The Electrical Contractor Network

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

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!


2017 NEC and Related
2017 NEC
Now Available!

Recent Posts
Parking lot pole light swap....
by gfretwell
10/23/16 11:04 PM
International Wire Colour Codes
by Tjia1981
10/23/16 12:08 PM
Son of Sparky
by HotLine1
10/20/16 07:43 PM
Speaking of Plugmold ...
by gfretwell
10/17/16 02:37 PM
Broken battery charger? Check for cobwebs!
by gfretwell
10/17/16 02:30 PM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 13
HotLine1 7
ghost307 6
renosteinke 6
Potseal 4
Who's Online
1 registered (LongRunner), 230 Guests and 4 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#129526 - 04/12/05 09:48 AM DC on AC rated devices
PEdoubleNIZZLE Offline

Registered: 06/16/04
Posts: 176
Loc: 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)

#129527 - 04/12/05 10:35 AM Re: DC on AC rated devices
BPiersel Offline

Registered: 01/06/05
Posts: 18
Loc: 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 - 04/12/05 10:39 PM Re: DC on AC rated devices
PEdoubleNIZZLE Offline

Registered: 06/16/04
Posts: 176
Loc: 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 ( 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 05:15 AM Re: DC on AC rated devices
pauluk Offline

Registered: 08/11/01
Posts: 7693
Loc: 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.

#129530 - 04/13/05 10:16 AM Re: DC on AC rated devices
Alan Belson Offline

Registered: 03/23/05
Posts: 1801
Loc: 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.
Wood work but can't!


ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals