Jump to content

Cat5/6 with SWA underground


Recommended Posts

 

We've got to run a Cat5/6 and a phone cable from the house to the gates - a distance of about 27m.

 

The cables will terminate at the gate controls which is next to the new supply point and meter. 

 

Sparky is suggesting that for a 27m run we should be using 16mm 2 core armoured with a 16mm CPC in the same duct, earthing the SWA as a secondary bond ( @ProDave, @Onoff, @Steptoe Comments welcome...)

 

Now if it was me, I reckon that the EMF of that suitably earthed SWA would be the square root of bugger all, and chucking a pair of CAT cables (one PoE) down the same duct would be fine .... 

 

But is it ..???

 

I can find various rules on separation in the street, and recommendations as to what to do but not a definitive statement 

 

My other option (preferred at the moment) is to bury the CAT cable in some 20mm conduit laid in the same trench but to one side and be done with it. At 100mm apart there should be no issue at all and I can at least get to replace it if needed. 

 

Thoughts..?? 

Link to comment
Share on other sites

Its not a problem with the emf, its more an issue with the cat5/6 not being rated at 230v, 

So really needs its own duct,

If you are running 2 cat6 with bends it might be a lot easier using 25mm conduit, and sweeping bends, cat6 doesn't like elbows. 

Why the separate cpc,? The armour of 16mm is plenty big enough, or, if you must, use 3core, but there's really no need, unless there is some other reason, 

Link to comment
Share on other sites

Cat5 and phone in separate duct at least 300mm apart.  In practice, you will be digging at least a 300mm wide trench so one each side before you back fill. SWA does not need a duct, use 3 core and then you have an earth core as well as the armour, and buy it from the right place and it's the correct colours. But personally I am just using the armour.

 

You will need an 80A switch fuse to feed a 16mm SWA and check your max load and volt drop to check 16mm is okay. (mine is okay at 25 metres)
 

Link to comment
Share on other sites

Thanks both - I had considered uprating to 25mm SWA but then looked at the incomer from the road and that appeared to be 16mm..!

 

@ProDave already got the 100A switch in place. 

 

Interesting on the 300mm separation - found anywhere from 50mm (MoD document) to 450mm depending on where I read so that sort of answered the question. 

 

Will also look at putting the water at 750mm in the same trench and backfilling just the once ...! 

Link to comment
Share on other sites

By preference I prefer using 3 core SWA, but have installed one run of 1.5mm two core where I've used the armour as the earth conductor.  If you do use 3 core you still have to bond the armour banjo/piranha to the internal earth conductor, so it is a bit "belt and braces".  The equivalent copper cross sectional area of the steel armour is usually greater than the core CSA for most domestic size range SWA cables, so using the armour is overkill in terms of conductivity. 

 

My preference for using 3 core, with the right colour codes, is that you have a continuous earth conductor, that doesn't have any joints, whereas with two core using the armour the integrity of the armour-to-gland connection is critical, long-term.  Having witnessed a supposedly competent and ticket-holding electrician leave off the collet ring on an IP66 gland, and then tell me when I pointed it out (I was walking by and saw the brass ring sitting on the ground next to the "finished" termination) that "oh, those aren't really needed, the nut will do the job", together with poorly fitted banjos (pretty common to have them fitted in the wrong place), I've never been that comfortable with using two core.  Having said that, piranha nuts have eliminated the banjo issue and made it easy to make a reliable earth connection to the gland, so as long as the steel is properly secured there's no reason to think there should be a problem.

Link to comment
Share on other sites

Your incomer may look small, but it will be a concentric cable and will be 25mm or even 35mm.

 

Put an 80A fuse in your switch fuse, or even 60A if your max demand is low enough to discriminate between the Dno's 100A fuse (and 100A is beyond the rating of 16mm SWA)
 

Link to comment
Share on other sites

Sorry, a bit lost tbh.....the 16mm2.....is that the proposed supply cable to the house? And you want to run the data and phone in the same duct?

 

In the same "wiring system" each cable needs to be insulated for the highest voltage present. Or you install the cables in separate compartments like trunking. Or you separate with an earthed metallic screen but that screen needs to have the "equivalent" current carrying capacity of the biggest Band II circuit in this case 230VAC I presume.

 

SWA provides no screening only armour. It's "leaky" between the strands. Screened cable is exactly that. 

 

Normal separation is 50mm for external cables but can be less if you install a non conducting divider. However.....

 

The BIG consideration though is that segregation is meant to prevent mains voltage appearing on the telecoms stuff through induction which you REALLY don't want. A bit of plastic won't necessarily prevent that IMO depending on how things "lay" which is why separate ducts are a good idea.

 

Your utilities company will likely have their own diagram showing trenching depths and segregation of services. Who's your DNO?

Link to comment
Share on other sites

7 minutes ago, Onoff said:

Your utilities company will likely have their own diagram showing trenching depths and segregation of services. Who's your DNO?

 

They don't care .... this is all between the meter box and the house so I'm on my own so to speak. 

 

Sounds like putting a 16mmSWA direct buried with the CatX in the duct on the other side of the trench is the way to go. 

 

Saved me some duct cost .... 

 

Link to comment
Share on other sites

16mm for 27m? Crickey how big is your gate motor?

Ours is closer to 60m and we ran 4mm 3 core SWA (as recommended by the gate motor company) and it works fine.

We also ran exterior grade CAT5 in a separate duct, in reality we probably only achieved 150mm separation and again its fine.

Edited by Barney12
Link to comment
Share on other sites

32 minutes ago, Barney12 said:

16mm for 27m? Crickey how big is your gate motor?

