Correct cable?

Fatherodonnell

Hi I am installing an alarm control panel and I have a 0.75 mm flex cable which I have wired from the alarm into the socket in my hall. The flex is running behind the plasterboard into the socket and everything seems to work ok.
Is this safe?

2011

Fatherodonnell wrote: »

Hi I am installing an alarm control panel and I have a 0.75 mm flex cable which I have wired from the alarm into the socket in my hall. The flex is running behind the plasterboard into the socket and everything seems to work ok.
Is this safe?

No.
In simple terms: The cable is too small to be part of a socket circuit.

As with most things electrical it is simple to get them to "work". The trick is to get them to work safely in a cost effective manner.

hufpc8w3adnk65

Fatherodonnell wrote: »

Hi I am installing an alarm control panel and I have a 0.75 mm flex cable which I have wired from the alarm into the socket in my hall. The flex is running behind the plasterboard into the socket and everything seems to work ok.
Is this safe?

And if you noticed smoke coming from your alarm control panel tomorow how would you switch the power off?

Fatherodonnell

Thanks for responding. But Is it really dangerous? What could go wrong if the alarm only uses a tiny amount of power?

Par1

Defiantly not as the flex is fused at 20 amps. Id replace it with at least 1.5 via fused spur then fuse accordingly. The alarm panel should ideally be fused on its own MCB as you may get nuisance tripping if covered by RCD. I appreciate the alarm panel draws a small load but don't forget relays can be used with panels which increases load (if used)... id disconnect it ASAP.

2011

Fatherodonnell wrote: »

But Is it really dangerous?

Potentially, yes.

What could go wrong if the alarm only uses a tiny amount of power?

I'm not trying to be smart but if we were confident that none of the cables in a house could ever be overloaded then we would not protect any of them with MCBs or fuses.

Fatherodonnell

Ok I don't have any relays on the alarm though.
I could go up to the fuse board which is nearby and connect it to a light circuit, would that make it safe or do I still need to get 1.5 cable?
Also do I really need yo install a fused spur? What's that for?

2011

Fatherodonnell wrote: »

Also do I really need yo install a fused spur? What's that for?

Yes.
All cables require appropriate protection.

Par1

2011 wrote: »

Potentially, yes.




I'm not trying to be smart but if we were confident that none of the cables in a house could ever be overloaded then we would not protect any of them with MCBs or fuses.

Agreed

Par1

2011 wrote: »

Yes.
All cables require appropriate protection.

Totally agreed

Par1

Fatherodonnell wrote: »

Ok I don't have any relays on the alarm though.
I could go up to the fuse board which is nearby and connect it to a light circuit, would that make it safe or do I still need to get 1.5 cable?
Also do I really need yo install a fused spur? What's that for?

Im not been smart either here but if you don't know what a fused spur is then you probably shouldn't be wiring the electrics or going near the fuseboard and may be better off getting a registered electrician to do that part for you. I know it will cost money but then it would be done right and you can then be assured that its up to standard.

Fatherodonnell

No I do know what it is, just wondering what it's for in this case?

2011

Fatherodonnell wrote: »

No I do know what it is, just wondering what it's for in this case?

Protecting the downstream cable.

Fatherodonnell

Ok thanks, if I wire into the light circuit in the fuse board can I use this .75 mm cable? Do I bring it from fuse board to spur and then on to alarm?
If yes then what protects the cable between fuse board and spur?

2011

Fatherodonnell wrote: »

if I wire into the light circuit in the fuse board can I use this .75 mm cable?

This would be considered bad practice.
It would be best to use a 1.5 cable.
Only a qualified electrician should work on a distribution board and only a Registered Electrical Contractor is permitted to.

Do I bring it from fuse board to spur and then on to alarm?
If yes then what protects the cable between fuse board and spur?

Generally a 6 or 10A MCB.

Fatherodonnell

Ok so the mcb is good enough to protect the cable? So what do I need the fused spur for?

2011

Fatherodonnell wrote: »

Ok so the mcb is good enough to protect the cable?

Assuming the cable is a 1.5mm^2 a 6 or 10A type B MCB would provide suitable over current protection for the cable.

So what do I need the fused spur for?

