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Green Building Bible, Fourth Edition
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    • CommentAuthorjohnnyh
    • CommentTimeDec 2nd 2015
     
    That's what i have, 3 port mixer which when opened too far, but not very far at all, heats us nicely but destroys stratification, when closed off a bit more the flow is so reduced, the rads areonly luke warm even with 80 odd degrees in the store. I don't mind this if i can adjust it from inside the house so when the boiler is burning i can open up and get quick heat into the rads without caring about stratification and then close it back down afterwards. You are probably right in that i don't have enough rad coverage but with some planned UFH i will hopefully have a more efficient system and more flexible too and the motorisation and mixer control will just make it more automated.
    • CommentAuthorgyrogear
    • CommentTimeDec 2nd 2015 edited
     
    "my store is the correct shape, it is approx 2.8m high and 1.1m diameter and it does stratify".

    No doubt, but does it stratify *optimally* ?
    Your store has an aspect ratio of 2.5 or thereabouts.
    My (bog-standard) DHW tank has an AR of 2.8...
    I should have thought that a thermal store would be more than a DHW tank...

    If I understand right, from this paper, *optimal* AR is between 3 and 4.
    http://www.arpnjournals.com/jeas/research_papers/rp_2011/jeas_0211_454.pdf

    They say, "Better stratification improves efficiency"

    "When a stratified hot water storage tank has closed water circuits, the water temperatures can be up to 90...95°C at the top - and e.g. 20...40°C at the bottom.

    Like PIH says, if too-hot of a return is directed back into the bottom of the tank...

    ===========
    " 5774w/h heating required (...) "So i suppose that's too much for a 2000 litre store then at the worst time of the year".

    On the face of it, your TS is probably holding upward of 100 kW of HEAT...
    It "ought" to be doing the business...

    gg
  1.  
    An alternative to increasing the number of rads to reduce the temp. required in each can you increase the insulation of the property to reduce the demand and so allow a lower CH temp. and flow rate. Have all the usual things banged on about on here been done - draught proofing, increased loft insulation, EWI? - if you have the budget for EWI.

    We were in the same position having insufficient rads to run with a low temp. low flow system. EWI solved the problem but painful at the bank!

    Our house is also stone (50cm + render) and block (38cm + render) and we found to better to run a constant temp. 24/7 rather than let the temp. drop and then have to blast the heat in. This applies before and after EWI, although as you would expect there is much less drop than before EWI
    • CommentAuthorjohnnyh
    • CommentTimeDec 2nd 2015
     
    I don't want to change the outside 'look' of the place so i've not gone for ewi. I've insulated all external walls from the inside and it's all double glazed.

    Maybe the tank is a bit below optimal but it is quite good at stratifying. On its first heating when the water was only 16 degrees we had 70 temp difference between top and bottom and that lasted for hours until the heat reached the bottom. I was quite impressed as it is only a repurposed water pressure tank but maybe it could behave better with regard to resisting destratification.

    I've got the boiler running now and for the last 2 hours i have watched it hit 85, switch pump on, drop to as low as 72 then climb back up. That is ranging over 13 degrees which to me seems crazy. It only spends a few minutes of every quarter hour in the gasifying zone.
  2.  
    As I have said before IMO the Laddomat should be running all the time (assuming the pump to which you refer is the Laddomat) If you think the Laddomat is running the temp. of the boiler too low the solution is not to switch the thing on and off but to change the thermostat cartridge in the Laddomat. They are available in the following temp. grades - 53°C , 63°C, 72°C, 78°C, 83°C and 87°C. and its a 5 min. DIY job to change.

    Edit - I haved just checked the Laddomat online manual and this says the standard thermostat cartridge is 72deg., so if you need a higher temp. then you should change the cartridge if you have not yet done so.
    The manual also says - The pump can be started by a flue thermostat. If extra safety is required, a water thermostat can be connected in parallel. - to me this says the Laddomat should be running all the time as a flue thermostat will switch on low flue temperature i.e.out of fuel

    Another thought - is your CH pump a modern variable output or is it the old fashioned type that has speed from 1 -3. If its the old type then you may be pushing the water around too fast, even on setting 1. If this is the case you could try closing the gate valve on the pump to reduce the flow, this should give you a greater temp. drop across the rads and thus lower return temp. at the TS
  3.  
    Johnnyh,

    I agree with Peter. Your pump, i.e. the Laddomat pump, should be on continuously from the early firing up stage of when it is just hot enough to get things going through to the very end stage of no fuel.

    If I understand your thinking, are you trying to use the Pump On (PO) setting of the Ekoster control (i.e. boiler) to effectively control the temperature of the output to the Laddomat and then onto the store? If I'm wrong I apologise. So ...

    The only thing that ultimately controls the thermal store maximum temperature is the target temperature that you set on the boiler. The Laddomat will hold the temperature at 72c (assuming it is fitted with the standard 72c wax cartridge) for a few hours until the return from the store reaches 72c. At that point the Laddomat cartridge will start to open to maximum allowing the the store to reach over and above 72c and onto your desired set temperature at the boiler (not the PO setting).

    The Eco Angus manual probably explains it better here ...

