Armoured cable

[dark star]

I am planning to get some armoured cable for running my 240v AC RA drive on my AE Luton type B mount outside. This is because it will be connected (only when observing, not permanently) through my bedroom window to the garden. I am worried about it being on grass and dew etc. I have a RCD and waterproof junction box.

The questions I have is a core size of 1.5mm squared the correct one? It is a 2 watt synchronous motor. Also, how do I connect the armoured cable to the plug from the very short lead on my mount and a plug inside the house, to connect to the mains?

David

[swamp thing]

Hi David

I would personally only listen to advice on mains power from a qualified sparks.

Exterior mains power is best dealt with by pros.

That way less chance of getting stuck to your scope all night gently cooking.

Regards Steve

[Lorne]

Would you not just be better with an extension reel with a 16 amp blue socket (caravan type) at the scope end, with your 13 amp plug/rcd at the other (bedroom window) end? Easier to run out than a roll of armoured cable which needs brass cable glands to terminate it

[dark star]

A number of people on this forum use mains power outside, I would hope/ assume that they have a much better understanding of electricity than me!

A lot of people use electric lawnmowers powered from the mains outside with an RCD without mishap.

Usually the electric lead would not touch the ground, it will go from my bedroom window to a waterproof box for the extension lead on a chair and then to the mount. The mount is pretty close to the window.

I am just thinking about being safe if the lead fell on to the grass.

Maybe a caravan extension reel with a 16amp socket would be fine in these

conditions, with an RCD?

The main thing I am worried about is dew. I have no intention of using mains power when the grass in the garden is wet from rain!

David

[ixalon]

I'm not a sparky, so agree best ask one. However for temporary use I'd suggest a normal extension reel with RCD too. Armoured cable can be a pain to work with, and you won't be able to correctly terminate to a normal plug/RCD. If not properly terminated, it could be more dangerous than a normal extension (e.g. sharp steel ends where the armour has been cut).

[Gina]

I don't think armoured cable would help for your situation. It is intended for running underground supplies between buildings permanently. An extension lead with a waterproof connector as mentioned above would be best as long as you use an RCD at the indoor end. If you don't use the equipment in the wet or on wet grass you are unlikely to have any problem. Modern plastic (PVC) covered cable is fine on grass as long as the ends are out of any damp/wet.

[dark star]

Thanks for all the advice.

A caravan extension reel with a 16 amp plug at the telescope end and a waterproof box for the plugs looks the best bet. I had no idea of the complications of using armoured cable!

David

[johninderby]

I use armoured cable to run power to the bottom of the garden for my shed, but that's a permanent setup. Armoured cable is so stiff it's totally unsuitable as an extension and it's not practical to roll it up.

Much better to get a good quality extension reel and an RCD as suggested in previous posts.

John

[swamp thing]

A number of people on this forum use mains power outside, I would hope/ assume that they have a much better understanding of electricity than me

The A&E department gets filled with people that assume they know what they are doing with mains power outside.

I am in the building trade and would never play around with mains connection. Leave it to the pros.

That's my advice

Regards Steve

[dark star]

Some last questions. Why a 16amp plug at the telescope end? Also, the caravan type leads seem to have a 3 pin plug which is different to the normal 3 pin house electric plugs, how will I plug this in to an extension to connect it to the plug from my telescope motor?

Forgive my ignorance about all things electrical!

David

[dark star]

Before I use the telescope hooked up to the mains I will be doing a lot of reading on every astronomy website I know of. I would be grateful for the opinion of anyone who is an electrician! I am using the telescope manually for the time being anyway.

David

[Chris H]

If as you say the motor your powering is 2 watts thats a very small amount of current 0.0083 amps so you don't need any sort of armoured cable or even a length or arctic cable (caravan lead type) a normal extension lead would do fine but put a 3 amp fuse in the plug. You just need to protect against live to earth leakage at the scope end and if your domestic switchboard has an RCD then that will cover you and you don't need an additional one. Dew is a very pure form of water and does not tend to cause electrical problems but you should still err on the side of caution. I would put the socket on the end of the extension and the plug from your mount in a plastic container, something like tupperware would be fine. For extra piece of mind you could mount this on a short wooden post to keep it off the ground. Anything more is overkill, if you use a caravan lead you will require adaptors at both ends so rather than a single connection at each end you would end up with two inside and two out.

[Helen]

Have a look in B&Q as last year they stocked waterproof boxes with extension cables and an RCD as a package designed to be used with Christmas lights. The cost was £25 I think. I've got a couple and they work very well.

Helen

[damnut]

Hi DarkStar,

All you need is a decent quality extension and one of these :-

Weatherproof Box Kit | Screwfix.com

Comes complete with an rcd and you will be fine, and the whole lot is 20 quid!.

Cheers

[Helen]

Hi DarkStar,

All you need is a decent quality extension and one of these :-

Weatherproof Box Kit | Screwfix.com

Comes complete with an rcd and you will be fine, and the whole lot is 20 quid!.

Cheers

That's exactly what I've got

Helen

[Karen]

Armoured (SWA) cable is meant for permanent installations and should only be installed by a qualified electrician. For any portable equipment outside the equapotential zone (that is outdoors) an extension reel plugged into a 30mA RCD protected socket is sufficient.

Karen, 17th edition I.E.E. Regulations qualified.

Now there's a surprise

[dark star]

I already bought the exact same Waterproof Box Kit form Screwfix, as it was recommended on this website before!

I just wanted to double check, the fuse in the plug for the lead which comes directly from the telescope motor (this is very short) should be 3 Amp (it may already be a 3 Amp fuse, I haven't checked!)?

I will then plug this in to the extension lead in the waterproof box (which came with the box), the extension lead then will plug in to a RCD in the mains in the house.

I am pretty confident the power of the motor is 2 Watts , as I have a manual for the mount very kindly sent to me by e-mail by Robert Mercer (thanks!)

Thanks again for all the advice. Now I just have to wait for it to stop raining!

I find a driven mount in RA even for just visual and with a rough polar alignment makes for a much more pleasant and relaxing experience.

Plus I still find the mount being able to track the stars magical!

David

[Karen]

2 Watts is a miniscule load. Only about .008 amps! The 3 amp plug fuse is about the best you can do for overcurrent protection. Really this type of equipment should have an internal fuse, like electronics which usually have one on the PCB.

[dark star]

I am glad to know someone has an understanding of electronics, which is more than can be said of me! Although I am learning, slowly!

I will be doing some reading about the old-fashioned type of AC synchronous motors.

I am a visual observer with some very amateur spectroscopy of stars thrown in. For this tracking for one or two minutes with a DMK41 CCD camera is sufficient, with a small amount of manual guiding if necessary.

David

[damnut]

Hi Darkstar,

WIth that current load you won't need the 10m spare swa hanging up in my garage left over from the hot tub that draws 36A :-)...

Cheers

[dark star]

The hot tub sounds great!

To be honest, I have only just learned the difference between Volts and Amps, to a small extent. I haven't progressed to an understanding of Watts yet!

I have some plans for very simple electronic circuits using batteries and a kit from Maplins, so I will be gradually learning. For some reason I find this relaxing in my spare time. Also, it stops me getting too annoyed with the clouds!

David

[damnut]

Hi DarkStar,

You are nearly there with watts ----- watts = Volts*Amps the three are interlinked, if you have two you can work out the other.

Cheers

[Telrad]

Have a look in B&Q as last year they stocked waterproof boxes with extension cables and an RCD as a package designed to be used with Christmas lights. The cost was £25 I think. I've got a couple and they work very well.

Helen

Helen's right - these boxes are ideal, plenty around this time of year