Heat output of a range rated appliance

[ericmark]

If a thermostat is not used to control room temp why is it adjustable ? why not just have a big red switch saying ON/OFF ?

It is so it can be matched to the TRV in the same room.

To the right is the wall thermostat, when the temperature outside is high this will switch off the boiler stopping the boiler from cycling, bottom left is the TRV that controls the room temperature in this case the hall. The wall thermostat is with a modern boiler a cheap way to stop the boiler cycling and also give a degree of frost protection. I turn the thermostat down to the stop in the summer, so should I forget in the winter the boiler will still fire up to stop anything freezing, and in the winter it is turned up to the stop, which is set to 19°C. The TRV in the same room is set so in heart of winter the wall thermostat never gets warm enough to switch off, however as spring arrives the TRV does not switch, but gradually turns off, so a point is reached when the thermostat does get warm enough to switch off the boiler.
First year fitted it took slowly opening the TRV when it was a warm day, until room got warm enough to switch the wall thermostat, once set, it is left well alone.

In the other downstairs rooms a better quality TRV head is used, these eTRV heads can be programmed to different temperatures through the day, and like the simpler TRV they also turn slowly giving more or less water flow, they do not switch. The modern boiler is the same, it does not simply switch on/off but the flame height alters to keep the return water at a pre-set temperature. Only when it can't turn down any more, does it start switching on and off, the anti-cycle software monitors after a set time allowed for the water to circulate if the return water is still too hot, or if it is cold, and the off time is adjusted longer if it returns too hot and shorter if too cold.

It is when the boiler starts this cycling that we want the thermostat to turn it off.

This means the boiler size is critical, with old boilers the radiators were critical as before the TRV we had to get all rooms warm together, and as long as the radiators can get rid of more heat than boiler produces all is great, but with the new type, we want the boiler to operate between the min and max output, if it reaches min too soon then it starts to cycle rather than give a analogue output to match the demand of the TRV, when it start to cycle then the hysteresis gets a lot worse, in the autumn and spring you can't stop it on the warmer days having some hysteresis but in winter the room should stay reasonably at the set temperature.

The ideal is no wall thermostat and for the eTRV to tell a central hub if it needs heat, which in turn tells the boiler when heat is required, but that means most rooms having eTRV fitted, so using a wall thermostat is a lot cheaper, and one has to except when using a cheap system it is not as good.

With non condensate boilers, and with open plan houses, then the old wall thermostat still has a place, also because the eTRV can send signals to the new bred thermostat like hive and nest, there is a cheap method where the ITTT system allows the thermostat to follow the eTRV in a similar way as the central hub, the advantage is it allows one to slowly one by one replace the TRV heads to eTRV type, however it will never be as good as a system like EvoHome, but it is getting near to same control.

With hot air the nest and hive work well, all rooms are at same temperature and we have air circulating between the rooms, but with our water system we have a huge advantage over hot air, each room can have a different temperature, and a different program which decides when the room is heated. From my bedroom even though heating not running today I see the living room is at 21°C and mothers bedroom at 19°C my room is 22.5°C garage at 26.1°C outside 21.2°C and not left my bedroom. This is the way we do it now, every room different. Even if you had a motorised valve in every room and a thermostat in every room, it could not control as well as the eTRV does because the eTRV does not switch, it gradually opens and closes, with heating we have left the digital age and entered the more advanced analogue age.

 

[Steelmasons]

Jeez I can't be bothered with this *

 

[PullerGas]

It is so it can be matched to the TRV in the same room. View attachment 122465To the right is the wall thermostat, when the temperature outside is high this will switch off the boiler stopping the boiler from cycling, bottom left is the TRV that controls the room temperature in this case the hall. The wall thermostat is with a modern boiler a cheap way to stop the boiler cycling and also give a degree of frost protection. I turn the thermostat down to the stop in the summer, so should I forget in the winter the boiler will still fire up to stop anything freezing, and in the winter it is turned up to the stop, which is set to 19°C. The TRV in the same room is set so in heart of winter the wall thermostat never gets warm enough to switch off, however as spring arrives the TRV does not switch, but gradually turns off, so a point is reached when the thermostat does get warm enough to switch off the boiler.
First year fitted it took slowly opening the TRV when it was a warm day, until room got warm enough to switch the wall thermostat, once set, it is left well alone.

In the other downstairs rooms a better quality TRV head is used, View attachment 122474 these eTRV heads can be programmed to different temperatures through the day, and like the simpler TRV they also turn slowly giving more or less water flow, they do not switch. The modern boiler is the same, it does not simply switch on/off but the flame height alters to keep the return water at a pre-set temperature. Only when it can't turn down any more, does it start switching on and off, the anti-cycle software monitors after a set time allowed for the water to circulate if the return water is still too hot, or if it is cold, and the off time is adjusted longer if it returns too hot and shorter if too cold.

It is when the boiler starts this cycling that we want the thermostat to turn it off.

This means the boiler size is critical, with old boilers the radiators were critical as before the TRV we had to get all rooms warm together, and as long as the radiators can get rid of more heat than boiler produces all is great, but with the new type, we want the boiler to operate between the min and max output, if it reaches min too soon then it starts to cycle rather than give a analogue output to match the demand of the TRV, when it start to cycle then the hysteresis gets a lot worse, in the autumn and spring you can't stop it on the warmer days having some hysteresis but in winter the room should stay reasonably at the set temperature.

The ideal is no wall thermostat and for the eTRV to tell a central hub if it needs heat, which in turn tells the boiler when heat is required, but that means most rooms having eTRV fitted, so using a wall thermostat is a lot cheaper, and one has to except when using a cheap system it is not as good.

With non condensate boilers, and with open plan houses, then the old wall thermostat still has a place, also because the eTRV can send signals to the new bred thermostat like hive and nest, there is a cheap method where the ITTT system allows the thermostat to follow the eTRV in a similar way as the central hub, the advantage is it allows one to slowly one by one replace the TRV heads to eTRV type, however it will never be as good as a system like EvoHome, but it is getting near to same control.

With hot air the nest and hive work well, all rooms are at same temperature and we have air circulating between the rooms, but with our water system we have a huge advantage over hot air, each room can have a different temperature, and a different program which decides when the room is heated. From my bedroom even though heating not running today I see the living room is at 21°C and mothers bedroom at 19°C my room is 22.5°C garage at 26.1°C outside 21.2°C and not left my bedroom. This is the way we do it now, every room different. Even if you had a motorised valve in every room and a thermostat in every room, it could not control as well as the eTRV does because the eTRV does not switch, it gradually opens and closes, with heating we have left the digital age and entered the more advanced analogue age.

My eyes glazed over after the first sentence..!!!!

 

[ericmark]

I will agree it took some time to trim the TRV and thermostat to complement each other, and that a heating engineers time would likely make it cheaper to use some thing like EvoHome where it is quick to set up and then they can walk away.

However it works, so for DIY and this is a DIY forum it is a viable option.

 

[PullerGas]

I will agree it took some time to trim the TRV and thermostat to complement each other, and that a heating engineers time would likely make it cheaper to use some thing like EvoHome where it is quick to set up and then they can walk away.

However it works, so for DIY and this is a DIY forum it is a viable option.

Eh..........you don't fit a TRV on a radiator if there's a Room thermostat in the same room mate!! Too much writing & not enough listening fella!!

 

[AGAS]

jeez I'm losing the will