Two zone valve - volt free conrtact to fire combi?

[Agile]

There is no such thing as extra low voltage.

Generally below 50v is considered as low voltage as you can fairly safely touch it without risk of death.

Many boilers use 24v switching but the digital connections are often 5v RS422 type current loops.

Tony

 

[Dan Robinson]

http://en.wikipedia.org/wiki/Extra-low_voltage

 

[DP]

Bolshy wrote

This enables 4 core and earth to be used from the programmable roomstat to the zone valve, and twin and earth from the zone valve to boiler. What could be simpler?

I think you mean three core flex as opposed to twin and earth (grey cable). Not the first time I have seen boilers wires with 2.5 T+E

 

[Agile]

Before anyone kills themselves, I suppose that I had better state that in the context of mains power distribution LV means 415/230v.

But there HV is 3300v/11,000 and higher!

Tony

 

[RF Lighting]

■Extra Low Voltage: AC below 50V and DC below 120V
■Low Voltage: 50 - 1000V AC or 120 - 1500V DC
■Medium voltage: 1kV - 35kV
■High voltage: 35kV - 230kV
■Extra-high voltage: >230kV

 

[Dan Robinson]

I was surprised Tony didn't know that TBH.