Grant Vortex Combi - Overheat

[clothahump]

All rads are hot, dhw hot, rad above boiler is first, no trv as in airing cupboard with it just cracked open.

Purged prv, opened all rads to max, fired it up, no air at all in the heating system now. Turned on dhw, can hear air circulating, not as bad as it was but still there, how do I purge that?

 

[oilhead]

See boiler bob's post re AAV's. I had similar on a Firebird combi where there are 2 pumps, which have non return valves fitted. Purgingthrough a closed NRV is near impossible. I think the Grants have a similar arrangement. All you can do is just keep releasing what gathers. The intervals should get longer.

 

[Terrywookfit]

If there is a AAV on suction side of the pump close it after venting.

I had one sucking in air when pump was running.

 

[clothahump]

If there is a AAV on suction side of the pump close it after venting.

I had one sucking in air when pump was running.

That could be it, it was closed off when I looked.

 

[clothahump]

UPDATE: This thing is still driving me mad, lost all pressure overnight, filled via loop, strangely the DHW pump was trying to pump while filling.
Not 100% sure but I think turning on the cold tap in the kitchen makes the boiler cut out when on central heating, only done it a couple of times. All very strange, and doing my head in.
I hear air moving when DHW is turned on, and an almost constant noise of fine bubbles last night through CHP.
PRV does not appear to be leaking.
Expansion vessel at correct pressure, but doesn't get hot???
Heat exchanger only gets hot when running dhw.

 

[oilhead]

When you installed it, did you put isolating valves on the flow and return? If so, with everything off and the boiler cold, repressurise the system and purge all the AAV's. Then isolate the CH and leave for a period to see if pressure falls. If it does, then you know you have a leak somewhere within the boiler. If it holds, open up the CH. If the pressure falls, then you have a leak on that circuit.
Do you know the history of your second hand boiler? I would always be suspicious any second hand boiler. If it was working O.K. why should anyone want to change?

 

[clothahump]

Boiler was removed from an NT property as they were upgrading to heat source pumps, supposedly it had done very little work.
There is one valve above the magnetic filter, can't see another one.