Why have CH thermostat in a hallway?

[jso]

I'm sure I once read on here an explanation of why CH thermostats are often/nearly always located in a room that can often be draughty, with multiple doors opening into it, and a space in which one does not tend to linger. Seems counter intuitive that it is the temperature of this space which will govern the temperature of other rooms in which one might be spending more time.

I've searched for such a thread but can't find it. Maybe I read the answer elsewhere?
Anyway, would anyone mind me asking the question again - what is the rationale?
And a subsidiary, but more basic question - do I need to have a thermostat all?

 

[Mottie]

When we moved into our hose it had the thermostat in the hallway. Every time we opened the front door, the heating came on and we were sweating our cobs off in the lounge. I moved it to the lounge and that’s where it’s been for the last 26 years.

 

[FiremanT]

Traditionally, the living room had a gas or solid fuel fire, so one would not fit the stat in there. Opening the front door introduces a temperature drop in the hall, so it IS logical that the heating be designed so the boiler kicks in to replenish that heat. The heat would not normally be on for long, unless you are one of those irritating folk who leave the door wide open while going outside to complete a task.

 

[Harry Bloomfield]

This house was refitted in the 80's with the stat in the living room, before it was plastered, I added an alternative location directly behind it in the hall and that is where it has been ever since, until last March, with TRV's on all but the hall rad and I had a new boiler. Last month added new controls. I then decided to move the stat, still in the hall but close to the kitchen door. That was a slight mistake, for whenever a ladyship does much cooking, the heat from the kitchen fools the new wireless stat, into turning off the heating, if the kitchen door is left open.

Our hall used to be a little drafty before I added DG and had a new door installed, now its fine. We tend not to use the front door, rather we use the back door most of the time. Stat is set a couple of degrees less than comfort level and it achieves comfort in the rooms due to the TRV's (apart from when cooking is taking place and door open). 18C in the hall seems to allow the living room to settle at 20C, but the Vaillant 470F can be taken to any room to sample temperature.

 

[stem]

It helps to find the best location for a room thermostat if you understand how it works and what it actually does:

Ideally the room thermostat should be located in a cool room, ideally the last room to warm up. That way the other rooms will be warm enough, (but not overheated because of their TRV’s) before the room thermostat switches the entire heating system off. Locate it elsewhere and it will turn off all of the heating before the rest of the house is warm enough.

The room thermostat should be in a room that is not effected by other sources of heat such as an open fire, cooking equipment, or sunlight etc. It should not be near a radiator, hidden in a corner or behind furniture.

The radiator in the room with the thermostat installed should not have a TRV fitted. Otherwise the TRV may interfere with the correct operation of the room thermostat.

Based on the above, the hall is often the most suitable location.

My thermostat is located in the hall, and the radiator there is slightly undersized compared to the rest in the house so that the hall doesn't heat up too quickly. The room thermostat in the hall is set to 19 C and because it is the last room to warm up, the bedrooms TRV's will start to shut the bedroom rads down at 18 C, the lounge & dining room will get to 21 C and the kitchen 19 C, all before the Hall reaches 19 C and shuts the entire heating system down. It works perfectly and maintains all of the rooms at the exact temperatures we want.

 

[Harry Bloomfield]

I will just add to that, a point you missed - It also should be mounted onto an internal wall, rather than an external one. External walls tend to be colder, especially in really cold weather, so sometimes well below actual room temperatures.

 

[Nintendofan]

It helps to find the best location for a room thermostat if you understand how it works and what it actually does:

Ideally the room thermostat should be located in a cool room, ideally the last room to warm up. That way the other rooms will be warm enough, (but not overheated because of their TRV’s) before the room thermostat switches the entire heating system off. Locate it elsewhere and it will turn off all of the heating before the rest of the house is warm enough.

The room thermostat should be in a room that is not effected by other sources of heat such as an open fire, cooking equipment, or sunlight etc. It should not be near a radiator, hidden in a corner or behind furniture.

The radiator in the room with the thermostat installed should not have a TRV fitted. Otherwise the TRV may interfere with the correct operation of the room thermostat.

Based on the above, the hall is often the most suitable location.

My thermostat is located in the hall, and the radiator there is slightly undersized compared to the rest in the house so that the hall doesn't heat up too quickly. The room thermostat in the hall is set to 19 C and because it is the last room to warm up, the bedrooms TRV's will start to shut the bedroom rads down at 18 C, the lounge & dining room will get to 21 C and the kitchen 19 C, all before the Hall reaches 19 C and shuts the entire heating system down. It works perfectly and maintains all of the rooms at the exact temperatures we want.

Does all that still apply if your thermostat is working as an Opentherm controller?

 

[stem]

Yes, because where it is measuring the temperature is still important. The room thermostat will still turn off all of the radiators when the room in which it is located gets up to temperature. Meanwhile the rest of the house could still be cold.

Any thermostat, Opentherm or not, will respond to the environment in which it is located.

 

[Nintendofan]

Yes, because where it is measuring the temperature is still important. The room thermostat will still turn off all of the radiators when the room in which it is located gets up to temperature. Meanwhile the rest of the house could still be cold.

Any thermostat, Opentherm or not, will respond to the environment in which it is located.

Correct me I I’m wrong then but I though the advantage of an Opentherm controller is to change the water supply temperature in the CH circuit once the set point is getting close. If that’s the coldest and last place to heat up then this modulation won’t happen will it?

 

[stem]

The principle is right, but the thermostat can only sense the temperature where it is physically located.

So, if the room in which the thermostat is positioned gets close to the set temperature it will indeed reduce the temperature of the supply water as you say, but meanwhile the living room next door for example; could still be quite chilly (the room thermostat won't be sensing this) and the radiator in the living room will also start to cool along with all of the others, which you don't really want just yet.

If the thermostat is in a cool position, (and by cool it should only be slightly behind the other rooms in warming up) it will still modulate when it gets close to the set temperature, but will give the other rooms chance to get warm also. Don't forget that it will still turn off the heating completely at some point, as the simple on/off thermostats do.

This is why ideally the thermostat should be somewhere cool that doesn't heat up faster than the rest of the house, and also isn't effected by other sources (drafts, sunlight, open fires etc.,)