long power run

larthehar

Hi all,

I have a shed that is approx 250m away from the main distribution board. Max load is going to be 20A..
any ideas on a cost effective solution?!

Cheers.

tomdempsey200

i doubt it for 250m at 20amps


what's the loading comprised of?

frankmul

It's a vy long run. The voltdrop in the cable will cause the cable to be large.

larthehar

Load would comprise of 10 double fluorescent lights.. a 500w halogen.. I would be using a 2200w angle grinder and maybe an inverter welder.. obviously not all at the same time..
if I had the lights it would be the most important element.
so maybe 10A for this..
16sq cable would probably do?

Are transformers a viable option?

tomdempsey200

new supply from esbn

cable for that would be prohibitively expensive

larthehar

tomdempsey200 wrote: »

new supply from esbn

cable for that would be prohibitively expensive

Surely €1200 euro would cover it? New connection would be €1.5-2k and standing charge on top of that..

tomdempsey200

250m of 16sq is showing up as 1700 euro on meteor online

and that will exceed the allowable voltage drop at 20amps

tomdempsey200

you'd prob need the 25 costing 2000 euro or more

+ 250m of trench

frankmul

Allowing 3% volt drop for the cable run, you have to use 35 mm sq for 20 amps!

2011

frankmul wrote: »

Allowing 3% volt drop for the cable run, you have to use 35 mm sq for 20 amps!

Yes, aligns with my calculation.

Here is what I get for XLPE armoured cable:

Conductor Size, (mm^2) mV/A/m Design Current, (A) Length of Run, (m) Vlot Drop, (V) % Volt Drop
1.5 29.00 20 250 145.0 63.0
2.5 18.00 20 250 90.0 39.1
4 11.00 20 250 55.0 23.9
6 7.30 20 250 36.5 15.9
10 4.40 20 250 22.0 9.6
16 2.80 20 250 14.0 6.1
25 1.75 20 250 8.8 3.8
35 1.35 20 250 6.8 2.9

Method of installation C, E, F, G.

2011

larthehar wrote: »

Load would comprise of 10 double fluorescent lights.. a 500w halogen.

Why?
This does not make sense.
Use more energy efficient lighting.

if I had the lights it would be the most important element.
so maybe 10A for this..

So this is ½ of your design current? :eek::eek::eek:

Are transformers a viable option?

What do you plan to do with a transformer?

Bruthal

2011 wrote: »

What do you plan to do with a transformer?

Transform up to 10kv close to DB, 1.5 square to shed, 10kv back to 230v at shed. A couple of mini pylons for the 10kv run, and job done.*







*Not a serious recomendation

larthehar

2011 wrote: »

Why?
This does not make sense.
Use more energy efficient lighting.



So this is ½ of your design current? :eek::eek::eek:



What do you plan to do with a transformer?

Ok.. so it is a shed used for agricultural purposes.. I would like to be able to do repairs/improvements requiring power tools but I can resort to the gene.. leaving only the lights..
I will do some research into the most energy efficient lights... hence the drop to 10A..

Out of curiosity, how much is 35mm sq cable per metre..

Transformer I was considering stepping down to 110v..

Bruthal

larthehar wrote: »

Transformer I was considering stepping down to 110v..

If you step down to 110v for the cable run, it would be 70 square needed for the run:eek:

2011

Bruthal wrote: »

If you step down to 110v for the cable run, it would be 70 square needed for the run:eek:

I think he means that he would like to use a 110V traffo in the shed for power tools. At least I hope that is what he means

Bruthal

2011 wrote: »

I think he means that he would like to use a 110V traffo in the shed for power tools. At least I hope that is what he means

That wont reduce the load anyway.

2011

Bruthal wrote: »

That wont reduce the load anyway.

I know, but I am guessing that it will suit the 110V power tools such as the aforementioned grinder

larthehar

Of course it is at the shed end I was considering the transformer.. allows more current draw...

So no ideas on price of the 35sq cable?!

2011

larthehar wrote: »

Of course it is at the shed end I was considering the transformer.. allows more current draw...

What do you mean "allows more current draw" ??

So no ideas on price of the 35sq cable?!

No idea.

freddyuk

larthehar wrote: »

Ok.. so it is a shed used for agricultural purposes.. I would like to be able to do repairs/improvements requiring power tools but I can resort to the gene.. leaving only the lights..
I will do some research into the most energy efficient lights... hence the drop to 10A..

