ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat Box
Recent Posts
"Electric furnaces" and other odd American heaters
by LongRunner - 07/05/20 12:21 AM
Questioning the electrical norms
by gfretwell - 07/05/20 12:03 AM
PC has killed Experimentation?
by LongRunner - 07/04/20 02:37 PM
Lock-down Thread
by LongRunner - 07/02/20 05:56 AM
What would be the ideal solution?
by gfretwell - 06/30/20 02:39 PM
New in the Gallery:
Facebook follies, bad wiring
FPE in Germany pt.2
Who's Online Now
0 registered members (), 14 guests, and 8 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 2 of 2 1 2
Re: Engineers get bad rap, what about Architects? [Re: SteveFehr] #182803 12/11/08 07:12 PM
Joined: Jul 2004
Posts: 9,498
G
gfretwell Offline
Member
I don't know about solars but my windows had to be 55 PSF plus large object impact protection.


Greg Fretwell
Work Gear for Electricians and the Trades
Re: Engineers get bad rap, what about Architects? [Re: gfretwell] #182805 12/12/08 02:28 AM
Joined: Sep 2004
Posts: 68
H
homer Offline
Member
Most of the inverters require input power to function, for safety reasons, I suppose. However, I install a two pole contactor with the coil powered by the normal source. If utility power drops off line, the contactor de-energizes and disconnects the invertor from the grid. I don't like to rely on electronics to keep people safe. There is also the issue of a disconnect at the point where the power enters the structure and labeling indicating multiple sources of power at the panelboard.

Re: Engineers get bad rap, what about Architects? [Re: homer] #182806 12/12/08 04:44 AM
Joined: Jul 2004
Posts: 9,498
G
gfretwell Offline
Member
I agree with you 100%. I doubt if any electronic switch could be called a "disconnect". I sure wouldn't trust it.


Greg Fretwell
Re: Engineers get bad rap, what about Architects? [Re: SteveFehr] #182814 12/12/08 01:34 PM
Joined: Oct 2000
Posts: 5,389
S
sparky Offline
Member
i thought we had art 690 for this...?

~S~

Re: Engineers get bad rap, what about Architects? [Re: homer] #182892 12/16/08 02:30 PM
Joined: Mar 2005
Posts: 1,213
S
SteveFehr Offline
Member
Originally Posted by homer
Most of the inverters require input power to function, for safety reasons, I suppose. However, I install a two pole contactor with the coil powered by the normal source. If utility power drops off line, the contactor de-energizes and disconnects the invertor from the grid. I don't like to rely on electronics to keep people safe. There is also the issue of a disconnect at the point where the power enters the structure and labeling indicating multiple sources of power at the panelboard.
Isn't the inverter in parallel with the utility, though? It seems as though the contactor would be self-sustanining, with the inverter powering its own coils even if utility power is lost. You couldn't even use directional CTs, as loss of utility power would be indistinguishible from selling power back to the grid.

Does this method rely on the impedance of backfeeding the grid to be so low that internal resistance depowers the coils below the sustainment threshold?


Re: Engineers get bad rap, what about Architects? [Re: SteveFehr] #182904 12/17/08 02:36 PM
Joined: Jan 2005
Posts: 354
P
pdh Offline
Member
There are different causes for loss of utility power. At one extreme your service drop is knocked down by a tree. Your inverter or generator could keep those wires hot without any significant current drawn. Someone picking it up could die.

If there is no damage in your area/town but the upstream transmission grid is what is out, you should see about the impedance of your nearest utility transformer. Unless we are talking about a solar/wind farm, it is likely all the other customers are going to overload the system. Current going too high and/or voltage going too low should ideally trip the disconnect.

Now you can monitor the utility for power restoration. But there is a new risk: someone else's power system could make it look like the utility is back.

Re: Engineers get bad rap, what about Architects? [Re: NJwirenut] #182913 12/18/08 09:51 AM
Joined: Jan 2005
Posts: 65
P
petey_c Offline
Member
NJwirenut, There's also Sol Rosenberg. He thinks the world revolves around him too....

Re: Engineers get bad rap, what about Architects? [Re: petey_c] #183105 12/26/08 12:24 AM
Joined: May 2007
Posts: 46
Samurai Offline
Member
I'm sure I've been an electrician for my entire working life; but when I read 'solar system' I thought - 'who can get out there to check outside of Earth?' and 'well, at least the rest of the Galaxy, and the Universe, have been left alone for now.' - photovoltaic arrays didn't even enter my mind.

Frenchy I'm figuring the 'fly apart' concerns regarding Florida wind generation would pertain to hurricane safety.

Re: Engineers get bad rap, what about Architects? [Re: Samurai] #183147 12/28/08 03:27 PM
Joined: Jul 2004
Posts: 9,498
G
gfretwell Offline
Member
I think designing a wind generator for 150 MPH winds is within the technology but wind borne debris is another problem. I would have the same concerns anywhere that has tornadoes, even the little "dust devils" some east coast folks call tornadoes. (compared to the mid west monsters)


Greg Fretwell
Page 2 of 2 1 2

Featured:

2020 National Electrical Code
2020 National Electrical
Code (NEC)

* * * * * * *

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
Joe Tedesco
Joe Tedesco
Boston, Massachusetts USA
Posts: 2,749
Joined: October 2000
Show All Member Profiles 
Top Posters(30 Days)
Admin 7
Popular Topics(Views)
267,033 Are you busy
201,852 Re: Forum
190,433 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.3