They agreed to send me a replacement for free even it is 4 years old, and ask me to send the old one back. Would consider smart radiator Control, but can see that isn’t cheap and not sure how good it actually is.

CM921 or CM927 Honeywell Sending a Binding signal from the CM921 or CM927 Honeywell

The Honeywell CM921 is wireless and can be controlled remotely using the Honeywell Total Connect Comfort app, available for iOS and Android devices. The Pro Series Programmable Wireless Thermostat replaces the discontinued Honeywell CM927/CMS927/CMS927B1049. Looking at replacing my CM921 and maybe even the receiver, it’s 10 years old and even with new batteries in the CM921 it seems to be temperamental to touch, in screen sometimes goes blank.The engineer scheme is here to support you and your clients, simply save yourself time and money on finding parts and gain access to our massive catalog of over 110,000 parts. With ‘wireless’ communication there is no need to provide a wired connection between the thermostat and boiler. However, the big difference is that the Pro Series Wireless Programmable Thermostat will bind directly to any existing Honeywell Wireless Relay Boxes, where the T3 Series won’t, so you don’t have the hassle of having to get an installer out to fit this.

Honeywell CM921 user manual (English - 18 pages)

Place the thermostat about one and a half metres above the floor, not in the sun and not on an outside wall. Optimum Start option is an advanced feature which ensures that the optimum temperature conditions are achieved at the required times (option set by your installer).

The Honeywell CM921 Wireless 24Hr Programmable Room Thermostat series of Wireless Programmable Thermostats is designed to provide wireless time and temperature control to heating or cooling systems in domestic and light commercial buildings.

Honeywell CMT921 Wireless 24Hr Programmable Room Thermostat

They are compatible with most central heating systems and are easy to install, perfect for new or retro fit projects. There is a great range of Honeywell room thermostats to choose from that enable users to control the temperature in each room individually. This is a 7 day wireless programmable room thermostat designed to control your heating system efficiently, providing comfortable temperatures when you are at home and energy savings when you are away.The device also features a frost protection mode that helps to prevent pipes from freezing during cold weather.

Honeywell CM921 Wireless Thermostat Problems - PlumbersForums.net Honeywell CM921 Wireless Thermostat Problems - PlumbersForums.net

Extra Large LCD (Liquid Crystal Display) Screen with Backlight provides added user friendliness and clearer viewing – even in the dark. so seriously considering this, radiator control is pricy, but if replacing the CM921 Ona like for like basis it probably works out cheaper for the new thermostat and receiver.

The following instructions explain how to set up, program and operate your Honeywell CM921 Programmable Room Thermostat. This Wireless Relay Box is a suitable replacement for the BDR91A and pre-2021 BDR91T (without house symbol on front) Wireless Relay Box made by Honeywell.