Secondary non-return valve

[Haytons7]

Worcester Bosch Greenstar 30 CDi Classic System ErP, Underfloor heating and DHWSystem.
I have non return valve in the secondary return before the pump (DAB 65/150-3) which constantly rattles when the pump is running. Its been tried in both the horizontal and vertical modes with no effect. The only way I can silence it is by throttling the isolation valve on the cylinder side of the pump to around 1/3 open but this just seems to defeat the object by having to wait ages to recieve hot water at the furthest bathroom in the line.
I have advised that installing a pump with a built in non-return valve could help but I have been unable to sourse one. Can you recommend any solutions?

 

[John.g]

Why is there a NRV fitted?
Is the NRV a spring loaded type or a swing check type, if a swing check then you could probably install the spring loaded type but on the circ pump discharge side.

 

[snowhead]

Is the Non return between the cylinder and the pump?
What type of NRV, spring or swing?

Beaten to it...

 

[ShaunCorbs]

Hot water secondary return

sounds like there’s too much flow going through the valve have you tried turning the pump down as it only wants a trickle through

 

[Scott_D]

Any pictures of the setup?

 

[John.g]

It seems to be a DAB 65..... which I think is 65dM or 6.5M, if so, this would circulate enough water for a small town, a DAB10 or less should be more than adequate, I think these pumps are single speed.