Thermostat behaving abnormally
- Thread starter collinsc
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When I got my mother's central heating working as it should, I sat back and thought I knew it all, but these people who think they know it all, are specially annoying to those who do, and I am sure I have annoyed people, because the same process which worked A1 with mothers, did not work A1 here.
I was under the impression that the TRV head did all the clever stuff, and unless a modulating wall thermostat, all they did was turn off the boiler when no longer required.
The thermostat for my beer brewing, most important in the house, has features not seen with central heating thermostats, one is the delay start, it is there because a heat pump has liquids and gases under pressure, so once it stops, it wants to remain stopped until that pressure has dropped to zero. So when it re-starts, there is no pressure to work against.
There is no reason for that delayed start with a resistive heater. But as technology changes, so we have to adapt, often we don't realise how old items are, I read the instructions for one thermostat, and it talked about "White Meters" that was a blast from the past, 70s and 80s, others refer to IEE, it has been IET for nearly 20 years.
Yet, Hive thermostats are reasonably new. "The thermostat should not be installed in the same room as a radiator that’s controlled by a thermostatic radiator valve (TRV). Installing the two in the same room may result in the central heating being permanently on." It seems to make little sense. Well, point one is why fit a wall mounted thermostat? Seems pointless when the TRV head can make a demand for heat. As to what reads that demand, I don't know, I don't use Hive. With Wiser and EvoHome, there is no need for a wall thermostat, Evohome has a wall controller
but not a thermostat as such.
With Wiser, I need my phone, at least to program it all. This is what we are looking at
the wall thermostat bottom says hall is at 18.5ºC and the TRV says hall at 14ºC. The wall thermostat is higher, and closer to the centre of the house, the TRV both lower, and likely in the draft from the cat flap. So the command "hey Google set hall to 16ºC" will set both to same temperature. Nothing will happen as wall thermostat showing 18.5ºC, unless either the living room, 
calls for heat, or bedroom calls for heat 
so it all gets rather complex.
However in my house, the TRV is king, I have 10 electronic TRV heads, which are programmed as to when each room is heated, it still needs a linked thermostat either of the two wall thermostats or Linda's bedroom TRV head to start the boiler running, but in the main rooms are controlled by the TRV heads.
Not claiming the best system, but the wall thermostat does not really control room temperatures.
I was under the impression that the TRV head did all the clever stuff, and unless a modulating wall thermostat, all they did was turn off the boiler when no longer required.
The thermostat for my beer brewing, most important in the house, has features not seen with central heating thermostats, one is the delay start, it is there because a heat pump has liquids and gases under pressure, so once it stops, it wants to remain stopped until that pressure has dropped to zero. So when it re-starts, there is no pressure to work against.
There is no reason for that delayed start with a resistive heater. But as technology changes, so we have to adapt, often we don't realise how old items are, I read the instructions for one thermostat, and it talked about "White Meters" that was a blast from the past, 70s and 80s, others refer to IEE, it has been IET for nearly 20 years.
Yet, Hive thermostats are reasonably new. "The thermostat should not be installed in the same room as a radiator that’s controlled by a thermostatic radiator valve (TRV). Installing the two in the same room may result in the central heating being permanently on." It seems to make little sense. Well, point one is why fit a wall mounted thermostat? Seems pointless when the TRV head can make a demand for heat. As to what reads that demand, I don't know, I don't use Hive. With Wiser and EvoHome, there is no need for a wall thermostat, Evohome has a wall controller
but not a thermostat as such.With Wiser, I need my phone, at least to program it all. This is what we are looking at
the wall thermostat bottom says hall is at 18.5ºC and the TRV says hall at 14ºC. The wall thermostat is higher, and closer to the centre of the house, the TRV both lower, and likely in the draft from the cat flap. So the command "hey Google set hall to 16ºC" will set both to same temperature. Nothing will happen as wall thermostat showing 18.5ºC, unless either the living room, calls for heat, or bedroom calls for heat so it all gets rather complex.However in my house, the TRV is king, I have 10 electronic TRV heads, which are programmed as to when each room is heated, it still needs a linked thermostat either of the two wall thermostats or Linda's bedroom TRV head to start the boiler running, but in the main rooms are controlled by the TRV heads.
Not claiming the best system, but the wall thermostat does not really control room temperatures.
They are the default settings, also check Cycle ratio 2:Cr, it defaults to 6 (cph, cycles per hour)
Even though it doesn't state it, I would think that controller has TPI control, normally, these controllers will demand continuous firing when the SP/flowtemp dT is 1.5C or greater (with your setting of 1.5C), once the dT is less than 1.5C then the TPI control takes charge and cycles the boiler on/off until it reaches a practically zero dT.
So, what is happening now with that controller, have you checked that the boiler is actually running when there is a indicated demand, get the boiler to fire one way or other even if you have to increase the SP to get a > than 1.5C dT, then see what happens?
Even though it doesn't state it, I would think that controller has TPI control, normally, these controllers will demand continuous firing when the SP/flowtemp dT is 1.5C or greater (with your setting of 1.5C), once the dT is less than 1.5C then the TPI control takes charge and cycles the boiler on/off until it reaches a practically zero dT.
So, what is happening now with that controller, have you checked that the boiler is actually running when there is a indicated demand, get the boiler to fire one way or other even if you have to increase the SP to get a > than 1.5C dT, then see what happens?
Thanks for all your help thus far.
This is getting a bit too technical for me; im going to have to accept it how it is until i get the annual inspection later in the year.
Depends how close the thermostat is to the nearest heat source , too far away and there will be a noticeable lag in achieving the set temp.
You must be very rich to run heating 24 hours .
You must be very rich to run heating 24 hours .
Not if you are running it at about 16 degrees just to make sure it doesn't go too low for the morning, and if it is only overnight it isn't 24hrs
Oh so you have the heating off during the day. ?Not if you are running it at about 16 degrees just to make sure it doesn't go too low for the morning, and if it is only overnight it isn't 24hrs
Yes. Most of the time the heating is off during the day.
Very strange.
We’re not in during the day so why would we want to have the heating on…
I’m maybe missing your point here…
we are manually setting heating OFF during day and then manually set it ON in evening to about 22 and then manually set it to 16 overnight so when we wake up first thing in the morning it isn’t too cold when we get ready for an hour before leaving the house
I think you said that if you increase the required roomtemp (in the morning) from 17.5C to 18.0C? or whatever, that the boiler fires and the room then heats up?, obviously not the way that you would like it to perform though.
Sorry if I have been confusing….
We set it overnight, say to 16 or 17, so that IN the morning it is that temperature.
I do not actually set it IN the morning.
Understood, but if the displayed temperature is within 1.5C of the required (setpoint) temp then the boiler will not fire, so if the required temp is say 17C and the displayed (actual) room temperature is 16C then the boiler will not or shouldn't fire because of this, it should fire at 15.5C or very slightly less, the question I asked was if you increase the required temp to ensure a difference of 1.5C or slightly more does the boiler then fire, as it should.
Ok- understood… now.
I will test this. This makes sense, I will increase it slightly tonight to test.
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