Ours is closer to 60m and we ran 4mm 3 core SWA as recommended by the gate motor company) and it works fine.

We also ran exterior grade CAT5 in a separate duct, in reality we probably only achieved 150mm separation and again its fine.

 

Probably for the gatekeeper's lodge! :)

 

I think he's meaning the 16mm2 is from the meter at the gate TO the house for the house supply.....but not sure.

Edited by Onoff
Underlined added
  • Like 1
Link to comment
Share on other sites

Didn't realise the 16mm was the incoming feed,

I'm in agreement, I don't think its big enough when you take into account VD,

With an 80a ocpd, I think you are going to have to go 25mm, but do the calcs, 

 

btw @JSHarris the collet rings are often used by some manufacturers where a gland has multiple cable sizes, so at the larger end if the scale they are often redundant

But very gland dependant, you can tell by the inner seating design.

Edited by Steptoe
More info
Link to comment
Share on other sites

1 hour ago, Onoff said:

 

Probably for the gatekeeper's lodge! :)

 

I think he's meaning the 16mm2 is from the meter at the gate TO the house for the house supply.....but not sure.

 

Correct..! Meter is at the gate ... 

Link to comment
Share on other sites

57 minutes ago, Onoff said:

You can get armoured Cat-5E / 6 out of interest.

 

You can ... and it looks like a teensy tree root when you're digging .... ask me how I know ..! 

 

Will swap sides and put 3 lengths of Cat5 in the duct and use SWA for the power. 

 

And yes I know I should go Cat6 but I've got 295m of LZ Purple solid copper in the garage ...! 

Link to comment
Share on other sites

1 hour ago, Onoff said:

 

Probably for the gatekeeper's lodge! :)

 

I think he's meaning the 16mm2 is from the meter at the gate TO the house for the house supply.....but not sure.

 

 

If that's the case then I suspect the cable's on the small side.  I was wondering a bit why a gate needed 16mm2...............

 

We needed 25mm2 SWA for the underground run from our external meter box to the house CU, as the voltage drop was marginal with 16mm2.  I used three core 25mm2 with standard the right colour cores (not essential, but is saves taping/sleeving the wrong colour cores at the ends).   I also did as Dave suggested earlier, and fitted an 80A fuse in the isolator, for the same reason.

 

As for the spacing, the Openreach guy was pretty hot on making sure we maintained 300mm separation between their duct and the DNO's duct with a diverted supply that was in the same trench, to the extent of checking before we backfilled (this was one of their 20 pair cables that was being relocated from overhead, along with the power cable).  As Onoff says, induction is the thing they are bothered about.

Edited by JSHarris
typo
Link to comment
Share on other sites

7 minutes ago, readiescards said:

 

Can you elaborate please? Just filled my house with CAT6 and plenty of 90 elbows (over 3-4 cm) 

 

 

Cat6 has a minimum allowable bend radius of 26mm, Cat5 is 20mm (IIRC).  26mm radius is too tight, IMHO, and I'd not go tighter than 50mm bend radius with Cat6.  If all your bends are over 30mm bend radius you should be OK, but the general rule is to have as few bends as possible, and keep them as gentle as you can.

  • Like 1
Link to comment
Share on other sites

8 minutes ago, readiescards said:

 

Can you elaborate please? Just filled my house with CAT6 and plenty of 90 elbows (over 3-4 cm) 

Cat 6 needs a fairly large bending radius compared with cat5 , that's all,

tbh, for point to point in the average domestic situation you are not going to see any benefit between cat5 and cat6 , not much equipment can handle the speed of cat5e even, and that's only for transferring internal files, ultimately you are restricted to your internet speed for external files. 

 

ps, remember and use proper copper cable, not rubbish CCS or CCA 

  • Like 1
Link to comment
Share on other sites

1 minute ago, SteamyTea said:

Not read the whole thread, but can't you just you one of those power line network things and forget about the CAT5/6.  Then just plug in a Raspberry Pi by the gate.

 

The Cat6 may not be running as Ethernet cable, though, it could be a proprietary protocol for the gate controls.  The only gate control system I worked on, for a friend, used phone cable as the link, with something a bit like RS485 as the signalling protocol. 

Link to comment
Share on other sites

9 hours ago, SteamyTea said:

Some things are getting to complicated, an electric gate should be simple and repairable.

 

From the experience two friends of mine have had with electric gates I think "repairable" is the number one priority! 

 

One of them, up in East Yorkshire, ended up removing the actuators and linkage stuff within a year and designing his own, as he was fed up with the thing failing, usually in high winds.  IIRC he had around 4 or 5 warranty repairs and when the warranty was up he decided to just re-engineer the whole electromechanical side of the thing to make it reliable.

 

The other has had similar reliability problems, but in his case it's the control system that isn't very reliable.  He has an intercom from the gate to the house (the house is around 100m away) together with remote operation from the house, and the major problem has been that the external electronics just weren't very weather proof.  He's also very fussy about the way it looks, so wasn't happy when I suggested just relocating all the controls into a properly sealed enclosure.

Edited by JSHarris
Link to comment
Share on other sites

The Vidor intercom needs 6 cores of either telephone or Cat5E cable from the gate unit to the house; the IP (PoE) camera needs the same hence why two are needed. Powerline would work for the camera but it would need a transformer and spur on its own at the gate where currently the only power that is being provided is for a lighting circuit and the gates themselves via a pair of RCBOs.

 

The 16mm is borderline according to Doncaster Cables at 81A and 3.3% voltage drop so will in all likelihood go for 25mm from the meter to the house. 

 

Thanks all

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...