CH fitted with timer and TRVs but no thermostat?!!

[sheff77]

Hi All,

I have recently moved house and the new house has a Worcester Bosch CD24i combi boiler. There are TRVs in ALL rooms and a timer to allow for hot water only/hot water and heating, all of which can be either continuous, once a day or twice a day.

Thing is... I can't find a thermostat. Anywhere.

Am I missing something here? I assume that the TRVs will enable me to maintain a comfortable room temperature, but surely the boiler will just be pumping continuously while it's switched on by the timer? Except, when I do switch it on it doesn't seem to be pumping absolutely continuously.

Is there a thermostat hidden somewhere that i just haven't found or would the system have some sort of cut-out so it takes a 5 minute break every now and then or similar?

My intention is to get a man in to fit a wireless thermostat/timer and service the boiler at the same time, but if anyone thinks I'm missing something obvious before I do that I'd be grateful to know.

Also, the boiler pressure increases significantly when the heating comes on (from ca. 1.1 bar up to 1.5-2 bar). I've not seen this size of pressure rise on any combi boiler before - is t normal for a CD24i or is there some sort of issue? The previous owner did seem to have run the thing into the ground as it had absolutely zero pressure when I moved in and the loft radiator contained seemingly no water at all. It has held pressure reasonably since topping it up and bleeding the rads though.

Any thoughts?

 

[flameport]

Thermostat - yes, get one. Should have been fitted when the boiler was.
Without it, the boiler will be on all the time, wasting fuel.

If the boiler/pump is going off at intervals, either there is a thermostat hidden somewhere (the wiring for it would be evident at the boiler even if the stat was hidden), or some other problem is occurring such as the boiler overheating.

Pressure rising - expansion vessel needs to be recharged. That should be checked when the boiler is serviced anyway.

 

[MANDATE]

The pressure rising from 1.1bar to 2bar is not a problem. That's what you would expect when air in the expansion vessel gets compressed.
If it starts going to 3.0bar and opening the PRV, then yes it would be a problem

 

[SimonH2]

Question - is this one of the newer boilers with a modulating pump ? If so, does it shut down under low CH flow ?

In that case, I'd suggest not having a room stat could be correct - after all, it will only fight with the TRV in that location. When TRVs shut down, the modulating pump would back off, and the boiler would then turn off the burner until the flow increases (rooms cooling off).
The OP may not be able to tell the difference between the burner shutting down and the pump (which could be at very low speed anyway) turning off - so the pump could be running all the time, it's just the burner lighting up as required that the OP can hear.

 

[sheff77]

Thanks gents very grateful. I'm going to get it serviced anyway, so if the chap spots a thermostat that I've missed then that can only be a good thing!!