No Heating and Hot water after 4 weeks, 6 engineer visits, a power flush and new pump - HELP!!! (please)

[Watergate]

Thanks for the various suggestions - appreciated, below is an update/progress made noting some thread responses also... and lastly ‘In summary what's happening now…’

Update...

1) The power flush engineer installed an 'automatic air vent' last week, which saw no real improvement, he said 'could be' the boiler thermostat, but having lost some confidence in him, called out someone new recommended by my uncle to get a fresh opinion as suggested by 'Last Plumber'***

2) The new engineer spent 30-40mins assessing/checking and concluded the boiler Thermostat!

3) Someone from the same company came out 48 hours later and installed the part... note it was xmas eve and all a bit hectic/rushed, had to grovel to get the work done on time.

The replacement thermostat didn’t actually improve things, nice chap he was, he checked the f & e tank/flow/valves/pump again, and said to let the system 'bed down' as there could be air in the pump (sealed) which will slowly discharge and could take hours... a bit speechless at this point tbh...

After several hours, no real joy... however, hot water appeared to be working, but noticed 3 or 4 radiators UPSTAIRS were again warm/hot - so I called someone I know who's handy/experienced! He said close those UPSTAIRS radiators to push the flow downstairs (eliminate a blockage/air etc)*** after doing this downstairs warmed up! I then did a bit of googling and re-opened the upstairs valves by a 1/2 or 3/4 of a turn (wasnt very scientific more on gut) - switched the system off for a bit and then fired it up again, and like magic the whole system warmed up... read on (not finished )

In summary what's happening now
1) The heating from a cold start heats up the house amazingly, boiler stays on for circa an hour... but then goes into a frequent stop/start cycle with only a few radiators staying warm/hot (mainly upstairs and one or 2 downstairs rads - note this is after my valve adjustment above) - so we have some heating, using sparingly/wisely, not ideal but in a better space than last week. Scared will conk out all together...

2) Hot water seems to be working

3) I've been trying different things, here’s the interesting thing I noticed, after an hour of heating, and when it goes into this stop/start mode of a few warm radiators, if I 'boost the hot water for an hour' with the heating still on constant, then after after 15-20mins (there is a delay) the entire heating system starts to come on and the house gets baking hot - i noticed this by fluke and replicated last night… could just be a coincidence that on 2 occasions same result...

Any further thoughts/ideas again welcome. Had some good feedback here and private messages - v helpful, so thanks again

Lastly I had a slight doubt on the thermostat in our hallway (radiator temperature), but might be getting paranoid...

Sorry above might be unclear (as another long post!), but we're getting heating but only for around an hour max (may be less) if we use as normal, whilst better than before boiler thermostat was changed still an issue as the house cools down with a couple of rads (mainly upstairs) remaining either mainly warm or rarely hot! So we're using heating sparingly morning and in the evening... allowing the system to 'rest'/cool down between usage!

 

[David Graham]

Sounds to me like there might be air in the boilers heat exchanger, you need a heating engineer (not a gas engineer or plumber) to connect a hose at a point on the system below the boiler and push water back through the system into your F & E tank, if that doesn’t work it sounds like the boiler is going off on high limit (temp too high) and I would recommend having the wiring and motorised valves checked on your s plan/y plan as they may be sticking and causing the boiler to “kettle”

 

[Vee]

Check for blockage in down feed where it meets the system. Beware there there may be an old anti gravity valve in the heating return pipework that has now failed if the system was once on gravity circulation. (Usually in the pipework rising by the side of the fireplace often hidden behind boxing in).