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JamesF

JamesF's observatory build

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Posted (edited)

I'd suggest you use dielectric grease on the LV connections, should help keep any moisture out and maintain a good connection over time. I use Servisol silicone grease on the CCTV LAN+power connections whether inside or out and applied to the connections inside the dome unit that is now skycam-2 before it was finally assembled and sealed up. 

No harm a light smear on any threaded components that might corrode over time too...

Edited by DaveL59
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Final HDMI cable arrived today.  I was hoping to get out and do the final cabling runs this evening, but it has been raining with a vengeance.  Water was hitting the observatory roof so hard that there were clouds of water droplets extending about 18" from the edge of the roof.  I decided it can wait until tomorrow :)

James

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Would it be uncharitable to suggest that you might have shared your excess of rain with us during last year's severe drought? ⛈️

While we do admire your unbounded generosity, on this occasion.. it's really all about the timing, you know. :wink2:

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You’ll never get it finished with an attitude like that!

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Well, this evening I did pull through the last of the cables.  Next I need to sort out what goes on the piers and think about organising all the cabling in the warm room.  Proper power has got to become a serious consideration very soon, too.  Time to do some more planning I think.

And on the subject of planning, what has happened at the end of this newly-laid track?

obsy2-build-01.jpg

I've only started work on observatory number 2, is what :D

Actually it's a case of planning way, way ahead.  The track will lead to the barn that's soon to be a holiday cottage.  On the southern (right hand) side of the track, because we're within a stone's throw of Exmoor, I want at some point to put a "guest observatory" which will require power, so before the track was laid I made sure we put in some ducting to take a cable and left a draw wire in at the bottom of this hole:

obsy2-build-02.jpg

The observatory itself should go in the space currently occupied by the heap of rubbish here:

obsy2-build-03.jpg

Other than putting a couple of vertical pipes in so we can backfill the holes and still find the ends of the ducting however, I think that's all that's going to happen for the foreseeable future.

James

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Well, at the moment I'm toying with the idea of a self-build dome.  I may yet change my mind though.

James

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11 hours ago, JamesF said:

Well, at the moment I'm toying with the idea of a self-build dome.  I may yet change my mind though.

James

Too much time on your hands :):)

Steve

 

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29 minutes ago, sloz1664 said:

Too much time on your hands :):)

I wish :)  But it's a different game when you're doing something because it's for pleasure rather than just because you have to do it.

James

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Given the weather perhaps it's unsurprising that I have made little progress this weekend.  And in fact I had to be at Millfield School at stupid o'clock this morning for a swimming competition (not me, but my daughter).  She did pretty well though, swam seven personal bests in eight races and came back with three medals including a gold for 50m butterfly in which she was faster than anyone else competing regardless of age, so I really can't count it as a day wasted.  It's still like having a seven hour sauna though :(

I did manage to fit a lock to the external door of the observatory yesterday, which means I no longer need to prop the door closed with a length of timber.  Unfortunately the only spindle I could find wasn't long enough for the width of the door so I haven't fitted any handles yet.  I've ordered a length of 8mm bar from ebay that I can cut to a suitable length.

The weatherproof boxes for the piers have also arrived.  They have a metal plate in the back which I'm tempted to remove.  Either that or I should probably earth it as there will be mains electricity in the box, even though there's no reason to believe it should be able to reach the metal plate.

And I need to find some trunking that will accept 13A socket faceplates, for the warm room.  I'm not entirely impressed with what I've found so far.

James

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Congratulations to your daughter, James, that's magnificent!  :thumbsup:

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well done to your daughter James, mine used to swim when she was young too 🙂

As for the metal boxes, yep for sure I'd earth them, better safe than sorry esp in an environment where external moisture could well lower the contact resistance when you touch the case. Ideally you should probably have a proper bonded earth too, you could probably drive a copper earth spike under the shed and run  to that as grounding via the power feed cable to the remote buildings isn't really a proper solution unless its a suitable gauge cable you're using.

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Yes, I think a bonded earth makes sense in this situation as it's a bit of a nightmare to export a suitably large earth from the house over such a distance (not to mention hideously expensive).  The electrician should be turning up at some point soon, so I'll discuss it with him.

James

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James, you're doing it all wrong!

You do the swimming and let SuperGirl build the observatory.

You know it makes sense. :D

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2 hours ago, Rusted said:

James, you're doing it all wrong!

You do the swimming and let SuperGirl build the observatory.

You know it makes sense. :D

Yeah, I could probably give some of the eleven year olds a run for their money :)

James

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On 16/06/2019 at 21:53, JamesF said:

Yes, I think a bonded earth makes sense in this situation as it's a bit of a nightmare to export a suitably large earth from the house over such a distance (not to mention hideously expensive).  The electrician should be turning up at some point soon, so I'll discuss it with him.

James

Is there an earth leakage circuit breaker installed? If so, then this should take care of the earthing issue for you. If not, then if you have run armoured cable, the armouring could be used as the earth. Glanding off the armoured cable with a metal gland in your electrical box will do the earthing there too. Have a chat with your electrician and hopefully you have a low cost solution available.

