Any interference from burying different cable types together?

summereire

Hi, are there any interference issues with running different cables in the same piece of buried pipe: I'm thinking either coaxial or cat 5 cables to cctv alongside regular mains electric cables and telephone/broadband wire. If there were to be issues I'd bury more than one pipe at this stage but rather avoid that if possible.

2011

Generally there will not be interference, but there is more to consider:

1) Interference would be proportional to the current flowing in the mains cable.
2) Best practice would be to run the cables in separate pipes.
3) This is against wiring regulations (National Rules for Electrical Installations, section 528). There are aways around this, but it just isn't worth it.

summereire

Great thanks. I presume another approach is to have one piece of wavin pipe but separate smaller pipes within it? Just want what I bury to work as efficiently as possible. The power cable in question is to power lamp posts. Btw are water pipes normally run in piping at all or just buried alongside?

Stoner

Having the power cable as swa will help, the armoured core if earthed can be considered a shield. The coax would be shielded already the data cable might be an issue but it depends on the length of the run.

summereire

Thanks. It will be up to 200 metres- and we're just deciding on coaxial or cat 5.

Stoner

200 M is a long run. Keeping them separated would be a necessary precaution imo. Is the power cable single phase 230V

Bruthal

Once it's an swa with properly earthed armour, it will be OK I'd say.

If you ever test with non contact testers, they detect nothing through swa cables.

summereire

Yes single phase 230v. I presume the armoured cable would be a cheaper option to running separate pipings? Everything you're suggesting is this just for electrical safety/best practice or is also likely there would be some interference to to coaxial, cat 5 or telephone wires if not seperated?

Stoner

Well couple of things it would most likely have to be swa anyway. The at 200M the data cable would fail the 90m max requirements for cat5/6 cables anyway.
It's need for interference protection against electromagnetic interference.

Being a single phase supply below 20 amps will help.
The armour of the swa would be necessary as will the extra mechanical protection from a duct for that type of cable installation from a regulations and safety perspective

2011

summereire wrote: »

is also likely there would be some interference to to coaxial, cat 5 or telephone wires if not seperated?

As per my earlier post the interference is a function of the magnitude of the current flowing in the mains cable. In other words, the higher the current the more interference.

As others have said, using a screened mains cable such as a SWA will help mitigate this issue. It is also possible to buy screened CAT5 and co-axe cables with additional screens / armour.

summereire

Ok so an armoured 1 phase 230v cable, and maybe I'd need cat 6 because of the distance possibly shielded? And the phone cable in there should that be ok?

2011

If I were doing this I would use one duct for power using an SWA and a separate for comms / CCTV. In fact I would rather direct bury the SWA than have it installed close to the other cables. This would also make it easier to pull the cables in.

As Stoner has stated 200m exceeds the maximum distance for CAT5 and for CAT6.


On another note, modern CCTV cameras tend to use CAT5/CAT6 not co-axe.

summereire

Yeah I'm trying to decide between analogue and IP cameras, may go for the IP to future proof things. I though cat 5, or at least cat 6 could deal with that kind of distance- on large sites isn't this kind of distancing quite common?

So realistically should I just dig a suitable wide trench and run three separating ducts; one for the electrics, one for cat 5/6 and telephone, and another for hydrodare mains water?

Stoner

That's sounds good. Using Cat6 does not mean the cable can be longer.

A cat 6 test and cat 5 test would both fail at 200 M for identical reasons.

summereire

Ok grand- appreciate the advice, I'll go with that. Re the cat 5/cat 6- what's normally done then, booster en route? Clearly people wire substantially greater distance with that for CCTV.

Stoner

summereire wrote:

Ok grand- appreciate the advice, I'll go with that. Re the cat 5/cat 6- what's normally done then, booster en route? Clearly people wire substantially greater distance with that for CCTV.

Yes the UTP properties for this cable seem to be good. Note there are signal and power concerns with these cameras, in many cases local power is required at the camera as power and signal combined over the one cable (POE) is limited to about 60M.
Maybe open a thread on the home security forum to discuss the camera you intend to use to see if you are on the right path.