Does doorbell wire need to follow safety cable zones?

[Mr Sparkle]

Does the doorbell wire coming out of the 0-24v transformer need to follow electrical cable zones.

Or could i bury it in any direction beneath the plasterboard/brick wall?

 

[JohnW2]

Does the doorbell wire coming out of the 0-24v transformer need to follow electrical cable zones.
Or could i bury it in any direction beneath the plasterboard/brick wall?

As far as I am aware (I may be wrong), the regs do not distinguish between cables used for different purposes or at different voltages.

However, common sense might suggest that to invoke such a distinction would probably not be unreasonable!

Kind Regards, John

 

[bernardgreen]

Running door bell cables in the safe zones would reduce the risk of someone drilling into the cable sometime in the future.

 

[JohnW2]

Running door bell cables in the safe zones would reduce the risk of someone drilling into the cable sometime in the future.

That's obviously true, and I would assume that the OP realises that. However, I presume he was asking whether there is a regulatory 'requirement' for such a cable to be buried only in 'safe (aka 'dangerous'!) zones'

Kind Regards, John

 

[Mr Sparkle]

That's obviously true, and I would assume that the OP realises that. However, I presume he was asking whether there is a regulatory 'requirement' for such a cable to be buried only in 'safe (aka 'dangerous'!) zones'

Kind Regards, John

Precisely.

That's exactly what I'm asking.

 

[JohnW2]

Precisely. That's exactly what I'm asking.

Thanks for confirming. It seemed pretty obvious (at least to me!( that that was what you were asking.

However, it looks as if what I originally wrote was wrong. The regulation (in the 'Wiring Regulations, BS7671) regarding cables installed in walls is 522.6.202, and one way of satisfying that regulation is by satisfying 522.6.204 - and, in turn, one way of satisfying that is:

(v) form part of a SELV or PELV circuit meeting the requirements of Regulation 414.4

It would therefore seem that Extra Low Voltage circuits, such as you are talking about, probably do not to have their cables in 'safe zones' when buried in walls.

Having said that, bernard is obviously right in saying that the risk of damaging such a cable (e.g. with a drill, nail or screw) when it's not in a 'safe zone' is the same as the risk if it were carrying 'mains voltage' electricity. If an Extra Low Voltage cable is pentrated, there will be minimal 'danger', but as much inconvenience in repair it as would be the case if it were a 'mains cable' - so keeping to 'safe zones', if one reasonably (or 'fairly easily') can, probably makes sense!

Kind Regards, John

 

[Mr Sparkle]

Thanks for confirming. It seemed pretty obvious (at least to me!( that that was what you were asking.

However, it looks as if what I originally wrote was wrong. The regulation (in the 'Wiring Regulations, BS7671) regarding cables installed in walls is 522.6.202, and one way of satisfying that regulation is by satisfying 522.6.204 - and, in turn, one way of satisfying that is:

It would therefore seem that Extra Low Voltage circuits, such as you are talking about, probably do not to have their cables in 'safe zones' when buried in walls.

Having said that, bernard is obviously right in saying that the risk of damaging such a cable (e.g. with a drill, nail or screw) when it's not in a 'safe zone' is the same as the risk if it were carrying 'mains voltage' electricity. If an Extra Low Voltage cable is pentrated, there will be minimal 'danger', but as much inconvenience in repair it as would be the case if it were a 'mains cable' - so keeping to 'safe zones', if one reasonably (or 'fairly easily') can, probably makes sense!

Kind Regards, John

That's brilliant. Thanks for confirming.

I am glad that the regs have taken a common sense approach.

Extra low voltage isn't dangerous/ fatal, so they should give you more freedom to bury the cable outside of the electrical safety zone.

The above is just my opinions.

 

[bernardgreen]

Extra low voltage isn't dangerous/ fatal,

Extra low voltage can be dangerous, in a fault situation that causes overcurrent items may overheat and cause heat / fire damage.

Door bell transformers are not designed to supply power for more than a few seconds. ( who holds their finger on the door bell push for more than a few seconds ? ) Shorted wiring could go un-noticed until the transformer overheats.

 

[Mr Sparkle]

Extra low voltage can be dangerous, in a fault situation that causes overcurrent items may overheat and cause heat / fire damage.

Door bell transformers are not designed to supply power for more than a few seconds. ( who holds their finger on the door bell push for more than a few seconds ? ) Shorted wiring could go un-noticed until the transformer overheats.

Thank you. Learning everyday.

 

[JohnW2]

That's brilliant. Thanks for confirming. I am glad that the regs have taken a common sense approach.

Yes, particularly given that common sense quite often seems to be lacking in the regs! I'm sorry that I initially did the regs an injustice (and misinformed you) in this respect.

Extra low voltage isn't dangerous/ fatal, so they should give you more freedom to bury the cable outside of the electrical safety zone.

I agree. However, bernard (in his usual ultra-cautious fashion, which I certainly don't 'knock'!) is right in saying that ELV can be 'dangerous'. It would be unusual (but not unknown) for 48V to result in serious, let alone fatal, electric shock. However, it is current, not voltage, that produces heat, and therefore introduces 'fire risks' - anyone who has seen what happens when a 12V car battery gets ';shorted' will understand that

Kind Regards, John

 

[FrodoOne]

Extra low voltage can be dangerous, in a fault situation that causes overcurrent items may overheat and cause heat / fire damage.

Door bell transformers are not designed to supply power for more than a few seconds. ( who holds their finger on the door bell push for more than a few seconds ? ) Shorted wiring could go un-noticed until the transformer overheats.

While I do not know what "regulations" concerning "Extra Low Voltage" overload protection apply in the UK, many small ELV transformers have an "internal fuse", which "operates" if the secondary is overloaded - and then you need to obtain a new transformer !

It always surprises me that persons who install ELV "Door Bells" and "Garden Lighting" do not consider that "overload protection" is necessary.
The simple inclusion of an appropriately sized "Fuse" in an "Automotive" type of "fuse holder"
(https://www.ebay.co.uk/sch/i.html?_...70.l1313&_nkw=automotive+fuse+holder&_sacat=0 ),
close to the Transformer Secondary seems to me to be a wise precaution.

 

[securespark]

ELV cables do not need to be installed in "safe zones" to comply, but wherever possible, I always have.

 

[JohnW2]

It always surprises me that persons who install ELV "Door Bells" and "Garden Lighting" do not consider that "overload protection" is necessary.
The simple inclusion of an appropriately sized "Fuse" in an "Automotive" type of "fuse holder"
(https://www.ebay.co.uk/sch/i.html?_...70.l1313&_nkw=automotive+fuse+holder&_sacat=0 ),
close to the Transformer Secondary seems to me to be a wise precaution.

In the case of a 'true' ('wire-wound'/inductive) transformer, it would be difficult to to agree that a fuse would be a 'wise precaution' (if not only to protect the transformer itself, since I suspect that a 'bell transformer' would probably not be able to supply enough current to represent a 'fire hazard').

It's many years since I had anything to do with a 'bell transformer', so I have no idea about what they now are. However, if, as with so many other things, such 'transformers' are actually SMPSUs then they will almost certainly have output current limitation ('short circuit protection') in its electronics. Indeed, even in the absence of any explicit 'short circuit protection', a short of the output will usually stop the oscillator working, hence effectively providing 'protection'.

Kind Regards, John