You won't listen fezster so what is the point?
The 15/60 that has been installed on the ground floor zone is 'robbing' (laymens terms so it is understood) any head/flow available from the 15/50 in order to circulate water through the upstairs zone (when both calling for heat) , it has been said umpteen times the circulators must be installed in series BEFORE any zone valves , either remove the 15/60 and install it downstream of the 15/50 or simply remove both circulators and fit a 25/80......................or leave the circulators in situ and install an additional 15/60 to first floor zone.
steelmasons,
Could you explain a little more on the term "robbing" please ? I've now purchased a Grundfos 25-80 (not the MAGNA1 series, but traditional fixed speed). As an aside, there seem to be multiple versions of this pump, as some have a head of over 8m, whilst others (the one I have) the graph shows a head of max 7.5m.
I intend on replacing the 26-50 with the 25-80, but want to leave the additional d/s pump in place, as removing this would involve draining down the system and pipework. Can you tell me if the problem of the d/s robbing the u/s remains with the bigger pump, and if so, what the reason behind it is ?
I've also been using my flow and return temps to try and "calculate" what my head is, using the pump graphs. For the single pump u/s, this is fine. Is there a way of calculating this for the two pumps in series d/s ? Is it as simple as adding the head together for the two pumps at a given flow rate (flow rate calculated by delta T) ?
Thanks.
