Quick voltage drop question

[rvr6000]

I understand the idea behind sizing wire due to voltage drop. But is the end result so you maintain 120 volts at the end of the line?

Here's where I'm coming from with this question - while poking around in the basement tonight I was looking at a 15amp circuit that appears to only feed four outlets on the opposite corner of the house. It's 14-2 wire but because of the way the wire is routed its probably about 80 feet from the panel to the last outlet. I believe rule of thumb is about 50' for 14-2?

Anyway - I put the meter on it and I'm getting 120.7 volts off that last outlet. First outlet is slightly more but it's only about 12 feet from the last outlet.

Voltage coming into the house is always in the 121-123 range - so wondering if this should be of any concern? I've actually had a computer plugged into this circuit for some time now so I'm thinking I'm cool. Thanks for any input.

 

[e-tek]

So you're getting 120.7.......what's the problem?

Wait, I know - Too much time on your hands.

 

[Alchymist]

All depends on the load you put on it. 14-2 @150 feet won't drop much with a 1 amp load. At a 10 amp load, different story. Your computer probably draws 2-3 amps, so not much voltage drop.

 

[Gary S]

As Alchymist stated, voltage drop is dependent on load. The more load you put on the circuit, the more voltage drop you will get from the resistance of the wire.
With no load on the circuit, you can expect to measure near 120v even beyond the recommended length, but with near maximum load, you will be getting voltage drop.

If you are really concerned, put a heater or other heavy use device on the end of the circuit, and measure the available voltage with that load.

 

[alfredeneuman]

Here's a free Voltage Drop Calculator from Southwire Cable

http://www.southwire.com/support/voltage-drop-calculator.htm

 

[Kevin C]

Almost every computer made has a switching power supply that works on a range of voltages. Typically, the minimum voltage on a 120v supply is 100V.

 

[larry_g]

As Alchymist stated, voltage drop is dependent on load. The more load you put on the circuit, the more voltage drop you will get from the resistance of the wire.
With no load on the circuit, you can expect to measure near 120v even beyond the recommended length, but with near maximum load, you will be getting voltage drop.

If you are really concerned, put a heater or other heavy use device on the end of the circuit, and measure the available voltage with that load.

X2 on this. Check the voltage under load.

lg
no neat sig line

 

[theoldwizard1]

Most voltage drop calculators work on percent voltage drop, under load, at the end of the wire. 3-5% is acceptable. 7% is pushing it. 5% of 120V is 6V (114V), but again, you can only accurate measure this at load.

You can run a 10A load over 100' of 14 gauge copper wire and still have less than a 5% voltage drop.

 

[rvr6000]

Thanks for the help, guys. I guess I didn't know it had to be under load to accurately measure the drop. Will try that tonight.

 

[eljefino]

Also your meter might be somewhat inaccurate measuring "true" AC. Wander from outlet to outlet measuring it and try to get representation from both phases.

From the power plant to the transformer to the meter, fusebox, outlet, and appliance power supply there are a series of (semi-) BS factors for loss. Where you really start having issues is when you break out the 16-18 AWG extension cord and then put a 1500 watt heater on it. As said above your computer will be fine; they take all sorts of brownouts in stride. It's those 1/2 second blackouts that mess my electronics up.