    "When the bottom temperature gauge reaches 72°C (which will take about 4 hours) it is then that the temperature will start climb into the 80’s on the control panel and eventually if there is enough wood in the loading chamber reach the 90°C to 92°C set temperature. This is because the Laddomat valve will be fully open when the return temperature from the accumulator tank is 72°C."

    All the Laddomat is doing is providing an optimal return temperature to the boiler and also ensures a gradual supply to the store by the recycling (thereby aiding stratification) as Peter mentioned. Once the boiler has reached its target temperature the fan will stop but the pump MUST carry on pumping to keep shifting the heat in the boiler to the store otherwise the boiler will overheat (with the fan off and with fuel it is slumbering but still generating a fair bit of heat). At this stage the boiler will drop in temperature (because the pump is on) until it drops by more than the hysteresis amount (standard 5c) at which point the fan comes on to get back up to target temperature (assuming there is enough fuel).

    As a test I suggest you run the boiler from start with the PO set at 65c and leave it and see what happens.

    In your other thread of "Ekoster 2 Settings" I only increase the PO setting in anticipation of it running out of fuel so as to minimise reverse heat transfer from the store to the boiler due to the pump still running. I only do this
    when the boiler has reached a steady higher temperature. I started our boiler a few hours ago and I just saw it has reached a steady 80c so I set the PO at 77c. If I were to stay up a another hour it might be at steady 87c so I'd set the PO at say 80c or 82c .... in anticipation of it running out of fuel in the morning so that when it drops to 82c the pump will go off and save heat in the store.

    The PO has nothing to do with it gasifying or the target temperature in the store.

    This new PO setting is usually a few degrees lower than the "Target Temp" minus "Hysteresis Temp". e.g. Target 92c, Hysteresis 5c then if boiler is currently at say steady attained 85c I'll set the PO at "85 minus 5 minus a bit more" say "85-5-2=77c". Ideally I'd like to set it at "92c" but then my pump won't be on as it is currently at steady 85c but then will rapidly reach 92c, pumps comes on and rapidly cools to 85c and so it cycles ... which is what you are seeing?

    However, your store destratification is the same with my setup which might be something to do the rads being sized for an oil boiler and the return to the bottom of the store being hotter than ideal (whatever that is).

    P.S I found the flue stat a waste of time hence my PO setting change.
    • CommentAuthorringi
    • CommentTimeDec 2nd 2015
     
    I just had a thought, is the boiler “pump on” output for controlling a pump that DOES not have mixing value? E.g is the boiler trying to control the loading pump based on the temp of the water in the boiler.

    Clearly as Peter_in_Hungary say, the Laddomat’s pump should start running as soon as the boiler starts to get upto heat, and keep running until the burn has finished on the boiler.
  4.  
    Peter ... not trying to distract from Johnnyh problems but for what it's worth ...

    "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."

    I tried this with my setup. What I found is that the difference in flue temp. in having a few embers and that when there was truly no fuel was too marginal for the stat to be of any use. This meant the situation of having a few embers with the pump off caused the emergency mains water quenching to activate OR truly zilch fuel but left the pump on and causing reverse heat flow from the store again.

    I still have the flue stat wired in but on its lowest unmarked setting to override itself. Hence my changing the PO to a higher setting during the burn.
    • CommentAuthorgyrogear
    • CommentTimeDec 4th 2015
     
    "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? "

    I hope it will, because this is what I will be looking to do, with our planned heat-pump water cylinder.

    Per HERE...
    http://ronblank.com/courses/reh23d/reh23d.pdf

    "One of the six primary benefits of radiant, is ADAPTABILITY..."
    "Use in floors, walls or ceilings, and/or combine it with other hydronic emitters"

    gg
    • CommentAuthorjohnnyh
    • CommentTimeDec 8th 2015
     
    Finally got my mixer control fitted and it works. It took a bit of setting up but now it opens and closes the mixer to suit the rad flow temp that i want. It works as it should and it has still a few more capabilities that i haven't utilised yet.

    It can control a CH or underfloor valve and it can work with a weather sensor (not fitted yet) and room sensor (not fitted yet) for better control. The response times for actual room temp with cast iron rads is very delayed but that is a consequence of keeping the flow pretty low and the cast iron rads i suppose.

    Will keep you posted when i get round to ufh and thanks for all replies.
    • CommentAuthorringi
    • CommentTimeDec 8th 2015
     
    @johnnyn,

    What control system are you using?
    • CommentAuthorjohnnyh
    • CommentTimeDec 9th 2015
     
    Hi Ringi,

    it's called a Tech eu-431n.
    • CommentAuthorjohnnyh
    • CommentTimeJan 8th 2016
     
    I have been happy with the mixer valve controller and i don't have any destratification problems anymore but i only have the valve temp at 35 degrees so i don't know if that is a major factor i.e. colder rad temp, colder return = less destratification. Will find out later in the winter if i have to turn it up a bit
    still, now i've got 3 things on the wall: a 3-level tank temp readout, a valve controller and the boiler remote readout.
    • CommentAuthorjohnnyh
    • CommentTimeMar 6th 2016
     
    A quick update: the higher the temp that i run the rads at, the more destratification. The mixer valve is not enough on it's own when the rad temp is set above 40 degrees. Perhaps some kind of multi-level manifold like Peter in Hungary has would be the solution although it would need the tank draining pretty much to the bottom and some welding out of position.
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