# Can a non-energized electrical component deliver a shock?

timmeister37
TL;DR Summary
If an electrical part has no voltage, can the electrical part shock you while the electrical part has no voltage on it?
I'm not an electrical engineer.

I'm a truck driver. So please don't expect me to know much about electricity. This is a serious question.

If an electrical part (such as the contacts of a contactor) has no voltage, can the electrical part shock a person while the electrical part has no voltage?

Mentor
Voltage with respect to what? If you are charged up with static electricity and you touch an electrical part that is not turned on, you may feel a shock if that part has a return path to ground or is connected to something that is large enough that it has parasitic capacitance to ground.

davenn
The only stupid question is the one not asked.
“The only interesting answers are those which destroy the questions.” ― Susan Sontag.

Averagesupernova
timmeister37
Someone edited my thread to call it a stupid question, and the person edited my thread to ask if a non-energized component can cause an electric shock to a person.

I don't even know precisely what non-energized electrical component even means.

MY question is if an electrical component with no VOLTAGE can shock a person.

Baluncore
Mentor
Someone edited my thread to call it a stupid question, and the person edited my thread to ask if a non-energized component can cause an electric shock to a person.

I don't even know precisely what non-energized electrical component even means.

MY question is if an electrical component with no VOLTAGE can shock a person.

And "non-energized" and "no voltage are synonymous, BTW.

timmeister37
timmeister37
Voltage with respect to what? If you are charged up with static electricity and you touch an electrical part that is not turned on, you may feel a shock if that part has a return path to ground or is connected to something that is large enough that it has parasitic capacitance to ground.

Voltage with respect to LINE VOLTAGE.

timmeister37
By the way, nobody yet has entirely answered the question of the OP, in my opinion.

Homework Helper
2022 Award
If you are at an electrical potential ("voltage")significantly different from the object in question (at "no voltage") you will receive a shock. The magnitude of the shock will depend upon circumstances: mostly the resistances and capacitances involved. These are not specified in the OP

'

berkeman
Mentor
Voltage with respect to LINE VOLTAGE.
Okay, that helps. Per most NEC code regulations in the US, AC Mains Neutral is grounded at the breaker/distribution panel. That means that Neutral is usually within a few Vrms of Earth ground and should not give you a shock. Obviously any Line voltages will deliver a (potentially lethal) shock with respect to Earth ground.

Can you say more about the shock you felt, and what situation you were in? I've been surprised with 60Hz shocks from cable TV feeds in the past, so there are situations that can lead to unexpected (but usually non-lethal below-SELV) shocks.

timmeister37
timmeister37
If you are at an electrical potential ("voltage")significantly different from the object in question (at "no voltage") you will receive a shock. The magnitude of the shock will depend upon circumstances: mostly the resistances and capacitances involved. These are not specified in the OP

'
That does not really answer the question, IMO
Okay, that helps. Per most NEC code regulations in the US, AC Mains Neutral is grounded at the breaker/distribution panel. That means that Neutral is usually within a few Vrms of Earth ground and should not give you a shock. Obviously any Line voltages will deliver a (potentially lethal) shock with respect to Earth ground.

If the two main electrical lines in a heat pump have no voltage with respect to each other, can the two main electrical lines shock you if you touch them with your bare fingers?

Can you say more about the shock you felt, and what situation you were in? I've been surprised with 60Hz shocks from cable TV feeds in the past, so there are situations that can lead to unexpected (but usually non-lethal below-SELV) shocks.

I did not get shocked.

Homework Helper
2022 Award
There is a reason Electricians are trained for years and are required to be licensed. You cannot learn what you need to know in a tweet.

Wrichik Basu and berkeman
Mentor
If the two main electrical lines in a heat pump have no voltage with respect to each other, can the two main electrical lines shock you if you touch them with your bare fingers?
Yes, if there is an electrical fault.

There are two main kinds of voltages that you run into in circuits -- differential mode and common mode.

That means that two wires can have a voltage between them (like wires off of a battery), or a common voltage for both of them with respect to something else (like an Earth ground reference).

Both situations can cause shocks that you can feel.

timmeister37
Yes, if there is an electrical fault.

There are two main kinds of voltages that you run into in circuits -- differential mode and common mode.

That means that two wires can have a voltage between them (like wires off of a battery), or a common voltage for both of them with respect to something else (like an Earth ground reference).

Both situations can cause shocks that you can feel.
Then how can an electrician ever know when it is safe to touch the electrical contacts in a circuit?

Mentor
Then how can an electrician ever know when it is safe to touch the electrical contacts in a circuit?
That's a good question. There are two main ways that we do it (I'm not a certified electrician, but I've done lots of that type of work for my homes to code with an EE's eye to safety)...

-1- Disconnect the circuit at the breaker box, and lock it out (with a visual indicator and/or physical lockout)

-2- Use a DVM or non-contact voltage detector to tell if the circuit you are about to work on is energized.

Quiz Question -- How does the small hand-held detector in #2 work?

https://www.amazon.com/dp/B001UAHZAM/?tag=pfamazon01-20

davenn
Mentor
Then how can an electrician ever know when it is safe to touch the electrical contacts in a circuit?
For each exposed conductor, check voltage between it and ground and also between it and every other conductor.

timmeister37
timmeister37
That's a good question. There are two main ways that we do it (I'm not a certified electrician, but I've done lots of that type of work for my homes to code with an EE's eye to safety)...

