[Nickd]

PDF, I was trying to model the systen P_Q curve for two blocks in parallel. Can then compare this to the P_Q curve of the pump and calculate flow rate through the system, and from that work out the pressure drop across the parallel pair. Once we know the dP across the blocks we can go back to the individual WBs curves and find the flow through each branch. Obviously most of the flow would go down the least restrictive path, and this would be shown by the above method.
Can someone confirm that I'm going about this the right way???
I thought it would be interesting to actually model the above scenario to see what it shows. We can take a WB, length of hose and a rad and model this as one restrictive block (same as we work out a P_Q curve for a series system) and then model two of these units in series and in parallel.

I think there might be something in BKs reference to "with a low powered pump" though. Might be that having all the above in series is sinply far to much for the pump to handle as it is operating very inefficiently at the end of its P-Q curve. By running these loops in parallel you'd be working the pump much closer to its point of maximum useful work (where P*Q is max - hydraulic power) and so get the best out of the pump. He'd be way underpumped for running two waterblocks, two rads and metres of hose with a 1048. Find it weird that his arguments were based on Cathar's "How much Pump Is Enough..." article. Methinks he was way underpumped for a full series system (as the article shows!).

/*Edit Thinking about what he said, he said that Cathar's article proved that parallel was best - so maybe he had worked through the simulation and realised that if he was stuck with his 1048 and couldn't get a bigger pump then he would in fact be better running his loops in parallel */