns the pump on there is a delay in which time the boiler hits 91 (fan stops) and then once the incoming cooler water has cooled the boiler a bit, there is another delay while the laddomat closes again and the temp drops to 79 and outside the 'zone'. Could i have a slow thermostat cartridge?

The boiler fan will (should) only stop when the upper temperature is reached. Yes combustible gasses will go up the chimney but the only way to stop this is to keep the fan running regardless of temp., boiling or any other event in the boiler. Don’t forget that when the fan is not running the fire is not out and so most of the combustible gasses will burn, you just won’t have the efficiency of the gasification.
For what its worth the fan on my boiler runs continually until the boiler reaches the high set temp. which is about 88deg. At this time most of the TS is at the same temp.

The Laddomat has a ‘wax type thing’ as a thermostat and as such gives a proportional control. The Laddomat controls the temp. of the water going into the base of the boiler. The temp. of the boiler at the outflow will be higher.

The Laddomat installation instructions say the the unit should be as close as possible to the boiler, mine is installed at the base of the boiler with only a maintenance stopcock between it and the boiler.

If the Laddomat pump is running continually then the thermostat will proportionally control the input (return) temp. of the boiler without temp. swings on the input flow.

The fan should run continuously until the top set temp is reached and it should then stop to avoid over heating the boiler. When the temp. drops the fan will start again (start point governed by the hysteresis of the thermostat switch) The output temp. will fluctuate once the top set temp. is reached due to the hysteresis of the thermostat switch

So.....the Laddomat provides a stable return temp. for the boiler by variably mixing the return from the TS with recycled water from the boiler output. This can only happen if the Laddomat pump is running – therefore it should run continuously. The control temp. of the Laddomat is adjusted by changing the thermostat insert within the unit for one of a different value. (easy DIY job)

The combustion fan should run continuously until the top set temp. is reached, it should then cycle under control of the boiler thermostat.

In practice on my boiler the Laddomat runs continuously until the boiler runs out of fuel (low temp. thermostat)
The fan runs continuously until top temp. is reached and then cycles. It is also switched off by the low temp. thermostat.
The TS rises in temp. gradually with the boiler running at a higher temp. until the TS reaches the temp of the boiler (which is controlled by the Laddomat) then both rise together until there is no more fuel.
If the boiler reaches the top temp. the fan stops but the Laddomat continues to run, removing any heat from the boiler

With advantage my system would benefit from a flue thermostat to signal end of fuel which would avoid the Laddomat pumping whilst the boiler temp. is falling at end of fuel. This would save some loss of heat back through the boiler........its on the ‘to do’ list.