Powering an Observatory

[old_eyes]

I could do the same. We regularly run a moth-trap overnight on a long extension lead from an rcd protected socket. Where we place it is only about 10 m closer to the house than the proposed observatory site.

Maybe that's the way to do it. Still a hassle clearing away the extension lead each time, but a way to get on with things and get the observatory the way you want it.

old_eyes

[earth titan]

Have to say I power all mine on a domestic 13A cable, plugged into an RCD protected socket about 15m from the house. The cable is ducted in some alcathene pipe buried around 0.5m deep.

Works fine. Most of the stuff in the obsy is very low power so poses little risk.

My old man, an ex sparky, helped me install it. His words - 'it'll be fine'.

Just bear in mind that as I understand the regs, as soon as you put permanent connections in, it has to be done or checked by a competent Part P qualified sparky. Others may be able to confirm or deny this.

[old_eyes]

Yes I will definitely get it checked over, whichever route I go.

conidering what we end up spending on our hobby, a professional safety check seems like money well spent.

old_eyes

[dmahon]

Part P has changed - my understanding now is you don't need to get it done by someone registered if you're connecting to a socket - only if you're connecting a new circuit to the consumer unit. The fact it is outdoors no longer matters. You still have to do it within the regulations though - total length of cable on the circuit remains important.

[Zakalwe]

I power my obs using an extension lead. I have an external weatherproof socket on the outside wall. It runs to a standard 13a plug inside the house that is plugged in, via an RCD, to the ring main. I then run an extension from the obs and plug it into the external socket. I use a Powerline adapter to carry the data over the extension. inside the house I have another PC that controls the obs remotely. The extension run is only about 5-7 metres. it#s not perfect, but its a damn site easier than digging the patio up to lay an armoured cable.

[Macavity]

I power my obs using an extension lead.

This idea has a lot going for it!

I have an RCD protected mains lead running (as needed) to a caravan style socket FIXED into the shed / observatory wall. I'm working on the "signal cables" for remote observatory operation.

The mains extension is usually only deployed to charge a deep cycle battery - When it isn't raining!

I do (exceptionally) run certain mains equipment in the observatory. Common sense?

I wince at some of the neighbours shed powering arrangements...

[Zakalwe]

This idea has a lot going for it!

I have an RCD protected mains lead running (as needed) to a caravan style socket FIXED into the shed / observatory wall. I'm working on the "signal cables" for remote observatory operation.

Ditto.

It's an easy, cheap solution, and it takes about 30 seconds to deploy.

I use these powerline adapters and they work great

http://www.amazon.co.uk/TP-Link-PA411KIT-AV500-Powerline-Adapter/dp/B0084Y9N3O/ref=sr_1_3?ie=UTF8&qid=1376314976&sr=8-3&keywords=500+powerline

One cable to power them all and in the darkness bind them (with apologies to JRR Tolkien )

[Earl]

I also ran a network cable as when needed, personally as i was using remote desktop connection I preferred to get the faster network connection that via powerline.

Is it really a hassle to hook up the leads on extension for the 5-10 clear nights a year?

[Zakalwe]

I also ran a network cable as when needed, personally as i was using remote desktop connection I preferred to get the faster network connection that via powerline.

The powerline only runs over the extension, as the house-end adapter plugs into an extension block that runs off the same 240v socket. my LAN switch is near this plug too. I'm getting 330Mb/s via the adapters, so there's no speed drop-off at all. I'm running Windows Remote Desktop from a Win 8 machine controlling the Win 7 obsy PC.

[yesyes]

Part P has changed - my understanding now is you don't need to get it done by someone registered if you're connecting to a socket - only if you're connecting a new circuit to the consumer unit. The fact it is outdoors no longer matters. You still have to do it within the regulations though - total length of cable on the circuit remains important.

Interesting. I already have a armoured cable going from the fuse box in the house (on a separate RCD) to the end of the garden next to the obsy. It was used for some outdoor lights and a pond pump/filter.

So I would now be allowed to wire this all up myself since it is an existing circuit?

[Earl]

The powerline only runs over the extension, as the house-end adapter plugs into an extension block that runs off the same 240v socket. my LAN switch is near this plug too. I'm getting 330Mb/s via the adapters, so there's no speed drop-off at all. I'm running Windows Remote Desktop from a Win 8 machine controlling the Win 7 obsy PC.

Nice performance there, mine was no way near that, which is why i used a separate network cable, mind you the electrics at that house were dodgy somehow and could of been the issue.

[Zakalwe]

Interesting. I already have a armoured cable going from the fuse box in the house (on a separate RCD) to the end of the garden next to the obsy. It was used for some outdoor lights and a pond pump/filter.

So I would now be allowed to wire this all up myself since it is an existing circuit?

What could possibly go wrong???

:grin:

With electrics I would always advise that if you have to ask the question then you are probably not qualified to do the work....

[yesyes]

I have the knowledge of how to do the wiring but I'm not certified, so I thought I wouldn't be allowed (rather than not able) to do it myself.

[dmahon]

If it's

1) The right size cable (max current and voltage drop for the distance)

2) Has the right earthing (what earthing is your house)

3) Has the right size MCB at the consumer unit (easily changed if not)

4) Is properly protected (RCD at the proximal end, or armoured/earthed conduit)

then you should be OK

http://www.planningportal.gov.uk/uploads/br/BR_PDF_AD_P_2013.pdf

[yesyes]

hmmmmm, reading some of these questions makes me wonder if it hasn't been too long ago when I learned all this stuff.

I learned this back in Germany around 20 years ago and was then certified for mains voltage installations. But I had then chosen a slightly different career path and never actually used that knowledge. And things seem to be done slightly differently here in the UK.

1) The cable is a 4 core 2.5mm² armoured cable about 20 metres long.

2) Did some gooleing of earthing types and it seems to be TN-S

3) I don't have a consumer unit for the obsy side yet. So I can still choose the correct MCBs. I was planning to use a 5-way CU so that I can switch off certain circuits separately. (for example: shed mains, outdoor socket, pier power, scope room power, warm room power). 10A each should be more than enough. Probably only 6A MCBs to the shed and pier.

4) The house side of the cable is terminated inside the fuse box with a 30mA RCD and 80A MCB (both in one unit). 80A seems waaayyyy too much for this. I should probably have this changed to 20A or so.

[Tinker1947]

There are MCB's with a built in RCD .....full range available....

http://www.tlc-direct.co.uk/Products/CPBR061.html

[dmahon]

I suspect that 80A is the maximum for the whole consumer unit, or the section protected by the RCD. You probably want to use a 32A or 20A MCB for the obsy circuit. 32A needs 4mm2 cable, 20A needs 2.5mm2 cable I believe.

If you expect to use 20A over 20m and you are going to feed a lighting circuit at the far end, I think you need to use 4mm2 cable to prevent too much voltage drop (3% drop allowed for lighting circuits).

TN-S could always be converted to TN-C-S in future - possibly by the electric company without your knowledge! If you want to export earth, you may need to use 10mm2 cable - either separate earth cable or use 3 core SWA.

[dmahon]

PS - if possible, connect up at the house end to a non-RCD-protected slot. Then use an RCD consumer unit in the obsy.

[martin_h]

I had a spare way in my consumer unit, so was able to use that for the obs, all the circuits are protected with RCBO's so I did the same using a 16A one. The consumer unit is at the front of the house, obs at the back and the only way to dig in a cable would have been to smash up all of the pathway down the side of the house!!! so I used conduit clipped to the house wall and ran single conductors out to the obs.

[martin_h]

I even built a pergola to get it over the path at the back!!