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Author Topic: Thermal store  (Read 2287 times)
duke700
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« on: January 07, 2019, 07:14:20 PM »

Hi
I have recently installed a 210 litre thermal store with solid fuel connections ,central heating flow  and return ,solar thermal connections and a future plate added as well.It came with two emmersiers which are a located at the bottom of the tank.
The stove is a Charnwood la50ib which is on a gravity circuit to the TS. The pump is fitted on the flow side of the central heating and at the moment is wire into a plug!
What I'd like help with is how to wire the pump and any other advice people could share good or bad!
Im worried I may have made a mistake in which store I've fitted but the company were very help full..
With regards to the pump I've notice that it takes an hour from lighting fire till TS reaches 75 degrees and this is store sitting at roughly 45 degrees.. Once I switch the pump on I get about 10 minutes of heat before store has dropped to 55 degrees.. Then its taking about 30 minutes for stove to bring store back to temperature... Is this normal? There's seven radiators fitted to system which is plumbed with 22mm pipe all the way to the radiator and then converted down to 15mm pipe.Pump is also on lowest setting. The emersiers are wired to switches.

Any help would be much appreciated.
Many thanks
Andrew
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oliver90owner
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« Reply #1 on: January 07, 2019, 08:13:18 PM »

Not much of a thermal store?  Many domestic hot water cylinders are 160 litres? Smiley

Sorry, but couldn’t resist!  Welcome to the forum.
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RIT
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« Reply #2 on: January 07, 2019, 08:38:51 PM »

First of all, welcome to the forums.

In reply to your question. As Oliver hinted at, the store is on the small size. When you consider just how much water is pumped through the TS during the 10mins you talk about and how much water there is likely to be in the radiator circuit (as well as the 7 radiators) it is not that surprising that you can lower the TS temp that quickly.

A store of that size would work well for domestic hot water as running a tap or even a bath would be an intermittent task allowing the TS to recover, but for a large radiator circuit, it will not have the storage capacity to all the pump to run constantly.

On the upside if you did have a larger tank you would then have the problem of the time it would take the stove to bring the tank up to temp, unless you ran the stove for much of the day.
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duke700
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« Reply #3 on: January 07, 2019, 08:50:32 PM »

Many thanks for both replys.
I discussed my requirements with the company and they were very help full and came highly  recommended as they are meant to be very good at what they do..
Thanks again for the info,much appreciated. 
 
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RIT
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« Reply #4 on: January 07, 2019, 09:09:54 PM »

Many thanks for both replys.
I discussed my requirements with the company and they were very help full and came highly  recommended as they are meant to be very good at what they do..
Thanks again for the info,much appreciated.  
 

It may be that they sold you a system that has the tank and stove well matched for each other, without providing many indications about the capacity limitations. By any chance were there physical limitations that they had to work within such as space?

One question for you. Was the aim to spread the heat from the stove out around the house as best you can or were you hoping to quickly bring the house up to temperature? If you are looking to just spread the heat around you need to find some sort of pump controller that will operate the pump down to the TS dropping to 50c and then not restart until the TS reaches 65C. This way the pump will not stop and start so much as I guess it is doing at the moment. It may also move heated water around the radiators better than a lot of short pump cycles.
« Last Edit: January 07, 2019, 09:19:44 PM by RIT » Logged

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daveluck_uk
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« Reply #5 on: January 07, 2019, 09:36:39 PM »

This is very similar to how my systems works.

I have a 475 litre store, the stove heats this by gravity until the store hits 70. Central heating pump comes on and pumps water until the store hits 60.

The first switch on is fairly short, 10 mins or so. As the rads warm up the time the pump runs is longer and longer as the same volume of water is being pumped but less heat is removed as the rads shut down and the water returns to the store and n effect the stove hotter.

In theory my hunter puts 12kw to the water, my rads add up to 11kw. ( 12 rads over 3 floors )

I have fitted cheapm as chips digital thermometers to all my pipes so I can now see that the water leaving the stove is around 75c. Its taken me nearly 10 years faffing around with trvs, moving the sensors in the tank, working out what temp to turn the pump on and off, whatnspeed to run the pump etc Every year ive used less and less wood and the house has got hotter and hotter!

Currently the outside temp is -5 the TV room is 21c, the bathrooms are ate 23c and the bedrooms around 18c.

So your system will work. You'll just have to faff around until you get the settings right.

What size is you fire output and how many kws do your radiators take?

Edit...

