Do you have to start every comment with...The regs are not statutory......They will be used in court if anything goes wrong
mixed cables in conduit
- Thread starter john4703
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Telephone cable can and do pick up interference quite easily.
Mains hum on the phone line etc.
To recall something similar from a year+ ago, I installed a large 240v pump that had an on/off signal going to it also.
Both cables were unscreened.
The pump control board was damaged because an induced voltage got onto the on/off signal line that was supposed to be no more then 24v - it was measured at about 90v.
Cost my employer about £2.5k for a new pump and we changed to screened cable.
Yet other instances of exactly the same install had worked OK (as far as we know).
IF you can try and prevent interference getting onto the phone line then it is best advised to do so as best you can.
Using a screened cable, (ensuring the screen is earthed at one end only) then do so.
OP - Try it, put a cable in the same trunk as the mains cable - if it works OK then good, if not and you get humming on the line then whip it out and go for something else.
Mains hum on the phone line etc.
To recall something similar from a year+ ago, I installed a large 240v pump that had an on/off signal going to it also.
Both cables were unscreened.
The pump control board was damaged because an induced voltage got onto the on/off signal line that was supposed to be no more then 24v - it was measured at about 90v.
Cost my employer about £2.5k for a new pump and we changed to screened cable.
Yet other instances of exactly the same install had worked OK (as far as we know).
IF you can try and prevent interference getting onto the phone line then it is best advised to do so as best you can.
Using a screened cable, (ensuring the screen is earthed at one end only) then do so.
OP - Try it, put a cable in the same trunk as the mains cable - if it works OK then good, if not and you get humming on the line then whip it out and go for something else.
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Indeed. As I said back in post #6 (currently of 64/65) on Page 1 (of 5) ...
Kind Regards, John
It seems the only problem might be a hum on the phone caused by induction currents.
I’ve run it on the surface for now, with a nice big loop of cable stapled to the skirting behind furniture so I can try the suck it and see approach (thanks John W) by running it in the buried conduit when I get some spare time. (Time kind of disappeared as it took me a couple of hours to find my spare phone that I keep in case the cordless one goes wrong, the good thing is that I now have a tidy cupboard and a load of junk in my wheelie bin.)
I’ve not heard from the alarm installers, so I don’t expect them to be here this year.
My assessment of this thread is that I’m sorry, I did not want to cause a massive argument. I expected two or three replies not five pages, but I do enjoy the discussions.
I did ask the same question on phones and alarms as I wondered if I’d posted it in the wrong forum. I always check this forum but seldom look at the others.
Merry Christmas to everyone who took the time to reply. I do appreciate your interest.
I’ve run it on the surface for now, with a nice big loop of cable stapled to the skirting behind furniture so I can try the suck it and see approach (thanks John W) by running it in the buried conduit when I get some spare time. (Time kind of disappeared as it took me a couple of hours to find my spare phone that I keep in case the cordless one goes wrong, the good thing is that I now have a tidy cupboard and a load of junk in my wheelie bin.)
I’ve not heard from the alarm installers, so I don’t expect them to be here this year.
My assessment of this thread is that I’m sorry, I did not want to cause a massive argument. I expected two or three replies not five pages, but I do enjoy the discussions.
I did ask the same question on phones and alarms as I wondered if I’d posted it in the wrong forum. I always check this forum but seldom look at the others.
Merry Christmas to everyone who took the time to reply. I do appreciate your interest.
You might also be surprised to learn that the BS 7671 isn’t a legal document in itself. It does, however, contain the guidelines and processes by which all electrical installations must adhere in order to comply with the legal requirements of the Electricity at Work Regulations. Therefore, it is treated in a similar way and is widely recognised in the industry as an authority
In itself, there is no legal requirement to comply with the requirements of BS 7671, however, much legislation including the Electricity, Safety, Quality and Continuity Regulations 2002 and Part P of the Building Regulations 2010 refers to BS 7671 as the standard to be achieved. Contractually, BS 7671 may be referenced as the standard to be complied with. Where this is the case, common law will apply.
The Health and Safety Executive offers the following guidance in their publication HSR25:
“BS 7671 is a code of practice which is widely recognised and accepted in the UK and compliance with it is likely to achieve compliance with relevant aspects of the Electricity at Work Regulations 1989”.
The Statutory Instrument to which we must adhere is the Electricity at Work Regulations 1989, made under Section 15 of the Health and Safety at Work Etc. Act 1974. This falls under the remit of criminal law and is enforced by a number of agencies, including the Health and Safety Executive (HSE) and Local Authorities.
The HSE caution that, with regards to BS 7671, ‘it is likely to achieve compliance with relevant aspects’. This caution should not be taken lightly, and it is important to recognise a number of relevant factors:
- BS 7671 only applies to Low Voltage and Extra Low Voltage electrical installations. The standard does not include the electrical installations associated with machinery (BS EN 60204), lift installations or high voltage systems: however, the requirements of the Electricity at Work Regulations 1989 includes all of these aspects;
- Electrical installations that do not meet the requirements of the current version of BS 7671, but comply with previous versions of BS 7671 or the IEE Wiring Regulations might still comply with the Electricity at Work Regulations 1989;
- BS 7671 focuses on design, construction, inspection and testing of electrical installations, however, it does not focus in any detail on the competencies of individuals undertaking the work (other than recognising the roles of skilled, instructed and ordinary persons), nor does it give detail on maintenance activities or standard operating practices to ensure that safe systems of work are followed;
- There are numerous examples of situations where BS 7671 does not apply, or is not relevant, and more specific standards should be followed.
..and the defence in court, when charged with the manslaughter of an Openreach engineer, who was killed when fell off a pole when he suddenly received a mains shock when working on what was supposed to be ELV telephone line - except someone had decided it was fine to ignore The Regs on segregation is???
It always rather saddens me when I see common sense going out of the window.
My view and comments do not relate to what a Court might decide, and on what basis, in a hypothetical situation but, rather that "it simply won't happen' (in terms of common sense).
If telephone conductors were to become 'live' (at mains potential), it would be far more likely to be due to a fault in some connected piece of equipment (cordless phone base, answering machine, computer, alarm, Sky box or whatever) than due to conductors in two insulated+sheathed cables coming into contact.
If the 'risk' which concerns you were something worth considering, then Heaven forbid that any telephone engine should ever touch a mains-carrying cable in a customer's home, since there would then only be half as many layers of insulation between him/her and the 230V.
Kind Regards, John
John, it is not a matter of how you assess the risk, the risks have already been assessed and The Regs require proper barriers and segregation between the two services. The OP is/was considering pulling in additional an additional cable into a conduit which already has cables in it. As you will no doubt be aware, one plastic cable pulled in where there are existing cables, unless extreme care is taken, the new cable can very easily friction burn the existing cables. So there is your first error, how many more slight errors have to occur before someone gets killed or injured?
The Regulation is there for a very good reason.
I have made my personal view very clear, and have nothing more to add.
Kind Regards, John
I missed that bit.
Maybe I'm wrong, but I strongly suspect that your view would be the same even if the cables were all pulled in together, wouldn't they?
Furthermore, I also strongly suspect that your view would be the same if the two cables were 'placed into' the same trunking/whatever, with no 'pulling through' involved, wouldn't it?
Kind Regards, John
Yes and yes. The Regulation stipulates segregation. You can buy trunking which includes the essential segregation.
I was only pointing out a likely point of failure, when installing the phone cable.
That's what I thought - so your comment about "... the new cable can very easily friction burn the existing cables" was actually a 'red herring'.
Kind Regards, John
Hardly, as you should now, it happens and much more likely if a DIY'er were trying to add cables.
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