General   (General discussion, talk about anything.)

peter g . It sounds like you had a poor job done, It could be air as PeterP suggests but, they should have got all the air out on commissioning the system, It could be loose pipes, maybe not clipped too well, or undersized circulation pipes so the heat cannot get round fast enough , another cause could be the TRV's are causing it, Try this open all the valves to full, see if that stops it, then go round closing one at a time, if it is a bad valve, you;ll find it when you close it,