An installers’ guide to TRVs

An installers’ guide to TRVs

With UK sales of thermostatic radiator valves, commonly referred to as TRVs, reaching nearly half a million in 2016, Gareth Ash of Danfoss offers an installers’ guide to these popular, high efficiency heating controls.

Regulatory requirements
Although many heating installers already recognise the increased comfort and energy saving benefits of TRVs, and encourage their customers to take them up, let’s start with a reminder of the regulations when it comes to TRVs in domestic heating systems.
TRVs are only mandatory when new heating systems are installedthey are considered to be good practice when replacing a radiator. As for the latter requirement, the nearly 500,000, annual sales of TRVs does not correspond with the 630,000 or so sales of radiators. The discrepancy in these figures (compiled by the leading trade associations for these products) is a cause for concern as it indicates that thousands of new radiator installations during 2016 did not have a TRV installed.

Although the Government’s new Boiler Plus standards, currently scheduled to come into force in April 2018, are not proposing to mandate the installation of TRVs, given that deployment is already high, Danfoss strongly recommends fitting them to maximise system efficiency and customer comfort.

Which sensor?
When installers visit their local merchant to buy TRVs they can be faced with a potentially daunting choice of products. The type of sensor used in the TRV can make a big difference to accuracy and efficiency – so what are the options?

As every professional installer will know, TRVs work by ‘sensing’ the air temperature around them and regulating the flow of water through the radiator to keep the room at the set level of warmth. To do this, the sensor is filled with a material that expands as the room temperature rises and contracts when it drops. Generally speaking, this material will be either wax or liquid. It’s not rocket science to realise that a lighter liquid filling will expand and contract more quickly than a heavier material like wax – resulting in a faster response to any change in temperature.

There is also another benefit to choosing a liquid-filled sensor rather than a wax-filled product. The crystalline composition of wax tends to get harder and heavier with constant expansion and contraction, causing a detrimental effect on the TRV’s performance.

Price factor
Price is, or course, an important factor when purchasing any product, but opting for the cheapest TRV could prove to be a false economy in the longer term. From our experience, cheap may not be so cheerful for installers who make price their overriding priority. Lower cost TRVs may use inferior quality components, which could compromise their overall performance and durability. And if the TRVs don’t perform as promised, the installer will have an unhappy customer to deal with, as well as the time and cost associated with a call-back to put things right.

Installation guidelines
Controlling a radiator heating system with TRVs ensures an energy saving, reliable and efficient heating system, creating comfort individually from room to room. There are, however, certain rooms that won’t necessarily benefit from fitting a TRV on the radiator, such as the bathroom. When the atmosphere becomes hot and steamy after a bath or shower, for example, the TRV in a bathroom will automatically shut off. As a result, the room will start to cool down, exacerbating the problem of condensation.
It is also not a good idea to install TRVs on radiators in the same room as the main thermostat. This is because the thermostat is controlled directly by the boiler, turning it on or off as required to maintain the set temperature for optimum comfort and energy savings. Installing a TRV will simply create a conflict of control in the room and possibly reduce the system’s overall efficiency.

What’s new?
This guide has highlighted the different types of TRV sensor but there are many new developments in TRV technology for installers to consider. Products like the Danfoss RTW, which features a flow selectable, bi-directional design. This means it can be installed horizontally or vertically, in flow or return, and so provides an innovative solution to the age-old problem of ‘water hammer’. If any system noise occurs after fitting it can be stopped by simply ‘revolving’ the barrel to reverse the flow direction,

Some of the latest TRVs also offer programmable control of individual radiators for even greater flexibility and heating efficiency. One example is the second-generation Danfoss Eco TRV. This intuitive device is quick and easy to program by consumers on their smartphone using the Eco App and Bluetooth wireless technology. These exciting new types of TRV give installers a great opportunity to offer their customers some of the key benefits of smart heating for a relatively low investment cost.

Keep up to date
Getting to know more about the TRVs they fit on a regular basis will enable installers to make a more informed choice and help increase their business profitability and customer satisfaction. So, instead of just sticking with the same TRV for every job, keep up to date with new developments by checking out manufacturers’ websites and the trade media or ask for advice at the sales counter. For more information visit