Hi,
Is there a online thermal store size calculator out there somewhere? Something you can feed required energy in MJ, store max/min temps, and it comes back with how many litres of water you need? Yeah I know it's only simple maths but...
I've googled but failed to find anything.
Google for Heatweb - IIRC that brings up something along those lines..
Is this any use
That's it...
Technical Menu > Flash Tools > Flash main page
Ha, found that when looking for custom heat store makers(*1). This machine doesn't have flash but will be playing with it later.
I'm thinking that I need a 1500l store(*2) which is just to damn physically big, by a *lot*, as a cylinder (Akvaterm Solar is 1250 x
2150) to get into the room I want to use short of taking the roof off and using a crane...(*1) Any one know of good custom heat accumulator makers?
(*2) On the basis that the woodburner stove will chuck out a max of
8.5kW to water for up to 6hrs/day. OK the stove probably won't be running flat out for 6hrs but as a max it's right. A 1000l(*3) store will probably be OK (approx 6kW for 6hrs, the nominal stove output to water), given that if the stove is on the house will most likely be calling for heat as well so all the heat generated doesn't have to be stored.(*3) Still too physically big from Akvaterm at 1050 x 2100. The damn things seem to be rather heavier than I expected as well, even before you add 1.5 tonnes of water. I can see the floor requiring to be strengthened...
Yes - Newark - they will take a standard cylinder size (from a list of many possible sized) and put any set of bosses in that you like exactly where you want them. And you get to say how much foam you'd like sprayed on afterwards...
I didn't know - but they tipped me off before starting, was that direct compression bosses areavailable rather that, as I'd asked for, BSP bosses. I changed them on the spot - one less adaptor...
If you stick 2-3 immersion heater bosses in (make sure they aren't too close) you will have a backup option of charging it electrically (Economy 7 et al).
Price goes up out of propertion with diameter, but less than proportion with height, so go for the tallest you can if you want it cheaper.
Worth noting that a 1/2" solar coil near the base costs sod all compared to the rest of it. And dry pockets for thermostats or sensors are cheap and worth having
Sorry I just have questions >>>
Do you envisage the thermal store just for heating, or for year-round DHW as well?
Will you burn wood year-round, or perhaps use solar topped up with leccy in the summer?
For the heating will you use radiators or UFH? Or both?
If UFH is it in a solid floor, or a suspended one?
+++++++++++++I'd be inclined towards a modest size high tech thermal store such as the heatweb/dps Xcel at the heart of the system....and use clever controls to divert surplus heat into a secondary lower tech but high volume store when necessary.
D
Ideally it is a sodding big insulated container of water to be heated from solar panels, woodburner, oil boiler and immersion heater(s). Outputs to CH and DHW.
Wood will probably only be burnt evenings when it's cold so from Oct/Nov through to Apr/May. Oil being used to make up shortfalls from solar/wood as required, leccy being last resort back up.
Rads only. The floors are already solid. Sister has UFH, we house sat the other year and didn't really like it, too slow to repsond to changing weather. Up here at 1400' and exposed the weather can change very quickly, minutes to go from bright sunshine and little wind to howling gale with lashing rain/snow and a many degrees temp drop.
The DPS stuff seems to have to much gubbins but I'll have a closer look at the Xcel. I want the system to work as much as possible passively. OK will needs pumps on the oil, CH and solar circuits but I don't see what advantage there is for an external heat exchanger and pump for DHW. The water here is soft so scale inside a coil in the primary heat store won't be a problem.
The primary advantages of the external heat exchanger for DHW are mains pressure, and that you decouple water temperature from the store temperature.
This in turn means the store can sit at 80C without scalding you when you have a shower. of course it holds much more energy that way too.
For secondary store(s) look at the "stelstor" at bes.co.uk. Very good value.
I have a 450 litre DPS Xcel with gas boiler, solar and immersion (all 3 are used in different circumstances) and I am pretty impressed.
Gotta go now...........
