ok here is my question to the experts.
i wired a house which has long home runs about 130-150 foot. the master bed room feeds only the master bed room and the master bath, a home inspector(not electrical) has a tester which can apply 15 amps across circuit and gives a percentage of the volt drop. he says i have a 13% volt drop at that outlet. at that same plug i get 120 volts. when i turn every singe light and bath fan and plasma tv on i get a 112 volt reading on my tester.
i am aware of the 5% and reasonable operation, since entitre circuit would have to be on to achieve such volt drop.
i calculated th volt drop for the home run @
2kil/csa =
2*12.9*15*130/4110
50,310/4110
12.2 volt drop
following the FPN the max amount of #14 wire would be 50 foot
2*12.9*15*50/csa
19,350/4110
4.7 volt drop
i never calculated volt drops for a house before, have always tried to keep branch circuit to min opening count(12 on a fifteen amp circuit)am i missing something here?
are my calcs right and have i been trained and practicing excessive volt drops?
if 15 amp branch circuits are limited to such small footage you would need a sub panel every 50 foot. and as far as the load calcs and min circuits required go i have more than tripled them. bedroom draws 8 amps with that load i mentioned.
please help with comments and criticism.
thanks,
H20

This is a difficult thread, where one must make a reply without getting passionate.

Just because someone makes a fancy meter (toy) that cranks out a number does not mean that either the toy or the operator are running the job.

Test results are meaningless without the ability to evaluate them. Neither the tester, nor the operator, can make those design decisions. They're simply not qualified.

One bit of information is useless, without being in context with much more information.

The 5% figure is a recommendation ... not a code requirement.
What is probably more important is the minimum voltage. NEMA standards typically call for equipment to operate at 10% under their nameplate voltage. For an appliance marked "120," this means that the appliance will operate at 106 volts, in a reasonable manner. If, under full load, you have 112 v, you don't have a problem.

Factors such as 'start up current' are not really relevant for a general purpose circuit; if it was for a specific appliance -say, an air conditioner- the matter is different.

Another cause of large voltage drop is bad connections. If the drop is pretty even across the circuits that is one thing; if most of it seems to happen at one device, then perhaps there is a problem that needs to be fixed.

For future jobs, you can reduce the problem by using a larger wire for home runs, or by using sub-panels. Voltage drop is something you need to consider. Yet, for all the fuss that has been made at the HI sites over voltage drop, I cannot help but wonder how the trade made is a century without those dang meters!

good point Reno ,, I will agree with you about the common sense with long run and my thumb of rules every 30 metre or 90 feet i useally upsize wire one size bigger or get subfeed panel to reduce the voltage drop depending on the design of the place.

but the HI [ home inspectors ] somecase the dont understand the system very clear at all and can get misunderstood it pretty easy.

Merci , Marc

I would also add that to have any general lighting circuit in a dwelling unit loaded to 15 amps would be an extremely rare situation and this is one of the problems with this type of tester.

If it could apply say 4 to 8 amps it would be more realistic but I would say in my house most general lighting circuits (excluding the kitchen and bathroom) never see more than 2 to 3 amps in a normal day.

Roger

Did anybody determine the available voltage at the main? Depending on the utility, time of day, time of year....available line voltage at the main may or may not be 120 exactly!

Many jurisdictions have adopted the ICC International Energy Conservation Code (IECC). For Commercial buildings, the IECC adopts the standard ASHRAE/IESNA 90.1. In section 8.2, feeders are limited to 2% VD, and Branch circuits to 3% VD.

One and two family dwelling wiring has no such requirement.

I have always been a bit skeptical of the readings on the SureTest. This has to be a very short pulse and it may not actually be there long enough to get a real world reading. I would prefer to back this reading up using a real meter and a hair dryer. They will provide a steady load of around 12a (ignore that "1800w" number on the case. It is the same type of rating as the "5HP" air compressors with the 120v/15a plug)

the nec makes reference in a FPN about volt drop, what is its intent? that at 100% of branch circuit is 5% or that at farthest point before plugging in is 5%? this is becomming a "he said /he said" issue between me and the contractor. this home inspector now brought in another electrician who supports his fancy meter and for few thousand bucks he will install a sub panel.
the same sub the contractor didn't want to pay for durring original construction.
i just cant get through to this home inspector that plugs are convienence and intended as such alarm clocks, lamps, tv's, vcr .... yada yada and whith all lights on this branch circuit the meter reads 112 volts
turn all lights off(master bath-tub,shower,fart fan,vanity,toilet fan/light) the meter reads 120 volts. where is this supposed volt drop? monday i will bring hair dryer and test as suggested by gfretwell, but i know with an 8 amp draw what the nuber already is since i tested the amps with all lights on.
please guys explain the intention of FPN to me.
thanks,
H20

The FPN does nothing more than remind you of an accepted guideline, or design goal.

So what is this voltage drop issue all about?
In the first case, it's about days past, where a 120v service might actually be delivering only 120 v to the customer. Lose a few more volts, and you no longer have the minimum 108 that a 120v appliance needs for proper operation. Of course, these days I quite often measure incoming voltages that are much closer to 130, than 120!

Secondly, a large voltage drop is a suggestion that there MIGHT be a problem. Far more than wire length, bad connections will cause such a drop.

It might be interesting to do the voltage drop test at the panel, as well as at the receptacle. Then, progress along the circuit, and see if the drop is gradual - or happens at one place.

If, even with the drop, you have more than 108 v at the receptacle ... and there is no mention of this testing in the contract ... I don't see a need for you to do any more. This time. What else you do is more of a business decision than anything else.

As mentioned earlier, a 'quick fix' would involve replacing the home runs with #10. Putting junction boxes in the attic, and replacing the bulk of the run, just might make everyone happy.

Otherwise, you've received a 'wake up call.' I'm sure you will forever consider voltage drop in your future work. Because, legalities aside, you can see where 'code minimum' and 'good design' are not the same thing.

As for the HI ... well, everyone has an opinion. Keep in mind that the HI is not the one licensed to do electric work - you are - so by definition you are qualified, and he is not. Keep in mind that he is not, in any way, the AHJ. He's just a spectator. You have no contractual relationship with him, and have no obligation to care in the slightest what he thinks.
If the customer is not happy, he can pay you ... and not hire you again. Or, future jobs will be planned / priced with this additional requirement in mind. Or, you can be NICE and accommodate him this time, for the sake of future business.

But the FPN has NO code significance, and is only a suggestion, without even the weight of the code saying 'may' or 'should.' It's NOT part of the code. This is explained in the very first pages of the code itself.

HI in general is just a way to force a seller to lower his price. I guarantee the buyer doesn't want the voltage drop fixed, he just wants a credit on the price equal to the work the HI recommends.
I do see some silly discussions over on the NACHI BB trying to make mountains out of molehills. I suppose if you pay someone $300-400 to give you a 2 hour inspection they feel obligated to find "defects". They argued for a week over multiple ground wires in a single lug on a bus. They lose their mind if you don't reidentify a white wire on a romex used for 240v. You would think babies were dying all over the country from this "defect"

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

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"!

< RANT MODE = ENABLED >

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!!!

< / END RANT MODE >

One last thing I want to cover:



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

Scott

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!

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.

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.