Power to and in an Observatory

[NicktheAstronomer]

Gday

I have an observatory in my garden, where I sit at my telescope, and enjoy the night sky.....when its not cloudy obviously!! As part of the observatory roof is open when I am at the telescope, dew can be a problem.

I need to run power out to the observatory to power my laptop and the telescope. The laptop needs 240V, the telescope needs 12V which I can provide using a small plugin transformer. Sadly the transformer is deeper than the usual UK plugs, and therefore will not fit in a water-proof plug housing.

I think I need to add a weatherproof passive RCD socket at the back of my house, some armoured cable under the lawn to the observatory, another watherproof RCD socket in the observatory for the laptop, and some sort of housing for the transformer.

Any thoughts or suggestions?

Nick

 

[Pensdown]

You only need one RCCD protecting the circuit, this can either be at the house or in your observatory.

Personally, I don't like the idea of extending existing house circuits to out buildings. Under normal circumstances it's not the correct way of doing things.

Is there anyway you can take a new supply from your consumer unit to the observatory.

A few photos of your CU and observatory would be very useful

 

[TicklyT]

How about a chunkier 12 Volt transformer that can stay warm and dry indoors, a suitably specified 12 volt extension lead and an in car laptop PSU for your computer, fed from the same 12 volt supply as the telescope?

 

[NicktheAstronomer]

Ahhh thanks for those posts. My consumer unit is at the front left hand side of the house, and the observatory is at the back right hand side, so to hook the conservatory up to the consumer unit I would have to run a new cable around the outside of the house, which I hope to avoid.

We have a single weather proof plug under the verandah at the back of the house, and it was this which I was going to replace with a weather proof RCD socket, and plug the observatory into it. I thought weather proof RCD plugs in the observatory made sense due to the problem of dew which happens when you are sitting out looking at the stars.

If I run 240V out to the observatory it would be about an 18m run of cable, which I assume I would need use armoured cable buried at an appropriate depth?

The 12V idea sounds interesting, and possibly safer. Can you suggest a cable type, and recommend a suitable transformer?

 

[electronicsuk]

You could use a similar setup to the outdoor socket kits sold at DIY sheds, i.e. 13A plug into weatherproof RCD outlet on the side of the house, into a weatherproof adaptable box and then onto SWA, terminating in weatherproof sockets at the observatory. I'd be more inclined to run in a length of 2.5mmsq SWA and install a mains supply over the idea of using 12v, and although I'm not keen on the above method, although it is an easier solution for a DIYer.

Of course, running everything at 12v would be safer, but laptop power supplies tend to be relatively high wattage (65w or more), and over 18m the volt drop could be quite significant. At a guess, you would need to be running in at least 4mmsq. For power supplies, you'll want a fairly large switch mode unit, perhaps something like this will do the job.

 

[NicktheAstronomer]

Thanks Matthew

I might stick to the 240V option. I will use Armoured cable out to the Observatory, which sits in the middle of the lawn...........do I have to earth the armour shielding, and if so, how?...........and how deep should I bury the cable?

Thanks

Nick

 

[ban-all-sheds]

do I have to earth the armour shielding,

Yes.

and if so, how?

//www.diynot.com/wiki/electrics:installation_techniques:swa_gland

and how deep should I bury the cable?

http://www.tlc-direct.co.uk/Book/7.13.3.htm