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!

Featured:
   

2017 NEC and Related
2017 NEC
Now Available!

   
Recent Posts
Live Chat Feature
by Admin
Yesterday at 09:52 PM
Safety at heights?
by gfretwell
Yesterday at 07:16 PM
failed home inspection.
by gfretwell
Yesterday at 07:03 PM
Webmaster > Admin
by Admin
Yesterday at 05:49 PM
Old Bath Fan
by gfretwell
Yesterday at 01:38 AM
New in the Gallery:
Desk-mounted "power-board"
Top Posters (30 Days)
Admin 33
HotLine1 21
Ruben Rocha 16
gfretwell 15
Trumpy 13
Who's Online
0 registered (), 0 Guests and 178 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#25873 - 05/21/03 10:33 AM Compact Fluorescent Bulbs
George Offline
Member

Registered: 02/23/02
Posts: 380
Just bought some Sylvania 27w Compact Fluorescent bulbs.

The note on the back reads:

"Do not use more than 25 lamps per 20 amp. branch circuit."

25 * 27 = 675 watts

675/120 = 5.6 amps.

Is the starting current high enough to require this limitation? Or is it just to accomodate substitutions by incedescent bulbs?

Top
Work Gear for Electricians and the Trades

Work Gear for Electricians and the Trades
Work Gear for Electricians and the Trades
Arc Flash Clothing, Gloves, KneePads, Tool Belts, Pouches, Tool Carriers, etc. etc....

#25874 - 05/21/03 02:08 PM Re: Compact Fluorescent Bulbs
wa2ise Offline
Member

Registered: 11/29/02
Posts: 773
Loc: Oradell NJ USA
The power factor on those may be quite poor. They usually have inside a small rectifier that converts the 60 Hz AC input to DC and then more circuitry to convert that to a high frequency to drive the florescent tube. So the bulb will draw large spikes of current at the peak of the 60Hz sine wave and nothing in between. This is quite similar to PC computer power supplies in this respect. If the place is fed by 3 phase 120V the neutral will see excessive currents from the harmonics due to the bad power factor. In a house with single phase grounded center tapped 240V(the usual power company feed in the USA) this shouldn't be an issue. Because the timing of the current spikes from bulbs on both sides of the center tap happen at the same time. And thus cancel out on the neutral.

Top


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