Worcester 240 Air-vent req'd?

[scones]

Hi all,

I recently fitted a new rad and on refilling the system found I had a problem with the boiler. The whole system is filled right to the top rad's bleed valve, but the boiler appears not to have filled up correctly. The pump does have some water in it but you can tell it's not fully submerged. The boiler fires up for about 10-15 secs and then the thermistor trips the burner and the pump overrun is activated. I suspect the automatic air-vent is not functioning correctly but would appreciate some confirmation of this or advice on what else I could try before getting a replacement.

Thanks in advance,

Confused in Calderdale

 

[ChrisOxford]

Hello,

Have you followed the manufactuer's instructions regarding filling? I have a 280, and I seem to recall that they recommend you manually move the diverter valve to a certain position when filling to minimise the risk of air trapped in the boiler's primary circuit. Think it's in the "comissioning" section. EDIT... Yours may well differ from mine in this respect.

Have you bled the pump (big silver slotted screw)?

What happens if you remove the plastic "valve cap" from the AAV (should be loose anyway) and depress the little plunger in the centre of the valve? Air or water coming out?

C

 

[scones]

Thanks for the response. I had removed the plastic cap last time I emptied the system and had tried the pump screw (water was forthcoming). I tried pressing in the top of the vent but it seems to have no moving part. Eventually I loosened the whole vent and after a couple of turns I heard air rushing out of it. Unwittingly I kept turning the thing and it eventually came loose showering me in green central heating water. I rushed to get the valve on again and nipped it up. The boiler must now be full of water. I had to fill the system a bit more. The main trouble is the electrics got sprayed with water so I'm leaving it to dry out before retrying it. Should really replace the vent too but that'll mean another system drain I suppose.

 

[ChrisOxford]

Well done, sort of!

The AAV sounds knackered, which is v. common from what I've seen. They're cheap enough, and you can even get them from Screwfix.

Buy one and keep it to hand, to fit next time you have to drain down.