electrical wiring question

[Somnium]

Hi all,

this weekend i am looking to wire up the electrics of my observatory. i am going to get all the cable laid and then have an electrician just connect it up (to save a bit). i am running an electric gate opener, computer, mount (i want to be able to support a heavy duty mount for when i upgrade), camera, 1 light but not all at the same time. i have got some 16A circuit breakers for the sub panel i will be installing in the observatory which will service the power outlets and a 10A breaker for the light, i have also got a copper grounding rod. the observatory is about 30 mtrs from the main electrical panel. does anyone have any idea what cabling i should use for


the power cabling
the light cabling
the mains panel to the sub panel


can i use the same cabling for all 3? if so, what should it be?

finally, what circuit breaker should i use on the mains. i am sure 20A would be sufficient, but i have heard others just using 60A for any sub panel.

thanks in advanced for the help

[glend]

Wow! I get by with one ten amp feed. Shouldn't the electrician spec the cable based on your probable draw? What about solar with a battery bank?

[gary]

Hi Aiden,

Just a reminder that the state of NSW does not allow for DIY electrical
work like you describe.

As the Department of Fair Trading warns,



See http://www.fairtrading.nsw.gov.au/ftw/Tradespeople/Home_building_licensing/Licence_classes_and_qualifications/Electrical.page

Most states in Australia also have penalties that include imprisonment if
illegal work results in death or injury.

So given IceInSpace is a public forum in Australia and that people
are likely to reply in good faith but without the necessary knowledge
or qualifications, it might be prudent to talk to your electrician first
for further advice. :thumbsup:

Best Regards

Gary Kopff
Mount Kuring-Gai
Member Institute of Electrical and Electronic Engineers 37 years.

[Somnium]

Thanks Gary, i wasn't intending on doing any DIY electrical work, just getting all the gear ready so the electrician doesn't need to take 2 days to complete the job.

[Somnium]

never mind, i will call the electrician tomorrow and have a talk with him.

[gary]

Hi Aidan,

That's the best approach. :thumbsup:

In some jurisdictions in the world, for example I believe in New Zealand,
you can legally do many wiring tasks on systems not yet connected
to the power box as long as you follow the Code of Practice and then you
have to have them certified by a licensed inspector.

In the various states of Australia, no such concession exists that I am aware of.
Certainly not in states such as NSW or Queensland.

However there is the potential for real hazard.

For example, there is the ongoing Infinity brand cable recall where
between 2010 to 2013 an estimated 40,000 homes and commercial
buildings in Australia have been wired up with cable that has poor
quality insulation that becomes brittle and fails, which can then lead to
the risk of shock and fires.
https://www.accc.gov.au/update/infinity-cable-recall-act-now-before-its-too-late

When you mentioned you have a copper grounding rod, that rang
warning bells for me. An additional safety earth may or may not be
recommended depending on the wiring code and what existing earth
leakage protection you may have.

Inadvertently bypassing an existing earth leakage detection by adding
a second grounding point may bring about a shock hazard for those
in the house. Years from now, perhaps after you have sold the house,
if a toddler were to poke something in a power point in the house and
the earth leakage not trip because of incorrect grounding practice
in the observatory, it could kill them.

Given that observatories are open to the skies at night where rain and
dew can be present, it would be best to treat them as one would an
outdoor installation.

So anyone reading this in the DIY Observatories thread is best advised
to ensure any electrical work is carried out in accordance to the laws
of the jurisdiction in which they reside.

Best Regards

Gary

[The_bluester]

Interesting reading given that I do plan an obs, and in particular we have just had a sparky out today for an RCD which died at 5am. Cue getting woken up by an ups beeping!

Gary, understanding completely that a sparky will be doing the work, any tips for an obs? I was looking at a design with a warm room and very limited AC power out in a RoRo area. Basically looking to run almost everything in the "outdoor" off 12VDC lab power supplies in the warm room, including DC LED lighting.

240v appliances and Kilmore dew leave me a bit cold I have to say.