If you tweak the lockshields you'll unbalance the rads so nope. Just TRVs open.

It's a simple sanity check. If I read correctly you used to have 30l/min (1.8 m3/h) before the buffer tank was installed. If the Wilo can push that flow rate at a reasonable pressure drop (check the display) through your installation with all TRVs open then:

1) the heat pump circulator which is about twice as beefy should work just fine with the tank as a volumizer.

2) there is no more crap stuck in your pipes, which is always nice to know!

Hi @bobflux and @jamespa 
tagging you as you both have been giving me advice which is invaluable and helpful. I have done the pipe trace and everything looks to be piped up how it should be. I think it was a case of misplaced probes, I also noticed the secondary Wilo pump was on the lowest setting whilst the heat pump is on the highest and I think what was happening is that the wilo pump was taking the bare minimum and the rest was mixing and returning back to the heat pump. I did put the Wilo on max give it a couple minute test and it worked better and saw the return on the bottom left come down. 

This is my trace and I hope it makes sense. 

loft

Airing cupboard

I know the drawings are crude but I'm trying my best to get the data across for a 2nd opinion. I think to turn it into a volumiser I'd have to connect the returns where I labelled it with a purple line. That way the return flow goes back into the airing cupboard via the flow setter and back to the heat pump. Then on the buffer plumb the heat pump flow in at the bottom left then cap the top left and bottom right. Remove the Wilo pump from system. 

Is this about right? 

What stiff baffles me....

How the loft flow setter which is the flow in is 28 and the return is 33. No matter what speed I use on the 2nd pump it stays relatively the same

@heymikey Perhaps the errors in the pump readings might suggest the actual flow rate is somewhere between (in the region of 30.5 lpm), they must match for the water circuit to run unless you have a constant top up of supply or an ever leaking pipe somewhere! Regards, Toodles.

@toodles yes I think ur right.

Any thoughts on my volumiser diagram? 

@heymikey Sorry, with my poor vision, I have great difficulty with diagrams and photo details so will refrain from comment on that.

For what it is worth though, my system has a Low Loss Header and a Wilo Pico pump for the secondary circuit. I calibrated four probes against each other and noted the differences before attaching them to the four ports on the LLH. The Wilo Pico pump has a variable speed facility and I have managed to tweak the speed so that the pairs of ports on that LLH match within 0.1 degree C. for the vast majority of the time. Of course, the LLH is much smaller than a buffer tank might be but the same principle applies; if you can match the flow rates, then the distortion within the LLH / buffer tank is minimised and thus more efficient. Is your secondary pump furnished with a variable speed setting? Regards, Toodles.

@toodles

This is the dial on the pump below .

So the left side is Variable differential pressure (Δp-v): .

The top has a fixed I, II, III.

I believe the right side is for under floor heating. 

@heymikey That looks as though you have a variable speed control to me; if you have the means to measure the temperature on all four ports of the buffer simultaneously, then you might care to try and match the ports (as pairs) as closely as you can using the variable speed. The aim is to match the temperature of the flow in and the flow out as closely as possible and in the same way, match the return in and out as closely as possible. You should expect to see the difference between the flow and return circuit as reflected by the Delta T of your system (typically ~5 degrees C) but the important bit is to match the temperatures in the flow (in and out) as closely as possible and similarly, the return in and out. The closer the temperatures, the less distortion is occurring and the greater the efficiency.

I had contemplated asking my installer about removal of the LLH but felt that with such a close match as I was able to achieve, I would leave well alone. Regards, Toodles.

@toodles thanks Toodles.

I do have 4 probes for when I was balancing radiators 2 at a time. Maybe I should leave it and do what u did as I feel my installer probs will not agree to it. I'm fairly sure I'm a thorn in their side. 

@heymikey Have fun!😆Toodles.