A socket circuit in a domestic installation is generally fed from a 20A type B MCB. This would not provide adequate protection for a 1.5mm^2 or a 0.75mm^2 cable. If it was decided to feed this smaller cable size from a socket circuit then a spur outlet fed by a suitable sized cable could be installed. This spur would contain a fuse that would provide the correct protection for the smaller cable size.

If I were doing this I would wire a 1.5 cable from the distribution board and feed it from a 6 or 10A type B MCB. This cable would feed a spur outlet containing a 2 or 3A fuse mounted local to the panel. The spur would feed the alarm panel. Apart from being inline with good practice this spur provides local isolation for the intruder alarm and lowers the overload current required to disconnect power from the intruder alarm.

If you were to supply the panel with mains power through a coaxial cable it would probably work and most likely will not result in damage to property and / or serious injury, but most sane people would not be prepared to take the risk :):D

Fatherodonnell

Excellent advice thanks.

2011

Fatherodonnell wrote: »

Excellent advice thanks.

No bother

The idea is that you understand why an electrician is doing a job in a particular way, not that someone without the required training performs open heart surgery on a distribution board.

There are certain types of electrical work that can be carried out safely by a competent person, but in my opinion working on a distribution board is something that should only be done by a qualified electrician or a good apprentice under the supervision and guidance of an electrician.

Good luck with it.

Fatherodonnell

Ok I have been pondering this and have decided not to go near the distribution board as it is safer to work off the socket s and I noticed that my toaster has a plug with a 13 amp fuse yet the cable is only small, perhaps .5mm? Then I realised that in Germany they don't even have fuses in plugs at all so they are plugging in small flexes for toasters and stuff into sockets with no fuses to protect these small flexes and nobody worries at all.
So my question is why do I have to worry about wiring in a 0.75mm flex into a socket when there is no danger of overload as an alarm uses a tiny amount of power? If my connection is good and sound then what could possibly go wrong?
Another thing I can't get my head around is the need for a fused spur? The alarm has a 1 amp fuse already to protect it
and if I want to isolate the alarm I have it marked on the consumer unit so I can just turn off that switch and the alarm actually says mains fault out loud so what is the purpose of the fused spur?
I don't intend to be a smart arse just can't see the problem?

pdiddy

Why come on here looking for advice if your not going to take it.
I agree with all the above posters. The way it should be done right is a minimum 1.5mm cable from the board and a 6/10 amp mcb to a fused spur then from spur to the alarm panel.
If you still want to use the socket circuit then bring a 2.5mm cable from socket to spur and then your .75mm flex from spur to panel.
The spur allows for local isolation of power to panel.

2011

Fatherodonnell wrote: »

my toaster has a plug with a 13 amp fuse yet the cable is only small, perhaps .5mm?

There are a few things to consider:
1) The toaster is on for perhaps 3 minutes at a time. Then it is off for long periods allowing the cable to cool. The alarm is powered 24/7

2) A smaller fuse would be more appropriate for the toaster.

3) The alarm is a fixed appliance, the toaster is a portable appliance.

4) The advice you have been given is based on best practice.

in Germany they don't even have fuses in plugs at all so they are plugging in small flexes for toasters and stuff into sockets with no fuses to protect these small flexes and nobody worries at all.

....and in France they put sockets in bathrooms, and when carrying out a little electrical work in Haiti I noticed that they used no earths whatsoever.
However in Ireland it is best to comply with the Irish rules & regulations, ET101:2008

why do I have to worry about wiring in a 0.75mm flex into a socket when there is no danger of overload as an alarm

What is the basis for the belief that an overload is impossible ??

uses a tiny amount of power?

......only when functioning correctly.
Ever hear of an electronic device failing and overheating??

Fuses, MCBs, RCDs etc. serve no function when everything is functioning correctly. You could replace your entire distribution board with a junction box and most likely it would make no difference (unless something goes wrong).

Compare it to driving without a seatbelt.

Are you forgetting that mains voltage has the potential to be lethal?
Have you ever been at the scene of a fatal electrocution ? I have, it helps me understand why regulations should be followed.

Fatherodonnell

I didn't think the cable to the alarm could overheat if the alarm malfunctioned because the 1amp fuse in the alarm would blow first.
In Germany they could have a fridge plugged in for years to a socket with 0.75mm flex and no fuse, isn't that more or less the same thing as I just did.?

