Honeywell CM921 and Vaillant EcoTEC

[mattallen01]

Hi All...

I currently have a Vaillant EcoTEC 824 combi boiler fitted wit TRV's installed on all the rads. I've noticed lately that the boiler seems to be running continuously, even though the TRV's are set a desired level. I've also just had my latest gas bill and for the last two months I've used almost £400 worth of gas!!!

Therefore, I've come to the conclusion that I need to install a room thermostat so that when the ACTUAL room temperature I want is reached the boiler shuts down for a period of time rather than keep on running.

I've been recommended to get the Honeywell CM921 wireless thermostat but would like the following clarification:

1. I know the thermostat wireless reciever needs to be hard-wired to the boiler using boiler terminal 3, 4 and 5, but which teminals on the thermostat do these correspond too?

2. Many websites advise not to have a TRV's fitted on rads in the same room as the thermostat? Is this true as surely if the TRV's are set to the highest setting the thermostat will switch off the system before the TRV has chance to conflict with it???

3. Is there an easy way to remove or better still disable a TRV?

Many thanks for any advise!

 

[REDSAW]

trv's on all rads?
£400 in 2 months on gas?

tell us who fitted the boiler and trv's
please?.

 

[mattallen01]

Many thanks for the reply? But why do you want to know who fitted it? I have no problem telling you, it was D S Heating, in Dunstable. Are you able to answer my queries? Boiler was fitted over 18months ago, still not got a receipt or Corgi cert after chasing. We didn't end on good terms after he did a bathroom install and left it in a bad state. I ended up fixing myself in the end.

 

[payney1974]

Just take the head off the trv where you fit the room stat, although i would fit a lockshield valve as it will look better. And honeywell products do tend to be the best in my opinion

 

[CharterGAS]

you want a cmt 927 wireless programmable room stat

you will need 4 core cable
L and N to the receiver taken from the Land N of the boiler then terminal 3 goes to terminal A on the receiver and B goes to 4 thats all

 

[newbie1]

or get the vaillant one so simple
reciever 2 wire connection between boiler and reciever
digital stat just screw to wall and hey presto