Non-coincident lighting loads

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Hey all, I have a couple of inquiries for electricians/code experts out there. I'm an electrical EIT, and I've used non-coincident heating/cooling loads (NEC 220.60) before to cut demand load during design before, but I'm curious as to if/how one can use this for lighting loads. Me and a couple of my colleagues are starting a side business in a different field and are working on preliminary design. We're going to open a grow shop, and we don't have enough service to run all the (HID) grow lights we want all at once. In the end, I'd like to run two grow light circuits, each with eight 1000W HPS fixtures for flowering. My question is this: is there a way that you think we could use a timer and lighting contactors to run two lighting circuits on opposing 12 hour cycles? Do you think this would be enough to satisfy local inspectors that these are indeed non-coincident loads? The idea is when one grow light circuit is on, the other is electrically disconnected so that the two circuits can never be electrically connected to the panel at the same time. Ideally, I'd like to have a 10 minute buffer between cycles. We're going to use lighting controls that keep the ballasts warmed up (hence the 10 mins to let the ballasts turn on and warm up), and they ramp up the fixtures instead of just turning straight on to 100% to mitigate large inrush currents. Please, let me know if I'm not clear enough in my explanation. Let me know what you think. Thanks!
 

mgookin

Senior Member
Location
Fort Myers, FL
Hey all, I have a couple of inquiries for electricians/code experts out there. I'm an electrical EIT, and I've used non-coincident heating/cooling loads (NEC 220.60) before to cut demand load during design before, but I'm curious as to if/how one can use this for lighting loads. Me and a couple of my colleagues are starting a side business in a different field and are working on preliminary design. We're going to open a grow shop, and we don't have enough service to run all the (HID) grow lights we want all at once. In the end, I'd like to run two grow light circuits, each with eight 1000W HPS fixtures for flowering. My question is this: is there a way that you think we could use a timer and lighting contactors to run two lighting circuits on opposing 12 hour cycles? Do you think this would be enough to satisfy local inspectors that these are indeed non-coincident loads? The idea is when one grow light circuit is on, the other is electrically disconnected so that the two circuits can never be electrically connected to the panel at the same time. Ideally, I'd like to have a 10 minute buffer between cycles. We're going to use lighting controls that keep the ballasts warmed up (hence the 10 mins to let the ballasts turn on and warm up), and they ramp up the fixtures instead of just turning straight on to 100% to mitigate large inrush currents. Please, let me know if I'm not clear enough in my explanation. Let me know what you think. Thanks!

Welcome to the forums.

You asked 2 questions:

1. is there a way that you think we could use a timer and lighting contactors to run two lighting circuits on opposing 12 hour cycles?

2. Do you think this would be enough to satisfy local inspectors that these are indeed non-coincident loads?

And the answers are:

1. Yes.

2. Maybe.

Now the why:
You can use a logic control or other arrangement to accomplish #1.
You're asking us if something will convince a local inspector ... I suggest you pose that question to the local inspector.

I'm also assuming what you are growing is legal to grow where you want to grow it (I'm not up on all the laws).
 

Smart $

Esteemed Member
Location
Ohio
Wire your two circuits to a contactor with one circuit through N.O. contacts, and the other through N.C. contacts. Control the contactor with your timer.

Never heard of pre-warming ballasts... :?
 
Thanks folks. Yes, everything I'm proposing is legal. I just wanted to verify that it was doable. Next stop is to get in touch with a local inspector and pose the question to them. I've never heard of pre-warming ballasts either, but the claim of the lighting controls and ballasts I'm going to use is that the ballasts are always kept in a standby mode that decreases large inrush currents. The ballasts are able to be put into an 'external' control mode and controlled with a master controller/timer via low voltage cabling. While I will have a controller for each circuit that are timers, I figured I'd have a much higher chance of these loads being considered non-coincident if they were hard wired to never be on at the same time. Thanks!
 
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