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
Forum Software Upgrade coming soon...
by HotLine1
01/17/17 03:23 PM
Would ELV branch circuits be a good idea?
by gfretwell
01/17/17 01:26 PM
Why cables look like they do
by Texas_Ranger
01/17/17 12:33 PM
Re: Fabricating Guards out of Lexan?
by ghost307
01/17/17 11:21 AM
100% breakers?
by Texas_Ranger
01/16/17 06:13 AM
New in the Gallery:
Desk-mounted "power-board"
Shout Box

Top Posters (30 Days)
HotLine1 20
Webmaster 15
Trumpy 12
ghost307 12
gfretwell 11
Who's Online
2 registered (HotLine1, frank), 0 Guests and 69 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#130819 - 03/08/07 04:32 PM Metal Halide Lights
aldav53 Offline
Member

Registered: 08/22/01
Posts: 547
Loc: Chandler, AZ USA
Installing 2 - 400 watt metal halide lights per pole. 4 parking lot lights in an existing light poles. Can I go with 3-400 watt lights per 20 amp 120 volt circuit? Do I need to allow for the tranformer in the light?
_________________________
The Golden Rule - "The man with the gold makes the rule"

Top
#130820 - 03/08/07 06:25 PM Re: Metal Halide Lights
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
This question sounds very familiar, but nevertheless here is my $0.02:

Use the listed Line Input Amperes for the Fixture or Ballast, which will reflect the computed VA Load value for a given Fixture.

This information may be found either on the Ballast's Nameplate, the Fixture's Nameplate, or from Cutsheets for the Fixture and/or a Ballast Manufacturer.

Typically, for any common Guesstimation, if the Ballast kit includes a Capacitor + is listed as "HPF" (High Power Factor), then the PF is somewhere in the 0.8 region.

A 400 Watt HID Ballast / Lamp assemblage with 80% Power Factor, should draw 4.0 Amps at 120 VAC during normal operation.

If the Ballast is CWA (Constant Wattage Autotransformer), the 4.0 Amps should remain somewhat steady from initial starting of the Lamp, throughout the normal operation; meaning:
* There should not be any high starting current demands to consider (some starting current demands may be in excess of 200% the stable operating current rating).

So, if a given Fixture draws 4.0 Amps at 120VAC, and you plan to install Three (3) Fixtures per 20 Amp Circuit, the "Subtotal" Load Current per Circuit would be 12.0 Amps.

Add 25% for LCL (unless these Lights will be on for less than 180 minutes at a time), and the resulting per-circuit designed load is 15 Amps per 20 Amp Circuit.

This conforms to the minimal NEC requests for using #12 with 20 Amp OCPD, and applying an LCL derating factor.

As always, verify that there will not be excessive Voltage Drop issues, as the HID Lamps may cycle excessively, or Ballasts may be damaged - or both.

Let me know if I did not address your question correctly, or if you have additional questions.

Scott35
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

Top
#130821 - 03/13/07 04:45 PM Re: Metal Halide Lights
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
aldav53 ,

Did this information help?

Scott35
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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