Inspector III proven useful

[Marc]

I purchased one a few months ago and the initial verdict was that it was too bulky to carry around in my waist pouch so I retired my new $300 investment to my computer bag and let it begin collecting dust.

Last week I pulled it out on a hunch and tried it on an 80's house and found many receptacle voltage drops as high as 12%. I've used it twice again, both on 80's houses and found VD's as high as 20% which I've now attributed to failing back-wired connections on the receptacles. So, the Inspector III has earned it's keep and I've a little more help now in translating my fees into service. The recommendation on each is to replace all wall devices (receptacles and switches).

Anyone else using this instrument?

Marc

[kurt]

No, I stopped commenting on voltage drop about 7 years ago. There's no way to "prove" it's problem, all electricians advised my customers I was a moron, there's no definitive NEC condemnation of the phenomenon, etc.

[Marc]

In the cases mentioned, I had suspected that the excess voltage drop was occurring at the back-wired connections on the receptacles. Now, power is the product of amps and voltage. Let's say you've 12% voltage drop, 4% in the wiring which leaves 8% across the bad connection. 8% of 120 is 9.6 volts. If you've a 15 amp load (which is what my Inspector III was generating for the test) the power developed is 144 watts. That's a lot of heat for such a small mass and within the confines of an electrical box. It could easily reach the ignition temperatures of many types of combustible building material nearby.

Let the electricians call me a moron. I'll challenge them.

Marc

[Bain]

Marc,

I've had the Inspector II for a decade or so, and my experience is similar to Kurt's. The electricians aren't going to have any equipment to check for voltage drop and, if the bulbs are lighted, they're gonna say everthing's just peachy. I've used my Inspector II maybe twice during the past five years . . . when seven dollar three-prong testers broke.

I also spent three-hundred bucks on a refrigerant-leak detector. Same story. The HVAC dude who came behind me had a bottle of bubbles, and said I was an idiot and the condenser was perfectly okay.

[hausdok]

Hi,

Well, if an electrician is saying he has no way to confirm whether the Inspector III is right or not, isn't the electrician basically admitting he's more of a math moron than I am?

Think about it, what's the voltage range that 120-volts stuff has to operate within? Isn't it 108 to 132 volts? That's 120-volts plus or minus 10% isn't it?

OK, if the Inspector III says that voltage drop is 11%, doesn't every electrician have a multi-meter? If he checks voltage at that receptacle and the needle is hovering at just under 107-volts wouldn't that agree with the Inspector III since 120 - 11% is 106.8 volts? Wouldn't that voltage be unacceptable because now the voltage is below the required operating range for 120-volt devices?

My guess is that the Inspector III measures existing voltage, determines if it's below 120-volts and then calculates what that voltage would be percentage-wise below the ideal of 120 volts. Seems like that would be fair.

ONE TEAM - ONE FIGHT!!!

Mike

[Jim Katen]

Hi,

Well, if an electrician is saying he has no way to confirm whether the Inspector III is right or not, isn't the electrician basically admitting he's more of a math moron than I am?

Think about it, what's the voltage range that 120-volts stuff has to operate within? Isn't it 108 to 132 volts? That's 120-volts plus or minus 10% isn't it?

OK, if the Inspector III says that voltage drop is 11%, doesn't every electrician have a multi-meter? If he checks voltage at that receptacle and the needle is hovering at just under 107-volts wouldn't that agree with the Inspector III since 120 - 11% is 106.8 volts? Wouldn't that voltage be unacceptable because now the voltage is below the required operating range for 120-volt devices?

It would. But that's not what's happening here. These devices measure the voltage drop that occurs under a load. If you just stuck a multimeter in the outlet, it wouldn't show a problem. You'd have to apply a load and measure the voltage at the same time. That's not so easy if you don't have one of these testers.

I gave up on those kinds of measurements long ago. Then about a year ago, I had a client who was buying a newly constructed house and he specifically asked if I could measure and report on voltage drop. I told him I could and I did. Some of the receptacles shows voltage drip up to 23 percent.

The electrician returned, removed every back-stab connection in the circuit, and rewired every box with pigtail connections -- I looked and confirmed the work. The newly re-wired circuit still had a 23% voltage drop.

I don't go near voltage drop measurements anymore.

[kurt]

That's my experience. I measured my own home. 18% vd in some locations.

I pulled the wire (we run everything in EMT), reconnected everything, tight, checked all connections, no back stabs, etc.

Still had around 18% vd. I don't know why.

