honeywell rf cm67

steveadi · 7 Oct 2006

i have just bought one of these and i want to fit it to my eurocombi,i know it needs a live and neutral so i gather i need 2 core 7mm wire as per instructions,but what wire do i need to go to the relay A and B terminals i know its 7mm do i also need a 10amp inline fuse? and do i connect the relay to the boiler as if i was connecting a wired thermostat?i am not too bad at electrics,but would i be better off paying an electrician to fit it,any constructive help appreciated.

thanks.

Rob · 7 Oct 2006

if its the same as most rf room stats. the reciever requires L-N and make and break if you like to and from boiler as a normal room stat, like you said.

so a length of 4core flex will do the trick. 0.75mm is the diameter of the wire.

simond · 7 Oct 2006

As described, you wire in a permanent 240v supply to terminals L &N. If you tee the L&N from the boiler supply there is no need for a separate fuse. 10A in any case is too high, 3A should be used.

You then connect the Eurocombi's thermostat terminals with a pair of cables from the CM67NG's A and B labelled terminals.

We fit lots of CM67s but not any Ariston boilers; we'd advise if the Ariston is switching at 24v to use a separate sheathed cable for this part.

NB: If you have not bought the unit it has recently been changed to the CM901, which is superior. Bigger backlit display, easier to use.

steveadi · 7 Oct 2006

thanks for the replies,the combi is plugged in with a 3 amp fuse so i will T off the combi,i was going to use 4 core like rob844 recommended,but if its better i will use two seperate cables, if i use two seperate cables i know it needs to be 7mm but will any 7mm wire do?acording to the ariston instructions i need 2 core and earth for a wired themostat,but on the cm67 instructions its only live and neutral,again any help will be appreciated.When i bought the thermostat it stated it was the newer model i am not sure what differences there is between the older model. forgot to menyion this is wireless

thanks

simond · 7 Oct 2006

If you have the CM67 RF you have the outgoing model.

CM67 is double insulated so does not need, and should not be fitted with, an earth connection.

If the Ariston has connections for a 240v thermostat then 4 core is going to be the neatest solution. If the Ariston mentions 'volt free' or '24v connections' for the thermostat then a separate cable should be used.

Once again, as Rob884 says, you should aim to use 0.75mm sq cable/flex for all connections, although you could also use 1.0mm twin and earth with the earth insulated off or 1.5mm t &e.

7mm cable would carry around 35amps and is not suitable - you would never fit it into the Honeywell terminals for starters, and then you would need an elephant to sit on the cover.....

steveadi · 7 Oct 2006

thanks last question,no mention of volt free or 24 volt connections so 4 core it will be,what is the safest and best method to wire up the electricity, the boiler is plugged into a wall socket. do i put the wires in the terminal block in the boiler along with the other live and neutral or do i cut the wires and put a junction type box in between? and if i do put the wires in the terminal box will they be protected with the 3 amp fuse in the plug. it does say 7mm diameter wire in the instructions honest

simond · 7 Oct 2006

Tee in at the boiler for the neatest job; anything after the fused plug will be suitably protected against overload.

PS: When its finished you would have doubled the value of your boiler!

Biggles.. · 7 Oct 2006

7mm flex is also refered to as 0.75mm. 7mm refers to total cable size and is the value stated when ordering clips for 0.75mm flex.0.75 is the conductor CSA.

steveadi · 8 Oct 2006

Thanks very much for the help i have fitted the unit and it seems to be working ok

i didnt wire the live and neutral in the boiler i decided to wire it in to a 3 pin plug with a 5amp fuse as that was the only fuse i could find,would it be better to fit a lower amp fuse 3 or 2 amp or will 5amp be ok.

thanks.

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honeywell rf cm67

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