D
And why do I want mains pressure hot water? I like the water to stay in the basin or sink when I turn ona tap not bouce out or scoot across the curved surface and out the other side. No taps here are at mains pressure they are all fed from the roof tanks. The only place that might want a bar or two are showers but then I prefer a shower of higher volume lower pressure than low volume high pressure. Low volume just takes to long to rinse, high volume high pressure gets painfull. The best "shower" I have ever had was several gallons/second under direct gravity, ie a water fall. Mind you the volume of that was borderline too much. B-)
I also like to have stored water so when the mains fails I can still have a cup of tea and flush the bog.
That is easy to solve with a mixer valve on the output of the tank. Mixer valves are "passive" in that they don't need power to operate unlike the pump for the external heat exchnager.
Ta will have a look.
I have mains pressure hot water - but limited on a per tap basis with flow restrictors. Which means a) no tap (or even 2 taps) can starve the system; b) the overflow on each sink is actually able to cope with taps on full (kids). This solves the "bounce" problem quite nicely - kitchen sink has a medium flow, bathroom sink is about half that.
I have rather got used to being able to drink from the hot tap - or fill a saucepan with it to get the cooking half started.
There is that though...
Unless the woodburner can directly heat the rest of your house then you'll probably want CH at the same time as your stove i srunning so, rather than trying to store masses of heat in a thermal store, you may be better off arranging to have the stove heat the rest of the house's rads when it's burning.
Non-issue for us. Whole house is regulated to 2 bar. Just right.
Before the upstairs shower had a head of about 1.2 metres. When I installed a shower pump it was the most unreliable piece of s**te we have ever owned.
That answers my next question. B-) Bunging pressure regulating valve in to keep things manageable, I assume they keep the pressure on the output side at the set point up to the maximum specified flow rate, regardless of changes in flow rate? How quickly does it respond?
What about static pressure? Presumably that rises to mains, how quickly does it drop to the regulated pressure when you slowly open a tap?
Doesn't help with the no stored water problem though. I don't know how often the mains water fails here as we have no tap on the mains. Mains water didn't arrive until about 25 years ago before that it was (unreliably) pumped up from a farm further down, hence three large storeage tanks that all water goes through. They are now properly covered and cleaned out, there was only one dead mouse and a handful of dead centipeds together with a the odd rock and general sediment in them when we moved in. B-)
The one I have regulates instantly.
It never rises much above the set point. I have 7.5 bar in, 4bar out. Very little variation from flows from 0 to 50l/m
Looks good but all cylinders. Had a quick look at the 1000l DPS Xcel (900 x 2200) by hacking a couple of cm of plaster off both sides of the access it would be possible to squeeze that in but the 2400 diagonal size is to big for it to rotate upright, ceiling is at
2300...1000l with 100mm insulation all round needs a box 800 wide 2000 high and 1100 long. That should fit through the available opening no it fing won't the opening is only 1830 high... So 1700 high (allows for it to be on a dolly/scaff poles to move it) means 1300 long. Of cousre if the insulation was detachable one could have a bigger container and insulate it when in place.
I would assume that taller helps with stratification as well?
heated
That is effectively what will happen the water in the rads, store and loops for the woodburner and oil boiler is the same. The size of the room that thw wood burner will be in limits it's size to a max of about 8kW to water (2kW to room). A rough guesstimate of the total heating demand is about 25kW (17 rads at 1.5kW each, some are smaller, some are larger, most are about 1.5kW) but that is to heat everywhere mid winter. One can turn TRVs down in unused rooms to reduce the demand. 8kW should keep main living areas tolerably warm mid winter without burning oil.
The store is really to buffer the heat from where ever it comes from, solar, wood, oil or leccy. The oil boiler is big, the plate says
35.2kW, but it's got a smaller jet than specfied in it. It tends to cycle on it's stat when just heating water or the house only needs a little heat and occasionally trips the overheat stat as well. Stopping that cycling and tripping is also part of this.
Agreed.
I use the Honeywell (Screwfix 68966). works a treat.
Thanks chaps, all filed away for later.
Same can be done on an unvented cylinder with a blending valve on the outlet.
(no need for annual safety checks on the store with plate HE version though)
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