Can a bad breaker affect voltage?

[ritelec]

On an forum. A gent is loading up a 120v-15 amp circuit to I'm thinking 14 or so amps.
He's having voltage drops down to 102v.
He seems to allude to a commercial install or other specifics. I'm thinking he has a voltage drop as when he mentions he turns more equipment on the voltage goes down and down (some type of metering on the equipment).


As a thought, if a non-continuous rated breaker had being running for a period of time, And maybe it started to fail internally,. Would it be possible for this breaker to add to any voltage drop?

Just thinking.....Just scratching my head a-little.

Thank you.

 

[kwired]

On an forum. A gent is loading up a 120v-15 amp circuit to I'm thinking 14 or so amps.
He's having voltage drops down to 102v.
He seems to allude to a commercial install or other specifics. I'm thinking he has a voltage drop as when he mentions he turns more equipment on the voltage goes down and down (some type of metering on the equipment).


As a thought, if a non-continuous rated breaker had being running for a period of time, And maybe it started to fail internally,. Would it be possible for this breaker to add to any voltage drop?

Just thinking.....Just scratching my head a-little.

Thank you.

There is a voltage drop across the breaker, if it is in good condition it should be negligible for most cases though. If the breaker is suspected to be making a significant contribution to voltage drop measure from bus to output terminal and see just how much drop there is.

 

[shamsdebout]

Has anyone ever measured the internal impedance of a circuit breaker and contrast the value with a new, older, or damged one?

To the original poster I can't say with certainty as I have never measured the internal impedance of a circuit breaker but I am of the understanding that the event old, or with loose connections the voltage drop would be relatively small.

 

[Smart $]

...
As a thought, if a non-continuous rated breaker had being running for a period of time, And maybe it started to fail internally,. Would it be possible for this breaker to add to any voltage drop?

...

Possible, of course. Measure as kwired suggests. However, that measurement would also include voltage drop caused by a bad breaker connection to the bus... which is a more common cause with stab-on breakers... not so much bolt-on type, but still possible .

 

[jim dungar]

As a thought, if a non-continuous rated breaker had being running for a period of time, And maybe it started to fail internally,. Would it be possible for this breaker to add to any voltage drop?

All breakers are continuous rated. Do you mean 100% rated? If so, there is little difference except for the ventilation of the enclosure housing the breaker.

What do you mean by "starting to fail internally"? Breakers are either on or off, do you mean bad contacts? You could conceivably have one with poor manufacturing tolerances or one that has seen too many short circuits. The NEMA test criteria for 15A (actually all <100A) molded case breakers is around 6,000 full load operations and 4,000 no-load operations but as little as 50 operations at 6X rating (150A minimum).

 

[Jraef]

On an forum. A gent is loading up a 120v-15 amp circuit to I'm thinking 14 or so amps.
He's having voltage drops down to 102v.
He seems to allude to a commercial install or other specifics. I'm thinking he has a voltage drop as when he mentions he turns more equipment on the voltage goes down and down (some type of metering on the equipment).


As a thought, if a non-continuous rated breaker had being running for a period of time, And maybe it started to fail internally,. Would it be possible for this breaker to add to any voltage drop?

Just thinking.....Just scratching my head a-little.

Thank you.

Before diving off the deep end on an unlikely cause such as a "bad breaker", what is the size of the conductor and how long is it? The 99% likely cause of VD on a conductor is too much length without thought of conductor size. Next in line would be a failing connection somewhere in the circuit. Is there more than one outlet connected to this? Every termination is a potential point of resistance / VD.

Always remember to elimiate all of the unusual things that cause problems before beginning to expect the unusual ones.

 

[ggunn]

All breakers are continuous rated. Do you mean 100% rated? If so, there is little difference except for the ventilation of the enclosure housing the breaker.

What's the difference between 100% rated and continuous rated? In error, perhaps, I have used the terms interchangeably.

 

[ritelec]

All breakers are continuous rated. Do you mean 100% rated? If so, there is little difference except for the ventilation of the enclosure housing the breaker.

