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Mend Honeywell CM921 Thermostat Boiler Heating

Programming Honeywell CM921?

Hi: The heating engineer installed this unit during installation of a new boiler. This is a 1 day wireless programmer. Unfortunately, I am finding it quite difficult to program this unit as the Honeywell user guide is quite complicated.

Can you please help me by providing a simple step by step guide to program this unit eg: heating twice daily, keeping the heating on 24/7 when weather is very cold etc. The unit is connected to an IDEAL combi boiler.

Our system is a bit different as we also have a hotwater storage tank connected to the heating system ie hot water is supplied to the tank via the CH system. There are to valves, installed underneath the boiler, which we have to open to start heating and then shut these to provide hot water in the storage tank.

With our old room thermostat it was easy because we were able to set the heating on " tiwice daily" which automatically supplied the hot water. During the summer, we could the the same but with the two vales shut so that hot water got supplied tothe storage tank. Our bathroom & shower unit are supplied with hot water via the storage tank.

I do hope I have manged to explain properly.

Tan
August 2010
I have had one of these programmers installed today and what i can make of it is you programme time against temperature.

So i have mine set at 21deg from 3pm then at 11pm i have it set for 17deg.

So during the day and night when we dont need a lot of heat the boiler will not fire unless it drops below the set temp.Between 3 & 11 the boiler fires unless its warm anyway.

ChrisK
January 2011

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