NEC Power usage recommendation

[ptobis]

On a percentage and total amp basis, what is the recommended max load per 110 VAC circuit? 208-250 VAC? for example, how many amps can I load on a 20 amp circuit? This would be in a data center installation with up to 16 devices going through a power strip to the 20 amp circuit. Further, do you know where I can reference this information. My information is that 60% is the recommended maximum load due to the Power-In rush coming from several devices at once. thanks everyone

 

[iwire]

Re: NEC Power usage recommendation

For continuous loads it would be 80 percent.

15 Amp circuit = 12 amps
20 Amp circuit = 16 amps
30 Amp circuit = 26 amps

The voltage is not relevant.

But you question goes against normal "Data center" practices

Usually run dedicated circuits so one circuit off due to a fault or being serviced only effects 1 piece of equipment.

Even when we have more then one outlet to a circuit we never load them to max allowed.

Bob

[ February 26, 2003, 06:27 PM: Message edited by: iwire ]

 

[Len_B]

Re: NEC Power usage recommendation

Bob, 30amp x .8 = 24 amp for 30 amp circuit. (edit: circuits sized at 125% per Art 645)
I agree with Bob on the dedicated (or logically grouped) circuits and would add not to run any multiwire branch circuits to IT equipment due to possible harmonics problems.

Len

[ February 26, 2003, 06:52 PM: Message edited by: Len_B ]

 

[dereckbc]

Re: NEC Power usage recommendation

I agree with the 80% rating. Data centers are my bread and butter and we use one dedicated 20-amp circuit per equipment rack/cabinet supplied from a UPS rated anywhere from 100 KW to 600 KW and conductors to keep VD at or below 3.3% at full load.

 

[iwire]

Re: NEC Power usage recommendation

Originally posted by Len_B:
Bob, 30amp x .8 = 24 amp for 30 amp circuit.

[ February 26, 2003, 06:53 PM: Message edited by: iwire ]

 

[iwire]

Re: NEC Power usage recommendation

To apply article 645 he needs to meet 645.2(1)(2)(3)(4)(5)

1)Disconecting Means
2)Seperate HVAC
3)Listed Equipment
4)limited occupancy
5)Fire rated walls

Hard to tell from his post if he can meet all
that.
Bob

I was thinking on the 125% #12AWG MC is rated 30 amps 310.16 90c (for rating purpises)

So for a 24 amp load I can run #12s.

125% x 24amps = 30

Max OCPD for #12s is 20 amps (240.4(D)

What am I missing?

[ February 26, 2003, 07:21 PM: Message edited by: iwire ]

 

[ptobis]

Re: NEC Power usage recommendation

Thanks everyone for your replies. I actually sell IP addressable Power Strips that sequence power on to each outlet, thus reducing the Power In-Rush. I just wanted to get a feel for how people are loading up their circuits.