Honeywell Programmable Room Thermostat 24 hour CM921

Product Information

The CM921 thermostat is designed to provide automatic time and temperature control of heating or cooling systems. It can be used as part of a system in conjunction with combi boilers, oil-burners and gas fired boilers, circulation pumps, thermal actuators, zone values and electric heating systems 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. The slim, ultra modern design complements the large LCD screen with the Line of Text (LoT) display and one function button to ensure simplified programming and operation for all users. Pro Series Wireless Programmable Thermostat – Replaces Honeywell CMS927 & CMS921 Wireless Programmable Room Thermostats

CM921 can be installed without disrupting your room decor as no wiring connection is required between the room unit and the boiler Am I correct in thinking that when the combi heating return temperature reaches the temp at which the combi is set at(not the room stat) it will turn the burner off until the temp dips below the the required temp,once all the trvs stop asking for heat?If you take a good look at the Pro Series Wireless Programmable Thermostat, you will see it is nearly identical to Honeywell Home’s T3 Series Thermostat (the user display menu is identical). 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. OFF mode has an integral frost protection setting at minimum 5°C (installer adjustable) so that pipes in the house will never freeze in winter The Pro Series Wireless Programmable Thermostat is a BRAND NEW 2021 launched, 7 day programmable room thermostat designed to replace all existing Honeywell CM Series Wireless Thermostats. The ‘Pro Series’ is made in the UK by Resideo (who were formally part of Honeywell International Inc.) and distributed to independent merchants via a national merchant wholesaler. Resideo (Honeywell Home) is the same manufacturer who made the CM700 & CM900 Series Thermostats.

The CM921 uses a feature called TPI to control when the boiler fires. The purpose of this is to prevent wide fluctuation in the room temperature. If the room is more than 1.5 degrees below the set temperature, the boiler runs continuously (controlled by boiler stat). Once the difference is less than 1.5 degrees the stat starts cycling the boiler based on a ten minute period. It will start off at, say, 90% ON 10% OFF and slowly reduce this mix 80/20, 70/30, etc as the room temperature approaches set temperature. This could be why you are finding that the boiler is going on and off all the time. The Honeywell CM921 Wireless 24Hr Programmable Room Thermostat can be used to control the heating circuit in a Sundial S or Y Plan and is particularly well suited to control combination boiler installations or additional zones in a S Plan Plus system. The Honeywell CM921 Wireless 24Hr Programmable Room Thermostat is for use where heating needs are the same from day to day. The CM927 can provide a different heating programme for each day of the week to maximise energy efficiency. Two wire, volt free connections are ideal for use with combination boilers. Honeywell CM921 Wireless 24Hr Programmable Room Thermostat Product Features: The Pro Series Wireless Programmable Thermostat will replace the following Honeywell CM Series products: Honeywell CM921 Wireless 24Hr Programmable Room Thermostat is p art of the Honeywell Controls Range from Plumbarena. Honeywell are one of the market leaders in heating control technology, providing quality products for domestic comfort.

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Direct replacement for a Honeywell CM927/CMS927/CM727/CM921, if you are unsure about compatibility please call us on 01302 279234.