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Home improvements: What is the point of a TRV?

时间:2017-05-06 14:28来源:未知 作者:kevin
Q: Having read your very interesting views about boilers and radiators, I am not clear on one point. If you recommend leaving thermostatic radiator valves fully open, why are they installed in the first place? AC, by email
A :Thermostatic radiator valves (TRVs) were invented in Denmark and introduced in the Seventies as a cheap and easy way of controlling zoned temperatures throughout a large building with a “wet” heating system fed by one central boiler (the origin of the term “central heating”).
TRVs can be useful in commercial buildings such as offices and factories, and are also widely used in apartment buildings in Europe, where one boiler in the basement often feeds dozens of flats. In this situation, the boiler is constantly fired-up and hot water is constantly circulating throughout the pipe network (so that the boiler is operating at optimum efficiency).
Individual flat dwellers control their homes’ temperatures using Thermostatic radiator valvesTRVs and quickly learn to judge the correct setting.
This is a totally different arrangement from the British system, where each individual house and flat has its own boiler, commonly programmed to fire-up for only two hours in the morning and six in the evening. In this situation, TRVs become something of an irrelevance and can create problems.
For example, a TRV should never be fitted to the radiator in the same room as the wall-mounted room thermostat, as the two thermostats will be fighting each other to gain or deny heat from the boiler.
They are also inadvisable in bathrooms, where the heat from bathing or showering can shut down the Thermostatic radiator valvesTRV (even when it is turned to “max”) just when warmth is most needed to prevent condensation.
TRVs are fairly primitive devices which rely on the thermal properties of a trapped bubble of gas, liquid or wax to expand and contract, and thus turn the radiator valve off or on. Once fitted, they are never checked or recalibrated, so there is no way of knowing whether they are working accurately or not.
TRVs control the temperature right next to the radiator, rather than in more habitable parts of the room; they are misled by draughts from adjacent windows (which make them sense too cold), radiator shelves (which make them sense too hot); and when they break, they are most likely to stick in the “off” position, further increasing the likelihood of condensation problems.
The mandatory use of Thermostatic radiator valvesTRVs has also resulted in a new generation of plumbers and heating engineers who have no interest in the traditional skill of balancing a central heating system by adjusting the lockshield valves at the opposite ends of the radiators to the main valves. Balancing the system to achieve an 11C drop across each radiator used to be an integral part of a plumber’s training, but is fast becoming a forgotten art.
Unfortunately, Britain’s energy policy is determined by politicians and civil servants rather than engineers, and it has therefore been decreed in the Building Regulations that all new and modified wet central heating systems must have these infernal devices fitted to every radiator (apart from one in the hall).
However, there is as yet no law which prevents home owners from unscrewing the plastic sensor from the valve body and removing it or, indeed, from replacing TRVs with traditional manual valves in existing systems.
Garage Banned
Q: Our house was newly built seven years ago. Unfortunately the boiler is in the attached garage and protected by a froststat. Every night in this cold weather I have to turn most of the radiators off so that we don’t fry, as the frost protection system overrides the room thermostat.
Do I need to heat and possibly insulate the garage to stop this happening? TS, Bucks
A :No, heating your garage would be a complete waste of energy.
The problem is that your boiler’s frost protection circuit was incorrectly installed in the first place. It should have a pipe ’stat fitted to the return pipe to the boiler, set at 20C , which will turn the boiler off before it starts heating the radiator circuit inside the house.
Kevin 5th May 
Ph(whatsapp): +86-15386899894