PJ Anway
Carpal Tunnel
Reged: 06/04/03
Posts: 2165
Loc: North Coast
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Quote:
I've got a disconnect panel ("farm panel") on the back of my house, so my own plan is to use that, drop out of that with some conduit for protection, with some 8-3 UF cable to a small panel on the observatory. Having a subpanel out there with its own ground rods makes me feel better considering recent lightning strikes in the neighborhood.
Mike,
A subpanel in an outbuilding has some rules that apply.
1) The gound conductor at the panel in your house must be continued to the subpanel
2) The neutral terminal bar in the subpanel must be isolated from the gounded conductor (i.e. - you don't bond the neutral terminal bar in the subpanel and you need a second bonded terminal bar for your ground wires)
Hope that helps.
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Clear Skies,
PJ
http://doublestarobserver.com
Refl.- 203/1420, Refr.- 100/1000, 75/500, 63/840, Bino.- 15X60, 10X50
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Mike Clemens
Frozen to Eyepiece
Reged: 11/26/05
Posts: 6707
Loc: Alaska, USA
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Thanks PJ, good stuff, I know exactly what you are talking about. I bought my house in 1995 and lived for 9 years with a subpanel where the original builder had bonded the neutral in. Around 2004 I had bought a BK Precision "voltage sniffer" and was miffed it didn't work well, it showed AC voltage on EVERY grounded item in my house. It was true!!
Ooo my 500th post... sage no more... fear me!
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Michael Rapp
Carpal Tunnel
Reged: 04/27/04
Posts: 2576
Loc: Dickinson, TX
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Thanks for the advice all. Here is my current plan with regard to power in my observatory. I'm going to get some bids for the entire job, and for just hooking the circut up to the breaker.
I'm also going to get some books on wiring today and read up on this stuff. From just a cursory investigation, it seems that wiring a disconnect (light) switch, and a receptacle is fairly straightforward.
If this turns out to be expensive (with or without me doing the "basic" wiring), I'll use the extension cord method for now during the winter months. The reason I would want continous power in the observatory is to power the dehumidifer.
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--Michael
Meade 8" f/6 Dob, Lunt 35mm | TeleVue 32, 13, 7.4 Plossls
Observatory: 10/27/2006 (First Light) - 9/13/2008 (Hurricane Ike)
My Sketches | Michael_in_TX on NSN
I am looking for a 1980s Edmund Scientific 3" f/10 red-tube reflector, PM me if you have or know of one!
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Richard B. Drumm
Pooh-Bah
Reged: 07/14/05
Posts: 1486
Loc: Albemarle Co. Virginia
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Yep, I wouldn't think you'd need the dehumidifier till May or so...
Rich
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AKA Richard Drumm The Astronomy Bum
Orion Atlas 10 (10" Newt on an equatorial mount)
Celestron 15x70 SkyMaster Binocs
Coronado Ha PST
President, Charlottesville Astronomical Society
IOTA member
38° 10' 57"N, 78° 23' 09"W
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Michael Rapp
Carpal Tunnel
Reged: 04/27/04
Posts: 2576
Loc: Dickinson, TX
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Hi all!
I've spent the past two evenings reading some books on electrical wiring. Black & Decker's Complete Guide to Home Wiring has been the best. Very clear information and lots of detailed photographs. Case studies and a good section on outdoor wiring.
I am so elated right now....for the first time in my life, I get it. I understand volts, watts, and amps. The veil of mystery is gone!  (Ohh...so that's what the "20" means on all of those circuit breakers!  )
In fact, this weekend, I'm going to make a circuit map of my house and check for any circuits that are getting close to their safety load. (I've also been walking around the house, finding random appliances and computing their wattage. My wife thinks I have lost it.  )
Outside in my backyard, I have a GFCI outlet on a dedicated 20 amp circuit. All I need to do is extend this circuit to the observatory, following the appropriate local codes.
This is so straightforward. Electrical wiring does not seem as horrendusly complicated as I thought and if I keep my attention to detail and safety, I should be fine. (Three wires? There is just hot, neutral, and ground? That's it?!) I really think I can do this (and save a lot of money doing it myself).
The books I got have great examples on how to provide proposed wiring diagrams to the City. I'll try to draw one up and run it by you guys first. 
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--Michael
Meade 8" f/6 Dob, Lunt 35mm | TeleVue 32, 13, 7.4 Plossls
Observatory: 10/27/2006 (First Light) - 9/13/2008 (Hurricane Ike)
My Sketches | Michael_in_TX on NSN
I am looking for a 1980s Edmund Scientific 3" f/10 red-tube reflector, PM me if you have or know of one!
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Moggi1964
Vendor - Astro Laugh
Reged: 11/07/05
Posts: 3636
Loc: Madison. NJ. USA
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Safety Tip:
If your hair stands on end you are doing something wrong!
Good luck!
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Morris
www.astrolaugh.com
Astrosystems Telekit 10" with F/6 JC Wilkinson mirror
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RogerRZ
Whatta you lookin' at?
