Sorry I know but… Had our annual Brit Gas Service under contract and now we have problems…only fault we did have was needing to top up the pressure fairly frequently but other than that was perfect ….He fixed that by repressurizing the system & now Combi Boiler fires up works fine for about an hour..lots of heat and hot water then the rads start to go cold and no matter what you do ( put thermostat on max or change to continuous heat) nothing will get them hot again until you switch off and let it cool down fully and then start again. Also the water is absolutely scalding hot. It appears to me that the system is responding to the thermostat and firing up the boiler but for some reason its not circulating the hot water to the rads.

Any boiler engineers know what Brit Gas may have done as they’ve had two goes at putting it right without success?

Bumpity bump

Not enough info , but could be a thermal trip in the pump. Pump on way out , gets hot and trips , goes cold and resets .

Or wonky diverter valve.

Does/is the boiler running or firing when the rads are cooling or is it dormant , but fires on hot water demand?

Had similar with ours last month, then it went completely
Was the pump, cost £200 for a replacement

iain1775 did you get my email about the wheels ?

Which make and model of combi ?

When you say the radiators don’t heat up, is the boiler still heating?

What pressure is it showing when its calling for heat but rads are cold ?
Does sound pump or diverter valve related.

Had a leak on our system last week, two pipes (unknowing to me) chaffing together under the landing finally burst. Soldering under the floor never nice, but fixed ok.

Thanx all for the replies ..here’s my responses

Singletrackmind- yes the boiler is firing when the rads are cooling/cold even if water is not being demanded..hence we have superhot water.

Peasant- Alpha CB50 I think

Turin- rads heat up and then go cold even though the boiler is still firing

Takisawa2-Haven’t actually looked at it at that point but pressure is sat just above the green band when I’ve looked at it.

For info The morning after the engineer “re-pressurised” the system I woke up to no heat or water as the pressure had dropped to the very bottom of the scale & the boiler had shut down. Had to top up with water and then the pressure has remained ok since..

Sound like your boiler going out on overheat check the boiler stat setting and also check he’s not left it in service mode

Thanx Leadbasher….whats a Stat setting and how would I check it plus whether its in service mode. There’s nothing in the manual about a service mode?

They are the dials on the front

Where are you based?

Hampshire- paulosoxo near Basingstoke

Expansion vessel needs fixing/replacing.