Mention voltage drop?

[dbucknavich]

Is voltage drop something you mention if you notice high readings? My suretest detected 33% on exterior and bedroom outlets. I know a drop of about 7 or so % is recommended, but not required. Any thoughts? Thank you

[David A. Andersen]

What was the voltage down to under load, and at start, and at the panel.

Voltage drop is often due to high resistance in the circuit. High resistance generates heat and greater resistance.

I think your client deserves to know this.

Often back stabbed outlets have bad connections and overheat the plug and lower voltage down line on the circuit.

[dbucknavich]

Sorry David, not sure what your asking me. I test by visually examining the panel and visible conductors, and by plugging in the suretest and reading. It tells me 7-10% on what I believe is the first outlet in the run and 30-33% at the end of the run on ext. and int. outlets. Not much else I can say. Sorry

[dbucknavich]

The way I see it, is I am getting over my head a little bit when I start pointing things like that out. I do have a narrative that you could look at. I have not submitted it yet, so any comments or "constructive" criticism are appreciated.

Higher than recommended voltage drop was observed. Current standards recommend, but do not require, a voltage drop of no more than 5%. Drops in the range of 30-35% were observed on exterior outlets and bedroom outlets. This condition can cause overheating in the conductors. This leads the inspector to believe that less than professional standards were utilized for installation of the branch circuits. You should consult a qualfied electrical contractor for more information, as this does exceed the scope of a typical home inspection.

[Speedy Petey]

A voltage drop of 33% means either there is a serious problem with the circuit, or a serious problem with your tester.

How does the SureTest measure VD?

[dbucknavich]

I don't know how, but it does. Just like those dupont commericials, I just plug it in and it works. I have a pic. This house is a remod with many defects in the new hvac, plumbing, and electrical. The client is an electric engineer so I took a closer look for him.

[William E. Siegel]

"This leads the inspector to believe that less than professional standards were utilized for installation of the branch circuits."

I would leave that line out. There are varying factors that could lead to a high voltage drop. That does not mean that less than professional standards were utilized. Why beat up the electricain before you know the cause. Just write what you see and defer it out.

[dbucknavich]

Good point William. That line is in there because of the rest of the house. The same company appears to have done all the work- hvac, plumbing, elec, and roof. Each component was "less than professional". Would you replace the line with something or just omit it?

[Speedy Petey]

Well, considering your explanation, and the assumption that other receptacles in the house don't have this much drop, I think we can rule out faulty tester.

[ccurrins]

This leads the inspector to believe that less than professional standards were utilized for installation of the branch circuits.

My opinion is the "leads inspector to believe that less professional standards were utilized" is speculating and really irrelevant anyway. You have already done your job and identified the problem. Just defer and let the "Pro" figure out the source and remedy.

[Vince Santos]

I find the newer suretest to be inaccurate when testing volt drops and, well pretty much everything..

If I plug in my suretest I get a reading of no ground, rev. polarity, high volt drop etc. but if I pull it out of the receptacle and plug it back in these "defects" are gone.


False readings
Sent unit in once already
Replaced cord twice

and I've had it for under two years..

[James H. Bushart]

Originally Posted by wsiegel

"This leads the inspector to believe that less than professional standards were utilized for installation of the branch circuits."

I would leave that line out. There are varying factors that could lead to a high voltage drop. That does not mean that less than professional standards were utilized. Why beat up the electricain before you know the cause. Just write what you see and defer it out.

I agree.

I ran across this, tonight.

Five Percent Voltage Drop - A Closer Look!


John M. Birkby ~ July, 1999




National Electric Code Articles 210-19(a) FPN No. 4 and 215-2(d) FPN No. 2 state in part, “...and where the maximum total voltage drop on both feeders and branch circuits to the farthest outlet does not exceed 5 percent, will provide reasonable efficiency of operation.” Section 90-5, Mandatory Rules, Permissive Rules, and Explanatory Material is defined as follows:

(a) Mandatory Rules. Mandatory rules of this Code are those that identify actions that are specifically required or prohibited and are characterized by the use of the terms shall or shall not.

(b) Permissive Rules. Permissive rules of this Code are those that identify actions that are allowed but not required, are normally used to describe options or alternative methods, and are characterized by the use of the terms shall be permitted or shall not be required.

(c) Explanatory Material. Explanatory material, such as references to other standards, references to related sections of this Code, or information related to a Code rule, is included in this Code in the form of fine print notes (FPN). Fine print notes are informational only and are not enforceable as requirements of this Code.

