Central Heating blockage?

[norwoodt]

I have been workig on a house, the central heating is open vented, with a floor standing boiler and standard cylinder in airing cupboard,

There are two moterised valves one for water, one for heat, and the pump sounds fine. (not sure about the room stat)

I have been to this house before (12 months) as the header tank was failing so i replaced the ball valve, and as far as im aware this cured that problem.

recently we got called back as the water in the rads appearded to have dropped, and the heating wouldnt fire up?

we searched for a leak, couldnt see anything, so we back filled the system, as it wasnt taking (and still isnt) water from the header tank.

once the system is full the heating works fine, however a couple of days later when the heating was put on, it didnt work, and the level was down on the rads again. this time we thought it was venting over, but we're pretty sure it isnt, but we extended the vent into the header tank anyway and now we have also put a seperate feed from the tank to a different side of the house (to cancel out the original being blocked)

We still cannot fill the system unless we back fill! then we are not confident thius will last as it loosing water somewhere!

if anyone could shed some light on this, or any advice or comments,
it would be greatly appreciated

Thank you in advance

 

[gavinda]

blocked cold feed. cut it, clear it, then flush and treat the whole system. make sure its confiugured the right way. vent>feed>pump.

 

[norwoodt]

Many thanx for your quick response

We have put a new feed in tho, it just didnt seem to come through

 

[gavinda]

new cold feed from the tank onto the heating system?

what about any high points that can collect air?

what was the system water like when you drained it to fit the tank?

 

[norwoodt]

new cold feed from the tank onto the heating system? yes

what about any high points that can collect air? non that im aware of

what was the system water like when you drained it to fit the tank? didnt seem bad (havnt fit a new tank)

 

[gavinda]

flummoxed

 

[JayJay1978]

As a DIY'er I'd like to hear more suggestions from the pro's on this one.

I know a little about these systems and would have thought that if you have definatly run a new feed from the tank and into the system then how can it not fill up?

Strange one................................................................

 

[numpty1]

As a DIY'er I'd like to hear more suggestions from the pro's on this one.

I know a little about these systems and would have thought that if you have definatly run a new feed from the tank and into the system then how can it not fill up?

Strange one................................................................

air lock or blockage are the only things to stop it filling,are the mv opened manually whilst filling?
incorrect configuration of vent/cf can draw air in
incorrect configuration of sys pipework can cause probs as well enjoy