Installing underground Cat5e cable

[YorkshireTechie]

Hi all,

 

i have been asked about connecting a nursery classroom to the network at a primary School i work at, the building is roughly 25 - 30 feet away from the main school. it is currently connected through wireless but has a poor signal and tends to not work very well.

 

it now seems that the fire alarm is to be upgraded on the building and there will be a trench dug up to install new wiring, i was quickly told by the Head on Friday to think about throwing:D a Cat5e cable in so we could connect them up.

 

i was thinking of running External grade Cat5e inside some Polypropylene Conduit as the cheapest option, does anyone know if there is any other factors i should think about?

 

not sure if there are any earth potential risks (lightening strikes) or fire risks, any advice would be much appreciated.

 

Cheers

[FN-GM]

Yep bit of cat 5e in plastic piping should do the trick. Nice and cheap there is no need for fibre as it’s so close. You can get armoured cat 5e cable you should consider that.

 

I am tempted to say get cat 6 so your feature proofed, it won’t be as easy to upgrade it underground.

[SimpleSi]

Remember to run at least 2 cables so if one fails you still stand a chance

 

regards

 

Simon

[FN-GM]

Remember to run at least 2 cables so if one fails you still stand a chance

 

regards

 

Simon

 

Very good point

[beeswax]

I worked at a place which had the cable slung from roof to roof, which was fine until you had a couple of hot days an the cable stretched and sagged some. Wagon deliveries had to be handled very carefully so they didn't bring down the cable.

[Guest Guest]

You could also run some string through so that should you want to put any more cables through you have something to pull them through with.

[localzuk]

Personally, I'd either install OM3 fibre or some cat6 cable rather than cat5e. Future proofing and all that. And at that length, an install shouldn't cost a lot either.

[maniac]

If they do it properly then the ducting they install for the firealarm should be bigger than needed diameter, both ends should be accessible, and there should be a pull cord left in place so any contractors or yourself can put in more cables in the future, save digging up the ground all over again.

 

I would use as a minimum a good quality external grade cat5 cable, or if finances allow use armoured cat5 cable as mentioned above. If installed properly the outer 'armour' can be (and should be) earthed, which can cut down on possible interference from any other cables that might share the ducting either now or in the future. The only problem with the armoured cable is it is expensive, but in the long term it is worth it, as the last thing you want to have to do is change it because it's been severed at some point along its route. Also as said above, run two or preferably more cables while you have the opportunity.

 

Mike

[scottyses]

The only problem is earth leakage between building you will need to get your sparkies opinion!

[Lurch]

If they do it properly then the ducting they install for the firealarm should be bigger than needed diameter, both ends should be accessible, and there should be a pull cord left in place so any contractors or yourself can put in more cables in the future, save digging up the ground all over again.

 

I'd be highly annoyed if someone did that to a fire alarm link I'd just installed for several reasons, possibly including but not limited to - alterations to the calculated spacing factors of the containment, damage to the fire alarm cables and segregation of cables. Easiest way is to drop a seperate duct in the trench solely for data cabling between the buildings, saves future buck passing and is actually future proof as cat6 or fibre isn;t really future proof as such, just a bit less non-future proof than cat5e.

 

I would use as a minimum a good quality external grade cat5 cable, or if finances allow use armoured cat5 cable as mentioned above. If installed properly the outer 'armour' can be (and should be) earthed, which can cut down on possible interference from any other cables that might share the ducting either now or in the future. The only problem with the armoured cable is it is expensive, but in the long term it is worth it, as the last thing you want to have to do is change it because it's been severed at some point along its route. Also as said above, run two or preferably more cables while you have the opportunity.

 

As mentioned previously, before connecting earths together between buildings have a word with the electricians looking after the site as exporting earths via the armouring of a cat5 cable can be very dangerous if done incorrectly and can make things worse. There are correct ways to earth armourings.

[YorkshireTechie]

Many Thanks all,

 

some really good points in there, giving me a lot to think about. Looks like ive got some cables to price up.

 

Cheers for your all input.

[dhicks]

I was quickly told by the Head on Friday to think about throwing:D a Cat5e cable in so we could connect them up.

