I Need More Power Scotty!

Hi all. Need some help here. I just moved into a four year old house (from a 25 year old house). I noticed that my power tools are acting different than in the old house. They seem to be less powerful, and also seem to have trouble starting up (a bit of hesitation). I'm an electrical buffoon, or at least I don't know enough the figure out what is going on here. Any ideas?

Volts, amps, and resistance are probably getting you.

Check the voltage on the circuit before you turn on the power. If it is lower than the voltage at the other place, that will slow the startup of heavy loads. The nominal voltage these days is 120 Volts but you could be getting as little as 110 if you or someone else on the transformer is using a lot of power.

If the distance from your main panel to the motor is greater, and/or the wire is smaller, you will get greater voltage drop when the high starting load demands more amps. #14 wire has 60% greater resistance, and therefore 60% more voltage loss, than #12. If you have a motor with 50 Amps locked-rotor (when motor is at zero speed at starting) current on a #14 circuit that is 100 ft from the main panel you will have 30 Volts of voltage drop. That is not unusual for a 3/4 or 1 HP motor, and some may have greater locked-rotor current.

You can improve the condition by running a circuit for a 100 Amp subpanel to your shop and connecting the motors to #12 circuits off that subpanel.

You can also improve things by connecting your motors as 240 Volt motors (if they can be so wired) and running a 240 Volt circuit off that new subpanel. That is usually possible only with tools that have better quality separate motors of 1/2 HP or greater.

Thanks Bob, this helps!

Bob NH said:

#14 wire has 60% greater resistance, and therefore 60% more voltage loss, than #12.

Click to expand...

Bob,

I didn't know there was that much difference. Thanks for the info. I'm wondering if you have answers to the following:

#14 Strand vs #12 Solid

#14 Solid vs #12 Strand

#14 strand vs #14 solid

#12 strand vs #12 solid

Thanks

Tom

Resistance ratios below. I suspect that much of the variation is due to rounding differences in the calculations from dimensions, and maybe due to small dimensional differences in standard wire stranding.

statjunk said:

Bob,

I didn't know there was that much difference. Thanks for the info. I'm wondering if you have answers to the following:

From NEC Table 8 DC Resistance ratio, first to second for uncoated copper, from the Ohms/kFt column:

#14 Strand vs #12 Solid = 1.627 --> 62.7%

#14 Solid vs #12 Strand = 1.551

#14 strand vs #14 solid = 1.023

#12 strand vs #12 solid = 1.026

Thanks

Tom

Click to expand...

I gave up trying to use my house wiring for heavy loads a long time ago.

I added a 50A 4 wire outlet and added a temporary panel that plugs into the 50A outlet. This panel then has 20A outlets and I then use rubber clad wire to run power to the equipment.

Another difference could be the power transformer the utility is using.

I'm luckily to have a 25kva transformer powering mine and the neighbor's house.

Bob NH said:

Resistance ratios below. I suspect that much of the variation is due to rounding differences in the calculations from dimensions, and maybe due to small dimensional differences in standard wire stranding.

Click to expand...

So a 14 strand is about on par with a 12 solid! Very interesting.

The one that really surprises me is the #14 soldid vs #12 strand. I would have thought the difference would have been huge given the higher surface area of the 12 strand. Also the 12 strand vs the 12 solid which I guess feeds into the first point.

So what I've learned is that strand wire, while having a higher surface area doesn't have as big an effect at heavier guages.

Thanks for the info.

Tom

wire

So what I've learned is that strand wire, while having a higher surface area doesn't have as big an effect at heavier guages.

Not quite true, because at very high gauges, such as power lines, a "solid" wire, which for those gauges would be stranded, creates strong electromagnetic resistance at the core, so a "hollow" wire gives greater capacity.

statjunk said:

So a 14 strand is about on par with a 12 solid! Very interesting.

The one that really surprises me is the #14 soldid vs #12 strand. I would have thought the difference would have been huge given the higher surface area of the 12 strand. Also the 12 strand vs the 12 solid which I guess feeds into the first point.

So what I've learned is that strand wire, while having a higher surface area doesn't have as big an effect at heavier guages.
Tom

Click to expand...

Where did you get that out of what I posted???!!! Are you trying to make some joke, or do you have some silly theory about surface area affecting resistance that you are trying to promote?

Here is what I posted in reply to your inquiry, comparing the conductors in YOUR list. It is COPIED from my post, which was based on QUOTING your post for the wire sizes about which you inquired.

From NEC Table 8 DC Resistance ratio, first to second for uncoated copper, from the Ohms/kFt column:

#14 Strand vs #12 Solid = 1.627 --> 62.7%

#14 Solid vs #12 Strand = 1.551

#14 strand vs #14 solid = 1.023

#12 strand vs #12 solid = 1.026

I posted the resistance ratio in red of the first wire in YOUR comparison to the second wire in your comparison.

#14 Stranded has 1.627 times the resistance of #12 solid. That means that the resistance of #14 stranded is 62.7% GREATER than the resistance of #12 solid.

The differences between stranded and solid as reported in NEC Table 8 are small; on the order of 2%.

EDIT:
I have just done some Google research on the effect of stranding and the increase in resistance of stranded wire is attributed to the increase in length of the conductors for the spiral strands of stranded wire.

http://www.fiskalloy.com/percon-19/cf-lay.pdf

hj said:

So what I've learned is that strand wire, while having a higher surface area doesn't have as big an effect at heavier guages.

