Looking for advice. I am a home owner with no plumbing experience. Recently we got a builder to extend a room, replacing the single radiator with two new ones with TRV's fitted. The builder brought in a plumber to attach the two new radiators to existing pipework but I was not impressed with him. Problem is that the TRV's have to be set at least to 4 to get the radiators to heat up even when the room is cold. None of the other radiators do this. If room is cold the other radiators on system will heat up even at 1/2. My concern is that the two new ones may not come on if I set them to frost when I am away. The builder says you cannot adjust a TRV so getting the plumber back will not help. Can TRV's be adjusted in some way or is there a different cause?