Inta I-Therm 15mm Angled TRV & Lockshield Pack. The inta i-therm range of thermostatic radiator valves are designed to be fitted in any orientation and with water flowing in either direction. Inta recommends that good working practice dictates that an automatic by pass valve be fitted to central heating systems that incorporate thermostatic radiator valves to prevent the pump pumping against a closed head as the valves begin to shut as the system gets to temperature.