-2- Use a DVM or non-contact voltage detector to tell if the circuit you are about to work on is energized.

To me, it seems like you have contradicted yourself.
In post #12, you said that if there is no voltage between the two main electrical lines in a heat pump, the electrical lines can still shock you if there is a fault. Therefore, just ensuring that there is no voltage alone will no guarantee that you won't get shocked.

Quiz Question -- How does the small hand-held detector in #2 work?

https://www.amazon.com/dp/B001UAHZAM/?tag=pfamazon01-20

View attachment 270591
I don't know.

Gold Member
In post #12, you said that if there is no voltage between the two main electrical lines in a heat pump, the electrical lines can still shock you if there is a fault. Therefore, just ensuring that there is no voltage alone will no guarantee that you won't get shocked.
Wrong. Suppose you have lost one side. An open circuit in the meter, this type of failure. Any 240 volt load will put voltage on the otherwise dead side. No voltage will necessarily show up there line to line. Yet there could be a full 120 volts from each line to ground.

Last edited:
timmeister37
timmeister37
Wrong. Suppose you have lost one side. An open circuit in the meter, this type of failure. Any 240 volt load will put voltage on the otherwise dead side. No voltage will necessarily show up there line to line. Yet there could be a full 120 volts from each lol be to ground.

In your last sentence, what does lol stand for? I doubt it stands for laughing out loud.

sophiecentaur
If an electrical part (such as the contacts of a contactor) has no voltage, can the electrical part shock a person while the electrical part has no voltage?
The simple answer is; “No it cannot”.
But don't try it because it might be live when you think it is safe.

Voltage is always measured as a potential difference. For current to flow, there needs to be a voltage and a circuit. If you touch two points that are at different voltages, current will flow through you.

timmeister37
Gold Member
In your last sentence, what does lol stand for? I doubt it stands for laughing out loud.
Ugh! My smart phone likes to change things. I corrected my post. Hope it makes some sense now.

Gold Member
Ugh! My smart phone likes to change things. I corrected my post. Hope it makes some sense now.
The ultimate misnomer!

Mentor
Quiz Question -- How does the small hand-held detector in #2 work?
I don't know.
It uses parasitic capacitance from the user's hand and body to Earth ground. It uses a high input impedance voltage detector to capacitively sense 50/60Hz AC voltage. It cannot detect DC voltages, since it is relying on capacitance to "complete" the circuit. It's a very handy tool.

Mentor
I recommend that you get a basic book on electrical wiring and read the entire book. An Amazon search for complete guide home wiring came up with the following: https://www.amazon.com/s?k=complete+guide+home+wiring&i=stripbooks&ref=nb_sb_noss. The Black & Decker book on the list is in the 7th edition, which is a good sign. And the price is dirt cheap at \$15.00. Then come back here if you still have questions.

Tom.G
If an electrical part (such as the contacts of a contactor) has no voltage, can the electrical part shock a person while the electrical part has no voltage?
The regular cases are pretty much covered already, but there is one more 'yes' around: when it is you who has voltage. Either some static voltage or something else by some unusual circumstance.

So the only 'no' is, when you and the contacts are on the very same voltage.

timmeister37
The simple answer is; “No it cannot”.
But don't try it because it might be live when you think it is safe.

Does the following sentence have the exact same meaning as your second sentence in the above quote: "But don't try it because it might have voltage when you think it is safe." ?

Voltage is always measured as a potential difference. For current to flow, there needs to be a voltage and a circuit. If you touch two points that are at different voltages, current will flow through you.

Two points? What about if you just touch one point on a live contactor on a heat pump? Wouldn't just touching the contactor at one point with a finger cause current to flow through one's body?

timmeister37
I'm very confused by your post.

Wrong. Suppose you have lost one side. An open circuit in the meter, this type of failure.

I don't know for sure what you mean by "Suppose you have lost one side." Do you mean "Suppose that one of the two wires carrying electricity into the heat pump" no longer carries electricity from the electric power plant?"
"An open circuit in the meter"----an open circuit in what meter, my multimeter or the electric meter for the house?

Any 240 volt load will put voltage on the otherwise dead side. No voltage will necessarily show up there line to line. Yet there could be a full 120 volts from each line to ground.

What you wrote here makes me think "an open circuit in the meter" does not refer to the multimeter.

By the way, you said that what I wrote in post #16 is wrong. I think I know why you think my post #16 is wrong, but I'm not 100% sure.

I will color what I wrote in post #16 in bold-faced orange font to make it easy to distinguish from everything else. In post #16, i wrote the following: "In post #12, you said that if there is no voltage between the two main electrical lines in a heat pump, the electrical lines can still shock you if there is a fault. Therefore, just ensuring that there is no voltage alone will not guarantee that you won't get shocked. "

If you say that my post #16 is wrong, then you are saying that just ensuring that there is no voltage alone will guarantee that you won't get shocked.

Did you say my post #16 is wrong because if you check and there is no voltage from both line 1 to line 2 AND there is no voltage from line 1 to ground and there is no voltage from line 2 to ground, then that would guarantee that you won't get shocked if you touch an electrical part such as a contactor?

Mentor