Rectifier demand load

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hhsting

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I have cell tower site with monopole tower. On ground are cabinets with rectifiers whose AC sides are fed by feeder breaker panelboard.
DC side feeds antennas, ray caps, the, etc etc equipment on monopole tower

I am reviewing plans which call for demand and load calculation for the AC panelboard at cell site and I looked into NEC 2014 Section 220 but there is no demand factor for it.

Anyone doing cell tower work does anyone know what they use for demand factor for AC side of rectifier? Where can this be found in NEC 2014?
 
430.22(A)(1) demands 190% of motor loads on DC rectifiers

If equipment is missing nameplate try instructions
 
I don't do cell phone tower work, so grain'o salt time:

A 'rectifier' in this context is a DC power supply. The unit will have its nameplate rating giving maximum power (and maximum current) input and output.

If you want to be most conservative, you would simply total up all of the power input ratings of all rectifiers on at the same time. This would certainly result in an oversized service.

The 'rectifiers' will themselves be powering loads, and will have an efficiency factor. So you could calculate the rated DC load placed on each rectifier, adjust for efficiency, and determine the actual AC power consumption based on DC usage, then total this up.

AFAIK there are no demand factors for this sort of installation in the NEC. I'm surprised that you are being asked to calculate the power consumption here; one would think that such would have been calculated as part of designing the actually cellular hardware.

-Jon
 
steve66 said:
Does the NEC even apply to a cell phone tower?

90.2 (B) (4) ??
Click to expand...
That is getting to be a big question for both communications and power. The rule in 90.2 was for 'regulated public unities".

Cell towers and even power plants are often owned by entities that are not "regulated public utilities".
 
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