2011

Fatherodonnell wrote: »

I didn't think the cable to the alarm could overheat if the alarm malfunctioned because the 1amp fuse in the alarm would blow first.
In Germany they could have a fridge plugged in for years to a socket with 0.75mm flex and no fuse, isn't that more or less the same thing as I just did.?

Hi, I only have access to this with my iPhone right now. Will answer this post when I am home. In the meantime I would be interested in reading you answers to the questions that I asked in my last post.
Thanks.

Fatherodonnell

I appreciate your time 2011 and i do get that mains is dangerous but in this case I am trying to understand what could go wrong with this set up and can't see anything. Isn't the example of the German fridge more or less the same? A .75mm flex off a socket with no fuse to protect the flex apart from on the consumer unit?
Nothing bad can come back from the alarm panel because of the 1 amp fuse there?
Also even if I accept the need for 2.5mm cable what do I need the fused spur for if I can easily isolate the alarm at the consumer unit?

Risteard81

Fatherodonnell wrote: »

I noticed that my toaster has a plug with a 13 amp fuse yet the cable is only small, perhaps .5mm?

Probably 0.75mm^2.

The BS 1362 upon which it will have been based permits protection by a 13A fuse for a flex not exceeding 2m in length where it is fitted with a moulded plug.

Then I realised that in Germany they don't even have fuses in plugs at all so they are plugging in small flexes for toasters and stuff into sockets with no fuses to protect these small flexes and nobody worries at all.

They don't have ring final circuits though and therefore there has been no need for protection in plugs. ET101 does permit ring final circuits (although with stricter Rules than those of the BS 7671 Regulations).

So my question is why do I have to worry about wiring in a 0.75mm flex into a socket when there is no danger of overload as an alarm uses a tiny amount of power?

A fixed load which cannot by its nature cause an overload does not, as you suggest, require overload protection. However you MUST still ensure that fault protection is provided. And I would imagine that you are not able to prove this.

Of course, it should also be remembered that it is unlawful for anyone other than a Registered Electrical Contractor (REC) to carry out electrical installation work in a domestic premises with the exception of Minor Works.

Fatherodonnell

Would wiring the alarm into the socket be classed as minor works?
What fault scenarios could occur?

Fatherodonnell

Risteard81 wrote: »

Probably 0.75mm^2.

The BS 1362 upon which it will have been based permits protection by a 13A fuse for a flex not exceeding 2m in length where it is fitted with a moulded plug

.

On this point would it be ok then if an electrician wired a .75mm cable into the consumer unit to a light circuit on a 10amp fuse if the flex is less than 2m distance to the alarm panel?.

frankxxxx

Fatherodonnell wrote: »

On this point would it be ok then if an electrician wired a .75mm cable into the consumer unit to a light circuit on a 10amp fuse if the flex is less than 2m distance to the alarm panel?.

no
the minimum size of the installation 'fixed wiring' permissible is 1.5mm

the 0.75mm flex on 13amp appliances is a different matter

Par1

Fatherodonnell wrote: »

I appreciate your time 2011 and i do get that mains is dangerous but in this case I am trying to understand what could go wrong with this set up and can't see anything. Isn't the example of the German fridge more or less the same? A .75mm flex off a socket with no fuse to protect the flex apart from on the consumer unit?
Nothing bad can come back from the alarm panel because of the 1 amp fuse there?
Also even if I accept the need for 2.5mm cable what do I need the fused spur for if I can easily isolate the alarm at the consumer unit?

I see where you are coming from with the example of the 'German Fridge'. Unfortunately we do not live in Germany so we abide by the ETCI rules here in Ireland. You have not considered fuse discrimination, PSCC, adverse/unforseen faults (i.e fuse failure) or the fact that the flex has to be fused (up and downstream). If we were to take bits of rules from other countries and apply them to our electrical installations then our industry would be very dangerous and in my opinion more hazards and accidents would occur. If you originally posted the question as a hypothetical question then yes the alarm panel will work but would not be considered the done thing here in Ireland (as 2011 previously posted). Therefore if you want to consider your installation Safe under ETCI rules then the answer is to wire the alarm panel on its own circuit and fit a fused spur local for isolation (preferred way).

