Heating effectiveness

[Flix]

Apologies for repeat thread, had trouble registering on my phone before starting it as a guest....

Hi, looking for some advice on an issue I have with my cental heating. I recently had cause to have the expansion vessel replaced in my Ariston combi boiler. Due to the restricted access I had the new one fitted externally, but ever since the heating hasn't been anything like as effective. Previously having the dial turned half way would have had the radiators pumping out heat, now they're only just warm unless I have it cranked right up.

I have bled them and they are actually cooler another bottom than the top so suspect it's not air, and they were fine before so assuming it's not sludge. It's as though the burner cuts out before they're up to temperature, as though the thermostat was faulty but this is only since the expansion vessel has been replaced. There's no external room thermostat so assume the boiler has one built in?

A mate suggested turning off all rads then turning them back on one at a time but that hasn't resolved it.


Any advice would be greatly appreciated

 

[lame plumber]

probably sludge if the bottom of the rads are cold, causing poor circulation. system needs a flush to clean it out, an expansion vessel swap would have no effect on the system heating up, unless it was drained down and sludge has moved around causing poor flow in some pipes

 

[Flix]

Just seems strange that it was immediately noticeable after the expansion vessel was replaced. All the radiators will get hot, just need to turn the dial about another quarter of a turn to get the same heat output as before.

 

[Scott_D]

Colder outside?

 

[Flix]

No, well maybe slightly, but it was noticeable as soon as it had been done. Never really have the dial turned past the '10 past' position, now having to turn it to about '25 past' to get it to the same temp.