I know I should know this and I read it in one of these post a long time ago. I did a search on this site but could not find it. What is the max voltage drop allowed on any given branch in a home. Does the IRC address this and if so where?

Thanks in advance guys!

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Mike Schulz License 393
Affordable Home Inspections
www.houseinspections.com

From the 2002 NEC. (bold is mine)- 210.19 Conductors — Minimum Ampacity and Size.- - (A) Branch Circuits Not More Than 600 Volts.- - - (1) General. Branch-circuit conductors shall have an ampacity not less than the maximum load to be served. Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the minimum branch-circuit conductor size, before the application of any adjustment or correction factors, shall have an allowable ampacity not less than the noncontinuous load plus 125 percent of the continuous load.- - - - Exception: Where the assembly, including the overcurrent devices protecting the branch circuit(s), is listed for operation at 100 percent of its rating, the allowable ampacity of the branch circuit conductors shall be permitted to be not less than the sum of the continuous load plus the noncontinuous load.- - - - - FPN No. 1: See 310.15 for ampacity ratings of conductors.- - - - - FPN No. 2: See Part II of Article 430 for minimum rating of motor branch-circuit conductors.- - - - - FPN No. 3: See 310.10 for temperature limitation of conductors.- - - - - FPN No. 4: Conductors for branch circuits as defined in Article 100, sized to prevent a voltage drop exceeding 3 percent at the farthest outlet of power, heating, and lighting loads, or combinations of such loads, and where the maximum total voltage drop on both feeders and branch circuits to the farthest outlet does not exceed 5 percent, provide reasonable efficiency of operation. See 215.2 for voltage drop on feeder conductors.

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"If con is the opposite of pro, is Congress the opposite of progress?"
Richard Rushing, HCRI
Duncanville, Tx.

It is in several places in the NEC, Richard posted one of them.

However, FPN means Fine Print Note, and a Fine Print Note is not enforceable.

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Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
www.AskCodeMan.com

True... a FPN is not enforcable. I think the question was not about code, but it was more about "what is the max voltage drop allowed on any given branch in a home."

No. The IRC does not (that I know of) specifically address max voltage drop.

rr

__________________
"If con is the opposite of pro, is Congress the opposite of progress?"
Richard Rushing, HCRI
Duncanville, Tx.

So what is the enforceable voltage drop for residental. Or what do you guys call out as to much drop for standard loads in residential receptacles.

Reason being is my Ideal tester I use on occassions showed 12% at some of the farthest runs but I don't have a bench mark to go from.

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Mike Schulz License 393
Affordable Home Inspections
www.houseinspections.com

Sorry by the time I got that last post out about enforceable Richard replied...........

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Mike Schulz License 393
Affordable Home Inspections
www.houseinspections.com

While I will agree with you on that, I will disagree also - because the question said, and you repeated in the quote "allowed", which implies something that "allows" or "dis-allows" something, and, in this case, that would be the NEC, and FPNs are not considered to be 'part of' the code, which is why they are not enforceable. Thus, if not considered 'part of' the code and thus unenforceable, FPNs may not "allow" or "dis-allow" anything.

Which brings us back to the use of the word "allow".

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Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
www.AskCodeMan.com

There is none.

I always noted if in excess of 5%, and made a much bigger deal about it if in excess of 8% and made a big deal about it if in excess of 10% (I've found as high as 43% as some GFCI devices which (apparently) did not reset making proper contact.

Also, AFCI breakers tend to create a little voltage drop in those circuits, unlike GFCI breakers.

I always recommended using #12 AWG as a minimum size instead of using #14 AWG - because #12 *cannot be backstabbed* into devices like #14 can ... and that (backstabbing) appears to be the greatest single cause of voltage drop (other than using runs which are just plain too long and voltage drop is created in the length of wire in that circuit).

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Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
www.AskCodeMan.com

quote=Jerry Peck

"Also, AFCI breakers tend to create a little voltage drop in those circuits, unlike GFCI breakers."