Starting temp in the store around 50c and it normally takes about 30 mins to heat up to 70c.
« Last Edit: January 07, 2019, 09:43:07 PM by daveluck_uk » Logged
duke700
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« Reply #6 on: January 08, 2019, 07:34:01 AM »

Thanks again for the reply's ,much appreciated..
As you mentioned the tank had to fit in an attic so space was an issue..They supplied me with a cube type tank.
Last night I left pump on for two hours and the stove kept the store at 50 degrees but it wouldn't climb back up in temperature.
The pump itself is on a shower pump setting,I've found if I increase speed then the temperature runs down quicker..
When pump is switched on it takes 8 seconds for first radiator to get hot water and 5 minutes for the system to be hot.
There are seven radiators which total 11kw , fire puts out 12kw to the water and 2kw to the room...Looking at it now I think fire is on the small side..
I also have a Jotul F400 in the living room if needed..
The information you have both given is great and your right it will take time to to understand it..
Do you put heat stats on the flow and return stove circuit and wire them to the pump?

Thanks again
Andrew
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Countrypaul
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« Reply #7 on: January 08, 2019, 08:23:26 AM »

The stove will only put out 12kW when burned hard with good dried wood otherwise it will delivery significantly less. It is quite possible that the gravity circuit also limits the rate at which the heat can be transferred to the store, often a loading valve such as a ladomat is used to aid performance and also reduce tar build up in the chimney due to the stove not working at optimum temperature as it fills with cold water when first lit.

Have you tried isolating some of the radiators and seeing what difference that makes to overall performance? If for example you found that the stove could easily keep 6 radiators and the store hot without issue, you might find other things you can do to increase the number of radiators it could easily support without trying to get everything working flat out at the first step.
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daveluck_uk
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« Reply #8 on: January 08, 2019, 09:49:57 AM »

Thanks again for the reply's ,much appreciated..
As you mentioned the tank had to fit in an attic so space was an issue..They supplied me with a cube type tank.
Last night I left pump on for two hours and the stove kept the store at 50 degrees but it wouldn't climb back up in temperature.
The pump itself is on a shower pump setting,I've found if I increase speed then the temperature runs down quicker..
When pump is switched on it takes 8 seconds for first radiator to get hot water and 5 minutes for the system to be hot.
There are seven radiators which total 11kw , fire puts out 12kw to the water and 2kw to the room...Looking at it now I think fire is on the small side..
I also have a Jotul F400 in the living room if needed..
The information you have both given is great and your right it will take time to to understand it..
Do you put heat stats on the flow and return stove circuit and wire them to the pump?

Thanks again
Andrew

Well I take the fact that the water stays at a constant 50c as a positive! If I just left my pump running, without trvs etc then my water sits at around 55c. All you need to do now is work out how to increase it!

Running a stove is a bit of a black art. Well, I think it is. I quite enjoy checking the temps, adjusting the air so you get a nice deep orange rolling flame that fills the whole fire box as you burn off the smoke etc.

Personally I use no pipe stats. I have an old navitron tdc3 to control the CH pump. When the water is hot it turns on, when its colder it turns off. I also don't use room thermostats. If the fire is lit them I'm cold and the trvs will look after the room temps.

I've been umming and ahhing over whether to install some kind of loading valve ( laddomat or whatever ) but decided against it.

Get yourself onto eBay and purchase some of these....https://www.ebay.co.uk/itm/Thermometer-Temperature-Universal-Tester-1x-Probe-Lcd-With-Mini-Indoor-Sensor/382620688453?ssPageName=STRK:MEBIDX:IT&var=651376153785&_trksid=p2060353.m2749.l2648&redirect=mobile

Attach them to your pipes with aluminium tape. Until you can see what your temps are you will struggle to optimise your system. Also attach one to your ch pump and one to the return. My water circulates at around 65c rather than the 70c but the return is around 11c difference.

Countrypaul is right about turning off a couple of rads to see if it makes a difference. Worst comes to the worst and you find that you cannot run all the rads at once you could get yourself some cheapish programmable trv heads and programme them so that the radiators come on and off in a sequence...or if the pipe layout allows it fit a zone valve and wire it up to a programmer and again switch the valve on and off to allow that section to be heated in sequence.

Don't worry, m certainty n you'll get it to work!



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duke700
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« Reply #9 on: January 08, 2019, 07:02:40 PM »

Thanks gentlemen for your advice ..
I've already turned a radiator of tonight so will see if that helps.
With regards to the loading valve..I read about it but as I'm a complete novice to this I didn't want to start spending more money and find I'd maybe bought the wrong thing..
I'm only burning pine logs a the moment which are well dried out as I've checked them with the moisture meter. I've got coal and peat so will experiment with it and see..
Ill certainly look at those temperature stats,thanks
I've only fitted manual valves as advised by a heating engineer.

Thanks again for taking the time to help.
Andrew
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daveluck_uk
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« Reply #10 on: January 08, 2019, 09:38:13 PM »

Thanks gentlemen for your advice ..
I've already turned a radiator of tonight so will see if that helps.
With regards to the loading valve..I read about it but as I'm a complete novice to this I didn't want to start spending more money and find I'd maybe bought the wrong thing..
I'm only burning pine logs a the moment which are well dried out as I've checked them with the moisture meter. I've got coal and peat so will experiment with it and see..
Ill certainly look at those temperature stats,thanks
I've only fitted manual valves as advised by a heating engineer.