Out of curiosity, how much is 35mm sq cable per metre..

Transformer I was considering stepping down to 110v..

LED tubes are about 65% of the wattage of 240v florescent tubes. DC 12v/24v tubes are available depending on your daily usage you can run lights off Solar battery system and have genny as standby. As you may need genny anyway for short bursts of high power for the tools the solar option becomes quite viable for lighting which is low power and intermittent.
Do the math on the cable option and go from there.

E. Fudd

Do like they do on the railway; step it up to 650vac and back down at the other end! (Again, not a serious recommendation)....

Cogsy88

2011 wrote: »

Yes, aligns with my calculation.

Here is what I get for XLPE armoured cable:

Conductor Size, (mm^2) mV/A/m Design Current, (A) Length of Run, (m) Vlot Drop, (V) % Volt Drop
1.5 29.00 20 250 145.0 63.0
2.5 18.00 20 250 90.0 39.1
4 11.00 20 250 55.0 23.9
6 7.30 20 250 36.5 15.9
10 4.40 20 250 22.0 9.6
16 2.80 20 250 14.0 6.1
25 1.75 20 250 8.8 3.8
35 1.35 20 250 6.8 2.9

Method of installation C, E, F, G.

If 3% of 230v is 6.9 volts would 16sq cable not be within the regulations.

sawdoubters

why use so many lights get efficient ones ,your not using the power all the time,
t5 fluorescents are good,
T5 fluorescent lights use special ballasts – the device that limits the amount of current passing through the tube to stop it from overloading. Additionally, these special ballasts enable T5 fluorescent lights to work at frequencies above 20kHz, giving you features such as instant start, rapid start and programmed start


the halogen you could swap with led spotlight,your grinder will use 10 amps but will only run a bit,put your lights on a few switches,you should only need 4 lights how big is the place,i would not worry about volt drop,you could run 2x20 amp circuits,you could run a 20 amp ring circuit 2.5mm don't forget rcd protection

http://www.etci.ie/docs/ET214.pdf

brightspark

Cogsy88 wrote: »

If 3% of 230v is 6.9 volts would 16sq cable not be within the regulations.

Regulation 525.2 allows 4% so 9.2V allowed.

Regardless 25sq is needed according to 2011's table

Cogsy88

So y is everybody saying 35sq?

2011

sawdoubters wrote: »

the halogen you could swap with led spotlight

Yes, more efficient lighting has already been suggested.

your grinder will use 10 amps but will only run a bit

True, but a large volt drop will mean that it will be seriously lacking in power.

i would not worry about volt drop

You should, it can cause a lot of problems.

In addition high volt drop can will also mean a high earth fault loop impedance.

you could run 2x20 amp circuits

It is expensive enough running one 20A circuit !
Why are you suggesting running a 2nd?

you could run a 20 amp ring circuit 2.5mm don't forget rcd protection

250m on a 2.5 sq. mm cable is a volt drop of 90 volts. So if it was wired in ring this would reduce to 45 volts :eek:
Not good!

gctest50

Cogsy88 wrote: »

So y is everybody saying 35sq?

Cos saggy power isn't nice when you're welding ?

Lights go a bit dim / fluctuate esp. if you like cutting rods etc

Cogsy88

Am I missing something in the regs. Is there different voltage drop aliowences for different cable installation methods?

2011

Cogsy88 wrote: »

So y is everybody saying 35sq?

You need to look at the overall volt drop and ensure that this is not excessive.

This will mean adding the following volt drops:
1) Volt drop to the main distribution board.
2) Volt drop from the main distribution board to the shed.
3) Volt drop on the final circuit in the shed.

Cogsy88

gctest50 wrote: »

Cos saggy power isn't nice when you're welding ?

Lights go a bit dim / fluctuate esp. if you like cutting rods etc

What about a 16sq supply and wire lights in 2.5 and sockets in 4sq.

2011

Cogsy88 wrote: »

Is there different voltage drop aliowences for different cable installation methods?

Yes.
Have a look on pages 289 to 292, Annex 52E.

Different installation methods can effect how easily a cable can cool.
The hotter a copper conductor is, the higher the resistance, the higher the volt drop for a given current.