The SureTest]® branch circuit wiring analyzer is becoming more and more, the tool of choice for many state, county, municipal and private electrical inspection agencies. The SureTest® is a true impedance tester and utilizes a patented full 15 ampere load test to analyze supply power and measure voltage drop and ground impedance. It is a hand-held, microprocessor controlled device with a digital display. The intent of the SureTest®is to identify and help isolate hazardous conditions in electrical circuitry. It will display the full load voltage drop in percent at the receptacle under test. A much higher than normal increase (2% or more) in voltage drop between adjacent receptacles on a circuit could indicate a potentially hazardous condition. These might include poor splices, high resistance or corroded connections, damaged conductors, improper wiring or inadequate connections at “back-stabbed” receptacles. A gradual, small increase in voltage drop along a circuit would not be indicative of a hazardous condition. This would be a normal increase in the total impedance of the conductors, splices, wiring devices, circuit breaker, service cable, etc.

In the NEC Fine Print Notes regarding voltage drops, it states a 5 percent maximum voltage drop “will provide reasonable efficiency of operation”. Nowhere does it imply that a voltage drop in excess of 5 percent is deemed a hazard. Much to the chagrin of the electrical contractors, some inspectors have decided to enforce the 5 percent voltage drop as the maximum allowable in their area of jurisdiction. In NEC Article 90-4, it does state “...The authority having jurisdiction for enforcement of the Code will have the responsibility for making interpretations of the rules, for deciding on the approval of equipment and materials, and for granting the special permission contemplated in a number of the rules.” Fine Print Notes (FPN) are not rules and, as defined, are clearly not enforceable.

Now, let’s take a closer look at a voltage drop in excess of 5 percent. If concern is for “reasonable efficiency of operation” and protection of equipment, the initial line voltage should be taken into consideration. For example, with a nominal voltage of 120 volts at the receptacle under test, an 8 percent voltage drop under full load would result in an operating voltage of 110.4 volts. 125 volts would drop to 115 and 114 volts to 104.9. Obviously, an 8 percent voltage drop at 120 to 125 volts is of little concern, while an 8 percent drop at 114 volts could seriously compromise the operation of equipment such as room air conditioners, refrigerators, high-amp vacuum cleaners, etc.

Some discretion should be considered when analyzing the voltage drops in a branch circuit. The SureTest®pulses a full fifteen ampere load to analyze the circuit, not just the receptacle under test. NEC Table 210-21(b)(2) allows a maximum total cord and plug connected load in amperes of 12 for a 15 ampere rated receptacle and 16 for a 20 ampere rated receptacle. Although there are appliances, such as hair dryers, available today with 15 ampere nameplate ratings, most UL listed appliances are rated at 12 amperes, maximum. Therefore, it may be anticipated that the maximum current flowing between the last receptacle on the branch circuit and the previous receptacle should be 12 amperes. Inasmuch as the [FONT='Times New Roman','serif']SureTest[/font]®imposes a full 15 ampere load at the last receptacle, a reading of 6.25 percent voltage drop would be equivalent to 5 percent at 12 amperes.

Many inspector members of the IAEI (International Association of Electrical Inspectors), ASHI (American Society of Home Inspectors) and NAHI (National Association of Home Inspectors) have reported feeling comfortable with gradually increasing voltage drops as high as 8 to 10 percent where the line voltage is near the nominal 120 volts. Most of the controversy over the 5 percent maximum voltage drop occurs during residential inspections. Some very capable contractors who are required to comply with the 5 percent drop, have reported experiencing a great deal of difficulty trying to achieve this in homes of 3,000 square feet or more. Even after all connections have been inspected and tightened, all receptacles “pig-tailed” and circuit breakers checked, the voltage drop remains in excess of 5 percent and yet, below 8 percent. One means of compliance would be to install sub panels, but in many instances, this would be physically impractical and cost prohibitive.

The SureTest®has proved to be an invaluable tool for inspectors and contractors alike. In addition to performing a full 15 ampere load test, the model ST-1D will also display percent voltage drop for a 20 ampere load. Also provided, are readouts of line voltage, ground-to-neutral voltage, estimated load on line in amperes, ground impedance in ohms and indications of false grounds or ground-to-neutral shorts. A unique GFCI test will verify the trip point of the device within the milliamperes-to-ground vs. time parameters set forth by Underwriters Laboratories, Inc. When used for its intended purpose, the will identify hazardous conditions including poor splices, high resistance connections, damaged conductors, false grounds, poor grounding, improper wiring, undersized wire, overextended circuits and faulty or mis-wired GFCIs. Visual inspections alone, cannot detect the hidden flaws in electrical circuitry which could result in a catastrophic fire or electrocution!