Boy... that's putting it mildly. AFCI's create between 10-12% regularly (at least what I've seen).

rr

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"If con is the opposite of pro, is Congress the opposite of progress?"
Richard Rushing, HCRI
Duncanville, Tx.

I believe you would find that the voltage drop of a circuit with an AFCI *and* with *no* back stabbed devices would not be that bad.

I regularly found 9-17% before AFCIs came in. Whenever the electrician would go back and pull the wires from the backstab holes and put them under the screws, the voltage drop would drop by an average if 2-3% *per device* in series which was also backstabbed. That means if there were 6 receptacle outlets in the master bedroom, you could see a 12-18% reduction in voltage drop.

The best evidence of that was (other than when the electrician would change them to prove me wrong, only to end up proving themselves wrong) is when you have 6 receptacles in that same master bedroom and the voltage drops might be 3%, 5%, 4%, 9%, 6%, 2% as you went around the room. There is no doubt that the 9% one is voltage drop at its backstab connection, and that 4%, 5%, and 6% are up because of their backstab connections.

Of course, I've also seen where those receptacle outlets averaged 16-18% around the room and only improved to about 6% when under the screw terminals - because of the length of wire in the circuit.

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Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
www.AskCodeMan.com

Just because someone makes a meter that says "X" it does not necessarily mean anything. Voltage drop is such an example of a 'factoid;' that is, a fact that may have absolutely no meaning whatsoever.

If all the voltage drop occurs at one point, there might very well be a problem. If it is gradual over the entire run ... well, that's simple physics.

The final voltage is relevant. A circuit supplying 132v ... not unheard of in new developments, or near the PoCo transformer .... you can have an 18% drop, and everything will work fine. Yet, if you're only getting 110v ... again, quite possible in an older part of town ... even a 3% drop puts you below the NEMA specs for most things - you're going to be damaging equipment.

Also relevant is the actual load. If the load at the end of the run draws but 5 amps, testing the circuit with a simulated 20 amp load will not give you any relevant information. Naturally, with general purpose convenience circuits, one cannot really say what the loads will be .... but testing to 'worst case' is something for engineers to fret over, not the inspector.

IMO, those testers might have some value in the context of troubleshooting or quality control .... but have no place in the HI's work. The information they provide is useless without being put in context ..... and, frankly, can be only described as 'electrical work.' As such, it is beyond the competence of anyone but a licensed electrical contractor / master electrician to offer an opinion.

Thanks for all the replies, it was quite helpful.

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Mike Schulz License 393
Affordable Home Inspections
www.houseinspections.com

Quite to the contrary.

Yeah, and that's why voltage drop is supposed to be factored into the calculations - to avoid that physics problem.

Quite the contrary.

Yes and no. The actual load will create a varying voltage drop based on the actual load, and, as the load changes (no load in a dwelling is going to be consistent 24/7) the voltage drop will change.

The PERCENT voltage drop at the circuits rated ampacity is what is important as a circuit MAY BE USED as its rated ampacity, thus ...

... testing the circuit at rated ampacity provides very relevant information about the ability of the circuit to perform as intended.

And in my opinion no HI should work without one, least they run across the work of an electrician who either does not know about voltage drop, or maybe simply does not care (there are many of both out there).

I've known many HI who have the knowledge and background to explain what, why, and how voltage drop is to a "electrical contractor / master electrician". Many of them just do not understand it and its consequences and thus take no steps to reduce it.

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Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
www.AskCodeMan.com

On the issue of testing for voltage drop, we will have to agree to disagree.

On the issue of competence, it's not out opinion that matters. "Competence" is very strictly defined by law ... if you don't have the license, you are, by definition, not competent. Period. It matters not how smart, educated, or experienced you may be. No license, no legal competence.

"Electric work" requires and electrical contractors' license. You might as well argue that HI's could write drug prescriptions.

Quite to the contrary.

A "license" does not mean you are "competent", it only means you are legally allowed to perform the *WORK*.

*YOUR* license says you can perform the electrical work.

*MY* license says I can inspect electrical work.

*YOU* perform the electrical work, *I* will inspect the electrical work.

__________________
Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
www.AskCodeMan.com