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#6071 - 12/21/01 09:47 PM Lighting contactor  
ayrton  Offline
Member
Joined: Dec 2001
Posts: 201
Pa
Question is, I am installing sixty 400w fixtures for parking lot lighting. Add up the wattage and you have 24kw. Now this is a three phase 208/120v system. Since the load is so high I am going to wire for 208v.
In order to size the contactor, when I do my division, do I multiply 1.73 for three phase, which gives me 66 and change or do I leave out the 1.73, because the fixtures are single phase? which would give me 115a.


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#6072 - 12/21/01 10:42 PM Re: Lighting contactor  
electure  Offline


Member
Joined: Dec 2000
Posts: 4,259
Fullerton, CA USA
Unless you are installing incandescent fixtures, the load will be more like 460W per fixture (HPS or MH).
Be sure to load the circuit to 80% (or less) of the circuit rating if the load is continuous (more than 3 hrs at a time).

[This message has been edited by electure (edited 12-21-2001).]


#6073 - 12/22/01 07:43 AM Re: Lighting contactor  
maintenanceguy  Offline
Member
Joined: Dec 2001
Posts: 300
Southern NJ, USA
I'd like to know the answer to this too. Anyone know?


#6074 - 12/22/01 11:08 AM Re: Lighting contactor  
Frank Cinker  Offline
Member
Joined: Jul 2001
Posts: 311
Pennsylvania
When sizing conductors, disconnect switches, contactors etc. I believe the amp value on each ballast must be used, not the wattage of the lamp. For example a 400 watt metal halide fixture operating at 208 V. has a ballast amp value of 2.30 or 478.4 watts per fixture. Multiply 478.4 watts by 60 fixtures = 28,704W / 208V x 1.73 = 79.73 Amps.

A 100 Amp three phase contactor should work fine.

Use 3AWG,THHN Conductor Size.

Assuming the single phase fixtures are balanced properly on the three phase system.

[This message has been edited by Frank Cinker (edited 12-22-2001).]


#6075 - 12/22/01 11:14 AM Re: Lighting contactor  
electure  Offline


Member
Joined: Dec 2000
Posts: 4,259
Fullerton, CA USA
Yes, if they are supplied by a 3Ø system, you will divide by 1.732
460 / 208 = 2.21A (load per fixture)
2.21A X 60 = 132.6 (total load)
132.6A / 1.732 = 76.6 (load @208v 3Ø)
76.6A X 1.25 = 95.6A (if a continuous load)

Looks like a 100A contactor to me!


#6076 - 12/22/01 01:16 PM Re: Lighting contactor  
golf junkie  Offline
Member
Joined: Apr 2001
Posts: 507
York, NE
>Use 3AWG,THHN Conductor Size.

Don't forget voltage drop if applicable.....sometimes those parking lot runs can get pretty long.

GJ


#6077 - 12/22/01 01:48 PM Re: Lighting contactor  
Bill Addiss  Offline
Member
Joined: Oct 2000
Posts: 3,878
NY, USA
To be more correct, We have to say THWN
Right? [Linked Image]
(assuming underground/wet location installation)

(I call it THHN too) [Linked Image]

Bill


#6078 - 12/22/01 03:21 PM Re: Lighting contactor  
electure  Offline


Member
Joined: Dec 2000
Posts: 4,259
Fullerton, CA USA
We must be careful! [Linked Image]
I've had my otherwise correct blueprints rejected from plan check 'causa my nasty habit of calling it THHN. They don't buy "You know what I mean". [Linked Image]
Here's a couple of things that might help (or maybe not).
Rather than a timed panel, (I'm doing some guessing here), you might consider putting in a large box with listed multi pole lighting contactors rated per your individual branch circuits.
Use a timeclock and photocell to operate this.
A contactor can be used to operate certain security lights that stay on all night via the P/C.
Others can be turned on by P/C, and off by the time clock (just series the P/C and T/C, set the T/C earlier than dark).
You're not limited to 20 amp circuits here if these are HID fixtures, it can be up to a 50A, but you certainly CAN'T use a 100A circuit with #3 wire for anything other than a feeder to smaller C/Bs or fuses.


#6079 - 12/22/01 05:36 PM Re: Lighting contactor  
Redsy  Offline
Member
Joined: Mar 2001
Posts: 2,056
Bucks County PA
Can someone explain how a 3 pole contactor will be used to operate these lights? Is a whole panel controlled by a timer a common way to do this?

[This message has been edited by Redsy (edited 12-22-2001).]


#6080 - 12/23/01 10:30 AM Re: Lighting contactor  
electure  Offline


Member
Joined: Dec 2000
Posts: 4,259
Fullerton, CA USA
Rojosy, [Linked Image]
The timed panel approach is not that uncommon out here. It's generally used in larger shopping centers where the tenants have their own meters, and the site lighting/signage power is provided by the landlord. With this setup, all the lighting/signage is sure to come on at once.
A smaller panel is usually non-switched, and provides the power for irrigation controls, timeclock power, etc.
I like the setup I mentioned above much better.
(I sure hope that nobody had in mind a single 100A contactor with that circuit run around the parking lot) [Linked Image]




[This message has been edited by electure (edited 12-23-2001).]


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