Im no expert in the alarm industry but i should imagine it is good practice to fit a fused spur for isolation/safety beside the panel, failing that then maybe a dedicated MCB which is clearly identified.

If we were to take the approach of doing the minimum needed to make appliances work and not consider safety then lets take an example of a particular eastern European country (without naming any names) that uses a principal to power appliances/tools (in industrial applications) where they string a bare conductor from front to back of installation then 'Hook' on cables where needed and not fuse them

Im not being smart but unless you follow some sort of rules/regulations then morons will just be morons and do silly things - its taken long enough to get electrical safety in Ireland to where it is today and a lot of people have been severely hurt or in some cases have died so lets abide by the rules as they are only here to make things safe.

I appreciate you are only asking questions but when given advice by several people on how best to do things then its probably better to take that advice and consider it rather than questioning it and replying to regulations with regulations that have no relevance in the first place......just my opinion though

Fatherodonnell

frankxxxx wrote: »

no
the minimum size of the installation 'fixed wiring' permissible is 1.5mm

the 0.75mm flex on 13amp appliances is a different matter

Ok thanks you are saying that a a regulation?
I don't get it though as it looks like 1 regulation says it's ok to protect a .75 flex with a 13amp fuse while another says it's not ok to use a .75 flex off a 10 amp fuse

frankxxxx

Fatherodonnell wrote: »

Ok thanks you are saying that a a regulation?
I don't get it though as it looks like 1 regulation says it's ok to protect a .75 flex with a 13amp fuse while another says it's not ok to use a .75 flex off a 10 amp fuse

fixed wiring minimum size is 1.5mm here..pretty sure it's in et101:2008 somewhere

0.75 flex connected to a portable appliance is different

2011

Fatherodonnell wrote: »

I am trying to understand what could go wrong with this set up and can't see anything.

I assume that you mean why can't a 0.75mm^2 flex be connected directly to a socket circuit?

In a domestic installation the cables that make up a socket circuit are generally 2.5 T & E and these are generally protected by a 20A type B MCB. This arrangement is inline with the rules, ET101:2008. As explained above the 20A MCB is unable to provide the 0.75mm^2 flex the protection that it requires to comply with these rules. One solution is to use a spur outlet in the manner described in my earlier posts.

Isn't the example of the German fridge more or less the same? A .75mm flex off a socket with no fuse to protect the flex apart from on the consumer unit?

The Germans have their own rules, they are not trying to comply with ours. Although the same laws of physics apply they same regulations don't.

Nothing bad can come back from the alarm panel because of the 1 amp fuse there?

What about local isolation?

What about the next person that replaces the alarm panel with a different fixed appliance that does not have an internal fuse?

Also even if I accept the need for 2.5mm cable

If you don't then why shouldn't we all wire circuits in undersized cables and save a fortune?

If nothing ever failed we wouldn't need fire alarm systems, fuses, MCBs, RCBOs, seat belts, airbags etc......

what do I need the fused spur for if I can easily isolate the alarm at the consumer unit?

In the real world this type of thinking causes accidents.
If local isolation is provided for a fixed appliance then a person working on it can isolate the unit and remove the cover knowing that the none of the internals are live. They could also do this at the distribution board, but there is a danger that someone will switch the power back on (yes this happens). There is also the danger that the wrong MCB is switched off (e.g. incorrectly marked). My advice is inline with best practice.

Local isolation points are important.
In Ireland local isolation is provided for the following fixed appliances:
Shower
Cooker
Boiler
Storage heater
Bathroom fan

All of the above could be isolated at the distribution board as well.
Why do you think local isolation is provided for the above?

The additional materials that are required to do it the way I have suggested would leave change from €5. Why on earth are you so determined to cut corners?
Assuming the electrical installation is wired properly (complies with ET101), why is there such a desire to make the installation noncompliant?

Fatherodonnell

Ok thanks for your response and I fully accept that the setup is non compliant, however I am not convinced that things are dangerous as they stand in this instance.
I take your point about local isolation but in this case the consumer unit is just above the alarm panel.
Because of the compliance issue I think I will follow your advice and get some 2.5 cable and a fused spur with a 3 amp fuse.
Thanks again