ashare 90.1,2004 voltage drop calculation
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Question

ashare 90.1,2004 voltage drop calculation

LEEDAPspain (Electrical)

(OP)

14 Apr 10 07:13

Hi Everyone,

I am working on a LEED® intenational project, that follows ASHRAE 90.1-2004 and we have some problems interpreting the concept of feeder conductors and its voltage drop (VD). I would be very thankful if anyone could help me with the interpretation, hope it is not too simple for this kind of forum. It might be easier if I ask it through an example:
I have a main feeder conductor (FC1)that ends in an "over current protection device"(OCDP). From that OCDP three feeder conductors start (FC2, FC3, FC4).
ASHRAE 90.1 states "Feeder conductors shall be sized for a maximum voltage drop of 2% at design load".
The question is if the voltage drop should be calculated through CASE 1 or CASE2:
CASE 1: VDFC1 + VDFC2 < 2%
        VDFC1 + VDFC3 < 2%
        VDFC1 + VDFC4 < 2%

CASE 2: VDFC1 < 2%
        VDFC2 < 2%
        VDFC3 < 2%
        VDFC4 < 2%
(I have attached a diagram of the question that might be helpful)
Thank you very much in advance!!!!

mauricestoker (Mechanical) · Answer 1 · 2010-04-20 16:19:08

Feeders require no more than 2%, branch circuits have an allowable 3%. The 90.1 User's Manual copies the NEC 2002 example exactly.

DRWeig (Electrical) · Answer 2 · 2010-04-21 09:14:15

Maurice is right, and as for your calculation, Case 1 is correct.

You're allowed 2% from service to the branch circuit origin, then 3% for the branch circuit.

That distance from the service to the branch circuit panelboard may actually be composed of several feeders, one from main entrance equipment to sub-distribution panelboard, then from sub-distribution panelboard to load center. 2% end to end.

Good on ya,

Goober Dave

LEEDAPspain (Electrical) · Answer 3 · 2010-04-21 09:26:02

Thank you very much both of you!!!! now is completely clear for me. Adapt to a foreign code is not always easy

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ashare 90.1,2004 voltage drop calculation
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