I wasn't aware that anyone was suggesting having just a stat and no TRVs.
The *ideal* system - from an energy efficiency point of view - would have a separate zone valve and room stat for each rad - an would be wired so that the boiler and pump would only run when one or more zones required heat. Better still, the room stats would be programmable - so that each room could have a heating profile to match its likely use.
Failing that, the next best solution is:
- a timer to turn the whole lot on and off at pre-defined times
- TRVs on all but one radiator
- a room stat in the room with the non-TRV radiator (whose lockshield should be turned down a bit to make this the last to get hot)
- an interlock which ensures that the boiler and pump both stop when the room stat is satisifed
My understanding is that new systems would have to have all of these features in order to satisfy the new building regs. Your solution (whilst legal for an existing system) wouldn't comply with the new regs - because you have no interlock which turns the boiler off when all demands are satisfied.
Roger