DIY Doctor

Thermostatic Valves

Postby pappyirl » Thu Jan 24, 2008 6:39 pm

I'm thinking about installing thermostatic valves on radiators in my house. The boiler is located outside and is on a frost thermostat located on a wall. There is also a thermostat attached to the boiler itself, currently set to 75 deg.

The thermostatic valves will control the room temperature and cut off once that temperature is met. In an extreme scenario all the radiators will shut off. This will result in less water flowing through the system and less heat loss. The boiler will reach the temperature on its thermostat and cut off quicker than if it was heating all the radiators to uncomfortable levels thus saving money on the amount of oil burned.

Is this correct? The boiler relies on its thermostat to turn itself off which occurs quicker than without the valves due to the valves reducing the amount of water flow/heat loss in the system.
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Simply Build It

Postby htg engineer » Thu Jan 24, 2008 9:38 pm

You can fit TRV's to all but one radiator. Normally the bath room on is left with 2 normal radiator valves, this is so that if there's a problem with the boiler or thermostat the water can still circulate.
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Postby Perry525 » Sun Jan 27, 2008 7:02 pm

The problem with thermostatic radiator valves is that they have a slow reaction time, this results in all the pipework getting hot before they switch off.
A better result is obtained by zoning, a system where the living rooms are controlled by one room stat and the bedrooms by another.

As the bedrooms are normally run cooler than the living rooms, their pipework will rarely get hot, thereby saving you lots of oil.

You can improve on this even further, if the bedroom radiators are small, then using 8mm pipe, with its much lower heat loss will save even more.

The trick is to start each zones pipework as close to the boiler as possible
using the correct size pipes thereby reducing the amount of water that needs to be heated before the rads kick in and the hot water that remains in the pipes, that is then wasted when they turn off.
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Postby frogger » Sun Jan 27, 2008 9:55 pm

If installing thermostats on all rads it is best to not fit one in the room where the room thermostat is located. Also it is advised to install an automatic bypass.
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