drained system now boiler firing up then shutting off

[micol1873]

hi, sorry if this seems long winded but want to tell as much as i can for major help... the boiler i have is about 30 years old on a gravity fed system. just moved into property and couple of rads were leaking, know 'basic' plumbing and decided to change them as well as remove all others to clean sludge manually. Read loads of forums how to but have failed somewhere... first turned off all rads flow and return, turned off boiler, and drained each rad individually from rad (no drain valves ) once all rads were off, drained system through flow valve on one of rads so i could fit new valves on 2 new radiators . filled each rad one at a time bleading as i went, once rads were filled turned on other valve on rad until warm to balance system, moved on to next closing first, and so on until got to 4th (out of 11) rad, getting water out bleed valve but not getting warm. Then boiler stopped firing and returned to pilot light. (pump sounds ok, no air in pump) and water sounds if still circulating through it. ) where have i went wrong .... HELP please.

 

[darren17]

system sounds like it still has dirt in it , you should have used a fernox system restorer for about a week then drained and flush the system not just the rads
has the f+e got water or has the ballvalve stuck shut
it would be a good idea to add a drain off to your system at it's lowest point
you should also think about installing either a fernox tf1 or magnaclean twin tech filter as these will trap magnetic and non-magnetic sediment.
you can do a mains flush by turning all but one rad off and connecting a mains feed and drain off.flush 1 rad at a time
then repeat on opposite connections.
if you then add the fernox and refill the system leave all valves fully open for a week to allow the fernox to do it's job
then drain the system and flush it completely for a few times
then add an inhibitor refill and balance all the rads.