Now THAT'S What I Call a Hot Tub

[Nick Ostrowski]

I pulled the access panel for the tub at yesterday's inspection and saw knob and tube wiring inside the wall cavity. As I went to put my voltage sniffer on the wires to see if they were hot, the sniffer lit up and I wasn't anywhere close to the wires yet. The entire backside of the tub and supply and drain lines was coming up as being hot or having some type of electrical current. And just before this, I had tested the tub and run water through it and put my hand in the water to check for cold on the left and hot on the right.

What could cause this condition but not be enough to shock/electrocute me? Did I get lucky?

[Rick Cantrell]

The tub drain and supply lines are not bonded to a ground.
They could have direct contact with a source of voltage but more likely what you are seeing is inductive voltage.

Voltage sniffers will detect induced voltage.
Induced voltage could be 90- 100 volts but more likely much less.
Even though there can be 90- 100 volts induced, most often there is almost no amperage.

[Benjamin Thompson]

Or you were just not well grounded.:)

[John Kogel]

The tub drain and supply lines are not bonded to a ground.
I think they are. All those pipes eventually go underground. Unless they're still using open sewage ditches in that part of Philly. :D

Nice catch, Nick. If the seller hasn't had a heart attack in the tub yet, he might have one when he sees your report. :D

[Rick Cantrell]

I think they are. All those pipes eventually go underground. Unless they're still using open sewage ditches in that part of Philly. :D

Or if the pipes have been changed to plastic. Like the white plastic drain line on the tub.
The House at one time had galv water lines, now it has soft copper.
There could be some part of the water line that is plastic also.

[Benjamin Thompson]

I have a friend that works for the power company. He stood on my asphalt shingle roof in his sneakers and changed out my splice blocks on the service conductors with no gloves or other protection. He retired healthy. Doesn't matter what the line voltage or amperage is if you are only dealing with one conductor and are not grounded.

[Garry Blankenship]

The tub drain and supply lines are not bonded to a ground.
They could have direct contact with a source of voltage but more likely what you are seeing is inductive voltage.

Voltage sniffers will detect induced voltage.
Induced voltage could be 90- 100 volts but more likely much less.
Even though there can be 90- 100 volts induced, most often there is almost no amperage.

Thanks for the sniffer / induced voltage info. Rick. Had no clue that was possible. Immediate shock hazzard or not, it, ( Nick ), did sniff out a problem.

[Rick Cantrell]

I'm not saying it IS induced voltage, only that it could be, and seams likely to be induced.
And, yes, it should be written up.

More on induced voltage
http://support.fluke.com/find-sales/Download/Asset/2514193_6001_ENG_B_W.PDF

Sniffers detect voltages at about 50 v AC, induced or not.
Sniffers detect an AC capacitance field near the wire or object.

Alarm panels do like like any AC voltages, so I test every wire for induced voltages. Cost me 2 alarm panels on 1 job to learn that.

[John Kogel]

I'm not saying it IS induced voltage, only that it could be, and seams likely to be induced.
And, yes, it should be written up.

More on induced voltage
http://support.fluke.com/find-sales/Download/Asset/2514193_6001_ENG_B_W.PDF

Sniffers detect voltages at about 50 v AC, induced or not.
Sniffers detect an AC capacitance field near the wire or object.

Alarm panels do like like any AC voltages, so I test every wire for induced voltages. Cost me 2 alarm panels on 1 job to learn that.What a minute. It was a home inspection, there was an electrical issue with alarm panels that could only be detected with a voltage sniffer, and you had to pay for replacements?

No, you were installing an alarm system and the panels picked up stray voltages and circuit chips were fried. Yes, that would be a crappy way to learn there was stray voltage on the wiring.

I was in a basement one time and there happened to be an electrician working on the panel. I showed him a funny phenomenon. There was abandoned K & T wiring on a joist with several new electrical cable circuits. You could see the end clipped off, dead wire. My cheapo sniffer detected stray voltage in the K & T wire. The higher end model did not, but picked up the juice in the new wiring if it was nearly in direct contact with the cable jacket or very close to it. The sparky tried his Fluke and same thing, no juice in the K& T. Technically, my cheap sniffer is maybe more sensitive, but more prone to false readings. So using that tester I could say, "Yes this circuit appears to be energized" when in fact it may not be. You need to use these tools a fair bit to get a feel for what they're telling you. I had one with adjustable sensitivity but it burned batteries and became untrustworthy. But as a rule, they are a great little tool.

[Rick Cantrell]

What a minute.
No, you were installing an alarm system and the panels picked up stray voltages and circuit chips were fried. Yes, that would be a crappy way to learn there was stray voltage on the wiring.

Yes, an alarm install
I agree
Lesson learned

[Lon Henderson]

Reminds me of when I lived in Central America many years ago. Winter time showers were chilly so I bought a shower head heater made in Brazil. It replaced the shower head and ran on 120v. It warmed the water pretty well, but the water flowed right through the live coils in the thing!

