Thermostats

[GreatGooglyMoogly]

We have never had a thermostat . We turn our combi boiler on when we're cold and off when we're too hot, or adjust the dials on the radiators. It means that it is almost always off at night as we overheat if it's on, however it can be really cold in the morning! Could someone please explain to me how thermostats work? Do you have one for the whole house? Where is it - in the coldest part? Do you have your radiators on full all the time? What if parts of your house heat at different rates?! TIA

Our timer and thermostat is wireless and is in the hall as it is the coldest part of the house. It is currently programmed to come on at 6 in the morning and go off at 8. But it only turns the boiler on when the temperature falls below the temperature set on the thermostat.
We have thermostic valves on each radiator so we can control the temperature in each room- DS has his turned off because he says it is too hot, the one in the utility room is turned up fully as I dry socks and undies on it.
I can advancve the programme and turn the boiler on (or off) by adjusting the temp on the base unit. I have had it a couple of weeks and I love it- it has given us so much more control and I have noticed that the boiler is not on all the time, like the old one was, so it's saving us money.
I can aslo programme it to come on at different times on different days- we have it on more often at the weekends.

Thermostatic valves on radiators (TRVs) and wall-mounted thermostats can cancel each other out. The key difference is that the wall-mounted thermostat can switch the boiler on and off but TRVs cannot. Plumbers generally say put the thermostat in the hall or the coolest spot and if there is a radiator in this space then it will usually not have a TRV fitted. The wall mounted thermostat will sense when the temp falls below your chosen setting and then switch on the boiler, sending water to the radiators - which are often/usually controlled by TRVs - and the TRVs will actually control how hot each radiator gets. Effectively (and this is the flaw in the system) if your hall is the coldest room, the thermostat will keep switching on your boiler and heating the non-TRV controlled radiator in the hall even if you're happy with the current temperature in the other rooms.
My opinion is that you should go for one or the other but not both. But perhaps this works better in a smaller property and if you're willing to adjust your radiators yourself and get off the sofa and switch the boiler on/off yourself.

TRVs limit the temperature in the room where they are fitted.

It is correct to have TRVs in all the rooms except the one (usually where you spend most of your time,) where you should have the room stat. The room stat should be in room that does not have other sources of heat, such as a gas fire, a big cooker, or a large sunny window, since this will make it think that the whole house is warm and the boiler can be turned off.

By balancing radiators (that's a different question) you can reduce the rate of heat output in rooms, so that the one in which you have the room stat heats up slowest, and all the others heat up at about the same rate as each other, even though they may have different sized rads. The TRVs will prevent any room getting too warm. You should keep internal doors closed when the heating is on, otherwise all the heat will disappear upstairs and the boiler will keep trying to replace it. The TRV will also cut off unnecessary radiator heat to a room that is hot enough due to, for example, a cooker, a gas fire, or a sunny window, without affecting radiators in other rooms.

It is (sorry) as foolish to turn the boiler on and off yourself, as it would be to not use the thermostat on your oven, and intsead to keep switching in on and off.

It is incorrect to have a TRV in the room where you have the room stat, because it is POSSIBLE for the TRV to turn down the rad in that room, causing the room stat to think the whole house is still cold, and keep running the boiler. If you do have a TRV in the room with the room stat, you should as a minimum turn the TRV to max, or preferably unscrew the thernostatic head from the valve and replace it withe the dummy plastic head ("decorator's cap") that was supplied free with it, or that you can obtain from the manufacturer as you have lost it.

If you have not already got a room stat, you can consider having a "programmable" one which will enable you to set, say, an overnight temperature of 15C between 23:00 and 07:00, a morning temperature of say 20C between 07:00 and 08:30, an unoccupied temperature of 12C between 08:30 and 17:00, an evening temperature of 22C between 17:00 and 23:00 (or any other temperatures and times that take your fancy) with different temperatures and times for Saturdays and Sundays, or other days when you have different activities. You can also (usually) tell it you are going on holiday for nn days, and it will keep the house an an "anti-damp and anti-frost" temperature of your choosing, such as 10C, until the day you are due to come back, when it will go back to your normal daily routine; and if you are staying up late (e.g. for as party), or staying at home all day, e.g. when ill, you can extend the timing, say, for that evening or morning, by 1, 2, or 3 hours, and it will reset to normal schedule the next day. Also, if you have not already got a room stat, you can get a wireless one and carry it around from room to room to see what suits you best (IMO however the chance of wireless faults does add another layer of possible problem)

Yes - if you have the room thermostat in your living room your central heating system may actually work as it's supposed to.
It's interesting that room thermostats are advocated as 'energy saving' devices and then most plumbers and many heating websites/info services recommend putting them in the coldest spot of the house with a radiator with no TRV. This will not save you energy - it will just keep switching yur boiler on and using up gas heating up the coldest area - which you probably don't use anyway.
Room thermostats can only be of any benefit if fitted in the room you use most - and you keep the doors closed.
Bear in mind all boilers have internal thermostats too and will switch off when the water reaches the desired temperature.
Although room thermostats are now required under building regs, they are not the great breakthrough in energy saving that a plumber may imply - but there's a nice profit margin on them if they get you to buy a nice one, perhaps with a shiny new programmer too - double bubble.

Thanks all - my head is spinning a bit!

So, the thermostat should be in the main living area with TRVs on all radiators apart from the one in the same room as the thermostat? Our downstairs (living/ dining/ kitchen) is all open plan so the oven is obviously in the same area, though it isn't a range or anything big - we only have one radiator in that area and no other sources of heat. Also the thermostat should be programmable but should it be wireless or not? It sounds like it may be more trouble than its worth if there can be wireless faults, and if the location is definitely right it shouldn't be necessary to move it.

I wouldn't have a wireless one (unless I was rich enough to buy a spare if it went wrong)

It's one more thing to go wrong (ordinary thermostats are very reliable) and if it does, you won't know if it's the transmitter, or the receiver, or the stat, or the batteries.

Otherwise I reckon you've got it. You can position the stat well away from the cooker and the rad, and any sunny windows, so it doesn't get misled. Wired ones will want a route for the cable to the boiler, so bear that in mind. Not so close to the boiler that heat from the casing will affect the stat.