 |
|
|
Home  Books GBEzine News HelpDesk Register GreenBuilding.co.uk
|
|
| Green Building Bible, Fourth Edition |
|
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment. PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book. |
Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.
Posted By: Peter_in_HungaryBenm85
How are the rads. fed from the thermal store (TS) ? This can be key. If the rads are indirect by some form then the 70deg. won't be going out to the rads.
Posted By: Peter_in_HungaryBenm85
Does the rad. output come from the same level on the TS as the temp.gauge?
Posted By: Peter_in_HungaryBenm85
Have you measured the temp. of the TS output to rads and at the input to each each rad.?
Have the rads. been sized correctly for the heat load of the building?
What is the output of the rads compared to the kWs of the combi.
Is the problem of rad. temp. the same with both the combi and the wood stove running?
Posted By: Peter_in_HungaryBenm85
Is the problem of rad. temp. the same with both the combi and the wood stove running?
Posted By: Benm85According to the internet, the intergas boiler has a maximum CH output of 30kw. Whether this is enough for a 350l thermal store, I'm not sure.
Posted By: djhIf you go back and edit your second post, you can change the format to Html and the quotes will then show up properly.
Posted By: djhIt sounds to me like the flow rate may not be sufficient. Water is reaching all the radiators and cooling down whilst it flows (slowly) through them so it is cold before it reaches the bottom. Assuming it is pumped it might be worth increasing the pump speed. What are the flow and return temperatures at the boiler and stove? Do you use both together or one at a time?
Posted By: djhIt's not really a question of the boiler being big enough for the thermal store. The question is whether the boiler is big enough to supply all the heat the radiators require. If you haven't already, make a list of all the radiators and their sizes and type (single, double etc). Then you can use tables to calculate the heat output from each radiator at a given temperature and start to work out what you need to be aiming for.
Posted By: GreenPaddyditto what DJH said.
think of your system as two separate parts. Boiler's job is to keep the TS hot. TS's job is to feed the rads.
If the TS is consistently at it's set point (ie 70oC) then the boiler is doing it's job.
If the rads are not giving out enough heat, then there is a problem between the TS and the Rads, nothing to do with the boiler.
Rad hot at top and cold at bottom is a flow rate issue, exactly as DJH explained. It sounds kind of unusual, as would have to be very slow flow rate, much less than I'd expect from a pump.
Log boiler stoves can send out bits of crud, into the system. I've seen this lots of times, and usually fit strainers to catch this. Of course the strainer gets blocked, and so needs flushing, but at least you've caught the crud and can flush it.
Increase the pump speed by all means, and that should show an improvement, but I've £10 bet on something being choked (blend valve, automated valve, pump inlet, strainer).
Also check that the balance valve (lockshield) on the other end of the rad from the TRV have been set properly, and not all closed down. One should be fully open (on longest part of CH run usually) with all the rest being appropriately more closed to balance the flow to rads.
Likewise, check any other valve in the CH circuit are not closed down, eg. gate valves on either side of the pump.
Posted By: Benm85Yes, the rads are fed from the thermal store, as is the DHW.
Posted By: Benm85Yes, the rads are fed from the thermal store, as is the DHW.One, at least, of those will be fed indirectly; that is, via a heat exchanger which might be internal to the thermal store (probably a coil but maybe tank-in-tank for the DHW) or externally in which case it's probably via a plate heat exchanger. Most likely the DHW is indirect. You wouldn't want to shower or do the washing up in water which has been through the radiators. I'm pretty sure that's what PiH meant by his question.
Posted By: Ed DaviesMost likely the DHW is indirect. You wouldn't want to shower or do the washing up in water which has been through the radiators. I'm pretty sure that's what PiH meant by his question.
Posted By: Peter_in_HungaryPosted By: Ed DaviesMost likely the DHW is indirect. You wouldn't want to shower or do the washing up in water which has been through the radiators. I'm pretty sure that's what PiH meant by his question.
Correct -but that doesn't stop the combi being indirect as well.
Posted By: Ed DaviesPosted By: Benm85Yes, the rads are fed from the thermal store, as is the DHW.One, at least, of those will be fed indirectly; that is, via a heat exchanger which might be internal to the thermal store (probably a coil but maybe tank-in-tank for the DHW) or externally in which case it's probably via a plate heat exchanger. Most likely the DHW is indirect. You wouldn't want to shower or do the washing up in water which has been through the radiators. I'm pretty sure that's what PiH meant by his question.
(PS, PiH's response cross-posted ahead of mine by 14 seconds.)
Posted By: Peter_in_HungaryPosted By: Benm85Yes, the rads are fed from the thermal store, as is the DHW.
If both the CH and DHW are fed from the TS then at least one of four connections if not two or three must be indirect. I would expect the DHW to be indirect with the other 3 direct but you never know.
Could you confirm which of the boiler, wood stove, DHW and CH is direct and which is indirect.
Posted By: Benm85I'm not sure what direct and indirect means.
Posted By: Benm85Should have probably explained, this system was in when we moved into the house 2 years ago. So none of this was my choice.....or fault!
Posted By: Peter_in_HungaryWhy are you not using the combi for DHW? Unless you have your own wood supply it will probably be cheaper to do the DHW with the combi and would produce much less pollution and you won't need to run the TS all year around (which will have its own additional inefficiencies)
Posted By: djhThe Gledhill TS use an external PHE to prepare the DHW. Central heating is direct. Solid fuel is direct. Gas boiler can either be direct or via a coil. Solar thermal (SOL variant of tank) is by a coil. There may well be one or two immersions.
edit: Ben are you sure the link you gave is to the right product? Gledhill change their product range fairly frequently and introduced stainless tanks fairly recently. There should be a manual with the tank that gives the full details. I don't remember if there's a model no. printed on the tank (on the control unit maybe?). We have a Gledhill TS, but not quite the same model.
