HEATING | PITRVS BALANCING ACT The growing range of PITRVs promises a simpler, more efficient and quicker way to balance heating systems than regular TRVs as well as offering potential long-term cost savings. Phil Lattimore reports Danfosss Dynamic Valve combines a thermostatic radiator valve and a differential pressure controller P ressure independent thermostatic radiator valves (PITRVs) started to appear on the market about 10 years ago, driven by a desire to hydronically balance domestic heating systems more effectively and quickly. A growing number of manufacturers and suppliers have introduced PITRVs into the UK, including Draytons auto-balancing TRVs, Danfosss dynamic valves, Inatecs PITRVs, and Giacominis DB-PITRVs. They are available in a range of specifications suitable for different applications of hydronic heating systems and types of radiator set-up. PITRVs are the evolution of thermostatic radiator valves (TRVs), which were developed more than 80 years ago. As well as offering self-regulating temperature control in a heating system, PITRVs effectively incorporate the differential pressure controller of a pressure independent control valve (PICV) into the body of a TRV package. In this configuration, PITRVs allow the thermostatic control valve to work more consistently as the conditions vary in the heating system, enabling the system to remain balanced as other valves modulate open and closed, and pressure fluctuates. Pressure independent valves for commercial systems have been around for some time, but it has taken a while for the technology to be adapted for TRVs, explains Merlin Milner, product owner at domestic heating manufacturer and supplier Drayton. There is greater focus on boilers achieving the best possible coefficient of performance [CoP] by reducing the return temperature back to 56 October 2023 www.cibsejournal.com the boiler for efficient flue gas condensing. By combining three key functions flow control, temperature control and differential pressure regulation PITRVs offer a number of advantages over regular TRVs. They are quicker and easier to set up than a standard TRV during system commissioning. As Milner notes: The engineer just needs to know the design heat output of the emitter [radiator or radiant panel] and the target flow temperature. They can then adjust the PITRV to the correct setting, safe in the knowledge that the required flowrate will be achieved, regardless of variations in pressure drop across different parts of the heating circuit. In comparison, the traditional approach of trying to balance a system with a lockshield valve (LSV) is virtually impossible, as many are not designed for this. Many LSVs have very poor valve authority, so they need to be almost completely closed before they make any significant change in the water flowrate. This makes system balancing particularly challenging as just a single turn on many hand-operated LSV can go from no flow to maximum flow. Set up correctly, PITRVs can help maintain the design efficiency of the system, reducing energy use significantly compared with more traditional set-ups. They are suitable for a variety of heating applications and can be integrated into new or existing systems. The need for balance Typically, a boiler-based heating system will include a number of radiators in different rooms around the property, usually varying in size to accommodate the output requirements of each room, with different lengths of pipework feeding them from the flow and return to the boiler. That means variances Set up correctly, PITRVs can reduce energy use significantly compared with more traditional set-ups