Auto by-pass valve stuck?

[s4522]

I think my automatic by-pass valve is stuck on my S plan heating system. No matter what setting I have it on (fully open/ fully closed) it looks like water/heat is going through it.

I have tried from system cold turning on zone 1+2 heating and the boiler return feed is a lot hotter than either of the zone returns even with the bypass set to closed (0.5 bar).

Does this sound like the valve has failed or is the value just not restrictive enough?

Current bypass: Danfoss ARV22
Pump: Grundfos UPS025-60-130 P/N:97781518
Boiler: Glow worm Flexicom 12hx

If I get a replacement I was trying to work out what I should set the new valve too however I was struggling to find the minimum flow rate of the boiler and pump curves.
Nearest pump curves I could find were:
https://product-selection.grundfos....tid=GMA&productnumber=96281480&qcid=755334215


The pump has a sticker on it saying:
Q= 1.0m3/h
H(m3) | P (W) | Speed
5.0 | 78 | 3
3.8 | 70 | 2
1.8 | 59 | 1

I currently run it on speed 1.

Any help on working this out would be appreciated.

Thanks

 

[John D v2.0]

Just to confirm your suspicion
1.8m of head (not m3) would be 0.18 bar so if it's on 0.5 bar and it's passing then it's faulty and needs replacing.
When setting it up for best tefficiency yes it needs to provide the boiler minimum quantity but really you need to balance the system, set the pump to give enough water to the furthest radiator, and then set the bypass to open just above the head needed for that radiator.
But I'm not sure anyone does it do scientifically, more like leave it and the pump set in the middle and see if you can balance the system.

 

[s4522]

Thanks. Replaced the bypass with a new one and works much better now.