honeywell cmt 907 digital thermostat & timeclock

[george07]

been suggested by my heating engineer that i need a honeywell cmt 907 stat/timeclock and mount it in my hallway which eliminates my built in segmont timeclock also...seen em on ebay £50 appox but after recent faulty products think im going to purchase it on amazon £70,,fair enough..as for the wiring im guessing i need a L-N supply,a pair for the stat wiring & a pair for the clock..6 cores in total all back to the boiler(2 x 3 cores or 3 x twin & earth 1.5mm ) my boiler is a vokera linea 24 by the way,the cmt 907 has very good reviews on amazon has anybody else used these and worked fine without any problems..or would reccomend any other good quality compatiable product(s) cheers again

 

[bookahandyman]

i have fitted many honeywell cmt's
i think they are very good quality and user friendly. try the cmt927 its a wireless one you just wire the reciever near the boiler and have the stat/programmer where you want. only needing three core from the boiler, live neutral and switch live. if your powering it from the boiler that is.

 

[aptsys]

There's a bug on the cmt907 which I've been able to recreate one several units with timer events spanning midnight while optimum start is enabled that'll make the stat call for heat between 00:00 and 01:00 even if the temperatures are fine.
Other than that, they're ok.

 

[mikely]

You only need a two core cable to a CM907. It's battery powered. See http://products.ecc.emea.honeywell.com/europe/ecatdata/pdf_cm900_cmt907a1041.html

 

[george07]

cheers guys for advice/replies have fitted the stat/programmer in the hallway as advised by my h/e..connected up terminals a) brown b)black c)grey at the stat(wired a 3 core 1.5mm to it) & have run the 3 core back to the boiler inserting through the cordgrip into the boiler etc i now just need to know which terminals to connect to in the boiler pcb.. i also want to disconnect & remove the old segmont timeclock fitted into the boiler so i can fit a blank plate to tidy it up..prob get 1 on ebay...& finally then setup & commision the new digi stat/programmer..any info/advice very gratefull cheers again

 

[mikely]

Having removed the internal timeclock, connect as per section 10 Fig 6 of the installation manual http://www.vokera.co.uk/wp-content/...8_installation_and_servicing_instructions.pdf
to terminals a and b of the CM907.
Note that wiring into the boiler should be made using heat resistant cable rated at 90C as per manual section 5.7.3.

 

[holmslaw]

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[george07]

ok holmes will bear that in mind..why is that though if dont mind me asking that i shouldnt discard the old timeclock ? cheers & what are the connections

 

[holmslaw]

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[aptsys]

Don't connect up the NC contact at the thermostat. You don't need it.

 

[mikely]

Because the old time clock is part of the dhw controls, thats why you should leave it in place.

The Vokera Linea is a combi. The internal clock only controls CH, so if you fit a programmable stat, you don’t need the clock.

 

[holmslaw]

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