Underground power cable

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raytaylor

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#31263 10-Mar-2009 22:58

Hey guys.

I am trying to connect 2 houses together and a wireless access point needs to go onto the roof of an unpowered shed adjacent to one of the houses.
I thought about power over ethernet but the distance is too long so my idea of running the ethernet cable down some black water piping underground is no longer going to work because i need to run 240v power as well.

I am going to use some shielded cat5 cable alongside a 50m orange heavy duty extension cable, but because I am running 240v, I think there would be some laws that apply. There will be a 2400w fuse at the house end of the cable, with a circut breaker, and will be just plugged into a standard wall socket. No problems there.

For the cable housing itself, what sort of thickness or kind of piping will i need to use? Does it need to be a specific colour and how far underground does it need to be?
Any product suggestions?

Ray Taylor

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#200544 11-Mar-2009 09:38

How far is the run? PoE may still be an option..

Bearing in mind that running cat5/cat6 outside is risky - to be 'safe' I'd recommend that you bury it nice and deep in an accessible trunk *with* a draw wire. Also note that running cat5/cat6 to carry ethernet beside an AC line will degrade performance significantly. you can get away with 2-ish metres down a wall, but I think over 5 metres or something you start to notice the effects.

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cyril7

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#200557 11-Mar-2009 10:25

How far is too long, POE if done properly is still the way to go and will go for the full 100m TIA recommendation. I recommend that if you are going to bury cat5 then use proper outdoor stuff that gel filled, be aware that you should not run this stuff inside a house to far (gel is a fire risk), the NZ rules dont talk about it, but the AU ones say that you can take it inside a house to a termination but may not extended it past that point, ie you must use normal cat5 from there on. Normal cat5 will let water in as the PVC is hydroscopic, outdoor cable has a polyethelyne sheath that is water resistant and the gel stops the water moving if you should let it in.

You should bury the cable in 20 or 25mm gray PVC conduit with glued seams at a depth of at least 400mm, different rules state different depths, but 400mm covers all.

Cyril

wellygary

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#200569 11-Mar-2009 11:02

raytaylor:
I am going to use some shielded cat5 cable alongside a 50m orange heavy duty extension cable, but because I am running 240v, I think there would be some laws that apply. There will be a 2400w fuse at the house end of the cable, with a circut breaker, and will be just plugged into a standard wall socket. No problems there.

If you are going to go with the above set up , I would make sure that either the circuit you are plugging into is RC protected at the fuse box, or use a specific RCD for your extension cable.

You should lay electrical marker tape above the conduit, in case in the future someone decides to install a washing line/deck/anything invoving digging a hole ( and by murphys law it will always be above where you have laid your volts)

raytaylor

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#200652 11-Mar-2009 16:53

Its about 20-30m.

I was going to use standard shielded cat5 to protect from the AC interference. The pipe is being used to protect from water. With a draw string, the cable is no problem to replace over such a short distance.

One of the guys has said he would like a light out there for the work bench so I am going to use a 20watt cfl. This means POE is out of the question.

Cyril - that 400mm depth - does that also include if the contents of the pipe is 240v? Or is it just buried cable in general?

Ray Taylor

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mjb

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#200654 11-Mar-2009 17:01

If you're going to run power regardless, run the correctly rated external cable at about 800-1000mm if you can get that deep - then fill the trench to ~400-500mm, and run the conduit for cat5. Fill to 300, and lay down some orange warning tape, then fill.

Run the external cable all the way back to your board inside the house. In the shed, fit your electrical outlets to the other end of the cable. Get a sparky in to check the outlet wiring, and to connect you to the board with a dedicated breaker. Do it properly the first time - you won't regret it.

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cyril7

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#200668 11-Mar-2009 18:04

I strongly recommend that you dont run power with it, just to save yourself some grief and trangress various laws, or if you do run it in a seperate orange conduit and use approriate signage (offical orange marker) to indicate power is there. Running power lead rather than TPS or screen neutral power cables in the ground will get you in legal issues with the authorities, best avoided or get a sparkie to install it properly and sign off for you.

20-30m is not too much for POE, I only last week remotely sighted a WRT54GL for a Zenbu site, there was 75m of cabling, the WRT has a 12V power supply but internally has both a 5V and 3.3V switching regulator to run itself, the DC that normally gets to the WRT when directly connected is around 13.2V (in my sample) when at the end of 75m of cat5 was 12.2V worked with no issues.

I just make my own POE injectors, its not hard, PM me if you want some made up or want to purchase 30m of outdoor cable as normally you have to purchase 500m or nothing.

