Neomitis RT7RF+ to Hive or Nest wiring help

[CER8ERU5]

Hi,

I am looking to change my current Neomitis RT7RF+ to either a Hive or a Nest thermostat. However I am unsure which one to go with for compatibility. I don't know much about it other than when it was originally installed the guy said it was using volt-free contacts. My boiler is a Buderus 500-24C.

Any help would be appreciated to find out where the wires go from 3 and 4 to both Hive and Nest receivers. Will be much cheaper than hiring an electrician by the hour to do something that's probably quite quick and simple.

Thanks

 

[Deleted member 267285]

I’d go with Hive over Nest, unless you want to charge the Nest with a usb plug? On Hive 3 (black) would go to 1 and 4 (grey) would go to 3 and make sure you park the earth.

 

[CER8ERU5]

Great thank you. I would like to learn about what each wire is rather than just doing it if you could explain for me please?

 

[Deleted member 267285]

Ok, but you didn’t ask originally. Live is a Live, Neutral is required to complete the circuit, 3 (existing) is the common wire (another live) and 4 (existing) is to complete the circuit (switch live).

 

[EFLImpudence]

3 and 4 are the (badly named) volt-free connections.

This does not mean 'no voltage', but rather that it is separate from the mains connections L and N.
It could be 12V, 24V or indeed also the mains 230V.

You will have to determine where in the boiler they come from to find out, although it doesn't really matter if you do as CBW has said above.

 

[ericmark]

Hive is designed to work with an on/off boiler control and allows the boilers own modulating controls to work, but in the mains needs one or two TRV heads to get the best out of boiler.

Nest has a better algarithum set up to hive, and can connect using OpenTherm, but it can't connect to TRV's so not very good for many homes.

The list goes on, Drayton Wiser seems to have best TRV heads.

EPL will work as master/slave with OpenTherm.

There is no one system that will work with all, so start with what you want it to do.