Receptacle Voltage Drop

[KEE]

When calculating an outlet branch circuit voltage drop what load value do you use? It is on a 20 amp breaker so do you have to use 20 amps? Or do you use the 180va per outlet? Or do you use the nec table 210.21b2 values?

If the inspector checks it with a sure tester he has the option of loading it to 12, 15, or 20 amps. What will he use?

 

[charlie b]

Re: Receptacle Voltage Drop

To be conservative, you could assume 20 amps at the far end of the circuit. With that load on a set of #12 wires, you reach 3% VD around 50 feet (one-way distance). But in practice, the rule of thumb I use is to increase the conductor size one step for each 100 feet of one-way distance.

But why would an Inspector be taking such measurements? There is no code requirement related to voltage drop?

 

[jtester]

Re: Receptacle Voltage Drop

There is a voltage drop requirement in the New Mexico Electrical Code. It has been modified for 2005 and now limits you to 5% for circuits exceeding 150'.

I'm not sure, but have heard that the inspector will put a 20 amp load at the end of the 120 volt, 150' long circuit, and measure the drop.

Jim T

 

[charlie b]

Re: Receptacle Voltage Drop

In that case, you will need to run #8 conductors, to keep the VD under 5%.