Air Lock Problem In Heating System

[Kezman]

I have just drained my heating system but when I started to refill it, the header tank filled up and then stopped when the water level had reached the pre-set point for the ball valve.

The rest of the system is not refilling (probably caused by an air lock between the header tand and the circulating pump).

This may been caused by my forgetting (!) to shut all the air valves on the rads.

I have tried the following:

1. Bled all the rads.
2. Tried to blled the circulating pump (no air).
3. Shut al the lockshield valves and bled the rads (very small amount of air but no water).

Can anyone please help?

Kez

 

[45yearsagasman]

It's more likely to be caused by a blocked cold feed pipe where it connects to your system pipework. When you drained, did you simply tie up the ball valve or shut off the water via a gate valve on the cold feed pipe?

 

[Kezman]

I had drained the system with the ball valve tied up. Also, I had emptied dirty water out of the header tank before refilling it. This is why mentioned the possibility of an air lock.

 

[45yearsagasman]

Air lock unlikely, blockage very likely. I don't know your system layout but this might help, as a general guide. View media item 39013

 

[Agile]

Blockages in this position seem to be formed from calcium compounds and dont respond to normal chemicals. So cutting out the parts and cleaning is the only option.

It is dissolved by HCl but you dont want chlorine compounds in a copper system.

If lucky it may be possible to cut each pipe and remove the section complete with compression couplers.

Tony

 

[Kezman]

Thanks for the replies regarding pipe blockage.

I am perplexed how this could have happened because the system was working fine before I drained it. Also, the drained water was relatively clear (i.e. slight greyness but not dark).

 

[45yearsagasman]

It was building up for a while and as long as the system was full there would have been no symptoms. Colour of the system water is not always a sign of a blocked cold feed. The only way is to cut out and manually clear any blockages.

 

[MANDATE]

There's no mention of motorised valves, but if the system has these, then they are provided with a lever for the purpose of holding ports open while re filling, this is to prevent air locks.

 

[Kezman]

The problem was a blocked 15mm cold feed just as 45yearsagasman diagnosed (very impressed). Problem cleared and have put in system cleaner.

The CH system is microbore (8mm) so I will need to get it poweflushed.

Thanks to everyone who chipped in with advice.