The installation directions were in Portuguese so I just followed the pictures and hoped it didn't electrocute me.........and it never did.

[Mike Borchardt]

Voltage sniffers are fine tools depending on the surroundings. Next time your near florescent lighting, haul out your sniffer and you will be surprised how far from the tube it will light up. The sniffer I have will pick up AC voltage down to the milliamp. Stray voltage, possiably from the knob and tube wiring being induced in to the tub may be giving a false indication. Assuming the copper plumbing is not grounded or has some resistants to ground, the sniffer will show voltage on the pipes. I Think if you want to verify voltage on the plumbing, go to another part of the building and sniff the plumbing with your tester. Like a bathroom or kitchen sink pipe, not in the basement as it may be to close to ground if its grounded. And thats assuming all the plumbing is copper. It looks like the drain switches over to PVC. Its to bad you don't have a ground source near the tub, then you could use a volt meter between the plumbing and ground. It looked to me this was a cast iron tub, great for picking up induced voltages. Just my two cents.

[Rich Goeken]

I'm not saying it IS induced voltage, only that it could be, and seams likely to be induced.
And, yes, it should be written up.

More on induced voltage
http://support.fluke.com/find-sales/Download/Asset/2514193_6001_ENG_B_W.PDF

Sniffers detect voltages at about 50 v AC, induced or not.
Sniffers detect an AC capacitance field near the wire or object.

Alarm panels do like like any AC voltages, so I test every wire for induced voltages. Cost me 2 alarm panels on 1 job to learn that.

I once was on a project where the electronic equipment we were installing was acting funny. Did some testing and discovered a sizable voltage on the cable sheath that didn't appear to be induced. Checked the pole line around the project and didn't see any trees down. Called power company. They found a faulty ground at the substation. From that day on I have a healthy respect for grounds and consider then live until fully tested.

[Garry Blankenship]

OK; time to expose the dinosaur in me. I do have some electrical background, but still do not trust electronic meters / gadgets. Trusting a digital number read-out on a screen has never digested well. When they fail there is no practical way to know other than to test them against other detectors. Give me an analog meter - - - a needle the moves - - - something mechanical that breaks or works. Outlet testers are famous for this. Looking at those color reads / patterns is like playing slots in a casino. When the fail they don't just die ~ they start random read-outs. I keep a little neon pig-tale tester and a cheap analog VOM meter for occasional confirmation.

[John Kogel]

OK; time to expose the dinosaur in me. I do have some electrical background, but still do not trust electronic meters / gadgets. Trusting a digital number read-out on a screen has never digested well. When they fail there is no practical way to know other than to test them against other detectors. Give me an analog meter - - - a needle the moves - - - something mechanical that breaks or works. Outlet testers are famous for this. Looking at those color reads / patterns is like playing slots in a casino. When the fail they don't just die ~ they start random read-outs. I keep a little neon pig-tale tester and a cheap analog VOM meter for occasional confirmation.It is certainly a good idea to have several testers and a meter or 2. I have a clamp meter for measuring amperage, but it isn't sensitive enough for stray voltages on plumbing under 0.01 amp, which is still enough to cause a human heart to fibrillate.

BTW, that induced voltage, if that is what it is in that iron tub, could still be deadly. Suppose the sink faucet is grounded, and the bather reaches over to shut a dripping tap.

In my workshop, I use a big old analog meter, in fact it's an Eico vacuum tube voltmeter. It has to be plugged in and warmed up for adjusting the alignment on old radios. The needle will jump when you pass the peak. A digital readout will miss the spot, because you just see a flicker of digits. Also, the old service manuals were written by technicians using these old meters, so the best way to match their voltages is to use the same tool. This old relic needs to be calibrated on a regular basis. It is fun, but not practical.
Digital meters are more reliable and more accurate in a general sense.

Also, cheap analog meters without their own power source have a low input impedance which means they add a load to the source you are testing, giving a false reading. The battery is usually only used for resistance measurements. Digital meters have their own power source to run their little circuit boards and a high input impedance and this makes them more accurate as well. FYI. :D

[Wayne Carlisle]

I had tested the tub and run water through it and put my hand in the water to check for cold on the left and hot on the right.

That was probably the problem right there!! You had reversed cold to hot! :)

[David Dolch]

Just to add more stories.

We use voltage probes in the phone company to test EVERYTHING when climbing. The pole, signs, the MGN, pole steps, terminals, strand, street lighting, etc.

Our probes are a bit more than a "normal" sniffer (high voltage flashover protection rings, a metal probe tip, etc) but are the same concept.

If we get a hit on an object, what you do is then put on your insulating gloves, run a ground bond from the lug on the probe to ground (again, this is how ours differ from the normal ones) and then test the object again. If it is an induced voltage, the ground will bleed it off, and it will test OK. If it is still hot, well then you have a problem.

-dave

[Robert Pike]

Off the subject, but Voltage sniffers work goodfor detecting broken lines in radiant heat ceilings.