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High Green Farm



Joined: 30 Nov 2004
Posts: 349
Location: Mid-Suffolk
PostPosted: Tue Oct 18, 05 9:54 am    Post subject: Armoured Cable  Reply with quote    

We are about to dig trenches (or rather a man with a large tool is about to) to lay water pipe around the fields. At the same time we are going to lay armoured cable to the field shelter and also to where we hope to build a farrowing shed in the future.

The total length of cable will be around 175 metres, but I need to determine what the expected wattage will be. In terms of what I am expecting to be able to do in either the field shelter or farrowing shed, I might need to boil a kettle (for mixing milk for lambs), and a heat lamp as well in the farrowing shed.

I guess a kettle would use around 2,500 watts and a heat lamp 500, plus perhaps three bulbs at 100 each takes me to 3,300 max in total. Plus 200 spare, and a nice round 3,500.

Based on this I am very much on the margins of what I can do with 10mm cable, so might need 16mm. But that is 140 more

Does this make sense to people? Or should I be thinking differently?

Thanks
James

tahir



Joined: 28 Oct 2004
Posts: 44129
Location: Essex
PostPosted: Tue Oct 18, 05 10:00 am    Post subject: Reply with quote    

No help at all, but I'd be interested in what people have to say.

jema
Downsizer Moderator


Joined: 28 Oct 2004
Posts: 26617
Location: escaped from Swindon
PostPosted: Tue Oct 18, 05 10:00 am    Post subject: Reply with quote    

It strikes me you would be mad not to fork out the extra.

You never know what the future holds and having infrastructure that can cope is likely to be cheaper and simpler in the long run.

jema
Downsizer Moderator


Joined: 28 Oct 2004
Posts: 26617
Location: escaped from Swindon
PostPosted: Tue Oct 18, 05 10:09 am    Post subject: Reply with quote    

where are you getting the cable?

http://www.screwfix.com/app/sfd/cat/cat.jsp?cId=101801&ts=29749

shows you could get 175mm of 4mm cable rated for up to 6000watts

http://www.diynot.com/pages/el/el004.php

for 294.

Nick



Joined: 02 Nov 2004
Posts: 33846
Location: Hereford
PostPosted: Tue Oct 18, 05 10:15 am    Post subject: Reply with quote    

I'm with Jema.

If you're up there, and lambing, might you need a heater for yourself at some point? Perhaps you'll want power tools running to put up shelves, or whatever. I'm prepared to bet that if you go for the cheaper option now, you'll regret it later.

High Green Farm



Joined: 30 Nov 2004
Posts: 349
Location: Mid-Suffolk
PostPosted: Tue Oct 18, 05 10:22 am    Post subject: Reply with quote    

jema wrote:
where are you getting the cable?

http://www.screwfix.com/app/sfd/cat/cat.jsp?cId=101801&ts=29749

shows you could get 175mm of 4mm cable rated for up to 6000watts

http://www.diynot.com/pages/el/el004.php

for 294.


You need to consider the length of the cable as well and those ratings are for non-armoured cable. The conductor diameter that I will need is 10mm or 16mm.

I agree it may make sense to future proof.

I was also considering running Cat 5 as well for webcams of farrowing!

tahir



Joined: 28 Oct 2004
Posts: 44129
Location: Essex
PostPosted: Tue Oct 18, 05 10:26 am    Post subject: Reply with quote    

High Green Farm wrote:
I was also considering running Cat 5 as well for webcams of farrowing!


funny enough I thought that might be handy for you

jema
Downsizer Moderator


Joined: 28 Oct 2004
Posts: 26617
Location: escaped from Swindon
PostPosted: Tue Oct 18, 05 10:38 am    Post subject: Reply with quote    

tahir wrote:
High Green Farm wrote:
I was also considering running Cat 5 as well for webcams of farrowing!


funny enough I thought that might be handy for you


though with 100m as the limit without repeaters, 175m is an issue. Wonder what wireless range is these days? hmm...

http://www.vnunet.com/active-home/hardware/2137336/belkin-pre-n-wireless-kit

implies stable at 100m!

Treacodactyl
Downsizer Moderator


Joined: 28 Oct 2004
Posts: 25697
Location: Jumping on the bandwagon of opportunism
PostPosted: Tue Oct 18, 05 11:04 am    Post subject: Reply with quote    

Would it be possible to lay a pipe that the cable could be routed through at a later stage?

High Green Farm



Joined: 30 Nov 2004
Posts: 349
Location: Mid-Suffolk
PostPosted: Tue Oct 18, 05 11:06 am    Post subject: Reply with quote    

I think I'll go wireless for the webcam! The farrowing shed will only be less than 100 metres from the house, and I can get line of sight between camera and house!

dougal



Joined: 15 Jan 2005
Posts: 7184
Location: South Kent
PostPosted: Tue Oct 18, 05 12:35 pm    Post subject: Reply with quote    

Its quite easy to extend wireless range for a fixed link.
http://www.solwise.co.uk/wireless-outdoorantenna-24-yagi-14yn.htm

As regards the rating of the power circuit, I'd suggest that *one* 13 amp socket's worth would be plenty useful.
You can easily find small low wattage ("travel"?) kettles, that wouldn't hog the entire output of the line.
A single socket can easily support most power tools and some lighting.

But with the other costs (not least the excavation) as well as the cable itself, and depending on what you want to use *simultaneously*, it may stack up for you that the extra capacity could be very useful and not make too much impact on the overall cost...

You pays *your* money, and you takes your choice!

whitelegg1



Joined: 05 Apr 2005
Posts: 409
Location: Woodford Green
PostPosted: Tue Oct 18, 05 1:50 pm    Post subject: Reply with quote    

Remember if you lay a pipe that long, to at least put a 'rope / string' through it to pull cables through.

Unless you have a well trained ferret.

High Green Farm



Joined: 30 Nov 2004
Posts: 349
Location: Mid-Suffolk
PostPosted: Thu Oct 20, 05 8:12 pm    Post subject: Reply with quote    

Any electricians out there who can confirm the below maths for me, as I am getting mixed messages?

I want a 20 amp supply, 175 meters from the house. The Volt drop per metre of 16mm is 2.4.

So total volt drop will be (length x amps x volt drop per m)/1000

So in my case (175 x 20 x 2.4)/1000 = 8.4 volts. This expressed as a % of mains (assuming 230v) is 3.65%.

I believe the limit according to the regs is 4%.

According to one manufacturer, they were saying I needed 25mm cable, and that blows the budget to the extent that we won't do it.

Help!

jema
Downsizer Moderator


Joined: 28 Oct 2004
Posts: 26617
Location: escaped from Swindon
PostPosted: Thu Oct 20, 05 8:33 pm    Post subject: Reply with quote    

If its not a daft question, are not the economics of this such that a small generator would be massively easier and more cost effective anyway?

High Green Farm



Joined: 30 Nov 2004
Posts: 349
Location: Mid-Suffolk
PostPosted: Thu Oct 20, 05 8:39 pm    Post subject: Reply with quote    

jema wrote:
If its not a daft question, are not the economics of this such that a small generator would be massively easier and more cost effective anyway?


I have thought about this as well. One of the things that we will need to power will be heat lamps for piglets, and using a generator would become a right royal pain in the **** after a while. Also as we are having the ditches dug for water, it makes sense to chuck electric in as well. The difference between 16mm and 25mm is around 400, and I'm just not convinced that the calc I was given is right.

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