Warranty inspections

Mike,

My nomenclature was off and your are right. I will ask the power company at the lake whats the power in suppose to be. This may be like herding cats though, Santee power and Electric Coop is not known for being coopertive…pun intended.

Curt

A transformer will work at any voltage. If I had a two to one transformer it wouldn’t care what voltage was applied it would simply give me a two to one voltage; 240 to 120 or 200 to 100 or 100 to 50 or 50 to 25 and so on. This is not true about autotransformers as they work just a little different than a regular transformer.
The insulation of the windings would regulate the maximum amount of voltage that could be applied.

If anything the transformer would produce less heat at a lower voltage than at a higher voltage. The same is true with resistive loads, the lower the voltage the lower the temperature of the device.

A simple experiment; wire a 40 and a 100 watt light bulb in series. Which bulb is the hottest? Did either bulb get as hot as it would if it were wired by itself?

We must remember that the voltage drop across any circuit or any branch of a parallel circuit will equal the voltage applied. In the experiment with the bulbs we designed a circuit that will have different voltage drops at each bulb. The total of the voltage drops will equal the total amount of the applied voltages. The lower voltage caused the 40 watt bulb to burn dim and not as much heat was produced by this bulb as would have been should it have been wired on a circuit by itself. The 100 watt bulb did not emit any light nor any heat.

Once again, voltage drop is NOT a safety issue but IS a design issue.

If it was such a safety issue it would be addressed in the rules of the NEC and the IRC which it is not mandated by either.

Connecting power tools like a heavy SawsAll via an extension cord or running a large hair dryer on a circuit that already has some general draw sure will get loads up around 15 amps.

At a 3% to 5% VD I would probably agree. However very high VD on a circuit could indicate such things as a loose connection, which sure is a concern.

I don’t subscribe to the practice of using specialized tools like a “circuit analyzer” for a home inspection … but for those that do I understand and agree with why they would report very high VD. The question that I always ask is not whats the purpose, but where do you realistically draw the line between what is normal and what is a concern.

JMO

Has anyone using a long cord on a Saws-All ever set a house or saw service on fire before? What normally happens? Saw gets hot and the breaker trips. Where is the danger?

As to the hair dryer and some other draw what would happen? The breaker would trip so where is the danger?

Would these things be inconvenient? Yes.
Would they be dangerous? No
It would all be a design issue not a life safety issue.

I would recommend using something like this and if it lights up correctly move on to the next device

.

What I wouldn’t be doing is trying to design the electrical system after it has been installed.

Think about the old farm house that was built back in the 40s and 50s that have a service drop so long that they are only getting around 110 to 115 volts at the meter. Where do we stop doing the voltage drop test?

Bottom line… voltage drop causes no problems in a dwelling. This nonsense about electronics and transformers is a mere strawman tactic. Voltage drop in a dwelling is hardly ever measureable with the loads commonly applied in a dwelling, and when the receptacle is loaded, the minimal drop from domestic appliances causes no problems. The reports of problems due to “voltage drop” are anecdotal, at best. The SureTest is an interesting gadget, so feel free to report it’s findings. It keeps me certainly employed, and makes me money. Just don’t take it too hard when I report back with my professional opinion that no problem exists. It’s probably worth reporting voltage drop for the 1 time in 50 that it might be due to a poor connection. Loose wires cause fires.

An 18% voltage drop at 15 amps is about 324 watts. If that is linearly distributed in a #14 wire that is a long run then it is indeed not a safety hazard. If it is concentrated at a bad backstabbed outlet connection then it can get pretty darn hot. I have a 250 watt soldering iron that does quite well at generating enough heat to solder small copper tubing.

As a HI, I don’t know which situation is present. So I opt to be safe for my client and recommend that at a minimum that the backstabbed outlet in question be hooked up to the screws.

10 years ago my wife was vacuming and said '“there’s smoke coming from the outlet the vacumn is plugged into.” It was a backstabbed outlet with a bad connection and very hot. The vacumn pulled about 10 amps. Excessive voltage drop can be a hazard. Not all the time certainly but once is enough.

Should you have a voltage drop 18% on a 120 volt circuit it would burn a motor up before it would heat a loose connection to the point of a fire. If it is a lose connection such as you point out in the statement then it is not a voltage drop problem but a mechanical problem.

The formula for voltage drop is VD = 2 x K x Q x I x D/CM
“VD” = Volts Dropped
“K” = Direct Current Constant
“Q” = Alternating Current Adjustment Factor: The “Q” adjustment factor is determined by dividing alternating current resistance as listed in NEC Chapter 9, Table 9, by the direct current resistance as listed in Chapter 9, Table 8.
“I” = Amperes:
“D” = Distance
“CM” = Circular-Mils
I don’t see any thing in this formula that allows for loose connections such as wire nuts or push-in type connections. Voltage drop is nothing more than the resistance of the conductor that is carrying the current and a loose connection is a mechanical failure.

