volt free stats ?

[sparxfly]

hiya everyone

new to all this but looks great,sparks helping sparks.
my problem is volt free stats, my mate has installed a combi boiler and it says it needs a volt free stat.it has 230v intake and another connector block with 3 cables marked up as brown , black , blue , saying it controls exterior controls. ( stat ) trouble is this heating is all new to me.
any help please .
many thanks.

 

[kendor]

I presume he means volt free as in contacts ie just a switch or pair of contacts instead of a unit supplying a voltage

 

[sparxfly]

thanks kendor for replying.
when combi fires up all 3 cores are live.........measuring about 60v thats what is so confusing. if no exterior controls are put in though , there is a link between 1 and 3 ( brown and blue ) does this make any sense ?
hope so

 

[baldelectrician]

what make is the boiler?

 

[ban-all-sheds]

You'd probably be better off on the plumbing and CH forum.

Volt-free means that the thermostat or programmer does not supply any power to the boiler. Some do, i.e. you supply them with 230V, and when they switch on, that 230V is sent to the boiler.

When volt-free ones switch on, they just connect two terminals together, completing a circuit at the boiler, just like a relay. So the boiler circuitry will have, in effect, a place where there is a switch to turn some function on, and that switch is at the end of two long pieces of wire, at the programmer. If you measure voltages at the terminals on the boiler, you will be measuring voltages across two parts of the control circuitry, and therefore they could be anything - you'd need to look at the maintenance documentation to find out what the expected readings are.

 

[sparxfly]

thanks for taking time to reply. will have another look at the boiler when i go back.
thanks again