Cheers
Cyril

scottjpalmer

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#200669 11-Mar-2009 18:16

The reason he decided against PoE was a light is also required in the shed :-)

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Glazza

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#200677 11-Mar-2009 18:58

Power cable needs to be buried at a depth of at least 600mm. It can not be installed in a duct with other cables that do not have the same high voltage insulation rating (ie CAT5 Cables etc), nor can it be installed down a wall with a CAT5 cable.

lxsw20

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#200695 11-Mar-2009 20:17

1) Fuses are not rated in watts.
2) There is a reason you can not buy 50m extension leads off the shelf, think of the losses over that distance!
3) Thats not even close to legal

Why not PoE and a solar shed light? or possibly even build a little LED light set up and run it off the PoE

larknz

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#200698 11-Mar-2009 20:22

Orange flex is not suitable for running underground, it is also illegal. If the shed burnt down the insurance company could use it as an excuse to deny a claim. As Cyril7 said you need to use either TPS cable or a neutral screen cable. I would recommend a neutral screen cable because it will the level of power frequency radiation. It also needs to be properly connected at each end.

raytaylor

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#200717 11-Mar-2009 21:03

Thanks guys. All that info was what I am after. I now have a basic plan and know the sorts of questions I have to answer.

I have an uncle who runs a bobcat operation so I am going to borrow one to dig the trench, then i will have all the stuff here in place for the electrician to hook up at each end, and sign off on.

I will then use MJB's suggestion of half filling, running the cat5 myself and putting the warning tape higher.

Am guessing all this can be purchased at Master Trade so I will go in on sat morning and see what is avaliable.

Thanks again.

Ray Taylor

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cyril7

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#200732 11-Mar-2009 21:49

Hi, I still recommend that you use outdoor Cat5 cable with a polyethelene sheath and ideally Gel flooded although not realy nessecary, normal (inlcluding shielded) will eventually fill with water even if in conduit (it just happens believe me) and once water is in cat5 the dielectric properties change and the data stops in its tracks.

Mastertrade and most wholesalers can get outdoor gelfilled cable but only by the 500m drum, I have access to both gel filled and just polyethelyne sheathed in meter lengths, PM me if you want some.

Technically if you are using a common trench you must stay 150mm away from a non neurtral screen LV cable or 450mm from a TPS(in conduit) cable. Regardless of all this, to lay a power cable between buildings will require an electrician to sign it off (and over see procedings). It is not acceptable to use power flex in this application.

Cyril

mjb

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#200772 12-Mar-2009 09:25

If Cyril7 can get you the gel filled cable you need in the length you need, I'd recommend you get some.

I was deliberately vague around the bit of my post about laying the 240v at the bottom of the trench - I was hoping someone else would chime in with the rules and regs. Both Cyril7 and Unison did so, so follow their lead on that.

@cyril7 - so laying of the cat5 in a conduit ~400mm above a neutral screen cable is ok?

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cyril7

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#200777 12-Mar-2009 10:12

Hi, the various rules are often not consistant, however TelecomNZ recommendation for the laying of there underground lead-in. It states that the leadin must be in conduit and must be at a depth of at least 450mm and can share a trench with other services (ie LV power) however must have a minimum seperation of 150mm from a Neutral Screened or armoured LV cable, however if mechanical protection is used over the power cable such as concrete or magslab then 50mm seperation is ok. For non armoured or neutral screeed the clearenace must be 450mm. Note that Telecoms conduit is 20mm ID and with white or green and can only be supplied to Telecom contrators. Private telecommunications cabling must go in Grey conduit.

The aussie wiring rules S009 on the other hand state that telecoms cables must be in conduit at a depth of 450mm under paths or public roadways, but may be only 300mm deep on private property. Clearance from LV services if in conduit (and no reference to whats in the conduit other than LV) can be NIL, however AS/NZ3000 should be observed at 100mm.

AS/NZ3000 electrical wiring rules require that normal sheathed cable (TPS) in heavy duty orange conduit must be layed at a depth of 500mm if no mechanical protection (concrete or magslab) is used and clear other services ie telecoms in a shared trench by 100mm. Neutral Screened cable can be directly layed at 500mm without conduit, and same 100mm clearance is required.

Therefore its pretty much normal practice to trench to 600mm place your power cable either Neutral screened or TPS in orange HD conduit, cover with 150mm of material, place orange marker tape over that, then put Grey conduit with Teleco/Data cables in it which will be at 400-450mm. Often if the trench is wide enough (ie 150 or more) then put both on the bottom at 500-600mm depth but either side of the trench to give 150mm seperation.

Cyril

raytaylor

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#202019 18-Mar-2009 20:32

Another question

Outdoor Gel Filled cat5 cable - can you run it along the outside of a house?
I know you are not allowed to run it inside the walls because its combustable but are you allowed to use it stapled to an outside wall or attached to the top side of a roof?

Ray Taylor

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