What do you mean by "starting to fail internally"? Breakers are either on or off, do you mean bad contacts? You could conceivably have one with poor manufacturing tolerances or one that has seen too many short circuits. The NEMA test criteria for 15A (actually all <100A) molded case breakers is around 6,000 full load operations and 4,000 no-load operations but as little as 50 operations at 6X rating (150A minimum).

I mean continuous duty rated JIM. So that would be 100%. Not non continuous like they take coffee breaks and are rated 100% yet for 80%.

All breakers are continuous rated. Do you mean 100% rated? If so, there is little difference except for the ventilation of the enclosure housing the breaker.

What do you mean by "starting to fail internally"? Breakers are either on or off, do you mean bad contacts? You could conceivably have one with poor manufacturing tolerances or one that has seen too many short circuits. The NEMA test criteria for 15A (actually all <100A) molded case breakers is around 6,000 full load operations and 4,000 no-load operations but as little as 50 operations at 6X rating (150A minimum).

What do you mean by "starting to fail internally"? Breakers are either on or off,

If I meant on /off I would have said on/ off....I'm meant voltage drop not no voltage yes voltage.

Not busting horns jim..........Can a bad breaker show as a symptom in voltage drop?

Yes a continuously rated breaker.........not at 100%.

 

[ritelec]

What's the difference between 100% rated and continuous rated? In error, perhaps, I have used the terms interchangeably.

jim was stressing it was rated 100 % of it's 80% continuous duty rating.......and is rated for 100% of it's rating.

I think

 

[Besoeker]

There is a voltage drop across the breaker, if it is in good condition it should be negligible for most cases though. If the breaker is suspected to be making a significant contribution to voltage drop measure from bus to output terminal and see just how much drop there is.

I'm inclined to think that, if there is significant voltage drop across the closed contacts of a breaker, it won't survive long.

 

[ritelec]

Before diving off the deep end on an unlikely cause such as a "bad breaker", what is the size of the conductor and how long is it? The 99% likely cause of VD on a conductor is too much length without thought of conductor size. Next in line would be a failing connection somewhere in the circuit. Is there more than one outlet connected to this? Every termination is a potential point of resistance / VD.

Always remember to elimiate all of the unusual things that cause problems before beginning to expect the unusual ones.

Thank you...
Most agreed.

Not troubleshooting......just a thought if breakers fail (and not just on/ off jim) and if they could fail in a voltage aspect.

 

[templdl]

"Bad breaker" I would interprete as a breaker that has contacts that have degraded. The contacts can corode or become contaminated to a point where they don't make good contact anymore. When this happens they add resistance to the circuit, resistance=voltage drop=heating.
Generally speaking there are 2 things to look for. Touch the breaker and compare the warmth to others that have a similar load. If it feels warmer this may be an indicator that they contactors aren't making good contact. Also, simply measure the voltage across the line and load end of the breaker under load. If the contacts are good there should be no real noticeable voltage. I had a service call t an apartment complex where one unit had either a low voltage of lack of voltage on one line. I trace the problem back to the main breaker to that unit. Bu exercising the main breaker I did get power back but a quick check with my Fluke26 with my IR temperature probe showed a significant temperature difference between the two poles of the breaker which require that the breaker be replaced.
If replacing the breaker is something that is not practical at that time operating the breaker by opening and closing it a number of times may correct the issue. The moving breaker contact actually rubs against the stationary contact in the process of being closed. It is a good practice to exercise the breaker of a regular basis which promotes low contact resistance as well as assuring that the moving parts of the breaker remain lubricated.
I realize that taking the time to exercise breakers is not something that is normally done as it requires someone to do it an the ability to tolerate a momentary loss of power such as resetting devices as well as those troublesome blinking digital clocks.