Posted By: GreenPaddyOk, so you've just mentioned that the TS won't/struggles to reach the 70oC setpoint. There could be an issue with the controller timings, set point stat location, or a physical issue with the TS coil arrangement. Your gas boiler should have no issue at all, keeping up with the CH energy draw. But taking things one at a time, that's quite separate from the rads having a large temp drop across them.
1. Sort out the flow issue with the rads, to get them performing correctly, with a much reduced difference between inlet and outlet for each rad. Even on the lowest circ pump setting, you should get a decent flow through the rads. Indeed, I would have suggested you set the CH pump to the lowest setting, to minimise stirring inside the TS.
2. In theory, since you would then be drawing more energy from the TS, the boiler will have even more difficulty keeping the TS up to set point.
3. Then you can start to investigate how the boiler controls are set up. At 30kW+, if the boiler is allowed to, it will easily match the CH draw, and also raise the TS temp. So that tells me either the controls are not set up to allow the boiler to drive the TS temp up, or that the heat transfer to the TS (which we still need to determine if it goes via a coil inside the TS) is restricting how much energy it can input to the TS.
We need a definite schematic/detail of the TS, to know if the gas boiler goes through a coil inside the TS, or into the main body of water. Your link implies the only coil is solar, with all other connections being to the main body of water, the DHW drawing that via an external plate heat exchanger (as DJH already pointed out).
I've upped my bet to £20 that there are choked items, in both the CH and also the gas boiler circuit, and more than likely in the stove circuit too. The Stove will have a load valve of some sort (or a thermostatic mixing valve), to ensure it always receives warm water, which it then makes hotter. Those TMV's also have mesh strainers, which get choked, and reduce the flow from the stove - again a good reason for that stove to not be able to impact the TS temp.
You'll see a low flow in the stove circuit exhibit itself by the outlet temp from the stove being much higher than the inlet to the stove. It would normally be say 5 to 10oC max difference. If the flow is restricted, the stove will be getting very hot, very quickly, and sending maybe 80oC or hotter water to the TS, even when the TS return to the stove is only in the 50's or 60's oC.
Posted By: djhThanks, that looks more like the generation of product that I have. So the description is athttp://www.gasapplianceguide.co.uk/Gledhill/Torrent%20Greenheat%20thermal%20store/Torrent%20Greenheat%20SOL.htm" rel="nofollow" >http://www.gasapplianceguide.co.uk/Gledhill/Torrent%20Greenheat%20thermal%20store/Torrent%20Greenheat%20SOL.htmand the full manual seems to be this onehttps://www.gledhill.net/uploads/Torrent-GreenHeat-5.pdf" rel="nofollow" >https://www.gledhill.net/uploads/Torrent-GreenHeat-5.pdfif you don't have a paper copy. You'll still need to trace the plumbing connections to figure out how the boiler is connected but at least you'll be able to identify things.
Posted By: GreenPaddyThose TMV's also have mesh strainers, which get choked, and reduce the flow from the stove - again a good reason for that stove to not be able to impact the TS temp.
You'll see a low flow in the stove circuit exhibit itself by the outlet temp from the stove being much higher than the inlet to the stove. It would normally be say 5 to 10oC max difference. If the flow is restricted, the stove will be getting very hot, very quickly, and sending maybe 80oC or hotter water to the TS, even when the TS return to the stove is only in the 50's or 60's oC.
Posted By: Peter_in_HungaryPosted By: GreenPaddyThose TMV's also have mesh strainers, which get choked, and reduce the flow from the stove - again a good reason for that stove to not be able to impact the TS temp.
You'll see a low flow in the stove circuit exhibit itself by the outlet temp from the stove being much higher than the inlet to the stove. It would normally be say 5 to 10oC max difference. If the flow is restricted, the stove will be getting very hot, very quickly, and sending maybe 80oC or hotter water to the TS, even when the TS return to the stove is only in the 50's or 60's oC.
To make things clearer perhaps,the the inlet to the stove mentioned here is on the stove side of the TMV, the inlet from the TS is on the outside of the TMV.
If there was a significant blockage in the TMV I would expect the boiler to boil if run on full chat.
This assumes there is a TMV on the stove. If there is a TMV you will see a pipe taken off the stove output pipe doing to a block with three pipes going in, one from the stove output, one from the TS an the third going to the stove return. - In case you don't recognise the TMV for what it is. Its function is to mantain the temp. of the stove to keep the stove temp. up to reduce pollution and chimney fouling.
Posted By: ListysDad- is the output from some radiators different to others?
Posted By: ListysDadSome questions if I may.
- do you have plastic pipework anywhere?
Posted By: ListysDad
- is the solar thermal system maintained / working fully?
Posted By: ListysDad
- are you SURE the store is full of water?
Posted By: ListysDad
- what is the condition of the F&E tank?
Posted By: ListysDad
- you talk about the store being set to 70oC but the PDF shared with us by DJH says when the boiler runs it should be to deliver 75oC. Why is yours at 70?
Posted By: ListysDad
I'm in Wetherby if it helps.
Posted By: GreenPaddyHaving a stat on the flow from the stove will not prevent it receiving a cold water input. Running a stove with a fixed temp stat from a thermal store is not very clever at all.
Anyway Benm85, my recommendation is that you draw out your system on a piece of paper, and share it on here. Otherwise you'll get a whole host of different theories based on a whole host of different assumptions, and you'll end up more confused than you are now. You'll also understand our system much better at the end of it.
