thought this was more straightforward

Status
Not open for further replies.
M

monkey_with_a_wire

Member
I seem to have lost all the tables I used to use to figure out a house's service rating.

I checked the NEC, and it says 3 volt amps per square foot.

What's the formula to turn that into a regular ol' 110 or 220 amp?

Thanks. I think this is my second stupid question, hopefully I'll come up with something better next time.
 
Re: thought this was more straightforward

The 3VA/ft? is for general lighting load. There are other loads that figure into the calculations. Read all of article 220.
 
Re: thought this was more straightforward

Residential calculations give many people a hard time. As John says, you must read all of 220, as well as have the basic ohms law formulas under your belt.

I would suggest investing in some training courses and books from Mike Holt, Tom Henry, or James Stallcup. (there are others also)

Roger

[ January 14, 2005, 05:48 PM: Message edited by: roger ]
 
Re: thought this was more straightforward

What's the formula? Add up all the VA per Article 220, taking advantage of any demand factors that are available. Then divide by 240 volts (presuming a 120/240V single phase service) to get amps.
 
Re: thought this was more straightforward

1. Lighting/Recep/Laundry/SA demand load
2. Range Demand
3. Dryer Demand
4. Fixed Appliance Demand
5. HVAC load
6. 25% Largest Motor

Divide by nominal voltage. Round up.

(Reading 220 didn't help me much. It would be nice if they'd have a summary in the beginning, and then expound on each step piece by piece, IMO.)
 
Status
Not open for further replies.
Top