Help in Setting up Solar Buffer Tank

BigGeorge

have a 1500 lit buffer tank (Tisun PCL1500) which is fed by 12sqm of solar tubes & a gas boiler. The temp at the top is approx 55C & the bottom around 25C. I;ve attached a simplified image of the set up. The DHW comes off the top ( via a coil) & hot water for a low temp / UF heating loop from near the top ( is about 45C coming off). The gas boiler is approx 10kw.

There is very little requirement for the UF heating loop & what there is could be satisfied by water at 30C. The water returning to the tank from the heating system in the house is coming back at about 20C.

Also the run to the solar panels is quite long & is not working that efficiently I believe. The tank is set up as per the manufacturers( Tisun's) instructions but I still believe its is not running anyway near efficiently & stratification not as good as it should be.

Any advice or experience on how to optimise these these tanks or type of set up would be really appreciated. Am open to changing the piping configurations and solar panel settings. Any questions on current set up please ask

https://plus.google.com/photos/102704024114110901673/albums/5810013175589283457

shane0007

When you say tank settings, what are you talking about, is it the stat settings?

If the solar circuit is very long, you could increase the flow rate, especially with 12sqm. What flow rate is it set to?

BigGeorge

The pump is operating at about 7lt/min, am not sure how / if I can increase the flow rate( the controller is a rebranded Resol C4) , the panels are calpak 12VTNs tubes, in 3 panels piped up in parallel

Was looking at the cut in & cut out temperature for the gas boiler, currently 53 to 57C & it does not come on during the day. Also if the heating curcuit in the house is low temp, then not sure why it is set up to takes water from so highup the tank, approx 47C, & then is diluting it down up use at the manifolds, then the returned cooled water (20C) is again not returned that close to the bottom.

In the shoulder months the panels appear to do a job job or harvesting a lot of 25-30C water & would like to find to use low grade heat for the heating looprather than just heating the start of the DHW coil.

if anyone has been successful in optimising one if these tanks or similar stratified tank would love to hear too : Tison Proclean PCL3 1500Lt

shane0007

You can increase the flow rate through the regulator on the pump station itself. You may have to increase the pump speed to achieve a higher rate if it is not already on speed 3. With 12sqm I would be trying to achieve about 10 litres per minute.

Increase the tank temperature to about 70C. The UFH will draw off what it needs as it needs it, it will send back a higher temp and the buffer will have a longer energy output. The boiler will be on for a bit longer but won't need to come back on until later.

Try a Resol TT1 controller. It has a built in high/low temperature cut in for the relay, so,you can programme boiler to kick in a say 40c and off at 70c.

BigGeorge

Have had a look at the DeltaSol C/4 manual & there is no mention of increasing flowrates - boosting the flow would prob make sense

As regards increasing the tank top temp, would increasing this not just mean that losses are going to be higher & will also harvest less solar...had always thought you were supposed to run at as low a temp as possible, but have loads to learn on this so the advice is appreciated

shane0007

BigGeorge wrote: »

Have had a look at the DeltaSol C/4 manual & there is no mention of increasing flowrates - boosting the flow would prob make sense

You cannot increase the flow rate via the differential controller, i.e. the Deltasol, it can only be done through the flow regulator that is built into the pump station. How did you know the system is set to 7 litres per minute?

BigGeorge wrote: »

As regards increasing the tank top temp, would increasing this not just mean that losses are going to be higher & will also harvest less solar...had always thought you were supposed to run at as low a temp as possible, but have loads to learn on this so the advice is appreciated

This is determined at the top of the tank, the take off point. Solar differentials are taken from the bottom of the tank so no effect.
The UFH will take what it needs, mixing the return temp and returns the higher back to the tank. Higher tank temps means longer storage which equals more efficiency.
Most modern tanks will only lose about 5 - 6C over a 24 hour period, unlike most copper DHW cylinders, which lose about 30C over the same period.

BigGeorge

Had a look at the wilo pump today on the pump station & its indeed set to speed 3. There is an inbuilt flowmeter in the unit & its showing that the pump is only producing 7 lt/min - dont know how I can adjust this up any more. The pump is a Wilo St 15/6 Eco & I seem to remember when it was commissioned first that the flowrate was a lot higher - is there anywhere a system that would usually foul & result in low flow rates?

shane0007

Did you put the pump into manual over-ride mode or did you just see the flow rate when it was on anyway? There is a difference as the controller modulates the pump speed to suit the temperature. If this is what you did, the. Put the pump into manual mode to see the true flow rate.
Once I manual mode, there should be a slot you can turn to adjust the flow rate.

BigGeorge

The pump was working at 100%. When i changed the speed setting on the pump the flowrates I got were as follow: 1 : 4 lt/min, 2 : 5 lt/min, 3 : 6 lt/min

Do these pumps have a strainer of filter that blocks maybe? I cannot see one in the manual though

shane0007

As I asked before, did you manually switched on the pump via the Deltasol?

You can adjust the flow via the flow regulator in the pump station, did you locate this?

BigGeorge

Not sure how to turn on manually, where is the switch?
The brass / metal flow adjustor just above the flowmeter is wide open

many thanks

shane0007

It is done through the settings menu of the controller. However, that particular controller tells you actual pump speed as a % so if is telling you it is running @ 100% then it should not be modulating at that moment.

If the flow regulator is completely open and the you are only achieving 6 lt/min, the. It sounds like pump head is under-sized for the size of the system. What diameter pipe work between the pump station and the panels is used? Also what is length of pipe run?