I'm looking to gauge the performance of my 3,000l thermal store compared to others. I know there will be differences in setup but this a rough comparison.

The store is connected to an Eco Angus Orligno 200 40KW log gasification boiler using Laddomat 21-60, Laddomat Thermomatic CC set at 60c output to a 90KW PHE, over 13m of Uponor district heating from boiler shed to house with 13 rads, 220l direct DHW tank, closed circuits, 33,000KWhrs per year demand. The store has a single return point at the bottom.

I can fully charge the store to 82c top to bottom after a 92c batch burn (getting higher is difficult). The store has two analogue temperature gauges top and bottom. After a typical evening of heating at 19c the store will deplete to 60c\45c top\bottom and settle at 55c\49c if pushed to a second day.

Our DHW tank has on occassion heated the bottom of the store by way of high return if DHW stat is higher than flow from PHE approaching store depletion (can raise bottom of store by 2c). This has not been solved yet.

I have a feeling that 49c depletion at the bottom of the store is rather high.

So how does your store perform temperature and duration wise? Any details of your setup would be much appreciated.

Thanks
Stuart

What does your store do if it is JUST running the heating?

What is the temp of the return to your boiler house?

And last months.

Can you design out the PHE, it will probably have a 10 degree difference between primary and secondary FT and usually results in higher return temps that de-stratify the store, plus you need another pump.

I added extra sensor ports when I ordered the store and have 11 1-wire temperature sensors at various heights from the top to the bottom of the store. The sensors are at least 300mm into the store so the are quite accurate.

The recording software is somewhat involved as it's developed from bits of software that I already have. The 1-wire sensors are connected to an HA7Net interface and Homeseer HS3 runs a script periodically to get the temperature values from the HA7. HS3 also runs a script to send the data to an Emoncms server running on the same machine. The Emoncms server logs the data and produces the graphs. The Emon server logs lots more data including power consumption and PV generation.

No doubt it would be possible to get the HA7 data into Emoncms more directly, but I'm running HS3 anyway and it works. To much trouble to change it!

http://emoncms.org/

http://www.homeseer.com/

Posted By: MonsterMonsterI'm looking to gauge the performance of my 3,000l thermal store compared to others. I know there will be differences in setup but this a rough comparison.

Only had a quick read though, so may be repeating stuff.
But I think you are looking to find out more that just the store thermal losses. But you have to start somewhere so that is a good place to look.

Charge the store up to the usual working temperature, leave it for 24 hours without taking any energy from it (so no hot water, heating etc).
Then charge it up again while taking a note of how much fuel you have used.
This will give you a combination of your heating system efficiency and the losses, but will give you an idea.

Alternatively, if it has electric immersions, you can use them, just measure how much power they take and for how long.

The scientific method is to measure the temperature rise while it is being charged, then the temperature drop while is is idle.
Take the time difference between each degree of rise and a corresponding degree in loss for each temperature.
It is dull work but easy to do.

SteamyTea, your approach looks interesting but I know the missus will have other ideas with no heating for 24 hours! We suffered that for three days last week when the boiler finally gummed up from a dodgy batch of fuel from early this year. But it would be an interesting experiment.

<blockquote><cite>Posted By: JonG</cite>Is there any chance of some schematics MM just so that we can have a look at the set up please?</blockquote>

Here's a rough schematic as best I can do without the proper symbols. The expansion vessels could be connected somewhere else but are for info only. The DHW tank is unvented mains pressure indirect CenterStore 176704. The whole system is unvented.

Lastnight, the boiler was started with a target of 95c. When the boiler had reached 82c and climbing the top\bottom of the store was 72c\60c; the Laddomat top temp. gauge was 72c; the Laddomat bottom right temp. gauge (return from store) was 60c; Laddomat bottom left temp. gauge was 62c'ish (from memory); the boiler had reached 82c and climbing. So here the boiler seemed to be behind by 10c compared to the rest.

This morning the boiler has reached its 95c with fuel left over so the fan was off and Laddomat was pump on and the store was sitting at 86c. The Laddomat temp. gauges were all roughly at 84c-85c so pretty close to the store's 86c. Again the boiler seems to be behind by 9c compared to the other gauges.

