80% rule twice?

[K2X]

I doing an estimate for a small grow house, (yes, we're legal here), and I have a question on the remote cord and plug hid ballasts. The ballasts draw 10.2 amps @ 120v or 5.1a @ 240 v. The boss says i have to use 2008 210.21(b)(2) which limits a 20 amp breaker to 80% or 16 amps plus he wants it reduced again using 210.20 (a), continuous load, to 12.8 amps. This means I can only run 2 ballasts on a 20 amp 240v circuit instead of 3 ballasts. ..
I've done commercial lighting for years and 16 amps was always the number we used for hid's on a 20 amp circuit so i'm a little confused on what the code is actually calling for in this case?
Thanks for any help.

 

[charlie b]

Your boss is double counting. The load is what it is. In your case, the load is 5.1 amps per ballast. One code requirement says the overcurrent device has to be based on 125% of the continuous load. So that limits the continuous load to 16 amps, and the number of your ballasts to three. The other code requirement says the plug and cord connected load can't exceed 16. This requirement does not bring the 125% factor into play. Both requirements, separately and independently, limit you to 16 amps. Three ballasts can be put on a circuit.

 

[petersonra]

I doing an estimate for a small grow house, (yes, we're legal here), and I have a question on the remote cord and plug hid ballasts. The ballasts draw 10.2 amps @ 120v or 5.1a @ 240 v. The boss says i have to use 2008 210.21(b)(2) which limits a 20 amp breaker to 80% or 16 amps plus he wants it reduced again using 210.20 (a), continuous load, to 12.8 amps. This means I can only run 2 ballasts on a 20 amp 240v circuit instead of 3 ballasts. ..
I've done commercial lighting for years and 16 amps was always the number we used for hid's on a 20 amp circuit so i'm a little confused on what the code is actually calling for in this case?
Thanks for any help.

The boss may not always be right, but he is always the boss. I don't see it as code required, but if he is sure that is the way he wants it done, what difference does it make to you? It is still a safe and legal installation and you still get paid by the hour. You just get a few extra hours of pay out of the deal.

 

[K2X]

The boss may not always be right, but he is always the boss. I don't see it as code required, but if he is sure that is the way he wants it done, what difference does it make to you? It is still a safe and legal installation and you still get paid by the hour. You just get a few extra hours of pay out of the deal.

I agree, and two on a circuit is fine with me and allows for expansion etc. I just like to get the actual requirements straight in my head. Comes in handy once in a while. Thanks for the replies..

 

[billsnuff]

What are the consequences here? 2 on a circuit, more material and more labor?
3 on a circuit, more profit? Which one satisfies the customer and makes the most money?

I'd let the boss know that 16A is good for 3 on a circuit and let him make the call.
After all it is his money.

 

[GUNNING]

If you are getting paid for it, do it.

If you are getting paid for it, do it.

If the control devices are not rated for more than the load, it might be why the limit on the number of lights. Do the grow lights need to be Ground Faulted?

 

[tryinghard]

What r ya growin - maybe it adds to the load[ed]

 

[LarryFine]

What r ya growin - maybe it adds to the load[ed]

From CA and you gotta ask?

 

[tryinghard]

From CA and you gotta ask?

Some kinda farmin, we got farmin here to but mostly tomaters, spargus, brokoly, stuff like that