Not quite true, because at very high gauges, such as power lines, a "solid" wire, which for those gauges would be stranded, creates strong electromagnetic resistance at the core, so a "hollow" wire gives greater capacity.

Click to expand...

I have just done some Google research on the effect of stranding and the increase in resistance of stranded wire is attributed to the increase in length of the conductors for the spiral strands of stranded wire.

http://www.fiskalloy.com/percon-19/cf-lay.pdf

anyone know anything about eddie currents?

Something else

This is all very educational for me, thanks guys. I do have another issue. I wasn't sure if I should post it here, or start another thread. I guess I'll pose the question here first.

I had the plumber come out and install a garbage disposal where there wasn't one before, but he was unable to do the electrical hook up. Upon close inspection of the electrical set up in the kitchen, there is a 120v circuit wired with 12/2 running in the island/bar where the sink is located that is dedicated to six power outlets, four of which are located above the counter close to the sink (one is GFI of course). These are meant for small appliances. I would like to replace one of these outlets with a wall switch for the disposal, and tie into this circuit at this point to power it. How do I do this without controlling the remaining outlets with the switch?

Electricity will tend to flow on the surface of a conductor, but it is very dependent on the frequency of the current being passed. At 60 Hz there is practically no effect. If you google skin effect you will probably find some nice equations. BY the time you are at say 100 KHz I believe you will be seeing the effect. At these increasing frequencies people may use fine stranded wire (called Litz wire if I remember correctly) to wind transformer coils because more of the current is near the surface. Go further up and you will see solid wire again but it likes to be silver plated. BY the time you are up into higher radio frequencies the current is mostly on the surface and the silver is there to improve conduction. Go even higher and it is essentially a surface phenomenon. Microwave systems completely surround the signal with surfaces and you have a waveguide.

Bob NH said:

Where did you get that out of what I posted???!!! Are you trying to make some joke, or do you have some silly theory about surface area affecting resistance that you are trying to promote?

Here is what I posted in reply to your inquiry, comparing the conductors in YOUR list. It is COPIED from my post, which was based on QUOTING your post for the wire sizes about which you inquired.

From NEC Table 8 DC Resistance ratio, first to second for uncoated copper, from the Ohms/kFt column:

#14 Strand vs #12 Solid = 1.627 --> 62.7%

#14 Solid vs #12 Strand = 1.551

#14 strand vs #14 solid = 1.023

#12 strand vs #12 solid = 1.026

I posted the resistance ratio in red of the first wire in YOUR comparison to the second wire in your comparison.

#14 Stranded has 1.627 times the resistance of #12 solid. That means that the resistance of #14 stranded is 62.7% GREATER than the resistance of #12 solid.

The differences between stranded and solid as reported in NEC Table 8 are small; on the order of 2%.

EDIT:
I have just done some Google research on the effect of stranding and the increase in resistance of stranded wire is attributed to the increase in length of the conductors for the spiral strands of stranded wire.

http://www.fiskalloy.com/percon-19/cf-lay.pdf

Click to expand...

Bob,

I'm not blaming my complete and total oversight of what you presented on the bad day I'm having so I won't even go there. I don't know where I got that from. I'm glad you set me straight though because I did completely twist the information you provided. Really strange.

Now I'm thinking I'm a complete dumb a$$.

Oh well tomorrow I'll wake up a genius again.

Also cool is the explanation on why strand doesn't give much more than the 2% because of the increased length of wire. Thanks.

Tom

Skaweee said:

I had the plumber come out and install a garbage disposal where there wasn't one before, but he was unable to do the electrical hook up. Upon close inspection of the electrical set up in the kitchen, there is a 120v circuit wired with 12/2 running in the island/bar where the sink is located that is dedicated to six power outlets, four of which are located above the counter close to the sink (one is GFI of course). These are meant for small appliances. I would like to replace one of these outlets with a wall switch for the disposal, and tie into this circuit at this point to power it. How do I do this without controlling the remaining outlets with the switch?

Click to expand...

First, if this is one of the required appliance circuits of NEC 210.52(B)(1) then it is a violation of 210.52(B)(2) to connect the garbage disposal to it.

If you do connect the disposal to the circuit, there is a small risk that you will trip the breaker when you turn it on if there is a 1500 Watt teakettle or griddle being used to make your breakfast.

Here is the simplest way to make it work. The disposer will be GFCI protected. It isn't required to be, but it is easier for me to explain it if we leave it that way.

1. Select the receptacle that you want to replace with a switch. Ideally, you would remove the last receptacle in the assembly; the one that has only a pair of wires coming to it and none going from it to another receptacle.
2. Remove that receptacle. You will now have a white wire, a black wire, and a ground. The white wire will be probably be connected to a silver terminal on an adjacent receptacle. If it is coming from a bunch wire-nutted together that is fine also.
3. Connect the black wire to one of the terminals of the switch.
4. Run a 12/2 from the box to where it will connect to the disposer. Connect the white wire of the new cable to the terminal that the white wire mentioned in (2) is hanging from (after you remove the little white wire) or to the white pigtail if it is not coming from an adjacent receptacle. Connect the black wire from the new cable to the other terminal of the switch. Connect the grounds with a wire nut and run a pigtail ground to the ground terminal on the switch. Mount the switch in the box.
5. Connect the black, white, and ground wires to the corresponding wires/terminals of the disposal.

Variations:
If you don't want to put the switch in the "last receptacle on the circuit" position, you can take any receptacle except the GFCI receptacle and rearrange the connections to make sure all of the receptacles are powered.