'Improving' my system

[Skywalker]

I was taken by the content of this thread:

http://www.navitron.org.uk/forum/index.php/topic,3231.0.html

As many I'm sure were.

It strikes me that fitting a (Navy fabricated) horizontal retrofit coil to my store in place of the existing immersion could be an option. Then I could fit the valves that Lightfoot linked to:

http://www.acaso.se/english/produktblad/TERMOVAR%20AF%20(EN)%200305.pdf

And heat up the top 90l or so of my store to a happy 80⁰

As a 30 - 45⁰ rise would only take about 4.5kw hours which the output from my 30 x 47 tubes should manage on a regular basis (current output about 0.6kw on an average day). So even on a really rubbish day I should get water to 50⁰ at the top of my store which would allow for washing up and a couple of quick showers and would be cheap to top up. The rest could then be directed to the bottom of the store as normal

Normally of course the temperature spends most of the day equalising in the store but I am guessing that the valve will cope with that if level with the feed boss to the retrofit.

Not ideal in a brand new system but cheaper/less hassle that fitting more panels - but will it work?

S.

edited for unit confusion! - the dreaded kw v kwh

[jwt]

I looked into using two of those units but the problem seems to be if you were to use 1 set at say 55 degrees for the top coil and diverting to the bottom coil for below 55 degrees what happens is the water in the tank sets the temp of the return from the manifold plus whatever the manifold generates.

So for example say your tank is at 30 degrees bottom and 40 degrees top.

The water entering the manifold is 30 degrees, gets heated up and leaves the manifold at 30 degrees plus whatever say 5* degrees so 35 degrees.

The thermic valve never operates until the bottom of the tank reaches 5 degrees less than the temp rating of the valve.

I wondered if the pump was off and the manifold reached 90 degrees and then you turned the pump on would that work but as far as I can see only if the temp at the top of the tank was already over 55 degrees assuming you are using two valves in parrallel for flow and return. And even then as soon as the water in the solar loop went around once or twice it would be back to running at whatever the temp of the tank plus 5* degrees was.

As much as I tried I couldn't visualise a situation where these would work effectively in this scenario. As a result I resigned my self to using an advanced controller with motorised valves to force the solar coil at the top to be used until such time as the top of the tank reaches temp then divert to the bottom.

At least that way I was guaranteed that the heat went where I wanted it and I could fiddle with the temp to activate the valve.

JWT

* % degrees is purely plucked from the air but other threads seem to show that the manifold runs only a few degrees hotter than the tank once the pump is on. A thermosyphon system might be different.

[Skywalker]

Doh

Logic circuts failing, these thing open at these temperatures, I would need ones which closed at them and some other complications for it to work.

Oh well.

What about the ARR 2 OS on the BS4. Presumably I could use the primary heating for the upper part of the store Linked to the S1 Location (top of the store) using a retrofit and then switch to afterheating for the lower part of the store.

Or am I clutching at stores straws.

S.

[JohnS]

I reached the same conclusion that the valves would not work as the initial flow through them would be at a low temperature and therefore would go to the bottom of the store.

My idea to get round this was outlined in by design proposal

http://www.navitron.org.uk/forum/index.php/topic,3592.0.html

This is based on hydraulic variant 5 for the TDC3 controller.  I have subsequently learnt that I shall need a TDC5 controller as this can control more than two relays - pump, valve/2nd pump and dump.  However, Navitron don't stock it yet but I have been told that this will soon change.  The hydraulic variants are slightly different and I may need two pumps instead of one plus a valve.

Assuming the sensors are
S1 - collector
S2 - bottom of store
S3 - top of store

the control logic will need to be something like

if S3 < 55 degrees and S1 > S3 + Delta T
circulate at top of store

if S3 > 55 degrees and S1 > S2 + Delta T
circulate at bottom of store

I have not yet determined if the TDC5 (or TDC3 without a dump) can support this sort of logic. Any views?

Of course another solution is to top load the store using a Willis Renewables Solasyphon.  Looking at their website and the tests, the overall efficiency is slightly down.  

JohnS

Edit - started writing before Skywalker posted

[dhaslam]

If you do fit a more efficient heat exchange system you will still end up with the initial problem  of  not having enough tubes so really that  is what you should do first.     

[Skywalker]

Dhaslam

If you do fit a more efficient heat exchange system you will still end up with the initial problem  of  not having enough tubes so really that  is what you should do first.    

I know

However in the greater scheme of things I have to get on with the insulation of the house or my fancy new heating system (all be it limping) will just be keeping the snakes up on Big Moor warm this winter. 
And they need their shuteye.

I was looking for a relatively quick (low price) fix for now which could be argued as an improvement on the system (if I go out and get some real rosey spectacles).

S.