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Joined: Oct 2000
Posts: 2,722
Broom Pusher and
I would like to add a few things to this thread.
Most items have previously been covered, but I would like to include my 2¢ redundantly wink

First and foremost: Sizing of Homeruns to avoid excessive Voltage Drop...

If you are installing a Homerun, which has a one-way circuit length = > 100 Feet, especially if it is only a 2 Wire Circuit, then it would be a "Good Design" idea to increase the Conductors' size - at least to the next size up.

This is also suggested for long runs through insulated attics, to compensate for high ambient temperature.

So if the Branch Circuit's OCPD is 15 Amps, use #12 Copper.
If OCPD is 20 Amps, use #10 Copper.

For a basic example (using my Volt Loss Spreadsheet), check these figures:

Circuit Length (minimal): 100 Feet
Load: 10 Amps
Circuit: 1 Phase 2 Wire
Conductor size: #12 Copper
Nominal Voltage at beginning of Circuit: 120 Volts.

* Voltage Drop = 3.29%
* Volts Lost = 3.95 Volts
* Nominal Voltage at end of Circuit = 116.05 Volts


If the Homerun was a Multiwire Branch Circuit, with 10 Amps on one Circuit and 5 Amps on the other, the Voltage Loss figures would now become:

* Voltage Drop = 1.646%
* Volts Lost = 1.975 Volts
* Nominal Voltage at end of Circuit = 118.02 Volts


As previously mentioned, the Nominal Voltage at the "Supply End" of the Circuit, at the time of any Circuit Voltage Drop Testing, needs to be used as the "Starting Point" for a Voltage Drop percentage figure.

In addition to this, someone needs to clarify if and/or when there may be a Hazardous condition, resulting from excessive Voltage Drop; - such as what would be an excessively low (or even high) Voltage reading and how it would become a safety hazard.

FPNs are not enforceable - nor are "Suggestions" set forth by "Non-Authorized Client Consultants".
Pre-sale Home Inspection personnel fall into this category.

The situation falls on what you agreed to in your Contract (or excluded from it), as being the "Project Completed According To Specifications and Proposal" deciding factor.
You should be paid the remaining Balance of the proposal amount, if you have fulfilled the contractual agreements (and you have final electrical signed off).

Not too many Home Owners fully understand the whole Voltage Drop concept - nor do most General Contractors, so for the most part, single family residential rough wiring is an "on-going design issue" for the Electrical Contractor.

On your future projects, it may be beneficial to consider the problems of long Circuitry Voltage Drops, figure to upsize by one wire size where needed, and adjust your proposed amount accordingly.

In addition, maybe consult the Clients (Home Owner or General Contractor) to the concept, and if they do not care, GET IT IN WRITING WITH SIGNATURES!!!
That way, when the H.I. comes along with the Plug-In tester, and notes the report document with "Excessive Voltage Drop", you simply produce the "Magic Disclaimer" document - effectively "Trumping" the H.I. voltage drop issue.

I do not use those testers, as they appear to simply "Pulse" a heavy load current level - and take a Voltage reading during that "Pulse" time, then figure a Voltage Drop as if there was minimum 120 Volts at the testing point prior to applying a load.

My way to test is similar to what others have mentioned - verify the ACTUAL Voltage at the test point prior to, during, and after applying a fixed load - drawing load current for at least 1 minute.
In conjunction to this, logging the Voltage before, during and after the testing, at the beginning of the Circuit (Panelboard or Service, where ever the Branch Circuit's OCPD is located at).
Clamp on an Ammeter also!

One person reads + notes the levels at the beginning of the Circuit, another performs the test and records the levels at the end of the Circuit.

If you have "Data Hold" features on the test equipment, one person may perform the tasks.

Now it's time for me to "Complain"! crazy


So why is the H.I. bringing in Electrical Contractors to support the claim?
Doesn't this go way outside the H.I.'s scope, and possibly become a conflict of interest?

Did the "Sub Panel" idea get presented to the Home Owner &/or the G.C. as "The Only Way To Fix The 'Problem' At Hand", or is it just something that has become "stuck" in the conversation?

What else would / could benefit from the installation of an additional Panelboard, now that the Finish work is nearing completion?

Where would it go?

Will a Permit be obtained for this Panelboard + Feeder?

Does the other EC have a License?

Is the other EC qualified to make such claims?

Does the H.I. have the authority, or the responsibility to both, make the claim, and involve a third party consultant (the other EC)?

Do you agree that there is/may be an issue of safety with the voltage drop, as measured by the H.I.?

What total liability / contractual obligation do you have, regarding this scenario?

Did the H.I. report the scenario as a "Code Violation", a "Safety Hazard" or simply as it should be - a "Suggestion"?

Sorry to go into rage mode here, but I get upset when things of this nature are being presented as "Must Do - No Discussion About It", or "He Said/She Said", with no valid or ACTUAL Legal, Technical, or factual backing!
If this isn't the case here, please accept my apologies for flame throwing...

Mistakes are mistakes, and sometimes one person does not fully comprehend what the other person had said - or interprets it incorrectly - this is Human nature.
The need to coordinate and verify both sides understand each other (just what is being disputed) must be achieved before ANYTHING can be discussed properly.

Until that time, everything is hearsay and irrelevant.

This is the P.M. and Engineer in me coming out!!! eek


One last thing I want to cover:


the master bed room feeds only the master bed room and the master bath

Does this mean that the Master Bathroom Receptacle(s) and the Master Bedroom Outlets are on the same Circuit?

Shouldn't the Bathroom's Receptacle(s) be on a Designated Bathroom Circuit?

Anyhow, hope this is useful


Last edited by Scott35; 08/05/07 01:59 PM. Reason: UBB coding mistake

Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
2017 / 2014 NEC & Related Books and Study Guides
Joined: Jan 2005
Posts: 5,316
Cat Servant
Greg, you're sure right about that! I've lost track of the buyers who were SO concerned about defects, until the deal was closed. Once it was THEIR place, they had absolutely no interest in fixing anything.

As I sit here. out my window I can see a house that sold three years ago. At the time, the "Insurance Company" "insisted" that the place be painted, have the roof fixed, and have a ramshackle storage shed replaced. Well, the sale was made ... and none of those things have happened. Nor have any of the other 'defects' been remedied.

I tell you, this game playing simply disgusts me!

Joined: Feb 2002
Posts: 375
130-150' home run is poor design.

But a 20' square room on a single circuit will almost certainly have the last recept 100' from the breaker. 6% voltage drop at breaker rating.

But breaker rating or even 80% of breaker rating is much more than a residential circuit will see in most cases.

Up sizing wire is not going to solve a voltage drop problem, but the problem almost never really exists.

Joined: Nov 2006
Posts: 348
ITO Offline
Almost ever set of plans that comes across my desk has a spec or a note saying to size the conductors to prevent more than a 5-3% voltage drop. I have yet to see one of my competitors actually do it on the jobs that I lost to them.

The problem is if you bid the jobs that way you wont get the work. Its only when the engineer has actually done their job and sized the home run accordingly that it gets put in everyone’s bid and wired that way.

101° Rx = + /_\
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