Reged: 01/09/06
Posts: 3082
Loc: West Collette, NB, Canada
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Another one:
Never touch two wires at the same time!
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-Roger Pitre-
1 X 7 binocular
MN65, Nexstar 8SE, SV70ED, Lunt 60 PT
EQ6 Pro, Canon 50D, Modified XSi, SBIG ST-2000XM, 70-200 f/4L, BackyardEOS
"He's got shoulders on him like a smelt..."--Anonymous
http://www.facebook.com/album.php?aid=10723&id=509325956&l=79d06a1d10
http://ajpobservatory.is-great.org/
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RobVG
scholastic sledgehammer
Reged: 01/09/06
Posts: 836
Loc: Seattle Washington
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(Ah, he hasn't wired a two way switch yet...) 
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NeoDinian
Experienced Postmaster
Reged: 10/05/05
Posts: 14043
Loc: Rockford Illinois
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Quote:
(Ah, he hasn't wired a two way switch yet...)
Actually, that would be called a 3-way switch. (Switch, light, switch)... 2-way is a normal switch.
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Neo... (Jeff)
-=-=-=-=-=-=-
10" LX200-GPS/SMT UHTC "Draco"
 Rockford, Il.
NeoDinian's Eye on the Sky!
Coming soon:
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RobVG
scholastic sledgehammer
Reged: 01/09/06
Posts: 836
Loc: Seattle Washington
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I stand corrected. 
(But you knew what I meant.)
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RogerRZ
Whatta you lookin' at?
Reged: 01/09/06
Posts: 3082
Loc: West Collette, NB, Canada
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I meant don't touch the white and the black. If the breaker is off, I guess it wouldn't matter... 
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-Roger Pitre-
1 X 7 binocular
MN65, Nexstar 8SE, SV70ED, Lunt 60 PT
EQ6 Pro, Canon 50D, Modified XSi, SBIG ST-2000XM, 70-200 f/4L, BackyardEOS
"He's got shoulders on him like a smelt..."--Anonymous
http://www.facebook.com/album.php?aid=10723&id=509325956&l=79d06a1d10
http://ajpobservatory.is-great.org/
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lineman_16735
Tak-o-holic
Reged: 12/04/04
Posts: 3118
Loc: Central PA
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[quoteIn that an outbuilding, such as an observatory, needs a method of disconnecting all current carrying conductors, (hot legs), from their source feed, then a light in the observatory that is controlled by a 3 way switch in the house and the observatory, would need to have as its source the panel in the observatory because if one were to kill the observatory panel the light would be dead. If you were to feed the light from the house, you could kill the observatory panel and still have a hot circuit to the light.
I think you mean all ungrounded conductors. The nuetral conductor is a current carrying conductor as well. As far as the 3-way controlled light supplied from the home with a fixture mounted on an outbuilding this is fine at least with my interpretation of the NEC. If you are running only branch circuits to your observatory, the disconnect means does not have to be in the observatory. As long as you are "the sole management" 225-32 1999 NEC. This is an exception in the NEC and could be interpreted differntly from inspector to inspector. It is a good idea to have the disconnect in your observatory. Hire an electrician, and not a fly by night guy. Find a well established electrician who is licensed and fully insured, avoid the handyman route. As someone elese said earlier electrical work is easy, maybe some of it is. Understanding the systems and how they function takes years and experience. Doing the job right is not the quickest or cheapest way but the safest and most efficient. I don't ever remember thinking electrical work was easy back when I was an apprentice, that was probably because I was trying to pull 4 strands of 750 MCM 150' through 4" conduit with a rope and block &tackle. Oh those were the days 
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Chris
X-Astronomer
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LateViewer
Pooh-Bah
Reged: 11/17/05
Posts: 1009
Loc: Manhattan
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225.36 Suitable for Service Equipment
The disconnecting means specified in 225.31 shall be suitable for service equipment.
Exception: For garages and outbuildings on residential property, a snap switch or a set of 3-way or 4-way snap switches shall be permitted as the disconnecting means.
NEC 225.38 Disconnect Construction
Disconnecting means shall meet the requirements of 225.38(A) through (D).
Exception: For garages and outbuildings on residential property, snap switches or sets of 3-way or 4-way snap switches shall be permitted as the disconnecting means.
225.39 Rating of Disconnect
(A) One-Circuit Installation For installations to supply only limited loads of a single branch circuit, the branch circuit disconnecting means shall not have a rating of less than 15 amperes.
Okay. I think this should make it clear that a residential outbuilding is required to have a disconnecting means even if that is just a 15a snap switch.
With regard to the 3-way for a light in the residential outbuilding and does it qualify as a disconnect? Yes, but, if you have a subpanel in the outbuilding, and you have duel power sources in that outbuilding, the branch circuit from the house and the branch circuits from the sub-pannel, you could have a situation where the subpanel is off but you still have a hot conductor from the outbuilding. Maybe, maybe that passes code but it is still not a good practice and I would not have it or install it myself.
