Article 220 Intention

[jsinclair]

Still discussing this load study issue...

Now haggling over article 220 and its intentions. I take the stance that the intention of the article is to give an outline for sizing electrical installations for things that are not built yet. For example, if one was building a house, the loads would unknown for the most part. You would use the values as a guide to determine the minimum sizes. For existing installations, actual loads should used in the calculations. Where unknown, then the values outlines in article 220 should be used.

Can anyone shed some light on the intention of the article? :roll:

 

[tonyyaroch]

Re: Article 220 Intention

You are right john, for new construction homes all I do is Take the SQ. feet of the home figure out min lighting VA , Minimum 20A circuits and MIN plugs req.and ask if there are any Air conditioners ,spas , Jacuzzi , air compressors ,,ETC>>> In a perfect world you could get all the info fill out dwelling calculation form and wallah your required panel size. Now a days with all the electrical equipment I use a 200 amp for anything above 1500sq. ft. This is are company system and it works good.

[ November 10, 2004, 08:55 AM: Message edited by: tonyyaroch ]

 

[physis]

Re: Article 220 Intention

I take the stance that the intention of the article is to give an outline for sizing electrical installations for things that are not built yet.

That's almost automaticly true just because if it was built yet there would already be a service.

If the building or other installation was complete except for the service installation you would still be required to use 220 to determine the load for 230.42(A).

The specific purpose of article 220 is to determine the load that will be applied to the service so the service conductors can be sized.

The intention is to allow a figure less than 100 percent of the attached load to size the service conductors because that's usually more than is actually needed.

Edit: What you get is the minimum requirement.

[ November 11, 2004, 02:49 AM: Message edited by: physis ]

 

[gndrod]

Re: Article 220 Intention

220 Calcs offers derating of load usage through Demand Factoring. Optional calculations are a good example of needing "balanced usage" by derating heavy loads such as space heating A/C-heatpump equipment etc... that tend to drive up the panel load capacity over the limits of the intended service rating.

Knowing the total load not only determines SE size but dictates what panel configurations are needed. A 400 amp service isn't out of the norm when wiring a modern home with all the whistles.

Knowing how to qualify load demand factors becomes really necessary when doing remods. A good example of this is a house I upgraded a little while back. The owner had been convinced by the GC and AHJ that the 200 amp service had to be upgraded. The AHJ had actually suggested adding on another box to handle baseboard heaters needed for the addition.

By re-using extended circuits, removing old circuits for replacement heating loads and applying optional calculations, the original panel was acceptable. 220.30 Part III is really the key to determining what is needed for both new construction and remod limits.

rbj, Seattle

[ November 11, 2004, 07:30 AM: Message edited by: gndrod ]