2011 proposals for voltage drop

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They're proposing a max of an 8% drop, but you can have a drop much lower than that and the OCPD will work just the same as always. That is an impractical and seemingly arbitrary limit.
 
Pierre C Belarge said:
I found this while surfing today. I thought it might interest some.
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That will be the most "violated" code section if it goes in to place. Especially since the use of MWBC is pretty well gone in residential use because of the need for combo type AFCIs. there will be a 10-2 NM shortage.:D
 
How could these rules ever be imposed on premises wiring systems when we have zero control over the voltage drop that exists on the outdoor distribution system?

My vote is for rejection.
 
peter d said:
How could these rules ever be imposed on premises wiring systems when we have zero control over the voltage drop that exists on the outdoor distribution system?

My vote is for rejection.
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This is a good point "where do you measure the Starting voltage at".
 
From the proposal:
100 Definitions I. General Voltage Drop. Voltage-drop is the difference in the voltage of a circuit created by the connection of a resistor or load to the circuit. Voltage-drop may be measured by connecting a known resistance at a certain point in a circuit. Since the applied resistance is a constant, the change in circuit voltage that is created by the known resistance can be calculated as the impedance of the circuit itself from the source of the voltage to the point of the measurement.
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I thought impedence was only used for AC. Seems like the definition could be reworded to include DC voltage drop too.
 
peter d said:
How could these rules ever be imposed on premises wiring systems when we have zero control over the voltage drop that exists on the outdoor distribution system?

My vote is for rejection.
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Who cares about VD on the POCO side? That's their problem.
 
peter d said:
How could these rules ever be imposed on premises wiring systems when we have zero control over the voltage drop that exists on the outdoor distribution system?
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The section applies to the branch circuit, not the total.

If the voltage at the breaker terminal is 115 you could drop 8% more.

What the section is missing and could cause it's rejection is an instruction on how it must be calculated. What current would we use, the breaker size, the connected load or the calculated load. And what is the calculated load of a dwelling unit receptacle circuit with 15 duplexes on it?
 
(A) Branch Circuits Not More Than 600 Volts.
(5) Maximum Permissible Voltage-Drop. Conductors shall be sized such that voltage-drop at the furthest outlet on a 120-volt branch circuit shall not exceed 8.0% to ensure sufficient available short-circuit or fault current to facilitate the operation of the branch circuit overcurrent protection device as required by Article 250.4(A)(5).
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What will be the load imposed on the circuit to check the VD? If its a 20 amp ckt. do you use 20 amps?
 
480sparky said:
Who cares about VD on the POCO side? That's their problem.
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You must live in a neighborhood that has updated power lines, VD is an issue in many older tracks where when Joe 4 doors down runs a power tool, your lights dim. And the POCO could careless.
 
480sparky said:
Who cares about VD on the POCO side? That's their problem.
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I care because they supply a certain amount of voltage drop to us already. Circuit length is from the source transfomer terminals to the last receptacle on the circuit.

Case in point. This last summer we were getting a final inspection on a duplex that we just finished. The inspector had one of those SureTest gizmos and he plugged it into the bedroom receptacle and did the test. Fail. We raised hell about it because as it turns out we were the very last house on the poco run. The transformer was also a good 200 feet down the road. To make matters worse it happened to be one of the hottest days of summer and AC's were running. Of course there is going to be voltage drop. :roll:
 
acrwc10 said:
You must live in a neighborhood that has updated power lines, VD is an issue in many older tracks where when Joe 4 doors down runs a power tool, your lights dim. And the POCO could careless.
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But it is not the ECs problem and that prosed section excludes the service and feeder voltages. :smile:
 
iwire said:
The section applies to the branch circuit, not the total.

If the voltage at the breaker terminal is 115 you could drop 8% more.
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But the branch circuit is still part of an overall system, and part of that system is beyond our control. If we can't control one part of the system the we can't control any part of it.
 
peter d said:
I care because they supply a certain amount of voltage drop to us already. Circuit length is from the source transfomer terminals to the last receptacle on the circuit.

Case in point. This last summer we were getting a final inspection on a duplex that we just finished. The inspector had one of those SureTest gizmos and he plugged it into the bedroom receptacle and did the test. Fail. We raised hell about it because as it turns out we were the very last house on the poco run. The transformer was also a good 200 feet down the road. To make matters worse it happened to be one of the hottest days of summer and AC's were running. Of course there is going to be voltage drop. :roll:
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The NEC could care less about the POCO side of the service. VD is based on percentage, not a definite number, anyway. If your available voltage is less, VD will be less.
 
peter d said:
But the branch circuit is still part of an overall system, and part of that system is beyond our control. If we can't control one part of the system the we can't control any part of it.
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Pete Article 210 applies only to BRANCH CIRCUITS, the proposed section says BRANCH CIRCUIT and the NEC has a definition of BRANCH CIRCUIT.

It really is that simple
 
iwire said:
Pete Article 210 applies only to BRANCH CIRCUITS, the proposed section says BRANCH CIRCUIT and the NEC has a definition of BRANCH CIRCUIT.
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I'm well aware of that too. You're just not seeing it from my perspective, which happens to be the correct perspective. ;) :D

I can see the point of VD rules in the NEC for quick operation of OCPD's. But I think this one will be hard to enforce.
 
iwire said:
But it is not the ECs problem and that prosed section excludes the service and feeder voltages. :smile:
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I know I was just responding to 480s comment. "Who cares" was the thing I was touching on.
 
peter d said:
I'm well aware of that too. You're just not seeing it from my perspective.
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Of course not because your perspective is wrong.:D

As 480 mentioned it is a percentage, seeing as the proposed section only addresses 120 volt circuits had they wanted a minimum voltage they could ave dumped the 8% and given a minimum voltage
 
peter d said:
I'm well aware of that too. You're just not seeing it from my perspective, which happens to be the correct perspective. ;) :D

I can see the point of VD rules in the NEC for quick operation of OCPD's. But I think this one will be hard to enforce.
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What does voltage have to do with the trip characteristics of a breaker? (other than being within the voltage range) I buy 15-amp, 20-amp, 50-amp breakers, not 117.2-volt, 115.7-volt and 123.1-volt breakers.
 
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