Thanks again for taking the time to help.
Andrew

Just had a thought....it is a 2 pipe system? Ie turning off one of the rads won't stop the water circulating.

When you say manual!valves I'm assume you mean on the rads? So they are not thermostatic valves? There is always hot water flowing through the radiators unless you turn off one of the valves? Or are they manual trvs?

Personally I wouldn't get a loading valve or at least if I did I would make up my own. It wouldn't be as slinky as a laddomat but it would do the job and cost about halff of the cost.

Burning coal and peat you'll need to change the airflows on the stove. Wood burns best with air from the top and coal burns best with air from below so needs to be on a grate. No idea with peat...never burnt the stuff.

Pines OK, burns hot and fast. I burn a lot of birch which has similar characteristics. I also burn a LOT of willow. Actually I burn anything,  oak, birch, chestnut, hazel, maple, willow, blackthorn, pine, pallets, ash, eucalyptus ( massive heat but a right pain to get going, smells lovely ) cherry, apple, old grape vines, buddleia and mimosa.  Far as I'm concerned if its wood, its seasoned, its cut, logged and stacked in your barn it'll burn and give heat. It may give more ash, it may mean you need to clean your chimney mid season, you may need to burn twice as much wood as oak, you may have tom faff with the air controls to keep!the heat up...but that's why we have wood burners!

What stove do you have?
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duke700
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« Reply #11 on: January 08, 2019, 10:18:49 PM »

Hi Daveluck

Its got a flow and return coming out of the ST , sorry I'm a novice at this.
Manual valves that you have to screw down..
I fitted a Charnwood La50ib as a heating engineer recommended it to me,trouble is it only has one air  control coming in at the bottom..
I was going to fit something else but was getting mixed reviews on any other stove I looked at..
I do have a grate on the fire so open that up a bit when burning coal.

I have some birch and beech which I'm keeping for when its colder.
I'll keep faffing with it.
Thanks again.
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regen
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« Reply #12 on: January 09, 2019, 05:44:08 AM »

There are so many variables these systems. Firstly wood stoves rarely deliver the manufacturers output often dropping as low as 50% with poor quality high moisture wood and poor firebox loading. The size and distance/rises from fire to store will effect the efficiency of heat transfer on a gravity system fitting a pump will remove this variation. That number of rads with a store which is so small will take all the heat from the store very quickly and the was will not be able to cope until the system reaches cycling point and recovers. The total amount of heat required will depend upon the levels of insulation-the poorer the insulation the lower the house temp will get and the more heat will be required.

I suspect that the system is undersized and will require constant nursing to get the best out of it. Perhaps a stat on the store which is linked to the CH pump would help. Set to come on when the store reaches 60 deg and turning off if the store drops to 50 may help.

Regen


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daveluck_uk
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« Reply #13 on: January 09, 2019, 10:08:26 AM »

Hi Daveluck

Its got a flow and return coming out of the ST , sorry I'm a novice at this.
Manual valves that you have to screw down..
I fitted a Charnwood La50ib as a heating engineer recommended it to me,trouble is it only has one air  control coming in at the bottom..
I was going to fit something else but was getting mixed reviews on any other stove I looked at..
I do have a grate on the fire so open that up a bit when burning coal.

I have some birch and beech which I'm keeping for when its colder.
I'll keep faffing with it.
Thanks again.

Everybody was a novice once so no need to apologise.

Looking at the manual the chanwood does have a top air vent but only to be used when burning anthracite

 CHARNWOOD LA45iB & LA50iB Roomheater With Boiler Operating and Installation Instructions
PDFhttps://www.nwleics.gov.uk › documents

Was there any difference when you closed off one of the rads?

What is attached to the tank in the loft? Does it have sensors? How do you know what the temperature is? Are there any controls? Can you post a photo?

Clearly heat is getting to the tank. Equally as clearly more heat is being taken out of the tank than what you are currently putting in. In and of itself that isn't necessarily an insurmountable problem. After all, that is what's supposed to happen.

Get those thermometers onto the incoming and outgoing pipes on the gravity circuit so you an see whats happening with the temps.

As Regen mentioned you will need to get some kind of temperature controller to activate and deactivate the pump.

He's also right that you'll probably have to nurse the system. The tank does seem a little small but if that's what you've got then that's what you've got and you'll have to optimise the system the best you can.

Chin up! Its early days yet.


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duke700
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« Reply #14 on: January 09, 2019, 08:56:25 PM »

Once again a massive thanks for the information.
I've got the pump wired to a plug in the kitchen and put it on when stove reaches about 80 degrees..
This where I could do with help as in whats the best way to wire it..
Yeah I do remember the little air vent at the top.
I'll keep experimenting with it,loft space is very small thats why this cube tank was sized by the company..
Would a bigger stove cope better ?
Any advice on best to wire pump would be appreciated.
There's a space for a stat to be fitted to tank but I believe it's for the overheat stat.

Thanks again.
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