Gurgling from primary circuit, Y plan system

[Derek]

I've noticed that my hot water primary circuit has started gurgling a lot.
My system is a conventional 'y' plan and the controller will not allow heating without hot water. The gurgling is at it's worst when there is only hot water demand.
I'm pretty sure there's no air in the system and in any event there is an open vent to the header tank so I can't see how air could be trapped. There is plenty of head to the pump, but I'm wondering if it's cavitating and if so how I overcome this. The pump is a Grundfos 15-50 and it's set on the mid speed setting so it creates enough flow for the heating circuit to work satisfactorily.
Any ideas would be welcomed.

 

[king of pipes]

Get a engineer in probably the 3 port valve playing up . Kop

 

[Ric2013]

Is the boiler kettling?

 

[townfanjon]

Has it got a air seperator on the system , post a pic of pump location / pipe work etc

 

[Derek]

Is the boiler kettling?

Not sure what you mean by jerking, but the boiler seems to be working fine

 

[Derek]

Has it got a air seperator on the system , post a pic of pump location / pipe work etc

No air separator on system, but the primary circuit vents direct to the headertank

 

[Derek]

Have had a further look this morning and it seems I have an open vented system that is fully pumped. Could the hot water circuit be drawing air in from the vent do you think??

 

[Ric2013]

Not sure what you mean by jerking, but the boiler seems to be working fine

I wrote kettling, not jerking!

 

[Derek]

I wrote kettling, not jerking!

Predictive text I’m afraid!! I hate it.

 

[Ric2013]

It's when it starts to bang and pop increasingly loudly as the water gets hot due to localised boiling inside the heat exchanger caused usually by sludge, scale, or voids formed by corrosion.

 

[Derek]

It's when it starts to bang and pop increasingly loudly as the water gets hot due to localised boiling inside the heat exchanger caused usually by sludge, scale, or voids formed by corrosion.

 

[Derek]

Ok thanks, doubt it’s that then. I think I just have an obstinate air lock in the primary circuit. Have tried pump on all settings in an effort to dislodge but no luck yet. Doubt it can be much else. Will persevere.