Then you should opt to start a trouble shooting business as I for one would hire you just to check my circuits for loose connections as you know which situation is present.

Why would you recommend something that is tested for the application be changed?

Here the problem was not a voltage drop as you are testing for with your 12 amp load. What you had was a failed connection and is far from being a voltage drop problem.

But then again I agree with Marc;

Tripped breakers from things like power tools, hair dryers, and appliances is just confirmation that loads on typical household circuits can indeed reach 15A or more. And what about window AC units, that draw a lot and often run overnight (and have intermittent load surges when the compressor kicks on).

The issue is what if there is say a bad connection on a 15A circuit that is loaded to 15A. That is typically not enough load to trip the breaker. But if there is a loose connection on that circuit somewhere it could initiate a fire that is not immediately apparent, or even further degrade a loose connection to the point where over time normal loads could initiate a fire.

Home electrical fires from things like loose connections is a real risk. If you don’t believe me check the NFPA site for more info.

That is generally what I do also. But some inspectors go beyond the standards/minimums and use higher end tools/equipment like a “circuit analyzer”. There are positives and negatives to both approaches.

JMO

Mike,

For anyone who gives a darn about it, here is a link to a better explaination of the formula you posted http://members.aol.com/ocsee/el_calc.htm. That allows you to calculate the VD in the WIRE.

If you read my previous comment, you will see that I said if the 18% voltage drop was distributed in a long wire run that there would be no safety hazard. There is even a formula to calculate how much that wire will heat up. The insulation on the wiring is designed with a large safety factor so that a 15 amp load will never bother a #14 wire in good condition.

Again, if the VD and the energy from it is concentrated in one point then it’s another deal. Since a poor connection can usually be considered purely resistive in nature we can use simple formulas the same as if we were dealing with DC. i.e. Power = current X voltage drop. 15 amps x (120 volts X 18%) = 324 watts. In reality, not all of the 324 watts will be in the poor connection since part of it will indeed be in the wire, depending on it’s length.

In my case 10 years ago, it was indeed a failed connection that caused a large voltage drop at the outlet which led to heat and then a bit of smoke. If my wife had not noticed it then fire may or may not have followed.

If you or any electrician wants to shrug off a 18% voltage drop at an outlet as no problem, just put it in writing on your company letterhead and sign it. Odds are high that the wrong set of circumstances will never develop to cause a problem and you and the homeowner are both fine and dandy. But if it by small chance it does turn out to be a big deal, the homeowner can then discuss it with you.

This has been a very interesting thread - filled with differing terminologies as well as some facts. When I step back and look at it from a distance, several thoughts come to mind (in the context of a Home Inspector).

a) If SureTest or other device seems to indicate a lower than ‘normal’ voltage at an outlet, as a HI we can’t determine the reason (i.e. stabbed connections?) without diassembling the outlet. Isn’t that outside the SOPs?

b) How many outlets would you test to make sure you didn’t risk missing the one that had the critical defect?

c) When I think about all the things a HI has to test, review, and observe, this seems like an unusual level of detail. To test every system to this level would require a day or more per house.

JMHO, of course.

a. I don’t really need to determine the reason. There is a problem that may or may not be serious. The electrician can figure that out. Just like if you report a light fixture as not working. The most likely reason is a burned out bulb but it could be socket, wiring, switch. I just report it does not function.

b. I test all accessible outlets. My state SOP states a representative sample. But it’s not much more to check all that are accessible.

c. Sticking the 3 light tester in a socket takes a second; using the Suretest takes 3 or 4 seconds. Not much additional time required.

Using a Suretest is not required by any known SOP. Some of us do use it; most do not. Personal choice.

As a mechanical contractor, I have found a bucket load of burnt wire, most of which never tripped the breaker and the equipment was still running and in service.

The further down the circuit you can test, the more connections that get tested.

Backstabbing is a big cause of heat and voltage drop.

I am concerned about electronic equipment using low voltage. Most of my customers have large home offices.

I don’t do cartwheels over a >5% drop, but in cases like this, where you can’t get 100 volts out of the plug, it’s getting a bit ridiculous.

Someone said something about a drill motor burning out before a fire starts? Well I guess that the low voltage CAN hurt stuff.

I have also found very warm wires running throughout the house with the IR Camera that had large voltage drops. How much is too much? I’m not going to test the theory with any one’s life to find out. I just report what I find.

How about the Escrow Check?