Grundfos Alpha 2 does not self prime

[doitmyself]

The HW circuit needs to be balanced in the same way as the CH. If it's not balanced the HW will grab the lions share of the flow.

Of course, if you timed the HW to only come on when CH is not required, e.g. during the night, balancing would not be so important.

Balancing is best done using one of the fixed speeds, not a CP or PP setting.

 

[John.g]

I thought that's what you had done; just wanted to be sure.

Don't forget that when the pump is in a constant pressure mode it will vary the output to maintain the required pressure. The fact that the pressure may be too high or too low is irrelevant.

That's correct and as flow is proportional to the sq.root of pressure then if the flow is 1/1.1 M3/hr@3M then it should be 1.34 M3/[email protected] so I would have expected the pump power when c/o to CP2 (4.5M) to be 45W and not 37W but no big deal really, its probably down to my interpretation of the pump curves.