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27 minutes ago, Bukko said:

Is there an earth leakage circuit breaker installed? If so, then this should take care of the earthing issue for you. If not, then if you have run armoured cable, the armouring could be used as the earth. Glanding off the armoured cable with a metal gland in your electrical box will do the earthing there too.

My recollection is that it gets more complicated than that.  I'm not certain without checking it up, but I believe the earth conductor in the armoured cable has to be suitably rated in terms of resistance and/or current-carrying capacity for a breaker at the house end to function correctly.  Over long runs that can mean the earth conductor has to be bigger, which in turn makes the cable bigger, more awkward and more expensive.  I can't remember if it's permissible to use the armour as an earth conductor (I think it might be), but it's not always suitable anyhow, as being made of steel it has a much higher resistance than copper and even though there's more of it that doesn't make up for the difference.

James

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Posted (edited)
3 hours ago, Bukko said:

Is there an earth leakage circuit breaker installed? If so, then this should take care of the earthing issue for you. If not, then if you have run armoured cable, the armouring could be used as the earth. Glanding off the armoured cable with a metal gland in your electrical box will do the earthing there too. Have a chat with your electrician and hopefully you have a low cost solution available.

an ELCB won't take care of earthing at all, only has the ability to detect a leak to "earth" from L or N. Problem can be if the earth floats as a result of resistance along the length of the wire which can lead to erronious/late triggering. Far better to drive an earth spike in and bond to that, they aren't expensive and so long as you protect the install with a suitable cover it'll be fine. I'd still install the RCB/ELCB too, safety first and all that. I've come across a few instances where earth has floated and got a buzz off equipment casings and in one case when my hands were under a running tap, not good!

Edited by DaveL59

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James,

How long is your cable run?

Mine is just over 60m of 4mm2 and the calculated numbers checked by my electrician for fault trip was fine. At my distribution point, there is an ELCB plus 16A breaker. I did not need to use an armoured cable. While I agree that steel is not as conductive as copper, it is still a reasonable conductor.. And as you said, there is a lot of it. Again, as I said, talk to your electrician. (again, assuming you used an armoured cable...)

If you have a really long run, then as Dave says, installing a ground spike would help deal with the grounding issue.

Good luck.

Gordon.

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On 17/06/2019 at 10:00, JamesF said:

Yeah, I could probably give some of the eleven year olds a run for their money :)

James

At my best in cycling I would've been fourth best junior girl in Britain over ten miles!  :D

I just wish your observatory would take on even the tiniest hint of scruffiness. As it is I daren't go up to mine for shame until it's dark and I can't see the inside!

Olly

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Mine is very scruffy too but it doesn't bother me.

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Beauty is in the eye of the beholder and, as my obsy is just a scruffy patch of back garden lawn, to my eye, any obsy building is an absolute gem.

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Earlier this week whilst sorting through what electrical bits I already had in the workshop I discovered about 15m of armoured cable.  That's not enough to get back to the house by a long way, but it was long enough to reach back to the distribution panel in the beer shack.  (The beer shack is fed from the house by about 40m of 2.5mm T&E that needs replacing.)

So today I dug a trench from the beer shack to the observatory and dropped the cable in.  At the same time I ran some cat5e down from the roof void of the beer shack under the ground to the observatory inside some old 43mm waste water pipe.

Now I just need to get wired networking out to the beer shack so I can connect that up, and at some point replace the mains supply to the beer shack (at the same time as putting in a local earth).  The latter is probably the more awkward job, but perhaps less urgent.

Having all the external cabling in place means that I should now be able to finish off the electrics in the observatory even if it isn't actually connected up yet, which will be another big step forward.

James

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ouch 2.5 T&E sure wouldn't cut it for earth  I'd say, is that direct from the fuse board or a spur off the ring? 

An earth spike (4ft) is relatively easy to do so long as the ground isn't littered with rocks under the surface. A 4lb hammer should drive it in ok, maybe easier if the ground is wet. Then fit the clamp on the end and 10mm earth wire back to the consumer unit to bond that to earth and the obsy should be fine.

I would suggest for the ethernet cable that you fit surge suppressors, I used these on the hard link out to my shed which is a lot closer but does have CCTV gear linked back to the house and now the sky cameras.

https://www.ui.com/accessories/ethernet-surge-protector/

 

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1 hour ago, DaveL59 said:

ouch 2.5 T&E sure wouldn't cut it for earth  I'd say, is that direct from the fuse board or a spur off the ring?

I'm sure it won't do the job either.  Makes me quite uncomfortable.  That's what was there when we moved in though, and I've been wanting to replace it for years.  I think it's off an MCB on the main distribution board, though I have to admit that since we had everything reorganised last year I've lost track a bit (we had a modern board put in last year when we had the cellar made usable, to replace the old one that used cartridge fuses).  We should have Western Power in very soon to deliver a second phase to provide power for the barn conversion, so I'll get everything sorted then.

I'm reasonably convinced that a local earth spike should do the job ok.  The ground around that area tends to be quite damp.  That's one for the electrician when he visits.

James

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