joneh
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| posted on 28/6/06 at 04:16 PM |
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Any electricians here?
Completley off topic but, is there a qualified electrician here?
I need to earth a metal case (telephone switching box). Can I LEGALLY strap it to a water / radiator pipe, or do I have to drill through and bury an
earth rod outside? This is for a commercial install and its the first time I've done one. I need to know where I stand on this legally. I
guess as its only an earth and the main unit has a pre moulded plug I don't need a qualfied sparky on site?
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scottc
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| posted on 28/6/06 at 04:21 PM |
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Having installed Alcatel Omni's, I normally just run the earth to the rack.
Thinking about it now, not sure it's the best way to do it, but thats what I was told.
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joneh
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| posted on 28/6/06 at 04:37 PM |
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I don't have a rack, its just a wall mounted pabx 
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Krismc
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| posted on 28/6/06 at 04:52 PM |
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im a sparky but couldnt tell you if just connecting to water pipe is ok, i would never do it as we have brilliant earth straps put in for us- ready!!
but the water pipe is earthed and i cant see a problem with it!
post up on the 16th edition site!
Built, Ivaed, Drove and now Sold - 2011 MNR VORTX RT+ 2000cc Zetec on R1 Throttle boddies.
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omega 24 v6
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| posted on 28/6/06 at 04:57 PM |
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If its got a moulded plug ( I presume you mean mains supply ) and it's already in the metal case I would expect it to already be earthed
internally. Check with a meter between the earth pin on the plug and and the body of the case for continuity. If the cable is not a mains supply (
comms) then I would think it preferable to run a seperate earth wire back to the mains box on the premises
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JoelP
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| posted on 28/6/06 at 05:04 PM |
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you cant earth onto water pipes legally, the water pipes themselves (in a domestic installation at least) need 10mm earthing. As omega says, just
earth it via the supply if possible. My mate did that recently with a kitchen extractor, which for some reason came with no earth.
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Avoneer
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| posted on 28/6/06 at 05:05 PM |
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Connecting to pipes if for equipotential bonding only - not for earthing.
What Class is the box I or II ?
If it has a plug and lead, it will probably be already earthed internally will it not?
Unless I'm completely wrong...
Pat...
No trees were killed in the sending of this message.
However a large number of electrons were terribly inconvenienced.
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quinnj3
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| posted on 28/6/06 at 05:33 PM |
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what avoneer says. You don't need to use any extra earthing if the unit comes with a plug top already attached. It will be earthed internally.
my aim is to build my own locost wether it takes me a week or 10 years to get started, i'm sure i will sometime
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joneh
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| posted on 28/6/06 at 05:34 PM |
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It is earthed internally, according to Panasonic this may not be enough in the event of a lightning strike, so the metal case also needs to be
earthed. See page 31 of pdf file here:
http://www.tibit.co.uk/temp/PA308_Installation_Manual.pdf
Cheers guys,
Jon
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Avoneer
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| posted on 28/6/06 at 06:01 PM |
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Definately don't link it to the pipes then if it could be hit by lightning!
Is it going outside?
Pat...
No trees were killed in the sending of this message.
However a large number of electrons were terribly inconvenienced.
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joneh
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| posted on 28/6/06 at 06:14 PM |
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Indoors.
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omega 24 v6
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| posted on 28/6/06 at 06:34 PM |
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In the event of a lightning strike nothing you earth it to or through will make a difference it'll all be cooked
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joneh
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| posted on 28/6/06 at 07:02 PM |
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Thats true. And I dont see how it'll help if you're touching it either - as you'd still get fried!
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wilkingj
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| posted on 28/6/06 at 07:39 PM |
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I would run the earth back to the Main Earthing Point where the mains / Eleccy boards earth comes into the building.
1. You cannot guarantee that anywhere else you pick up an earth will be there next week, ie a water pipe can be cut and pieced out with a bit of
plastic pipe.
2. Any leccy earth point can also be cut or removed elsewhere.
3. The manual mentions Noise, so you will want a good clean earth. IMHO that means the Main Incoming Earth point.
I think you will find there are regulations covering this, Certainly the IEE regs, and probably some comms regs as well.
Where were you trained ?? If you dont know what you are doing with electrical installations then you shouldnt be doing it.
Sorry to be blunt, but people can be injured or even killed through half baked electrical installations. I know, I nearly lost a colleague through a
faulty phone system that was incorrectly installed.
Its your responsibility for a safe and correct installation.
