4) My main problem is hot water out of one outlet is fine, as soon as I try two at the same time they run cold
I have a suggestion. If you can find a couple of pipe thermometers, stick one on the DHW pipe where it comes out of the cylinder, and one on the DHW pipe after the blending valve. They will need to have good contact, and ideally some thermal contact grease (or just a dab of ordinary grease at a pinch). Get someone to draw off water from one outlet and observe the thermometers, then get them to turn on a second outlet and see what happens. It will take some time to settle, so it might be best if you can combine this with normal DHW usage (such as running a bath) to reduce waste.
If you can't get hold of thermometers, then you could just try it by feel - but that's very subjective, and the pipes shoudl be too hot to touch anyway (at least the one coming out of the store should be).
What I'm angling at is this - does your hot water go cold because the store can't heat it properly (the pipe coming out of the store will go cold when running two outlets), or is the store doing it's job and there's another fault (the store outlet will stay warm, but the blending valve output will get cool) ?
Lastly, have you measured the flow rates involved. It's worth doing to see if you are drawing significantly more or less than the store is supposed to be able to supply. To measure flow rates, use a large jug or bucket and a stopwatch - it's then simple maths to get flow rates.
It's not easy to find somebody who knows TS well. The guy who fitted it has emigrated. I've had three or four plumbers look at it for various reasons over the last couple of years
a) BG guys just couldn't figure it out.
Not really a surprise - they'll be doing combis, S plan and Y plan all day long and probably very little else.
b) The guy who changed my boiler 18 months ago did figure out how the whole thing works. He is a straight up guy but says that my system is not how he usually does things ie he does mainly mega flows.
That's part of the problem - people are only "comfortable" with a limited range of systems. That's not a criticism, people can only be fully conversant with a limited amount of stuff - and thermal stores are still quite uncommon. This guy is at least honest and tells you that, rather than ...
c) The sub contractor who just moved the TS for the loft conversion company (as mentioned my loft conversion is under way)
He tried to tell me this is some kind of ancient system and I should consider ripping it out and installing a mega flo.
I think this is quite common - both from personal experience, from people I know have told me of their experiences, and from threads on here. Too many are prepared to tell you it needs ripping out for no other reason than they don't understand it and aren't prepared to admit that.
BTW - did the contractor install the automatic bypass valve in the heating loop, or was it already there ? It really shouldn't be there at all with your setup and the only thing it can possibly do (other than nothing) is to confuse the modulating pump and make it pump faster/harder than it should.
I have guy b) coming around next week to have a look and tell me whether he thinks a Mega flo would solve my issue.
Well it would, but then you'd lose the benefit of running the heating off the store rather than direct off the boiler.
