CH thermostat

[Fred]

Hi,

I am thinking about upgrading my CH thermostat to a programmable thermostat. I was looking at something like the Horstman Centaurstat.

I already have a "basic" Horstmann digital thermostat but when it switches on or off, there is a big click. Does the centaurstat make a similarly big click; do all thermostats?

I would like to put a separate thermostat on the upstairs CH but I don't want a thermostat that will wake me up clicking in the night.

Thanks.

[Harry Bloomfield]

We (now) have one of those remote wireless types and it is absolutely silent. As it doesn't do the switching, there is absolutely no need for it to contain a relay - but then nor do most stats. Even the old type which switched the heating on and off, didn't have a relay - the click was just the contacts of the stat switching over.

[Roger Mills]

Assuming you're not talking about a wireless stat, the stat logic is battery driven, and it has to have a built-in relay to switch the mains. The relay may make a click - but it shouldn't be loud enough to wake you up unless you are either a very light sleeper or you mount it in the middle of a hollow wall which acts as a sounding board. If this is a problem, mount it on something solid with a rubber pad behind it - or use a wireless stat whose actual switching is done remotely.[1]

[1] Probably close to the pump and valves in the airing cupboard. If *these* wake you up, there ain't a lot you can do!

[Roger]

The message from Fred contains these words:

Yes the Centaurstat does and no, not all thermostats are anywhere near as loud.

I have mine in my bedroom. It doesn't actually wake me up but I can sleep through thunderstorms so YMMV.

The downstairs stat is a Danfoss TP75. That is audible but at a different magnitude to the Horstmann.

[EricP]

Says it has "micro-disconnection changeover" but 8 amp contacts.

So you might get click or CLICK

[Fred]

The pump is nice and quiet. The valves do whir when they switch off. Only time will tell if that becomes a nuisance. Perhaps the system should have been designed with them in the kitchen? Too late now, or could they be fitted to the return pipes? That's more of an academic question; I doubt they will be a problem with the doors closed.

Thanks.

[Fred]

Thanks. I have used Horstmann products so far, partly because they were relatively cheap and readily available from my local Screwfix counter. I was saying in another post that the valves whir when they close. Are other makes quieter? I don't think the whir will be a problem with the airing cupboard door closed but the click of the 'stat might be. What make do you recommend for a quieter click, and why are Horstmann so much noisier?

Thanks.

[Roger Mills]

The whirring is from the gearbox. The motor drives the valve through a very high reduction gearbox. When the valve closes, using the spring return, the gearbox then becomes a high ratio step-up jobby, driving the motor round at a fair rate of knots.

Whilst you *could* put the valves on the return side, it is far more usual to do as you have done, and to have them on the flow side immediately after the pump.