voltage drop
- Thread starter darrenh
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With very few exceptions (example Art 647), the NEC does not directly address voltage drop so "acceptable" is determined by other than the Code.
A FPN at Art 219 provides some guidance on what is normally "acceptable".
A FPN at Art 219 provides some guidance on what is normally "acceptable".
The ramifications depend on load type. Motors don't like voltage drop, as they draw more current as voltage drops, which causes more voltage drop, which causes more current,...
A resistive load just makes less heat or a light bulb glows less brightly. These items draw less current as voltage drops, so they are a more stable load in a voltage drop situation.
A resistive load just makes less heat or a light bulb glows less brightly. These items draw less current as voltage drops, so they are a more stable load in a voltage drop situation.
T
taylorp
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I would keep the voltage drop as low as possible within the limits of reasonable cost and efficiency. Articles 210.19(A)(1) and 215.2(A)(4) have information notes on what voltage drop percentage is considered "reasonable efficiency of operation."
I agree with Augie47 and suemarkp. In my opinion, I think the Ugly book "goal" of 2% is a good one to shoot for.
Thanks for the advice.
I was asking because someone asked me about it and I wasn?t sure. They were running power to a small lunchroom which consists of just small appliances microwaves toasters cock pot fridge and stove not much in it. He said the panel was about 220' away from the room and was wondering if the voltage drop on #12 thhn would be to much. If I?m doing the voltage drop correctly I think it would be 2x12.9x220x20amp/6530 cir.mils=17.3 volts. If so that seems like a big voltage drop. Also the voltage drop formula ask you for the amps on the load so on general receptable circuits you don't really know the full load so do you use 20 amps because its on a 20 amp circuit breaker even though the circuit will rarely ever see 20 amps if ever.
I was asking because someone asked me about it and I wasn?t sure. They were running power to a small lunchroom which consists of just small appliances microwaves toasters cock pot fridge and stove not much in it. He said the panel was about 220' away from the room and was wondering if the voltage drop on #12 thhn would be to much. If I?m doing the voltage drop correctly I think it would be 2x12.9x220x20amp/6530 cir.mils=17.3 volts. If so that seems like a big voltage drop. Also the voltage drop formula ask you for the amps on the load so on general receptable circuits you don't really know the full load so do you use 20 amps because its on a 20 amp circuit breaker even though the circuit will rarely ever see 20 amps if ever.
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