Service Calculation

[charlie b]

Re: Service Calculation

Originally posted by buggaboo14: With all the info given, I have a calculation of 203.4 amps. Could someone check my calculations?

You had some math errors in the earlier calculation. Also, you came up with the 203.4 number before you acknowledged the need to add the sign and the show window.

Here's my shot at it.

Lighting (1500 x 3) = 4500
Outlets (20 x 180) = 3600
Furnace (20 x 120) = 2400
A/C (40 x 240) = 9600
Heat = 0 (non-coincident with A/C)
Tanning Bed #1 (45 x 220) = 9900
Tanning Bed #2 (26 x 220) = 6240
Tanning Bed #3 (21 x 220) = 5040
Tanning Bed #4 (21 x 220) = 5040
Tanning Bed #5 (16 x 220) = 3840
Sign = 1200
Show Window (8.5 x 200) = 1700
Total = 53,060 VA
Total = 221 amps.

 

[charlie b]

Re: Service Calculation

Originally posted by jwelectric: What we do know from the original post is that the shop is 1500 square feet. This would equate to 1500 X 3 X 125% for the lighting.

You don't add 25% to the "general lighting load" values, such as the 3 VA per square foot in this example. Neither do you add 25% to the show window values of 200 VA per linear foot.

Check out Example D.3. It adds 25% to the actual connected lighting load, compares it to the "general lighting load" value calculated from the table (i.e., VA/ft2). It does not add 25% to the general lighting load. In our case, we are not given the actual connected lighting load. So we just use the 4500 value.

 

[jwelectric]

Re: Service Calculation

Originally posted by charlie b:

Originally posted by jwelectric: What we do know from the original post is that the shop is 1500 square feet. This would equate to 1500 X 3 X 125% for the lighting.

You don't add 25% to the "general lighting load" values, such as the 3 VA per square foot in this example. Neither do you add 25% to the show window values of 200 VA per linear foot.

Check out Example D.3. It adds 25% to the actual connected lighting load, compares it to the "general lighting load" value calculated from the table (i.e., VA/ft2). It does not add 25% to the general lighting load. In our case, we are not given the actual connected lighting load. So we just use the 4500 value.

Good call Charlie. Should the total lighting load have been known, let?s say that it was 5000va, and then the 125% would need to be added.

When using the table the 3 watts per square foot then the 125% is not added.

I was trying to give him a good exercise of the brain.