Comfort level

[ryan_618]

I was doing a plan review on a business shell the other day. The EE had a computed load of 748 Amps, ws using parrellel 500's and an 800A breaker. I reviewed the calculations and found that he/she had used 2VA per square foot instead of 3 for lighting. Once I re-figured the calculations, I came up with 790 amps. I included on my list that he would have to re-size his conductors to greater than 500's, but I couldn't write anything about the ACPD rating.

What is your comfort level? If you were designing this building (future provisions for 5 small mercantile tenants), would you keep the 800 OCPD, or would you increase it once your calculated load was within 10 amps of the rating of the switch?

 

[bwyllie]

Re: Comfort level

Why did you increase the lighting load from 2 to 3? Local code may stipulate the 2. Besides that, at 790 I think I would stick with the 800 as long as you feel confident in the watts/sq.ft for the overall building and use. The next standard size for that service would be 1000A which would add significant cost to the project.

 

[ryan_618]

Re: Comfort level

Considering the fact that I am the one responsible for enforcing "local code" I think I would be aware if there was an amendment. There is not. Table 220.3 plainly states that 3VA is to be used.

 

[don_resqcapt19]

Re: Comfort level

Ryan,
I'd have no problem with the 800 amp switch, but only because the calculations in Article 220 result in artificially high loads.
Don

 

[roger]

Re: Comfort level

Don, is right. This is one section of the NEC that can't be considered "the minimum" in the true sense.

Roger

 

[ryan_618]

Re: Comfort level

Interesting. Thanks guys, I've never put an ammeter on the service entrance conductors, so I wasn't sure. The rest of the story is that the EE didn't include show window lighting calc's, which put the EE above the 800 amp range, so he/she will hafe to put in a 1000 service. I was very curious about what you guys thought. Thanks again.

 

[ryan_618]

Re: Comfort level

I was talking to a gentleman named Noel Williams about this the other day. Noel is on the board of directors with me at our local IAEI chapter, and is considered by many to be one the most knowledged individuals in the state.

I asked him about people using 2VA. He told me that he submitted a change for the 05 cycle to allow this. His logic is that the International Energy Efficiency Code will not allow more than 1.8VA per square foot for general lighting. Considering that, he tried to change the table to 2VA, but the submittal wasn't thought highly of.

 

[iwire]

Re: Comfort level

Ryan we do a lot of larger services, 800 to 3000 amp.

I have gone back to many of these and most have a built in logging meter.

On the 3000 amp services I have not seen peaks over 1300 amps and averages of 700 or 800 where normal with a completed building 1 to 3 years old.

Another way to look at it is how Charlie the utility guy explained how the POCO he works for sizes transformers.

He stated they go with 50% of the NEC service size.

So I guess I would ask do you really see the need to increase the cost to the customer by going up to 1000 amps?

I know you can make them do it.

 

[ryan_618]

Re: Comfort level

Bob, I understand your stance on this, but what would you do if you were in my shoes?

I get paid to verfy that the EE has a compliant set of drawings. Is this something I should roll over on? IF so, where do I draw the line?

 

[iwire]

Re: Comfort level

Ryan of course you must always enforce the code.

No one ever simply does not notice something like the absence of show window lighting calc's.

I am not giving you a hard time you are trying to do a perfect job and have no problem asking questions to help you get it done, that IMO is an excellent trait.

Bob

PS by posting all this on the board plausible deniability is out the window.

 

[ryan_618]

Re: Comfort level

Originally posted by iwire:
I am not giving you a hard time you are trying to do a perfect job and have no problem asking questions to help you get it done

You hit that one out of the ball park! I'm definatly a perfectionist, at least, I try to be!

...that IMO is an excellent trait.

Thank you!

PS by posting all this on the board plausible deniability is out the window.

 

[steve66]

Re: Comfort level

One question I have: Do the lighting loads have to be multiplied by 1.25 to determine the main breaker size? I ask because lighting loads are continuous, and the breaker will probably only be 80% rated.

Also, when you said a "business shell" I think of offices. That would require 3.5 VA per square foot for a lighting load, unless you are sure that all the tenants will be stores. I also assume you have added 1 VA per square foot for receptacles for the buildouts.


Steve

 

[bwyllie]

Re: Comfort level

Didn't realize you were the one as you say " the one responsible for enforcing "local code" I think I would be aware if there was an amendment. There is not. Table 220.3 plainly states that 3VA is to be used." I guess I missed that in your post didn't mean to bruise your ego.

 

[ryan_618]

Re: Comfort level

Originally posted by bwyllie:
I guess I missed that in your post didn't mean to bruise your ego.

I don't think you did that.

 

[bwyllie]

Re: Comfort level

whats the overall squarefootage of the building & voltage?

[ December 29, 2003, 08:42 PM: Message edited by: bwyllie ]

 

[ryan_618]

Re: Comfort level

Originally posted by bwyllie:
whats the overall squarefootage of the building & voltage?

Voltge was 120/208, but I don't remember the square footage. I'm flying out of town first thing in the morning, and these plans are at work. I won't be able to answer that question until Monday. I'll take a look for you though