RossS
Member
- Location
- Research Triangle, NC USA
Three questions in here:
I recently had a design where the civil engineer chose to place the utility transformer over 200' from the MDP. I was running over 1000A through 4 sets of parallel conductors and I wanted to verify that the long run and high amperage weren't going to create an unacceptable voltage drop.
1) Would using the calculated demand load be acceptable (it's a restaurant so the demand load is significantly lower than the connected) or should the connected load be used?
I was doubtful that the relationship between the calculated voltage drop and the number of parallel conductors was linear; that is, 4 times the cross section = 1/4 the voltage drop. So I used Chapter 9, Table 8 to get the total cross-section and then used the largest wire size that was less than that and did the calculation by hand. So my questions are:
2) What's the most accurate calculation, and;
3) What's the most practical, that is, what's the easiest calculation that doesn't introduce excessive error?
I found what I thought was a pretty decent calculator online that provided parallel solutions, but as I used it I discovered it had prohibitive limitations - it chose the number of conductors and size, and you couldn't play around with configurations. So it ended up being pretty worthless, and I couldn't find any decent calculator that let you input the desired number of conductors. If anyone knows of a really good calculator, I'd be really interested in that - especially if it was available as an iPhone app.
Thanks...
I recently had a design where the civil engineer chose to place the utility transformer over 200' from the MDP. I was running over 1000A through 4 sets of parallel conductors and I wanted to verify that the long run and high amperage weren't going to create an unacceptable voltage drop.
1) Would using the calculated demand load be acceptable (it's a restaurant so the demand load is significantly lower than the connected) or should the connected load be used?
I was doubtful that the relationship between the calculated voltage drop and the number of parallel conductors was linear; that is, 4 times the cross section = 1/4 the voltage drop. So I used Chapter 9, Table 8 to get the total cross-section and then used the largest wire size that was less than that and did the calculation by hand. So my questions are:
2) What's the most accurate calculation, and;
3) What's the most practical, that is, what's the easiest calculation that doesn't introduce excessive error?
I found what I thought was a pretty decent calculator online that provided parallel solutions, but as I used it I discovered it had prohibitive limitations - it chose the number of conductors and size, and you couldn't play around with configurations. So it ended up being pretty worthless, and I couldn't find any decent calculator that let you input the desired number of conductors. If anyone knows of a really good calculator, I'd be really interested in that - especially if it was available as an iPhone app.
Thanks...