480 to 277 lighting load

[morg123452000]

I have a 150,000 sq foot warehouse wanting to convert over to 277 volt lighting from 480..how would I figure the new load....this is an exam question. ..that's all they told me

 

[augie47]

Not sure what they are shooting for but to maintain the same level of lighting the "load" would not change in terms of "kw". 220.12 calls for 3 watts per sq ft lighting load and that's respective of voltage. Table 220.42 will allow a demand factor.
If i did the math correctly the result would be 231.25kw at any voltage.

 

[morg123452000]

Well I figured the warhose at 1/4 VA/SQ foot that's what I thought the lights should be figured at..I'm not sure where you get 3 VA sq foot..maybe I'm looking at something wrong

 

[augie47]

Well I figured the warhose at 1/4 VA/SQ foot that's what I thought the lights should be figured at..I'm not sure where you get 3 VA sq foot..maybe I'm looking at something wrong

nope, my error.. I am still learning to read.. I looked at va/sq meter... :dunce: (scary that I teach)
you are correct at 1/4 va/sqft then apply 220.42

 

[dionysius]

I have a 150,000 sq foot warehouse wanting to convert over to 277 volt lighting from 480..how would I figure the new load....this is an exam question. ..that's all they told me

Question as posed is not answerable since incomplete.

 

[Electric-Light]

Not sure what they are shooting for but to maintain the same level of lighting the "load" would not change in terms of "kw". 220.12 calls for 3 watts per sq ft lighting load and that's respective of voltage. Table 220.42 will allow a demand factor.
If i did the math correctly the result would be 231.25kw at any voltage.

I used teh table, derating factors, etc. Not coming together with your number even after dividing yours out by 12 to cancel out your mix up in units.
I got 20.32kVA. But my opinion is that it doesn't matter.

I think the original quest. is a tarp.
VA new = VA old.
The new amperage is the same as, or greater by up to 1.73 times depending on the actual situation, but not enough info was given.

 

[dkidd]

I have a 150,000 sq foot warehouse wanting to convert over to 277 volt lighting from 480..how would I figure the new load....this is an exam question. ..that's all they told me

The new load in kva would be the same as the old load in kva. Other than that more information is needed. Just changing from 480 to 277 doesn't has any obvious purpose.

 

[kwired]

Question as posed is not answerable since incomplete.

I agree.
Is most likely a poorly worded question when it comes to the exercise in using calculations they maybe intended the exam participant to use.

Why not just straight out ask what is the minimum VA necessary for lighting load for a 150,000 SF warehouse, or what is the minimum amp capacity needed for lighting load @277/480 volts for a 150,000 SF warehouse? The VA version of the question is the most proper way to ask IMO.

Asking like OP says they did leaves all sorts of what if's.

 

[morg123452000]

Yes but I'm testing oregon...im good with tests but this one was tough on the calculation part...very frustrated

 

[stevenje]

Yes but I'm testing oregon...im good with tests but this one was tough on the calculation part...very frustrated

You must be referring to the 12 question section of the supervisors exam. It is a tough one. Keep trying!

 

[augie47]

With morg1234 input on my error, if I was given choices, my answer would be 25 kva based on 1/4 va and the 220.42 demand factor.

 

[Besoeker]

The new load in kva would be the same as the old load in kva. Other than that more information is needed. Just changing from 480 to 277 doesn't has any obvious purpose.

Well,it's an exam question. I'm sure many of us have seen questions that have little bearing on real life situations.
The answer is, as you stated, the kVA is no different.