After all YOU are the one that will sign off the installation as being correct and safe when you hand it over to your customer.
What ever you do PLEASE GET IT 100% CORRECT.
PS.. Above is MY OPINION. Please do not take this as being correct as I am possibly wrong as well. You need to consult the Manuals and Regulations
covering such installations or a Qualified Technician / Electrician.
Taking advice fom possibly unqualified people on the forum (NO Offence intended to anyone), however well meaning, could leave you exposed to legal
action from your customer, or the authorities if it all goes pear shaped and someone is subsequently injured as a result of your installation work.
Again... NO Offence intended towards anyone, but this could have serious implications if it all went wrong.
1. The point of a journey is not to arrive.
2. Never take life seriously. Nobody gets out alive anyway.
Best Regards
Geoff
http://www.v8viento.co.uk
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omega 24 v6
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| posted on 28/6/06 at 07:58 PM |
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I agree with the other post that if you are not sure then you must clarify the situation before proceding. Having looked at the PDF item 2.25
regarding earthing there is no way on god's earth that a 0.75 wire will conduct a lightning strike safely However it does say to connect
it to the main unit (does this mean the incomer earth at the mains board??? or is it an extension of an already installed phone system).
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DIY Si
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| posted on 28/6/06 at 08:16 PM |
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I install mains meters and I can say that not all earths that you use/see are good. Have a look at the main meter position and if it says pme the
earth should be good. If not, it will be a seperate wire from either the sub station or a seperate earth rod on the property. Even so, do not
implicety trust this. I have been to many houses where due to earth faults, the earth is actually live by a good few volts. Even so, lightning stricks
will vaporise any wire less than the thickness of at least your leg! So, is it really worth worrying about for such a situation?
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joneh
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| posted on 28/6/06 at 08:20 PM |
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I think its just panasonic covering their arse. As you say any cable that thin will just melt at that sort of ampage. I'm not doing any
electrical installations, its just an internal telephone system, with a moulded plug.
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mark chandler
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| posted on 28/6/06 at 08:32 PM |
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Having worked for BT years ago as both a fitter and maintainer of PBX's you need to ensure that the earth uses the same source as the plugs
earth.
Simply strapping to the local radiator is not good enough, if this is not properly bonded in the building you could have different potentials between
the two earth sources, not a good thing.
By the book you should have a seperate earth wire back to the consumer unit, in reality provided the ring carries an earth then tee into the
green/yellow in the rear of the plug socket. We were not allowed to do this in BT as we were not allowed to unscrew the socket.
I believe you need the hard wired earth incase someone crushes cables together introducing mains to the various phones. This is why using the plug is
not okay, what if someone unplugged the system ?
Regards Mark
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omega 24 v6
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| posted on 28/6/06 at 08:34 PM |
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IMO I'd plug it in and leave it. If there is background noise or interference then you might have too look for a clead earth.
All IMHO only.
Sorry I meant clean earth (bloody hayfever)
[Edited on 28/6/06 by omega 24 v6]
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omega 24 v6
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| posted on 28/6/06 at 08:37 PM |
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quote:
This is why using the plug is not okay, what if someone unplugged the system ?
A very very good point. And along the same lines why does a puter not have the same setup??????????????????
[Edited on 28/6/06 by omega 24 v6]
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tony9876
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| posted on 28/6/06 at 08:53 PM |
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I am an electrical engineer and these boxes require a clean earth from the point of supply i.e main earth terminal.
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joneh
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| posted on 28/6/06 at 09:29 PM |
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OK. Its a new build so I wouldn't have thought they'd earth each of the sockets seperatley. Are there any laws governing unscrewing a
plug socket and checking? I have done this sort of work many times before around the home but I don't know if you need to be qualified to do
such a thing commercialy as you're not modifying or adding anything.
For safety reasons adding an earth rod would be the easiest solution, but this won't help for nosie, correct? With regards to lightning
striking the phone wires, wont a surge protecter act as a cut off instead?
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JoelP
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| posted on 28/6/06 at 10:39 PM |
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you can open sockets no probs, in fact you might even be able to repair some sockets in certain areas (dont quote me on that).
If its a new domestic build there will be test certificates available, and the installation should be perfectly to the regs. Ie, you will have an
adequate earth in the socket ring.
I believe you can add to the earthing arrangements without qualification. If it needs a seperate earth like tony says then the sockets wont provide
this, and you will need to add one.
[Edited on 28/6/06 by JoelP]
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