Lesson 10
Controls & TRVs
Work out which control senses, which changes the flow and which tells the boiler to fire, and what happens when two of them disagree.
Builds on
Three controls, three jobs
Oli’s flat has a programmer, a wall thermostat in the hall and a TRV on every radiator. Each does a different job:
- the programmer, or timer, decides when the heating is allowed to run;
- the room thermostat senses the hall’s temperature and tells the boiler whether to fire;
- each thermostatic radiator valve (TRV) senses its own room and throttles the water through its own radiator.
Some systems combine these in one smart control, but the three jobs are still there: sensing, changing the flow and calling for heat. An ordinary mechanical TRV does only one of them. It throttles water, and it has no wire or radio to tell anything else what it’s doing.
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