Is my shop going to burn down?

[KDT]

I know there are number of very skilled guys on this forum and I'm hoping I could get a little advise.

The high limit switch (red button) popped on my electric water heater in my shop a couple of days ago. I reset the button and the water heater seems to be working fine. This morning I turned off the 30 amp 2-pole breaker and put a volt meter to the water heater to see what might be going on.

With the breaker open in the panel and when I test from each hot wire to the ground at the water heater I still read about 1.25 volts on one of the hot wires and about .25 volts on the other. I get the same results when I perform the same test at the feed panel.

So I performed the same test on other breakers in the panel, I shut the breaker off, tested each hot wire to ground the same way with the volt meter and I get the same results on all breakers.

This isn't right, right? I'd assume if all was well I'd read zero volts when a breaker is turned off. I'm a little concerned about this. Should I be?

Thanks in advance for any advise I can get.

Ken

 

[walrus]

I know there are number of very skilled guys on this forum and I'm hoping I could get a little advise.

The high limit switch (red button) popped on my electric water heater in my shop a couple of days ago. I reset the button and the water heater seems to be working fine. This morning I turned off the 30 amp 2-pole breaker and put a volt meter to the water heater to see what might be going on.

With the breaker open in the panel and when I test from each hot wire to the ground at the water heater I still read about 1.25 volts on one of the hot wires and about .25 volts on the other. I get the same results when I perform the same test at the feed panel.

So I performed the same test on other breakers in the panel, I shut the breaker off, tested each hot wire to ground the same way with the volt meter and I get the same results on all breakers.

This isn't right, right? I'd assume if all was well I'd read zero volts when a breaker is turned off. I'm a little concerned about this. Should I be?

Thanks in advance for any advise I can get.

Ken

Using a digital meter? If so I'm surprised you only got 1. something volts. Don't worry about it. If you used an analog meter you'd see 0 volts. Digital meters don't load the circuit at all so you'll get ghost voltages or maybe they're induced voltages?

 

[jhelrey]

There can be many things causing voltage to remain.... It happens in computers, etc.

 

[toolchaser]

If your high limit sw. continues to trip, it's probably the thermostats, easy fix, no H2O to drain, most models available at the big box home centers. A spike took mine out last year

 

[KDT]

This is great news guys. I can breath a little easier now.

If I've learned anything over the years, it's that you can never be too careful (paranoid) when it comes to electrical.

I appreciate your expertise and thanks for taking the time to respond.

Ken

 

[Charles (in GA)]

As noted, digital meters will show all kinds of strange/stray voltages on a supposedly dead circuit. Its nothing to get concerned about. Try an analog meter on it, then if you show voltage, you need to look for problems.

Charles

 

[Norcal]

Are you using a digital voltmeter? If so your seeing ghost voltages.....

 

[rockchucker]

If you are worried about it then flip the Breaker off and unhook the wires to the H2o Heater until you replace/fix it.

 

[ddawg16]

BTW....that AC voltage you are measuring is called stray induced voltage....it's the result of the wires being close to other live wires....

It's not unusual to have up to 60Vac or more on a couple of wires that are turned off. I see it all the time.

In extreem cases where the wires feed a low amp load (indicator light), you have to install a relay so as to put enough load on the wires when not activated so that the light does not appear to be on all the time.

 

[hillbilly1]

Usually when the red button "pops" it's due to the water heater getting too hot. This is usually caused by a defective heating element or a defective thermostat. Depending on the size of your water heater, you may have two thermostats, an upper and a lower. The upper is the primary, when it is satisfied, it throws power to the bottom thermostat. Each thermostat drives a heating element. Both elements are interlocked to prevent them from coming on at the same time. Sometimes one of the elements short to ground, but not with low enough resistance to trip the breaker. Since the thermostats break only one power leg, if that leg goes to ground, it will continue to heat until the the high limit (the red button) trips disconnecting all power. An ammeter can be used to verify if an element is shorting out or has gone bad.

 

[Torque1st]

hillbilly1 has a good test.

ddawg has a good explanation. To measure voltage use a CHEAP analog meter, -one with low impedance, not a good high impedance analog meter. One can also load the circuit with a clip on load, such as a light bulb, to remove the induced voltage.

 

[comedyman809]

my fluke always read OL on a dead circuit.

 

[hillbilly1]

my fluke always read OL on a dead circuit.

With a name like comedyman, I'm assuming your not serious! If you are, you have it set on resistance, not voltage. Flukes do not like voltage when set to ohms!

 

[comedyman809]

forgot we were talking about voltage!!!! woopsie!!!!

 

[ForceFed70]

Like mentioned, this sounds like induced voltage.

My brother is an electrician and has a great story about induced voltage. It goes something like this:
He was working at a comercial site on a scissor lift when he got a nasty shock from one of the large 300+Volt lines they were working on. Apparently this voltage kills more electricians than any other. Something about not blowing you back but enough to do serious damage, or something like that. Being that it's this dangerous voltage, he says "This line is F'in hot, I'm not touching it". At the time he was just an apprentice and was working with some cranky journeyman. They got into an arguement about it, the Journeyman swore up and down that it was disconnected. My bro stuck to his guns and wouldn't touch it. The Journeyman got all pissed off and was telling my bro that it was just induced voltage and he should "bleed it off" by touching it against a nearby metal water line. My bro refused. Eventually, the journeyman told my bro to get off the lift and "I will f'in do it you stupid apprentice". Cursing at my bro the whole time, he get's up on the lift and puts the wire to the water pipe. You guessed it, the line was live after all (400amp feed at that) and when the Journeyman touched the line to the water pipe it resulted in a huge explosion. The Journeyman ended up in the hospital, but survived mostly unscathed. He had some fairly minor burns and temporary hearing loss. I was really proud of my brother for not caving in to that ***. It's not easy to tell your boss (that's basically what he was) "no" like that.

 

[hillbilly1]

Induced voltage on a normal < 600 volt electrical system is very rarely high enough to cause a shock, The previous post was obviously not induced voltage, but the circuit was still on. Multiple wires bundeled together usually causes this, more common in commercial and industrial settings than residential.