I'm currently looking for a decent portable temperature probe to accurately check the pipes.

Plates are notorious for raising the return temp to the store and also require a differential between primary and secondary due to losses across it.

If the return is coming back higher than the bottom of the store temp when it is at rest it will rise through the cooler layers and de-stratify it due to mixing.

On the ETA boilers we do we can control the rad circuit from the boiler and electronically mix it out of the buffer onto a weather compensated curve, to suit the building and heat emitter design, even if the max FT is 70 this is only required in the depths of winter.

If the boiler was 95 with fuel left this would imply to me that the store isn't big enough to accept the toatl output of the fire box?

How was the store sized calculated?

Posted By: GotanewlifeSo eg as I speak, WBS was started 1 hour ago, TS is 35 deg apart from very top (ie below the CH take off), pump speed 5W, i'll be off to up that speed soon, to 18W, then, when the whole TS gets to 60 deg or so, I'll up it to Max 45W but that will be on the control the volume setting rather than constant speed setting so it will start at around 45W and finish around 34W. By that time I will decide whether to chuck in a couple more logs or not - probably not as was v sunny today. Pretty soon the TS will be 75 deg (my max WBS is set to 86 deg) and there won't be much fuel left so I'll drop the speed back to 5W again until tomorrow.

Way too much 'user intervention' for me, I have a warning light in the house that comes on when 3/4 up the TS get to 65deg. and another when the top gets to 60deg, (the useful limit for DHW, at which point the 3/4 level is somewhere around 40-45deg). Based on these lights and time of day I decide when to light the boiler. I light the boiler, full fill, and walk out of the boiler room to wait for the lights to come on again. Duration between firings depends upon summer or winter, DHW useage etc., at the moment I am about 1.5 days average between fireings. (DHW is a seperate tank alongside the TS heated by a coil within the DHW tank)

Posted By: Peter_in_HungaryWay too much 'user intervention' for me

You're just jealous of all them dials, switches and user settings I can play with!

Just another thought too, you have to be careful about timing with pumps either side of a plate.

If the system is at a higher temp than the cold water being displaced out of the primary pipework at switch on, the heat transfers backwards across the plate and can end up artificially heating the primary return, de-stratifying the buffer and cooling the system or cylinder in the process.

We do aim to design them out whenever possible.

Posted By: JonGIdeally the primary and secondary pump would be controlled on delta t to minimise the risk

Do you mean the change in time, or the change in temperature, delta T.

I can see having two pumps, in effect on the same circuit, could lead to problems. Bit like having a car with independent drive to each side, going to be wobbly to drive most of the time.

The variable speed pump on the primary should be controlled based on the ‘secondary required flow T’, ‘current secondary flow T’, ‘secondary return T’, ‘primary T’ and ‘secondary flow volume’ so as to put as little heat as is needed into the PHE. The controller needs to PREDICT how much heat needs to be put into the PHE, rather than just respond to the ‘current secondary flow T’.

Such controllers and variable speed pumps don’t seem to be on the UK market. Without controlling on ‘secondary flow volume’ the system will take some time to respond to changes in flow rate. Whenever a TRV operates the flow rate changes. (For DHW the flow changes whenever a tap is turned on, or a shower operated.)

A PHE does not have enough thermal mass to remain stable if the control system is slow to respond.

Even if the primary pump is controlled in the best possible way, the ‘primary return T’ to the store will ALWAY be higher than the ‘secondary return T’. By increase the size (cost) of the PHE, the difference can be reduced.
For DHW, when I modelled it, it seem that the ‘primary return T’ would often be 20c more than the incoming cold water at full DHW flow rate using a PHE at it claimed KW rating. So the bottom of the FS would never be much below 30c.

Given a choose, a coil that runs from the bottom to the top of the FT, with a 3 way mixer seems to be a better way to separate the liquid in the FT from the liquid in the secondary. However a coil has a lower KW rating, so limits how quickly heat can be taken out of the FT.

<blockquote><cite>Posted By: djh</cite>.... 'm not actually too concerned about the temperature at the bottom of my store, since all it does is reduce the available volume without reheat. It's not as though energy is lost from the system.</blockquote>

Unless you want your store to last longer between firings.