Circulation pump

[pj]

2807,
Have you seen this document, which I think is relevant:

http://www.ukcopperboard.co.uk/literature/pdfs/pub-150-copper-tubes-in-domestic-heating-systems.pdf

I think you do need to get to understand the dynamics of flow rate for your system, specially as you have systems with 10mm pipe in parallel with 15mm. Looking at table 2 in the document, for 22mm pipe work and above, resistance to flow is neglible. At 15mm, it starts to get significant, and at 10mm it can get terminal, depending on run lengths.

I think I understand your system has 20m of 10mm pipe for some panels, and 15mm pipe feeding other panels. This will result in most of the flow going through the 15mm route.

[2807]

Hello all & thanks for your input

The manifolds are plumbed in 4 lots of parallel, 60x58mm, 100x47mm (soon to be 120x47mm), 36x58mm & 60x47mm.  Each set of parallel manifolds have about the same length of 10mm copper leading upto them & away from them, so I would have thought that the flow restrictions and therefore (if I understand correctly) flow rates through each set of manifolds would be similar.

Desperate - The difference in manifold temps was between the entry & exit points on the manifolds i.e. the rise in temperature of the water in the solar loop as it passes through each set of manifolds.  I agree that pipework is definately on the small side for the current set up, but after going on the Navitron course I was so impressed with evac tubes that I bought 200 (10x20x47mm) tubes for £1,500 on fleabay to heat my hot water & swimming pool, but then couldn't resist the offer of as many 58mm tubes as I wanted for £8 each including manifolds - I bought about twice as many as I could fit on my roof & then decided to mount the excess on south facing walls which get shaded by eaves & hollyhocks in the summer.  In the summer I have more energy collection than I know what to do with - so I hit on the idea of plumbing some radiators in the house to help the woodburners keep us warm.

Justme - I am trying to achieve exactly what you are saying will happen if I manage to shift the water round the loop faster i.e. to reduce the peak temperature (and raise the lower return temp).  I am aware that I will still have the same total energy available to heat the rads, & am fitting another 20x47mm tubes to increase the energy collection (when it stops raining....)

Higher temperatures = higher heat losses (don't they??) so I would like to cool the manifolds faster & therefore lose less energy in the transmission of the water round the solar loop.

I have received a response from Grundfos, to the same question as I asked at the top of this thread, who advise that a UPS 25/55 pump should help solve the problem & they are how much?? http://tinyurl.com/5tjqzxu  £165 (ouch).  Anyone in here know if a 25/60 for £50 http://tinyurl.com/5wegh65 might do same job?

Like I said at the outset, thanks to everybody for all your input.

2807

[pj]

The manifolds are plumbed in 4 lots of parallel, 60x58mm, 100x47mm (soon to be 120x47mm), 36x58mm & 60x47mm.  Each set of parallel manifolds have about the same length of 10mm copper leading upto them & away from them, so I would have thought that the flow restrictions and therefore (if I understand correctly) flow rates through each set of manifolds would be similar.

Sorry, I mis-understood your system. I fully agree that the 20m of 10mm in each string should ensure an almost identical flow rate in each.

Looking at the table 2 in the pdf, it recommends a max flow rate of 0.08 l/s for 10mm pipe, giving an equivalent resistance of 0.247 m/m. For 20m at this rate, the resistance to flow is approx 5m. Thus you need a pump that happy to give a head of at least 5m, with a flow rate of 4*0.08 = 0.32 l/s (for the four separate strings, assuming they all split and then join again at the same points). Looking at the spec for the grundfos UPS 15-60, at that flow rate, it only gives a head of 4m, and in fact a 5m head is just outside it's recommended operating range. Also, the flow resistance in the rest of the pipework needs considering, but without knowing the bore, lengths and parallel-ness, it's difficult to take this further.

I believe to know if a better pump will solve your problems, you're going to have to better understand your flow dynamics. The 10mm pipe in your setup is the limiting factor to flow(not the inserts I mentioned earlier!).

IMHO

[2807]

Hello pj

I don't disagree at all with your statement

"I believe to know if a better pump will solve your porblems, you're going to have to better understand your flow dynamics."

But feel that it will be much quicker & easier to buy & install a bigger/more powerful pump rather than to learn about flow dynamics.

That way I get to know whether a better pump will solve my problems in a practical, rather than theoretical way.

Now - anyone know the difference in specs between the grundfos UPS 25/50 and the grundfos 25/60?

2807

[KLD]

May be a distraction, but what about having more than 1 pump? If your friendly local plumber even had a second-hand 15-50 that you could get for a fiver, then your learning-by-doing route might be quite cheap. Also, you could then select to have a higher flow rate through those strings with more oumph (120x 47 and 60x 58) compared to the other two strings, and thus get similar temperature increases from all 4 strings?

Klaus