As to Article 225.32 Location
Exception No. 1: For installations under single management, where documented safe switching procedures are established and maintained for disconnection, where the installation is monitored by qualified individuals, the disconnecting means shall be permitted to be located elsewhere on the premises.
This does not apply to a residential electrical situation.
All quotes from the 2005 NEC
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Chance favors the prepared astronomer.
Yeah I have some stuff.
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lineman_16735
Tak-o-holic
Reged: 12/04/04
Posts: 3118
Loc: Central PA
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Quote:
Exception: For garages and outbuildings on residential property, a snap switch or a set of 3-way or 4-way snap switches shall be permitted as the disconnecting means.
NEC 225.38 Disconnect Construction
Disconnecting means shall meet the requirements of 225.38(A) through (D).
Okay. I think this should make it clear that a residential outbuilding is required to have a disconnecting means even if that is just a 15a snap switch.
With regard to the 3-way for a light in the residential outbuilding and does it qualify as a disconnect? Yes, but, if you have a subpanel in the outbuilding, and you have duel power sources in that outbuilding, the branch circuit from the house and the branch circuits from the sub-pannel, you could have a situation where the subpanel is off but you still have a hot conductor from the outbuilding. Maybe, maybe that passes code but it is still not a good practice and I would not have it or install it myself.
As to Article 225.32 Location
Exception No. 1: For installations under single management, where documented safe switching procedures are established and maintained for disconnection, where the installation is monitored by qualified individuals, the disconnecting means shall be permitted to be located elsewhere on the premises.
This does not apply to a residential electrical situation.
All quotes from the 2005 NEC
I could not agree more, it may be acceptable by NEC, but like I said I would not do it. Install a disconnect. But in regards to 235-32 exception 1, I don't see any mention of only commercial or industrial applications. Again I am not arguing the need for a disconnect, just pointing out the exception. In all seriousness please point out the article which discusses sole management situations. I don't mind being wrong, I just would like to know where this is written.
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Chris
X-Astronomer
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LateViewer
Pooh-Bah
Reged: 11/17/05
Posts: 1009
Loc: Manhattan
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Article 225-32
Exception No. 1: For installations under single management, where documented safe switching procedures are established and maintained for disconnection, where the installation is monitored by qualified individuals, the disconnecting means shall be permitted to be located elsewhere on the premises.
1. Under single management
2. Documented safe switching procedures.
3. Monitored by qualified individuals.
While most residences are under single managament, the remaining criteria indicates a commercial property.
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Chance favors the prepared astronomer.
Yeah I have some stuff.
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lineman_16735
Tak-o-holic
Reged: 12/04/04
Posts: 3118
Loc: Central PA
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Hmmm, I will have to look in my 2005 NEC as the 1999 simply says nothing about qualified individuals. Notes 1 & 2 are the same. Ahh hah there it is in the 2002 NEC infact the words qualified individuals are indeed added near the end of the exception. This does change things. IMHO it does point more towards commercial or industrial applications. Although the definition of qualified person in the NEC leaves much to be desired and would not eliminate anyone from being a "qualified person". This was definatly a change in the NEC that I would have never noticed, although one that I would have never tested as you said it is best to have a disconnect means. I do very much enjoy these conversations just for the reasons of learning things such as this. I love arguing exceptions to the code as they are very static to say the least. Thanks I hope we can do this again soemtime:-)
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Chris
X-Astronomer
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LateViewer
Pooh-Bah
Reged: 11/17/05
Posts: 1009
Loc: Manhattan
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From one "Code Warrior" to another, we will do it again sometime.
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Chance favors the prepared astronomer.
Yeah I have some stuff.
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lineman_16735
Tak-o-holic
Reged: 12/04/04
Posts: 3118
Loc: Central PA
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Chris
X-Astronomer
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Michael Rapp
Carpal Tunnel
Reged: 04/27/04
Posts: 2576
Loc: Dickinson, TX
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You guys are great! Even where there are points of minor disagreement, I know that on that which you agree....I'd better do it right! 
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--Michael
Meade 8" f/6 Dob, Lunt 35mm | TeleVue 32, 13, 7.4 Plossls
Observatory: 10/27/2006 (First Light) - 9/13/2008 (Hurricane Ike)
My Sketches | Michael_in_TX on NSN
I am looking for a 1980s Edmund Scientific 3" f/10 red-tube reflector, PM me if you have or know of one!
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Mike Clemens
Frozen to Eyepiece
Reged: 11/26/05
Posts: 6707
Loc: Alaska, USA
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Of all the back breaking and time consuming aspects of construction, I find electrical the easiest and most enjoyable. Precision measurements? Nope. Huge structures that need to be perfectly square? Nope. Take your time, do it right, add that disconnect even if code doesn't require it.
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http://www.pbase.com/mclemens1969/tec_200_observations
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