Incoming overhead mains

[eyecatcher]

We have a typical incoming aluminium core mains like an old washing line on leaning connie posts 

Its always at risk when the neighbours trees break in the winds so i want it in a conduit on top of the boundary wall.

 

The sparky is advising that to re use the aluminium core it must be set at 2.4 high but my wall is about 1.6

 

To use the wall then i must change the cable to copper core.

I will need about 140m at 60bt i think.

To duct underground the duct will be cheap but the cables even more expensive.

 

Does this seem a fair assessment; really hate to change 140m of service  if not absolutely necessary.

[Artisi]

Why not conduit with vertical stand-offs at the appropriate height above your wall. Still vulnerable to falling branches etc, but certainly a lot more secure than the unprotected cable.  

Edited October 27, 2017 by Artisi

[eyecatcher]

Yes Artisi the sparky also suggested that option but I reckoned it was still vulnerable to damage plus the unsightly stanchions every 2m or so that would have a cost also.

 

I have done some pricing research today which is enlightening.

 

The copper core 16mm mains cable at Global; two brands 3800 and 4080bt for 100m roll. At Home pro the same BCC cable 4700bt

Now compare that to the aluminium core cable; a few brands all circa 550/650bt for 100m roll

I couldnt find anyone who sold a 50m roll so for me its 2 rolls or have it cut by the metre.

 

Step in wonderful wife;.... sister and b.i.l are electrical contractors in Patts.

They can ship up to CM, on the bus 140m for 30bt/m which is an excellent option.

 

Such a vast difference in the price between aluminium and copper, ( 7x ) is there any difference in the electrical performance i wonder?

 

[Artisi]

21 minutes ago, eyecatcher said:

Yes Artisi the sparky also suggested that option but I reckoned it was still vulnerable to damage plus the unsightly stanchions every 2m or so that would have a cost also.

 

I have done some pricing research today which is enlightening.

 

The copper core 16mm mains cable at Global; two brands 3800 and 4080bt for 100m roll. At Home pro the same BCC cable 4700bt

Now compare that to the aluminium core cable; a few brands all circa 550/650bt for 100m roll

I couldnt find anyone who sold a 50m roll so for me its 2 rolls or have it cut by the metre.

 

Step in wonderful wife;.... sister and b.i.l are electrical contractors in Patts.

They can ship up to CM, on the bus 140m for 30bt/m which is an excellent option.

 

Such a vast difference in the price between aluminium and copper, ( 7x ) is there any difference in the electrical performance i wonder?

 

Seems there are pro's and con's for both, probably better for someone like Crossy to define the best option for you and best cable size to use. 

[Crossy]

9 hours ago, eyecatcher said:

Such a vast difference in the price between aluminium and copper, ( 7x ) is there any difference in the electrical performance i wonder?

Yes, aluminium is a rather less good conductor than copper you need at least one size bigger in Al for equivalent performance but it's still cheaper than Cu and is less likely to grow legs in the night.

 

Assuming your run from the meter is 160 metres and you have a 15/45 service I suggest you need 35mm² Cu. If you really need to squeeze the budget and you don't have a massive connected load (no big water heaters) then 25mm² Cu would do it at a push (but volt-drop on load may be an issue). Cable size calculator here http://www.doncastercables.com/technical-help/

 

Local regulations don't allow Al on anything other than poles and insulators (which is where the 2.4m figure came from).

 

In reality how often has your overhead come down? It's simple, cheap and easy to repair.

 

 

[wayned]

IMHO if you are worried about trees falling I would go underground.    If you have overhead  wires and a "big" tree falls it will break the cable and you will have one end electrified but easy to repair.  If you run it in metal conduit on top of the wall and a "big" tree falls the wall is going to collapse and most likely break the conduit.  If the broken conduit severs the wire inside and comes in contact with the electrified wire then the entire conduit and anything attached to it becomes electrified, not what you want!

 

Do you want to attend my next Doomsday Prepper meeting?

[eyecatcher]

The doomsday prepper meeting sounds right uo my street.

I would not be fitting steel conduit tho as I could already see the potential for disaster.

Plastic at 10bt/m is good enough.

 

Our max run to the meter is 70m and currently the alu cable is 16mm .

I did already have a 16mm planned in copper and the cable calculator confirmed this.

 

So I assume from whay you say the 16copper should be better than the 16 alu

 

My biggest draw is a 6kw water heater and we do have that slight flickering of lights at night when the shower is used.

 

The 16 cable is rated at 9.5kw or so it says so what would happen if a 6kw and 4.5kw showers are used.

 

Thank you for the advice.

[Crossy]

16mm² THW is rated to 90A+ in free air so the 10.5kW of your two heaters (about 47A) won't worry it.

 

On a 70m run 16mm² copper will be better than 5% volt drop, and yes, it will be better than 16mm² aluminium.

 

[impulse]

Keep in mind the biggest issue with aluminum wiring is the poor corrosion resistance compared to copper, especially where the aluminum is crimped or screwed into a dis-similar metal fitting. 

 

Make sure your fittings are compatible with aluminum wires and that they aren't in wet locations.  And check them occasionally to make sure you're not getting corrosion that will cause the connection to lose conductivity.

 

It's not as critical in the runs of wire itself, but there's also an issue of water getting inside the insulation and corroding wire from the inside, invisible unless you can look inside the insulation.  Not so common on solid wire where there isn't any interstitial spaces for the water to move, but pretty common on stranded cables where water can get in at a connection (or through the plastic itself) and migrate freely between the strands. 

 

Edited October 29, 2017 by impulse

[carlyai]

This is our set up. Al from the street pole to the house pole, then in conduit on top of the fence to the outside Consumer Unit. The fence is 2 m high, and I can't remember if it's Al or Cu. Then NYY underground to the house. Passed electrical inspection.

Sent from my SM-J700F using Tapatalk

[eyecatcher]

On 29/10/2017 at 10:39 AM, impulse said:

Keep in mind the biggest issue with aluminum wiring is the poor corrosion resistance compared to copper, especially where the aluminum is crimped or screwed into a dis-similar metal fitting. 

 

Make sure your fittings are compatible with aluminum wires and that they aren't in wet locations.  And check them occasionally to make sure you're not getting corrosion that will cause the connection to lose conductivity.

 

It's not as critical in the runs of wire itself, but there's also an issue of water getting inside the insulation and corroding wire from the inside, invisible unless you can look inside the insulation.  Not so common on solid wire where there isn't any interstitial spaces for the water to move, but pretty common on stranded cables where water can get in at a connection (or through the plastic itself) and migrate freely between the strands. 

 

Thanks for the info.

We have aluminium already but to tidy it up seems I have to use copper instead.

I have ordered copper already so corrosion is not a concern just now.