Radiators getting too hot after new boiler installed

[GBengineer]

We've just had a new Grant Vortex Pro 15/26 oil fired boiler installed to replace an old Worcester that died. We have fully pumped "Y" system with a 3 port valve. The boiler has been installed outside the house. We have also had a room stat fitted for the first time (all the radiators have TRVs). Since the new boiler has been in, the radiators stay very hot regardless of the room stat setting and the temperature in the house just keeps rising.

To add to that, last night was frosty, and the boiler frost stat kicked in - at 2:30 am, all the radiators were red hot! This is despite the controller being on timed and the room stat being above the set point.

Any ideas anyone? The radiators have been balanced using the lock down valves and none of the TRVs have been closed completely.

 

[Corgigrouch]

I'd be inclined to have a close look at the frost stat.... It'll fire your boiler at around 5c and will stay on until it is higher... it would be far better to also have a pipe stat connected to the frost stat on the return pipe to cut the boiler once the pipe has warmed a little.... thus nothing gets too hot but it does stay frost free