Thermal Store / Solar / WBS / CH - Is my Setup Correct?

[feeta]

Hi Guys,

After looking at my thermal store design here, its now time to start working out the plumbing configuration of the various systems connected to the store.

Just for a bit of background info, we currently have no central heating at all so it will all be going in from scratch.  We`re hoping to use solar (topped up by immersion) for DHW in summer and a wood burning stove for CH.

The first bit I`d like to look at is the solar.  Our store is going to be 250L and I was recommended that a 50 tube 47mm system would be well suited (5L in store per tube) - The roof is SSE facing and has sun for most of the day.

Please see the attached image of my first draft layout.  You can see here that I have specified using twin coils for solar (using a Solarplug Horizontal for an additional higher coil)  My reasoning being that when the panel is producing good (high) temp water, we can switch the flow in to the upper coil and heat the DHW top section of the tank first.  It would work something like this:

If tank stat 3 is above (60? - what is a good temp for the top of the store to be to produce DHW through coil) solar flow is sent to main lower coil. If not, if temp at panel stat is the same as, or above tank stat 2, then solar flow is sent to solar coil 2, if not, it is sent to main coil.

This should avoid cooler water heading to the top coil and actually cooling the tank.

Also, is it good practise to use a TMV on the return to the panel to warm the temp up a little of the water being sent to the panel, or am I right in thinking that solar panels work best (more efficently) with as low as possible temp being sent to them?

In terms of Check/Non Return valves, I originally decided to put them in to try and stop the thermal store heating the panels over night when they are cold.  But after reading the topic WBS is now heating my Solar tubes, I think maybe NRVs aren`t the answer, but a loop in the piping might sort the problem.

Any help would be very much appreciated.

Cheers,

Pete  

[feeta]

Just out of interest, does anyone have any experience of using a SolarPlug Horizontal? 

[Brandon]

as I recall, you mentioned that one of the solar plugs cost £250ish?

When you specify your store, you could have a second "real" solar coil for less than half that.

[feeta]

Hi Brandon, yes that`s correct, Navitron have them for £258.  I had thought of a second solar coil in the store (but wasnt sure on price) and I`m going to be speaking to Mark at Newark tomorrow so will ask price of adding an additional coil.  As you say, hopefully it will be less than the Solarplug (and possibly more efficient?)

Do you have any advice regarding the plumbing diagram of the proposed solar circuit?  Does it look like a pretty standard twin coil setup?

Pete 

[Brandon]

I would put the diverter in the return, as it will then be cooler, and thus less prone to heat damage.

[feeta]

Ah yes, good idea, will do that.

I spoke to Mark at Newark today and he told me its only an additional £70 to add a 1.6m2 coil to the upper area of the cylinder - So much cheaper than the £250+ Solarplug.  Ideal! 

[CantSpell]

feeta - do you live in a hard water area?  If so, have you considered the effect, over time, of scale build up in your DHW coils?

Just wondering because my water is quite hard - this has persuaded me against using a DHW in-tank coil in favour of an external PHE for my planned new system.  So I guess more of a heat bank than a thermal store. 

[feeta]

CantSpell, hard water shouldn`t be a problem for us as we are in a "soft" water area according to South West Water.

We dont ever seem to have a problem of scale build up in our kettle etc.

Thanks for the advice.

Also, out of interest, how many people use 10mm pipe instead of 15mm for their solar circuits?  We`re looking at 50 tubes and I believe 10mm is fine for this?

[solarsmith]

Also, out of interest, how many people use 10mm pipe instead of 15mm for their solar circuits?  We`re looking at 50 tubes and I believe 10mm is fine for this?

 personally i would stick with 15mm..good flow ..have you looked at solarflex??? (stainless twin hose) dn12, prelagged twin with sensor wire.

[feeta]

Hi Solarsmith,

I did look at Solarflex but at over £500 for 25m, its a bit too expensive.  Have you had experience in using it?

[solarsmith]

hi feeta,
            ouch...! that seems expensive....yes i do have experience use solaflex..i use it dailly lol. i work for a company specialising in renewables so installing solar is a pretty regular thing for me..
the flex is very easy to install, and cheap? i cant see why they quoted 500£?

[feeta]

From this site: http://www.rensus.co.uk/index.php/Flexible-Pipe-and-Fittings/Solarflex-DN12/Detailed-product-flyer.html it looks as though its £545 for 25m.

[solarsmith]

looking at origanal post feeta, in not to sure if the use of a TMV is needed or particully helpfull? (another valve to go wrong). performance would be effected at lower temps, collectors could overheat.
Heat being drawn from store could be corrected with simple loops or good quality solar rated NRV's - paw.

[feeta]

Solarsmith, thanks for your input. I took the TMV out of the system just to keep the system simple.  I havn`t updated with a new schematic yet but will do hopefully later today. 

[solarsmith]

  no worries .. yeah, best keep the sysem as simple as necessary...even solar rated stuff fails, less valves etc = less chance of failiure.

did you get my pm?