In an earlier contribution to this discussion,
blister72 wrote:

I've done a bit more investigating this morning.....

The boiler fires up when I switch the heating and water on.
The cold entry pipe into the boiler is cold, as it should be.
The hot water pipe from the boiler is lukewarm.
The boiler itself is hot but not very hot as it usually is.

After about 5 minutes, the boiler then shuts down.

I am now wondering if there is an airlock in the boiler itself????

The cold entry pipe has a drain cock but there isn't one on the hot
pipe. I wouldn't be able to get rid of the airlock by draining water
out of the cold drain cock.

I wonder if it will be worth draining the whole system completely??

Any other ideas?????

Cheers

blister72

Is it a vented system with a small fill & expansion tank in the attic? (Not
to be confused with the large header tank for the domestic hot water).

If so, is there any water in it? It's not uncommon for the water to leak
and/or evaporate and for the ball valve to stick shut. This can deprive the
primary circuit of water - and may possibly explain your symptoms.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.