As for the 5 percent voltage drop, it’s still as it should be --- a Fine Print Note - with the inspector also considering wire gauge, length of run, no of receptacles in the circuit, and workmanship.


This material has been reviewed and approved by Mike Holt of Mike Holt Enterprises, Inc Telephone: 1-888 NEC-CODE ~ FAX (954) 720-7944 ~ Website: www.mikeholt.com

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[dbucknavich]

Good find, James.

[David A. Andersen]

Originally Posted by wsiegel

"This leads the inspector to believe that less than professional standards were utilized for installation of the branch circuits."

I would leave that line out. There are varying factors that could lead to a high voltage drop. That does not mean that less than professional standards were utilized. Why beat up the electricain before you know the cause. Just write what you see and defer it out.

I also agree that this does not have any place in any home inspection report. It is not factual and you have nothing to support this other than opinion.
Someone can build a house not the standard as we would expect and it will last as long as any other. This really has no bearing on the inspection. If the nonstandard practice results in a deficiency, write it up.

Just because an electrician backstabs the plug outlet, does not mean it's substandard work; even though in most cases where voltage drop exist, it is a result of this practice. It doesn't make it nonstandard (because it is practiced the majority of the time). That's what the sure test is for, to locate these deficiencies.

I highly recommend that before you start reporting anything in your inspection report based on an electronic measuring device, that you understand what the device does and what substandard readings indicate.

I have the same beef with home inspectors that try to report the age of a piece of HVAC equipment as being "close to the end of its expected life" when they have no supporting evidence, nor are they required to evaluate or predict this life expectancy. Just because there's very little that anyone can do to inspect HVAC does not mean you have to make stuff up to impress your client or cover your butt. Your client can see that the appliances are old, I don't see any reason to try to cover your butt because it may break in the future.

Someone posted a picture of a "about to expire" furnace this week, and it looked 10 times better than the two HVAC units on my house (which are a functioning better than any in my neighborhood). Yes, they will need to be replaced in the future (most likely because the cabinets will rust out and not support the condenser fan). Both of my units have thermostats to prevent the auxiliary heat from coming on unless it's actually cold outside (so people playing with the thermostat don't turn it on when they crank up the heat), it has multiple defrost sensor systems to ensure there is 1/8 of an inch of frost on the condenser coil before going into a defrost cycle (not just real cold outside), it has a time delay on the indoor fan to allow a coil to warm up in the heat mode before blowing cold air in the house, it also has a purge cycle to get the heat out of the air duct, the heat banks are staged based on return air temperature so they don't overheat and waste money, both have new compressors, both have new accumulators, both have new compressor contactor's, both have new indoor fans which are now variable speed controlled so they don't blow so much air in the wintertime and make you feel cold .

So, when you come to my house and look at the unit and say it needs to be replaced based on age (though you can't read their nameplates anymore) and the outside Cabinet has rust on it, you are condemning a piece of equipment that operates more efficiently and cost effective than anything new that you can buy.

Is the inspector going to report that the unit has been worked on under less than normal standards? Only if they can figure it out! If I move, the units will most likely be replaced because the HVAC technician can't find a wiring schematic.

Your inspection report should educate your client and report on significant deficiencies. You spent good money on a device, learn to use it properly and document accordingly.

In the case of my house, it would be prudent to admit that you don't have a clue about what's going on because some anal HVAC engineer must have previously owned this equipment! But its running fine, looks like crap and will eventually need replacing (as they all do).

[David A. Andersen]

Good article Jim !

Sorry David, not sure what your asking me.

Dylan, this article is discussing the other readings I was talking about and their relationship to what is a significant problem.

You should always follow up electronic measurements with other investigative techniques or equipment when possible. As Speedy Pete mentioned, comparison of baseline test (outlets next to the service panel versus outlets at the furthest distance from the panel) gives a differential that is probably more meaningful than the actual numbers displayed.

I look at the percentage of voltage drop, and when I find it high I look at all of the other information the testing device gives. Beginning and ending voltage, resistance on the conductor, which conductor has the high resistance etc.

This is one way I follow up.