Don't see how thermostatic rad valves save money

tim091

Hi,

Just moved into house and the central heating has no room thermostat, which I find really odd. The rads have TRVs but I cannot understand how they can help me save money. By lowering the temp of the TRVs they aren't going to shut the boiler and pump off (are they) so how can that save money? Basically, as I understand it, TRVs have no influence on the boiler operation (unlike a room stat). The boiler and pump are on constantly when programmed surely?

Any advice welcome.

reeac

The boiler will have an internal thermostat which will switch off when the water exceeds a certain temperature. When all the TRVs have closed the temperature of the boiler water will rise rapidly and actuate the boiler 'stat.. I fact building regs. require that there should always be a circuit open for water to flow through [so that there's always a degree of cooling] and usually one radiator has a conventional valve to serve this purpose.

red_flump

They will save some money as they shut down the warmer radiators, the water flowing back to the boiler will not have cooled so much so the boiler will turn down its flame and then off to maintain the water temperature it is set to (up to 80C). The boiler will only relight the flame when the returning water has cooled a bit.

If the whole house is up to temp and all the TRVs have shut down then it is better for the boiler and pump to be switched off completely.

Red

welda

tim091 wrote: »

Hi,

Just moved into house and the central heating has no room thermostat, which I find really odd. The rads have TRVs but I cannot understand how they can help me save money. By lowering the temp of the TRVs they aren't going to shut the boiler and pump off (are they) so how can that save money? Basically, as I understand it, TRVs have no influence on the boiler operation (unlike a room stat). The boiler and pump are on constantly when programmed surely?

Any advice welcome.

I have exactly same setup as you, except my two en-suite rooms rads, are the open circuit rads, you should have at least one rad non-TRV?

My system works a treat, you are not dis-advantaged not have having an internal room stat installed.

:beer:

Careful_with_that_Axe

I have this on my central heating system and find it a bonus. Downstairs is open plan with the stairs at one side of the living room so I turn the rads off upstairs and the heat rising is just enough to take the chill of and make upstairs comfortable.

tim091

Thanks all. Always assumed that by the time the water had circulated around the house (regardless of if rads are shut off or not) it would have cooled so much by the time it gets back to the boiler that the boiler stat would never come into play.

whowants2brich

Also, remember that although it's not much heat, the heated water flowing through the pipes will give off a small amount of heat. And since the hot pipes usually run next to the cold pipes, they might even give enough heat to stop pipes from freezing as quickly...

I found out that the TRVs in our house have been invaluable, the hardest part though is getting them all set properly with the heating timer to come on and heat the property properly...

flashnazia

Personally I think you should get a room thermostat put in too; don't rely on trvs only.

Owain_Moneysaver

You're correct.

Eventually the boiler stat will cycle off and on. However this is inefficient and wastes energy. New installations must have some form of interlock to prevent the boiler cycling when the house is warm enough, and this is why new installations usually have 1 radiator without a TRV, and a roomstat in that room. That should be the last room to get warm, so when it's got warm the house needs no more heat and the thermostat cuts off the boiler.

There are other ways of providing boiler interlock, but a roomstat is usually used for domestic installs.

ariba10

And when the room that has the room stat in it is warm enough, it shuts the central heating off, making the TR Vs useless.

Meatballs

Not if you find another room becomes too hot when the central heatings on...