Residential wiring/ voltage drop

[nizak]

Just curious as to how much attention is paid to voltage drop in residential wiring.

Looked a new build today that just got framing completed. Owner had a rather unusual request. In the future he will be finishing the basement but leaving the floor joists exposed .

He would like for all home runs to be routed through the attic space and then down to the panels in the basement.

He wants to see as little wiring as possible in the basement floor joist areas.

It's adding additional lenghth to every run, and putting many of the home runs at about the 100' mark.

The way the house is laid out ( heavy load draws kitchen/ bathrooms/ garage) setting a sub panel doesn't really help.

Are 100' feeds of 12/2 a concern to be worried about?

Lighting loads aren't an issue with everything being LED.

Thanks for your comments

 

[luckylerado]

I would not be terribly concerned about runs at 100' but if I-joists are used he will probably end up putting sheet rock up if being inspected under current IRC.

 

[Coppersmith]

I used this VD calculator:

http://www.nooutage.com/vdrop.htm

and it said that 100' of 12/2 at 16 amp would have a VD of 5.6% and 4.2% at 12 amps.

14/2 at 12 amps would have 6.5%.

Using 10/2 would give 2.5% at 12 amps.

 

[nizak]

Even with the added expense and labor of installing 10/2, would still be pushing 3% at a 16 amp load.

I would have to think with the competitive market not too many contractors install 10/2 for residential receptacles.

 

[ActionDave]

I would run 12AWG and never give it a second thought.

 

[JFletcher]

and what is he going to do about all the plumbing? all the drain lines have to go where they fall, and the red and blue pex is going to look like bent up mess that it is.

My point is I'd mention this to him, and get him to agree to let you run your electrical thru the basement - you can make it look neat, especially if you drill thru the joists dead straight (and up high) where you cross them. You could bring all the wiring out to the band board and have the framer build a soffit or chase to hide the wiring. Or keep it all up in the joists, only dropping down where the panels are.

No wiring in the basement will not only increase your home run distance, it will increase the length of your daisy chains between receptacles where you have to bypass a door or the like; instead of diving down 2' into the basement, over, and back up the the next receptacle, you're going to have to go up 6+', over thru the ceiling joists, and back down 6+'.

You could also locate the panels on the 1st floor rather than the basement.

 

[mayanees]

meter pan to transformer distance?

meter pan to transformer distance?

The only way that I could see this being a problem is if the utility delivery voltage was low, and that could happen if the service transformer is very far away.
Otherwise I think the use of #12AWG as you described is sufficent overbuild to accommodate the lengths.

 

[GoldDigger]

A larger than normal VD is not necessarily a problem unless the customer is religious about energy efficiency.
What would be a real perceptible problem would be any circuit that had both lighting loads and non-continuous high current loads. The resulting flickering/dimming of the lights could be undesirable.

 

[gar]

180206-1224 EST

JFletcher:

Not a good idea to drill holes at the edge of a beam. They should always go in the center. This you study in engineering mechanics.

The greatest stress (force) in a loaded beam is at the outer edges of the beam. Thus, by removing edge material in a beam you reduce its stiffness and strength.

I beams exist because they use the least material (weight) by moving the majority of the material to the outer edges of the beam where stress is greatest.

If you take a 2 x 8 and drill a 1" hole at the edge, then you have effectively made the 2 x 8 into a 2 x 7. Load capability will vary by approximately the square of the beam height. A 1" hole in the middle of the beam has practically no effect on the strength or stiffness of the beam. At the center of the beam the stress is zero.

A beam supported at two end points and with a concentrated force at the mid point of the beam length has the greatest stress at the length midpoint.

As you move from the beam length midpoint toward either end support points the outer edge stress level in the beam gets less.

.

 

[JFletcher]

180206-1224 EST

JFletcher:

Not a good idea to drill holes at the edge of a beam. They should always go in the center. This you study in engineering mechanics.

The greatest stress (force) in a loaded beam is at the outer edges of the beam. Thus, by removing edge material in a beam you reduce its stiffness and strength.

I beams exist because they use the least material (weight) by moving the majority of the material to the outer edges of the beam where stress is greatest.

If you take a 2 x 8 and drill a 1" hole at the edge, then you have effectively made the 2 x 8 into a 2 x 7. Load capability will vary by approximately the square of the beam height. A 1" hole in the middle of the beam has practically no effect on the strength or stiffness of the beam. At the center of the beam the stress is zero.

A beam supported at two end points and with a concentrated force at the mid point of the beam length has the greatest stress at the length midpoint.

As you move from the beam length midpoint toward either end support points the outer edge stress level in the beam gets less.

.

I never suggested drilling the edge of the joist. Holes in dimensional lumber may be drilled a maximum d/3 the wood size, and the holes cannot be located within 2" of the edge or another hole. TJIs can have larger holes in the plywood center section, tho iirc the end 1' cannot be drilled.

What I was envisioning is that the OP drill his holes a bit higher than center to help conceal the wiring. In a 2x12", that would move the wiring up approximately 3".

Drilling the edge is basically creating a notch, which has much more severe restrictions as to size and placement than a hole does. TJIs cant be notched anywhere, and dimensional lumber not in the center third of the span, only the end thirds, and the notch can only be d/6 deep.

 

[jumper]

I never suggested drilling the edge of the joist. Holes in dimensional lumber may be drilled a maximum d/3 the wood size, and the holes cannot be located within 2" of the edge or another hole. TJIs can have larger holes in the plywood center section, tho iirc the end 1' cannot be drilled.

What I was envisioning is that the OP drill his holes a bit higher than center to help conceal the wiring. In a 2x12", that would move the wiring up approximately 3".

Drilling the edge is basically creating a notch, which has much more severe restrictions as to size and placement than a hole does. TJIs cant be notched anywhere, and dimensional lumber not in the center third of the span, only the end thirds, and the notch can only be d/6 deep.

Easier to just swipe a picture than type.