I also know I've run entire constructions sites with compressors, tools, lights, equipment on a couple 100' extension cords daisy chained across vacant lots (and standing water), measured voltage drop > 30%, and everything operated just fine for the whole project.

Not saying it's ok, in fact, it's "wrong", but I've never found any negative effect from voltage drop.

So, I don't bother with it.

[Chad Fabry]

Not saying it's ok, in fact, it's "wrong", but I've never found any negative effect from voltage drop.

So, I don't bother with it.

It has an effect on high load power tools to be sure. I've made the smoke leak out of stuff at the end of long cords more times than my wallet could comfortably bear.

Belt Sanders and recip saws top the melted plastic heap followed closely by compressor motors.

[Marc]

Hi,

Well, if an electrician is saying he has no way to confirm whether the Inspector III is right or not, isn't the electrician basically admitting he's more of a math moron than I am?

Think about it, what's the voltage range that 120-volts stuff has to operate within? Isn't it 108 to 132 volts? That's 120-volts plus or minus 10% isn't it?

OK, if the Inspector III says that voltage drop is 11%, doesn't every electrician have a multi-meter? If he checks voltage at that receptacle and the needle is hovering at just under 107-volts wouldn't that agree with the Inspector III since 120 - 11% is 106.8 volts? Wouldn't that voltage be unacceptable because now the voltage is below the required operating range for 120-volt devices?

It would. But that's not what's happening here. These devices measure the voltage drop that occurs under a load. If you just stuck a multimeter in the outlet, it wouldn't show a problem. You'd have to apply a load and measure the voltage at the same time. That's not so easy if you don't have one of these testers.

I gave up on those kinds of measurements long ago. Then about a year ago, I had a client who was buying a newly constructed house and he specifically asked if I could measure and report on voltage drop. I told him I could and I did. Some of the receptacles shows voltage drip up to 23 percent.

The electrician returned, removed every back-stab connection in the circuit, and rewired every box with pigtail connections -- I looked and confirmed the work. The newly re-wired circuit still had a 23% voltage drop.

I don't go near voltage drop measurements anymore.

Do you remember about how big the house was? #12 copper NM consumes about 6.4 volts at 16 amps and 100' long (half on the neutral and half on the hot wire, derived from Table 8 in the NEC). That comes out to about 5.3% of VD. My own 200 amp SE yielded 0.4 % as measured at a receptacle immediately adjacent to the load center. Combine these two and you have just under 6% for a 100' long branch circuit.

Pardon the math Mr. O.[]

Marc

[kurt]

It has an effect on high load power tools to be sure. I've made the smoke leak out of stuff at the end of long cords more times than my wallet could comfortably bear.

Belt Sanders and recip saws top the melted plastic heap followed closely by compressor motors.

Truly. I've had a couple memorable meltdowns when no one cared about a beater tool and fried it so we could keep going. But mostly, you run that way for a day until you get real power strung. Meaning, voltage drop just doesn't concern me.

AFAHI, voltage drop is somewhere in about the eleven-teenth priority level in my approach. It always brings bad and no traction.

[Erby]

I've made the smoke leak out of stuff

Did you try spraying them with some of that "Leak Stop" stuff?

[John Kogel]

If the excessive voltage drop is being caused by backstabbed receptacles, then using that tool has some merit, I think. It will depend on the circumstance.

The first reaction from home owner's sparky will be "the inspector's an idjit".

Back stabs:

I had a flickering, dimming bedroom light in my place a couple of years ago. The switch and the light fixture checked out ok. The wall outlet was scorched. In the pic, you can see the metal is discolored from heat.

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Smoking cords and voltage drop:

Way back in my youth, I was drying out some gear in a shed with a heat lamp on about 100 feet of extension cords. Good thing I was home to put the fire out.

[Marc]

Not saying it's ok, in fact, it's "wrong", but I've never found any negative effect from voltage drop.

So, I don't bother with it.

It has an effect on high load power tools to be sure. I've made the smoke leak out of stuff at the end of long cords more times than my wallet could comfortably bear.

Belt Sanders and recip saws top the melted plastic heap followed closely by compressor motors.

Interesting. Most power tools have ac/dc motors which means they are actually DC machines with the commutator brushes angled slightly off of optimum setting to reduce arcing when using them on AC power. They're not induction motors. They just lose power when loaded.

Marc

[John Kogel]

My Lectric leaf blower can fry a cord in two minutes! It takes about 2 minutes for heat to build up on the neutral blade of the power cord.

It's due to a bad connection creating resistance. That resistor gets hot!