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?

I have a location that wants a 800 Amp 120/208v of current 480v gear.

They have drawn up and requested a 480V 350Amp breaker to feed 300KVA transformer feeding a main lug 800-Amp panel.

They didnt account for 125%

Calculated at 350A 480V primary i get a KVA of 290.976, that gives me a 807.69 Amp on secondary, can this still feed a 800-amp main lug panel or do i need 800-amp main breaker to protect the buss,

feeders are listed as parallel 500 MCM 90*C for 430 amps

Thanks in advance

]]>They have drawn up and requested a 480V 350Amp breaker to feed 300KVA transformer feeding a main lug 800-Amp panel.

They didnt account for 125%

Calculated at 350A 480V primary i get a KVA of 290.976, that gives me a 807.69 Amp on secondary, can this still feed a 800-amp main lug panel or do i need 800-amp main breaker to protect the buss,

feeders are listed as parallel 500 MCM 90*C for 430 amps

Thanks in advance

Hi

My question is related to the derating rules applied to 90 degC cables.

When I am using a 90 degC cable in 40 degC ambient temp, I will apply correction factor 0,91 and check if this complies with 75degC conductor of same size.

Example:

Amb = 40 degC

Non-continous current = 100 A

90degC conductor - 3AWG : 115A x 0,91 = 104,65A

Check with 75 degC conductor 3AWG: 100A ampacity = OK to use 90degC 3AWG conductor.

For parallel scenario is:

6 current carrying conductors in conduit = 0,8 adjustment factor

30 degC amb = 1 correction factor

Non-continous current: 650A

2 x 500kcmil 90 degC conductors are chosen.

Total ampacity = 430*2*0,8 = 688A

Check with 75degC conductor: 380 x 2 = 760A --> OK

My question is, should I do the 75degC check as above or should I also add adjustment factors to the check as below?

380 x 2 x 0,8 = 608A --> NO OK.

Hope that my question makes sense to you.

Thanks in advance

]]>My question is related to the derating rules applied to 90 degC cables.

When I am using a 90 degC cable in 40 degC ambient temp, I will apply correction factor 0,91 and check if this complies with 75degC conductor of same size.

Example:

Amb = 40 degC

Non-continous current = 100 A

90degC conductor - 3AWG : 115A x 0,91 = 104,65A

Check with 75 degC conductor 3AWG: 100A ampacity = OK to use 90degC 3AWG conductor.

For parallel scenario is:

6 current carrying conductors in conduit = 0,8 adjustment factor

30 degC amb = 1 correction factor

Non-continous current: 650A

2 x 500kcmil 90 degC conductors are chosen.

Total ampacity = 430*2*0,8 = 688A

Check with 75degC conductor: 380 x 2 = 760A --> OK

My question is, should I do the 75degC check as above or should I also add adjustment factors to the check as below?

380 x 2 x 0,8 = 608A --> NO OK.

Hope that my question makes sense to you.

Thanks in advance

The size of a single-family dwelling is 25,117 square feet. The service is 120/240 volts single-phase. Without application of demand factors, what is the minimum number of general use, noncontinuous 120-volt, 15-ampere branch circuits?

1. 45

2. 32

3. 42

4. 14

See steps below:

Step_1: Table 220.12 lists 3VA/sq-ft. Calculate; 25,117 sq-ft x 3 VA/sq-ft = 75,352 VA. (Note: Lighting is considered a continuous load, however, do not apply this demand adjustment as stated for this specific question.)

Step_3: Calculate the power per circuit; P = I x E = 15 amperes x 120 volts = 1,800 VA / circuit.

Step_4: Calculate the number of 15 A circuits; Total Power / Power per Circuit = 75,352 VA / 1,800 VA = 41.86. Therefore, size up to 42 Circuits.

Do y'all agree that 42 circuits is the correct answer to this question?:?

]]>1. 45

2. 32

3. 42

4. 14

See steps below:

Step_1: Table 220.12 lists 3VA/sq-ft. Calculate; 25,117 sq-ft x 3 VA/sq-ft = 75,352 VA. (Note: Lighting is considered a continuous load, however, do not apply this demand adjustment as stated for this specific question.)

Step_3: Calculate the power per circuit; P = I x E = 15 amperes x 120 volts = 1,800 VA / circuit.

Step_4: Calculate the number of 15 A circuits; Total Power / Power per Circuit = 75,352 VA / 1,800 VA = 41.86. Therefore, size up to 42 Circuits.

Do y'all agree that 42 circuits is the correct answer to this question?:?