I think I would be inclined to split the difference. If budget is an issue maybe go a little more toward the optional calculated value. But one thing I would due for sure is run a full size neutral to help offset any load imbalance due to the fact that your VD calcs are using 240 volt as a basis.
Get serious!:jawdrop: I've never amprobed a house that was drawing more than half the optional, with the heavy loads on. I was thinking a conservative number would be the optional and neutral averaged.
Well, then you do what you think is best. If you use your method I guess you don't even have to do an Art. 220 calculation as you have never "amprobed a house" that approached the calculated load. Why bother to do the calc? Sorry for offending you, but I hope you will pardon me, as I have only been in the trade for a few months. I used to sell ladies shoes, so I'm still learning.
Allright, that's fair, and funny; texie, thank you. I'm actually a little OCD when it comes to following the code. However, I don't see a clear answer on this one and I was hoping not to have to rely on just my judgement.
I was thinking the exact same thing.
I would use the optional method and not worry about it a bit. You said yourself you have never seen a house load pull near the calculated load. What is it about this guest house that would make it any different?
One issue is it's 3% to the panel, a total of 5% to the load. Another is it's a 110A service. And I simplified the example, there's a building half way, so I'll have to do the VD calcs in two stages. 1 1/2% for each section.
Daughters use more electricity than sons or son in laws no doubt. More hot water too. I know, I am the father of two teenage females. I still don't see any reason to worry about the feed to the guest house. It's NEVER going to pull the calculated load.
Can you get that in direct bury?
I took my lumps, acknowledged same and thanked texie in post 7.
None, it's in the code as a Fine Point Note. I'm just trying to do the right thing at the right price.
Voltage drop is a design issue. The 3 and 5 percent figures are nothing more than suggestions. Some cases specifications for sensitive equipment may require even less voltage drop. Otherwise in a case like yours it kind of comes down to how much load do you wish to have before you start considering the effect of voltage drop. Starting of large motors like an AC compressor are what will be most noticeable but are just about impossible to avoid unless you use soft starting methods.