volt free contact inside electric heating boiler

[Kev2632]

http://www.electric-heatingcompany....0/03/electric-boilers-tech-install-manual.pdf

Go down to page 8 of this document, you will see it asks for the contacts to fire the boiler up to be volt free, now i do finally understand i think what this means, it means that those two contacts R+P are independently volt free from the power being supplied to boiler, now what i cant understand with the way the booklet is telling you to wire the boiler up is, when wiring a normal 2x 2port valve set up, we supply either the orange or grey with 240 and the micro switch closes sending 240v down the other core, how can this boiler work when there will be no voltage at all applied to either orange or grey cores?? and is it possilbe to feed 240 volts onto one side of the R+P volt free contact at all ? and have 240 come out the side of either R+P ??

thanks again guys

 

[Kev2632]

Voltage free contacts is a term given to contacts which you apply your own voltage signal, or signal or 4-20ma etc.
Voltage free contacts as in a relay or microswitches will be rated and shown with max amps and max voltage. IE 2amp/230v or 24volt dc/5amp etc etc.
This boiler manufacturer seems to have used unfortunate wording in their description of R and P. I read it like has already been stated and is 4-20ma (with 10 volts to carry it) or 24volt etc. Looks to me like they have had a lot of returns/faults which are site based and so the emphasis on warning after warning.
The easiest to explain it is if you think of P as power (leaving the boiler at whatever voltage) and R as return (going back to tell the boiler to go). Therefor self contained and no voltage to be applied by your wiring.

Thanks Boydy

 

[Kev2632]

The voltage only appears across the coil, the contacts are independent.

okay so i could feed the coil with 240volts and take a two core from the relay contacts to the boiler is that correct yea, and that will provide "volt free" contacts to the boiler correct yea??​

 

[Deleted member 72666]

okay so i could feed the coil with 240volts and take a two core from the relay contacts to the boiler is that correct yea, and that will provide "volt free" contacts to the boiler correct yea??

Yes on both counts! But are they actually asking for you YOU to provide the volt-free contacts i.e. are the terminations available or are they internally provided by the boiler/controls themselves? Without looking I can't say!

 

[Geoffsd]

If you study the wiring diagram on page 8 you will see that the greys of the valves are connected to R and the oranges are connected to P.
These are connected when the valve is opened.

It is (unusually ?) using the valve as 'volt-free' contacts for the boiler terminals (R and P) and has no connection with the 240V supply.

The valves are powered by the browns at 240V from the thermostats.

You do of course need 240V L,N,E on the terminals where it says Boiler Main Supply even though the wiring is not shown.

 

[Deleted member 72666]

okay so i could feed the coil with 240volts and take a two core from the relay contacts to the boiler is that correct yea, and that will provide "volt free" contacts to the boiler correct yea??
​

You would also need to know whether it needs n/o or n/c contacts.

 

[Geoffsd]

It's bound to be n/o isn't it?

 

[Deleted member 72666]

It's bound to be n/o isn't it?

Usually yes, but it depends on the application, but that's my point... they would specify say a 'n/o' but in this case they haven't and that's why I think it's provided internally via the valve controls.

 

[Geoffsd]

There's no doubt.

The valves are being used as a relay with a motor rather than a coil.


However, if wired correctly as per the diagram it doesn't really matter how it works.

 

[stuartcourt]

has anyone ever seen a boiler with only volt free connections

 

[Mork]

agree, if you follow geoffsd post 34, this is a common way for connecting many Grant air source pumps that require volt free contacts.

 

[stuartcourt]

Just phone up monday morning and ask tech support they will tell you in about 5 seconds and that is a risk free option, Its what they are there for

 

[guest119]

Phewwwwwwwwwwww, 3 pages.

 

[stuartcourt]

Ha ha bit of overkill poor sod

 

[Deleted member 72666]

It might even stretch to 4!!

 

[stuartcourt]

especially if we fill it up with idle chit chat