Volt Free Contacts

[wreck-it-steve]

Hi,

I have a boiler that has "volt free contacts" for the thermostat. I need to relocate it to another room and try not to disturb our decor...

Seen as they are volt free is it acceptable to use wire such as alarm cable and run it under carpets etc?

or does it still need twin and earth?

Thanks

 

[EFLImpudence]

Seen as they are volt free is it acceptable to use wire such as alarm cable

If suitably rated so probably not.
Volts free does not mean what it says.
Is it to carry 240V or 24V?

and run it under carpets etc?

Of course not.

or does it still need twin and earth?
Thanks

Or flex.

 

[ericmark]

I think you have miss understood what volt free is.
Where a thermostat is mains powered it can have a link to the contacts so 230 vac is sent to the boiler. In some cases this link is removable so although the thermostat runs on 230 vac the contacts could switch 24v. This means the contacts are called volt free. As to if it switches 24v or 230v depends on the boiler design.

So a volt free thermostat or programmer/timer could have two independent supplies or it could have 230vac to all.

As to if alarm cable would do the job this would depend on two factors. One as you seem to have grasped is the volts the other is the current.

The both will depend on what it powers, although many boilers have a low current extra low voltage supply often the control is not direct. What happens is the thermostat moves a motorised valve and then the valve tells the boiler what to do. This way if a valve sticks the boiler will not fire up.

So the information given does not tell us or you if the voltage is extra low or what the current is. And with so many radio controlled units on the market there is really no need to botch it with alarm cable anyway.

 

[ericmark]

As a P.S. flex should be visible so one should never run any flex under a carpet.

 

[JohnW2]

Volts free does not mean what it says.

Indeed it doesn't. Another wonderful piece of totally ridiculous/confusing terminoloy - and, in this case (as we've seen from the OP), potentially positively dangerous.

Who invents all these weird bits of terminology/jargon?

Kind Regards.John

 

[RF Lighting]

It means these terminals should be controlled by volt free contacts which are well erm contacts with no voltage. Volt free if you like.

Nothing ridiculous / confusing about that. Perhaps the label is missing the word 'use' from it if you wan't to be really pedantic about it (which I have no doubt you will), but if you don't understand that, then you really shouldn't be working on this sort of thing.

 

[ban-all-sheds]

Au contraire - it means exactly, and precisely what it says, and absolutely nothing else.

The terminals are volt free.

Anyone who doubts that should try connecting the non-load side of the thermostat or programmer or relay or contactor up (unless it's a basic mechanically adjusted bimetal strip type of thermostat, in which case it has no non-load connections) and seeing if they can detect any voltage between the terminals or between any terminal and any other point in the universe.

And anyone who doesn't understand what the term means and what it implies about the use of the device the moment it is explained to them should not fiddle with it.

Look at it this way - you take a light switch out of the box and hold it in your hand. You use one of your fingers to flick the rocker back and forth. The terminals remain resolutely volt-free. It really should not be a difficult concept to grasp that a programmer sits there and opens/closes switches.

 

[JohnW2]

It means these terminals should be controlled by volt free contacts which are well erm contacts with no voltage. Volt free if you like. Nothing ridiculous / confusing about that. Perhaps the label is missing the word 'use' from it if you wan't to be really pedantic about it (which I have no doubt you will), but if you don't understand that, then you really shouldn't be working on this sort of thing.

I do understand what the phrase is used to indicate, but that does not make me feel it is any more sensible or logical (or necessarily 'safe'). Far from being a pedantic improvement, I would have thought that adding the word "use" would make it even worse - since, if the contacts are ever to serve any useful purpose, when "in use" they must have a PD between them ('volts') when they are open. I suppose that, by the same 'logic', the contacts of any relay or contactor could be called 'volt free' (until one connects them to something). Indeed, as BAS has pointed out, any electrical accessory (as bought) remains 'volt free' until it is connected to something!

If you don't think the term is confusing (and potentially dangerous to the unaware) then, as I said before, just look at the OP.

Kind Regards, John

 

[ban-all-sheds]

When I look at the OP I see someone who should not be fiddling.

 

[JohnW2]

When I look at the OP I see someone who should not be fiddling.

Maybe, but you also see someone who has interpreted a bit of terminology (on the basis of what the words say) in a manner that is potentially dangerous.

IMO, at the very least you should acknowledge that some people who should not fiddle do fiddle, and that, for them, this terminology is potentially misleading and dangerous.

Kind Regards, John

 

[EFLImpudence]

I started to write a reply but it seemed so obvious as to be insulting.

So I will agree with and quote -

I suppose that, by the same 'logic', the contacts of any relay or contactor could be called 'volt free' (until one connects them to something). Indeed, as BAS has pointed out, any electrical accessory (as bought) remains 'volt free' until it is connected to something!

And for the OP -

Probably not with your boiler but when in service such 'volt free' contacts could be at 240V to earth.

 

[ban-all-sheds]

IMO, at the very least you should acknowledge that some people who should not fiddle do fiddle, and that, for them, this terminology is potentially misleading and dangerous.

The device provides no voltage to the contacts, it simply does not, and that's all there is to it.

The description of "volt free" is entirely correct, and that's all there is to it.

I can guarantee that the the device comes with a wiring diagram which shows quite clearly that it provides no voltage to the contacts.

It would be impossible to arrange life such that descriptions of things were not misleading to people who should not need descriptions of them because they are incapable of dealing with them.

 

[JohnW2]

It would be impossible to arrange life such that descriptions of things were not misleading to people who should not need descriptions of them because they are incapable of dealing with them.

Agreed. However, that should not stop us doing what we can to minimise risk. The possible (and potentially dangerous) 'misinterpretation' of "Volt free" is so obvious that I'm surprised that people are disagreeing with me. There simply must be better terminology that could have been chosen - off the top of my head, how about something like 'isolated' or 'independent'?

Kind Regards, John

 

[PrenticeBoyofDerry]

If you don't want to route/chase cable through walls and it is not advisable to have flex/cable under carpet.
I would suggest going down the wireless RF road!

 

[ban-all-sheds]

how about something like 'isolated' or 'independent'?

How about people finding out what "volt free" (or any other term which they know they don't know what it means) means rather than thinking it's OK to do circuit design on the basis of ignorant assumptions?

It really doesn't matter how you try and spin it, every one of your "yes but it's confusing to the ignorant" simply reinforces the position that the ignorant should not fiddle.