ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals

ECN Shout Chat
Top Posters(30 Days)
Admin 19
Recent Posts
Anyone hiring inspectors?
by HotLine1. 03/27/17 08:03 AM
Old decora style outlets
by Admin. 03/25/17 11:40 AM
ESA Arc flash course
by TheShockDoctors. 03/24/17 10:15 AM
fuse rejectors
by HotLine1. 03/24/17 07:53 AM
Another Forum Update
by Admin. 03/22/17 03:04 PM
New in the Gallery:
SE cable question
Popular Topics(Views)
231,583 Are you busy
166,394 Re: Forum
160,691 Need opinion
Who's Online Now
1 registered members (HotLine1), 76 guests, and 15 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#129526 - 04/12/05 12:48 PM DC on AC rated devices  
PEdoubleNIZZLE  Offline
Member
Joined: Jun 2004
Posts: 176
McKeesport, PA, USA
I know most, if not all, devices used in AC wiring are not rated for DC. What would happen if, say a fuse, switch, lampholder, receptacle, incandescent bulbs, were used on a DC circuit at the same rated voltage (let's not worry about what it would do to appliances). is there an overheating issue? What about using a higher frequency AC (say 600hz instead of 60)
Thanks,
Josh


Tools for Electricians:

#129527 - 04/12/05 01:35 PM Re: DC on AC rated devices  
BPiersel  Offline
Member
Joined: Jan 2005
Posts: 18
Minnesota
Switches and fuses (or breakers) rated for AC only should not be used on DC. The problem is that DC is more difficult to interrupt due to the greater tendency to arc. Any wire will have some amount of inductance, and this will cause a voltage spike if a switch or fuse is opened. This voltage spike may be much higher than the nominal voltage and it may be enough to create an arc across the opened switch or fuse.

Lampholders probably will not have a problem on DC, as long as you don't try to remove the lamp with the power on. Incandescent lamps will work fine on DC.

I've never worked with high frequency AC, so I can't answer that part of your question.


#129528 - 04/13/05 01:39 AM Re: DC on AC rated devices  
PEdoubleNIZZLE  Offline
Member
Joined: Jun 2004
Posts: 176
McKeesport, PA, USA
That's good enough reason not to use them. I'm trying to incorporate a little bit of 12 or 24V solar/wind power in my house. I've been designing systems for the past 5 years (www.otherpower.com my systems are less crude than theirs, but it's the same basic idea.) I'm just trying to find some type of receptacles/fuses rated for DC. I've found compact fluorescent bulbs for 12VDC with a Medium Edison base. I would never use a NEMA receptacle of any kind on my system just because I don't want to plug the wrong thing in the wrong plug. I am trying to shy away from cigarette lighter plugs.


#129529 - 04/13/05 08:15 AM Re: DC on AC rated devices  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
The possibility or drawing an arc is why switches rated for DC need to be a quick-break type. Back when DC supplies were in use here, DC-rated light switches had a spring-action toggle mechanism, so that no matter how slowly you tried to move the operating handle you'd just reach a certain point, then the spring would snap the contacts right open in one go. Ditto for the main switchgear.

I had an inverter in for repair a few weeks ago, a fairly high-quality true-sinewave unit from a Swiss manufacturer. Yet they'd used a circuit breaker on the 12V input which was a regular domestic type rated for AC only. [Linked Image]


#129530 - 04/13/05 01:16 PM Re: DC on AC rated devices  
Alan Belson  Offline
Member
Joined: Mar 2005
Posts: 1,803
Mayenne N. France
Since you have been experimenting for some time, you will be aware of the transient nature of wind/solar, and will probably have incorporated a storage battery(s) - (deep-draw Golf-Buggy type I hope- and do some searching on the net to see how to make these have a long life) - in your design. Why not put a 12vdc-120/240vac inverter at your 12V output- then all 'your' power can use standard ac parts and you can wire everything to US Codes, nice and safe.
(Kept ABSOLUTELY TOTALLY separate to your POCO supply of course!!) I have a UK catalog here now-
330W =US$9O 1000W = US$350- & a LOT cheaper in the US- you lucky buggers! Inverters do burn some power when unloaded, so you do need a 12vdc switch(s) for isolation- and I know just the place- Auto-breakers yard- a key/ignition switch & relay for a car starter motor- one of those mothers will switch 200A! Sounds a good project.
Alan.


Wood work but can't!


Member Spotlight
HappyElectrician
HappyElectrician
Penn USA
Posts: 31
Joined: December 2011
Show All Member Profiles 
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.016s Queries: 14 (0.003s) Memory: 0.7676 MB (Peak: 0.9062 MB) Zlib enabled. Server Time: 2017-03-27 20:31:11 UTC