I've been told I need a 25/6 rated circulating pump for the central heating. What doe these numbers mean exactly. I want to know because I discovered my existing pump is rated for a 6m head.
It has been a few years since I looked at specs on one but the two numbers are identified as Q/H or (m3/h by m). (m = meters)
To my understanding Q is volume of flow in m³/h (25), so how many cubic meters of liquid can flow in a hour period.
With H is delivery head in m (height) which is the height you can pump a liquid to straight up.
These are the basic description for standard values. In an exact case to determine what values are needed in a specific application would be based on all the variables such as pipe sizes in the entire system, desired pressures, suction tank/source levels and more.