 

I'm no expert on this myself, but for our new building (also having a cable for fire alarms connected to it, like yours) we're having fibre installed - just a length of pre-terminated cable, costs around £200 for 75M (I think), and that was for 8 strands. Admittedly you'll need switches at either end capable of taking fibre links, but heck, you'll need switches of some kind anyway, and fibre capability doesn't add much these days (our 24-port, gigabit, fibre-capable switches were £300). You'll also need GBIC modules for the fibre connections and (seemingly) a fibre patch panel (around £20-ish, if I remember).

 

--

David Hicks

[FN-GM]

This kind of situation myself I would keep it as simple as possible.

[torledo]

This kind of situation myself I would keep it as simple as possible.

 

yes, but theres no such thing as simple when you advocate copper inter-building in order to save costs....as someone else has said when you start using any kind of shielded or armoured cat5e/cat6 cable you need to make sure you maintain equipotential between buildings, i believe that both the buildings inspector and fire inspector will have something to say about an installation that could a) be a potential fire risk b) not meet the required standards for bonding of telecommunications equipment.

 

using flexible conduit and suitable rated cable for the task is fine, but it doesn't protect against lightning strike and what an installer will need to avoid is a ground loop.

 

much easier and better ROI if TS were to go with fibre....once you start talking about using armoured cable, the cost difference between that and pre-terminated fibres isn't a great deal. Plus fibre means you don't have to worry about transient voltage and you've got plenty of capacity for future expansion.

 

it's a no-brainer.

[broc]

I agree with torledo, if you do the job professionally (rather than just string a length of CAT5E in ordinary polythene conduit) then the cost differences between fibre & copper are less than you might imagine.

 

We linked to our sports hall via fibre a few years ago, having looked at wireless point-to-point, copper cable & fibre. It also had the advantage we gained spare bandwidth & were able to use the sports hall as an 'offsite' DR location for backups. When we installed long-term temporary classrooms last year we installed fibre there too while they were digging a trench for power/alarm systems.

[ahuxham]

Run 2 x Cat5E cables,

And 3-4 pieces of sturdy string/wire as well, so if you ever do get Optics in there, or need anything else, you can just pull it through,

[Andrew_C]

Fibre all the way. Your sparks WILL be concerned about a copper connection between buildings, or rather they should be...

[Geoff]

Also be aware that electrically connecting two buildings like that may be a breach of your local building codes.

[jcollings]

I agree with what others have said - stick some fibre in and be done. It's the right way to do the job.

[fafster]

In my last job, a school had a cat5 cable suspended between two buildings, naked to the elements. As far as I'm aware, it's been working without issue for quite a few years.

 

Don't worry too much about insulating the cables using armoured CAT5. There's a reason why the wires are twisted

[localzuk]

In my last job, a school had a cat5 cable suspended between two buildings, naked to the elements. As far as I'm aware, it's been working without issue for quite a few years.

 

Don't worry too much about insulating the cables using armoured CAT5. There's a reason why the wires are twisted

 

That is terrible advice! The twisted nature of the cable is there to prevent crosstalk between the individual wires inside the cable. *Not* to protect against external interference!

 

Also, running a cable between 2 buildings, naked to the elements, is simply dangerous. If it is not grounded etc... then it is a lightning strike risk and as such you could lose equipment due to it, or even cause serious injury to someone should they be touching the equipment at the time!

[Geoff]

then it is a lightning strike risk and as such you could lose equipment due to it, or even cause serious injury to someone should they be touching the equipment at the time!

 

This risk also exists with buried cable unless it is deeper than 18 inches/3 feet.

[localzuk]

This risk also exists with buried cable unless it is deeper than 18 inches/3 feet.

 

which is it? 18 inches or 3 feet?

[Geoff]

which is it? 18 inches or 3 feet?

 

Yes.

[imiddleton25]

We have done this in a few buildings

we put in a 4" drain pipe with Cat5 E cable , Fibre and most importantly a draw rope to pull in more cables. One important thing is Fire regulations we had a fall out with fire officer on this as cable entry points are a possible route for fire to enterr bulidings. We used low smoke cable but each end of the pipe had to have a fire proof gromit fitted. Fibre is now cheaper than copper wire as price off copper gone through the roof recently.