✔ Includes full PTD thermostat display, 4‑channel receiver H3747, user manual, and original box. – H3747 receiver unit with channel select/boost button. ✔ Direct retrofit for Horstmann ChannelPlus systems (H37XL/H47XL) – uses existing backplate.
3 Channel Time switch. Have used them in the past when they were made by Horstman. I know of no other that has 3 channels which are needed for a boiler which has central heating, hot water and a cooker