 

[shamsdebout]

"Bad breaker" I would interprete as a breaker that has contacts that have degraded. The contacts can corode or become contaminated to a point where they don't make good contact anymore. When this happens they add resistance to the circuit, resistance=voltage drop=heating.
Generally speaking there are 2 things to look for. Touch the breaker and compare the warmth to others that have a similar load. If it feels warmer this may be an indicator that they contactors aren't making good contact. Also, simply measure the voltage across the line and load end of the breaker under load. If the contacts are good there should be no real noticeable voltage. I had a service call t an apartment complex where one unit had either a low voltage of lack of voltage on one line. I trace the problem back to the main breaker to that unit. Bu exercising the main breaker I did get power back but a quick check with my Fluke26 with my IR temperature probe showed a significant temperature difference between the two poles of the breaker which require that the breaker be replaced.
If replacing the breaker is something that is not practical at that time operating the breaker by opening and closing it a number of times may correct the issue. The moving breaker contact actually rubs against the stationary contact in the process of being closed. It is a good practice to exercise the breaker of a regular basis which promotes low contact resistance as well as assuring that the moving parts of the breaker remain lubricated.
I realize that taking the time to exercise breakers is not something that is normally done as it requires someone to do it an the ability to tolerate a momentary loss of power such as resetting devices as well as those troublesome blinking digital clocks.

Thanks for including prior experiences with this post.

 

[ritelec]

So correct me if I'm wrong please. But yes, there could be a VD accureing from a breaker also along with distance and conductor size.

 

[kwired]

I'm inclined to think that, if there is significant voltage drop across the closed contacts of a breaker, it won't survive long.

Correct, or a bad bus connection, conductor termination...

What's the difference between 100% rated and continuous rated? In error, perhaps, I have used the terms interchangeably.

100% rated means rated for continuous operation at 100% of rating. This is probably the more proper term to use, if that is what one is talking about.

Continuous rated? Not so clear. There can be a continuous load supplied, but without any further information doesn't necessarily mean at 100% of rating.

 

[templdl]

Correct, or a bad bus connection, conductor termination...

100% rated means rated for continuous operation at 100% of rating. This is probably the more proper term to use, if that is what one is talking about.

Continuous rated? Not so clear. There can be a continuous load supplied, but without any further information doesn't necessarily mean at 100% of rating.

Bringing up the subject of being 100% rated will only confuse this issue as it has nothing to do with it. Please understand that 100% rated breaker are no different than the standard breaker other than their UL listing and are allowed to be applied. The question of a 100% rated breaker should not even be a topic of discussion. It all has to go back to the application of 90degC rated wire and the latitude that you are allowed in selecting a wire size which is where the money saving is. It simply is not the breaker but how the breaker is tested with the rated wire!! The IS NO MAGIC with 100% rated breakers believe me. It is ther label. Also, you will not the 100% rated breakers have electronic trips. I could explain why but that's not important but I have yet to see a 100% rated breaker with a common thermal magnetic trip unit.

 

[jim dungar]

All circuit breakers and fuses are tested at 100% of their rating, continuously, when in open air.
All circuit breakers and fuses are rated to carry 80% of their rating, continuously, when they are installed in enclosures.
All 100% rated enclosed circuit breakers and fuses have additional ventilation and cabling requirements. '100% rated' equipment is rarely found below 400A frame size.

Breaker contacts can become 'bad' through repetitive short circuit interruptions and closing on inrush currents, they rarely become bad through simple on-off switching operations even at 100% rating. There is almost no way for them to become bad simply by having current flow through them regardless the amount.

Voltage drop across breaker contacts does exist, although it is usually miniscule compared to that of conductors and connections. Contact resistance testing should be routine for large breakers (>200A).

Along the lines of what Templdl said: when you hear hoof beats think of horses, not zebras.

 

[ggunn]

jim was stressing it was rated 100 % of it's 80% continuous duty rating.......and is rated for 100% of it's rating.

I think

Now I'm even more confused.

 

[zog]

when you hear hoof beats think of horses, not zebras.

Stealing that one

 

[templdl]

All 100% rated enclosed circuit breakers and fuses have additional ventilation and cabling requirements. '100% rated' equipment is rarely found below 400A frame size.
(>200A).

It relates to what money can be saved by being able to apply a smaller wire sizes and the opportuninty to jump down a frame size with the breaker. If you can get this to work then there would be a cost savings. One must also consider the additional cost of the 100% rated breaker. It is very rare that there would be a cost savings with breaker smaller than the 400A frame as you stated.

It's a matter of cost engineering the job as one may also do when considering series rated breakers.