I'm working through Annex D Example D3(a) and need help understanding why the 3,960 VA of receptacle load is assumed to be equally distributed between all three phases when performing the conversion to amperes if we are dealing with 22 receptacles... If we assume near equal balancing, why wouldn't one phase have 180 VA more than the other two phases? and why isn't this reflected in the neutral load even if its fed from a SDS?

Secondly, why are they using 99,000 VA instead of 113,200 VA for determining the ungrounded feeder conductor size?

In the example, 195 amperes X 0.96 X 0.7 = 131 A does not have sufficient ampacity to carry 136A.

Wouldn't this require 3/0 instead of 2/0 since 225 amperes X 0.7 X 0.96 = 151 A and is greater than 136 A?

Thanks in advance.

]]>Secondly, why are they using 99,000 VA instead of 113,200 VA for determining the ungrounded feeder conductor size?

In the example, 195 amperes X 0.96 X 0.7 = 131 A does not have sufficient ampacity to carry 136A.

Wouldn't this require 3/0 instead of 2/0 since 225 amperes X 0.7 X 0.96 = 151 A and is greater than 136 A?

Thanks in advance.

If the ambient temperature is 59° with #3 copper 90C wiring then can I actually load my conductor to 112 amps and use a 125 amp breaker.

#3 at 75C is 100-- 100 * 1.12 (temp correction) = 112 amps or do I have to use the correction at the 90 C and never be over the 75C at 100 amps.

]]>#3 at 75C is 100-- 100 * 1.12 (temp correction) = 112 amps or do I have to use the correction at the 90 C and never be over the 75C at 100 amps.

Here is the problem.

I am trying to practice solving for Apparent Power and Impedance.

I get different angles when I try solving for the apparent power.

Maybe I am using the Conjugate of the current incorrectly when solving for this problem.

I'm not sure what I am doing incorrectly.

20190221224308.pdf

I'm working through Annex D Example D3 and need help understanding what is the point of talking about 125% under the *General Lighting** asterisk note. It seems arbitrary to be talking about 125% when comparing the minimum lighting load with the actual connected lighting load...

Thanks in advance.

]]>Thanks in advance.

I'm working through Annex D Example D2(b) and need help understanding why a 55% demand factor is being applied to "Two-4kVA ovens plus one 5.1-kVA cooking unit".

Clearly the 55% demand factor applies to Table 250.55, note 3. However consider that Table 250.55, note 4 states, "The branch-circuit load for a counter-mounted cooking unit and not more than two wall-mounted ovens, all supplied from a single branch circuit and located in the same room, shall be calculated by adding the nameplate rating of the individual appliances and treating this total as equivalent to**ONE **range."

Consider the example does not specify whether this equipment is or is not on a single branch circuit or located in the same room. The conservative approach is to apply note 4 but to get the minimum calculated load we would use note 3. Any insight on how to make sense of this is appreciated. Thanks in advance.

]]>Clearly the 55% demand factor applies to Table 250.55, note 3. However consider that Table 250.55, note 4 states, "The branch-circuit load for a counter-mounted cooking unit and not more than two wall-mounted ovens, all supplied from a single branch circuit and located in the same room, shall be calculated by adding the nameplate rating of the individual appliances and treating this total as equivalent to

Consider the example does not specify whether this equipment is or is not on a single branch circuit or located in the same room. The conservative approach is to apply note 4 but to get the minimum calculated load we would use note 3. Any insight on how to make sense of this is appreciated. Thanks in advance.

I recently came across a small xmfr. in looking at the nameplate a question on the diagram not your typical D-Y; curious if this is a D-[open]D?? Any thoughts

I don't see any NEC restriction on installing a receptacle next to a gas meter. Does anyone else know of any restrictions from gas companies?

Thanks for any help.

]]>Thanks for any help.

Does anyone know when the NEC first strated requiring hard conduit for LS and Crit and the additional ground in AC cable for hospitals? Even if roughly?

]]>Suppose the GEC required is a 2/0 AWG. If you run 3 sets of #4AWG and irreversible bond both ends of the cables, would that be a code violation?

]]>I have a 307A /480V transformer generating 708A of 208V.

I need to send underground 708A this 350ft. no room for a transformer at load center.

THWN Copper @ 75degrees on the Ampcity chart can only handle 665A at 2000mcm, THWN Aluminum @ 560A was my preferred.

Thoughts on a solution for this?

thanks

]]>I need to send underground 708A this 350ft. no room for a transformer at load center.

THWN Copper @ 75degrees on the Ampcity chart can only handle 665A at 2000mcm, THWN Aluminum @ 560A was my preferred.

Thoughts on a solution for this?

thanks

can class-320 service used in duplex apartment

or they are designed only for 1-family homes

for example;

for a duplex home/apartment a 2-gang/meter service requiring more than 200A (demand calculated loads)

used CL 320 or 400A bussed service.

Thank you

]]>or they are designed only for 1-family homes

for example;

for a duplex home/apartment a 2-gang/meter service requiring more than 200A (demand calculated loads)

used CL 320 or 400A bussed service.

Thank you

So normally if we have equipment such as a natural gas rooftop unit, or other packaged equipment, I take the MCA of the nameplate, turn it into VA based on the voltage/phase and divide that by how many poles are feeding it. I put that value into each leg of the panelboard schedule. I take a 100% demand factor to size feeders, service, etc. The maximum overcurrent protection device is selected based on the value given on the nameplate.

Is this the correct way to do this?

]]>Is this the correct way to do this?

Newby here,

I want to confirm my understanding for this?

480V load (solar) 208 Utility

I have a (480V * 316A * 1.732) = 262.7k kVa / (208 v x 1.732) = 729A 208V

For transformer sizing?

208V * 729A * 1.732 / 1000 = 262.70 kVA transformer

Thanks

]]>I want to confirm my understanding for this?

480V load (solar) 208 Utility

I have a (480V * 316A * 1.732) = 262.7k kVa / (208 v x 1.732) = 729A 208V

For transformer sizing?

208V * 729A * 1.732 / 1000 = 262.70 kVA transformer

Thanks

PF 70e.

I'm supplying the drive with 0-20 ma.

8 should = 30 hz if vfd set for 4-20

10ma=30 hz if set for vfd set for 0-20

81 & 82 equal 0&60

91 & 92 eqaul 60&0

My drive does not give me either at the given Input.

About 80%. ?

Which parameter am I missing?

Why is available network always furthest from project?

]]>I'm supplying the drive with 0-20 ma.

8 should = 30 hz if vfd set for 4-20

10ma=30 hz if set for vfd set for 0-20

81 & 82 equal 0&60

91 & 92 eqaul 60&0

My drive does not give me either at the given Input.

About 80%. ?

Which parameter am I missing?

Why is available network always furthest from project?

This note is referencing a MWBC, correct?