Testing circuit breakers with a welder...

B

bob prohaska

Guest
I\'ve been given a collection of residential service panel breakers
and would like to check them to see if they trip correctly. They
were in use before I got them, so they certainly close correctly,
but it\'s unknown if they trip correctly.

As it happens, I have an AC arc welder which can be set between
about 20 and 200 amps, with an open circuit voltage of about 80 V.

Anybody ever tried this? Does it seem an unrealistically harsh
test?

Thanks for reading,

bob prohaska
 
bob prohaska wrote:
--------------------------------
I\'ve been given a collection of residential service panel breakers
and would like to check them to see if they trip correctly. They
were in use before I got them, so they certainly close correctly,
but it\'s unknown if they trip correctly.

As it happens, I have an AC arc welder which can be set between
about 20 and 200 amps, with an open circuit voltage of about 80 V.

Anybody ever tried this? Does it seem an unrealistically harsh
test?
Click to expand...

** Nope - such breakers are rated to open instantly with fault currents in the thousands of amps.
At rated current they will take a while, maybe 20 minutes, since the trip mechanism is thermal rather than magnetic.
FYI:
A neat, low cost test is to connect an electro cap of about 100uF / 400V with a 6 amp series diode across the output.
The peak surge should trip the breaker pronto.


....... Phil
 
On 5/06/2023 11:50 am, bob prohaska wrote:
I\'ve been given a collection of residential service panel breakers
and would like to check them to see if they trip correctly. They
were in use before I got them, so they certainly close correctly,
but it\'s unknown if they trip correctly.

As it happens, I have an AC arc welder which can be set between
about 20 and 200 amps, with an open circuit voltage of about 80 V.

Anybody ever tried this? Does it seem an unrealistically harsh
test?

Thanks for reading,

bob prohaska
Click to expand...


At least traditional welders (line frequency not switched mode) look
very inductive, and are designed to sustain an arc. Whilst I would hope
that the circuit breakers are able to break the arc, it is a much
harsher test than with a resistive load. If the welder is able to
sustain an arc after the circuit breaker opens, then this will destroy
the breaker.
 
Chris Jones <lugnut808@spam.yahoo.com> wrote:
At least traditional welders (line frequency not switched mode) look
very inductive, and are designed to sustain an arc. Whilst I would hope
that the circuit breakers are able to break the arc, it is a much
harsher test than with a resistive load. If the welder is able to
sustain an arc after the circuit breaker opens, then this will destroy
the breaker.
Click to expand...

I agree it\'s a harsh test, but the breakers were free. I\'d rather not
use them without some evidence they work.

After posting my question I again searched the web and found one set
of YouTube videos demonstrating overcurrent testing of breakers and
connectors. One suggests that at least some circuit breakers can stop
an arc welder without self-destruction. It\'s at
https://www.youtube.com/watch?v=fhXtXVBvSfg

Thanks for writing!

bob prohaska
 
On Mon, 5 Jun 2023 21:31:38 -0000 (UTC), bob prohaska
<bp@www.zefox.net> wrote:

Chris Jones <lugnut808@spam.yahoo.com> wrote:

At least traditional welders (line frequency not switched mode) look
very inductive, and are designed to sustain an arc. Whilst I would hope
that the circuit breakers are able to break the arc, it is a much
harsher test than with a resistive load. If the welder is able to
sustain an arc after the circuit breaker opens, then this will destroy
the breaker.


I agree it\'s a harsh test, but the breakers were free. I\'d rather not
use them without some evidence they work.

After posting my question I again searched the web and found one set
of YouTube videos demonstrating overcurrent testing of breakers and
connectors. One suggests that at least some circuit breakers can stop
an arc welder without self-destruction. It\'s at
https://www.youtube.com/watch?v=fhXtXVBvSfg

Thanks for writing!

bob prohaska
Click to expand...

DC ratings of standard breakers seldom exceed 40V, due to arcing.
AC arcs are interrupted by line voltage reversal, preventing
damage. But even these have a limited guaranteed operation count.

RL
 
legg wrote:
-----------------
DC ratings of standard breakers seldom exceed 40V, due to arcing.
Click to expand...

** However most *mains rated* breakers employ magnetic or physical barrier arc quenching whenever contacts open.

> AC arcs are interrupted by line voltage reversal,

** Strange how AC arc welders work so well then.

FYI:

Relays and most switches suffer from limited DC switching capacity, usually limited to 24 or 30 volts at rated currents.
Any more results in a permanent arc bridging the contacts, followed by complete self destruction.
Relays used as \"speaker protection\" generally do not.


....... Phil
 
On Tue, 6 Jun 2023 20:12:24 -0700 (PDT), Phil Allison
<pallison49@gmail.com> wrote:

legg wrote:
-----------------

DC ratings of standard breakers seldom exceed 40V, due to arcing.


** However most *mains rated* breakers employ magnetic or physical barrier arc quenching whenever contacts open.
Click to expand...

Not so much quenching, as sacrificial absorption, in locations that
are not relied on for physical working contact area. Life-limited,
bulky and $$$.

AC arcs are interrupted by line voltage reversal,

** Strange how AC arc welders work so well then.
Click to expand...

Wadabaudit? Nobody\'s saying that AC won\'t arc.

They don\'t work so well, because an arc has to be re-established
on every cyclic reversal. Breaking the AC arc is \'easy\'. Maintaining
one is hard. AC arc welding produces spatter. Industry preference
is for smooth.

What AC welding is, is cheap.

Sometimes, for some types of metal, or for delicate work, having
an easily broken arc, or repeatedly forcing a restart has an
advantage. For highly magnetic material, it avoids \'wandering\'.

FYI:

Relays and most switches suffer from limited DC switching capacity, usually limited to 24 or 30 volts at rated currents.
Any more results in a permanent arc bridging the contacts, followed by complete self destruction.
Relays used as \"speaker protection\" generally do not.


...... Phil
Click to expand...
 
legg wrote:

------------------
legg wrote:
-----------------

DC ratings of standard breakers seldom exceed 40V, due to arcing.


** However most *mains rated* breakers employ magnetic or physical barrier arc quenching whenever contacts open.

Not so much quenching, as sacrificial absorption....
Click to expand...

** Hello to the smug troll calling itself \" legg\" .

The term \"quenching\" here clearly refers to physically breaking an arc by extending it.
Rest of your pedantic, tedious, self aggrandizing, spew inducing BULLSHIT snipped.
Have a really rotten day.

..... Phil
 
On Wed, 7 Jun 2023 06:07:59 -0700 (PDT), Phil Allison
<pallison49@gmail.com> wrote:

legg wrote:

------------------

legg wrote:
-----------------

DC ratings of standard breakers seldom exceed 40V, due to arcing.


** However most *mains rated* breakers employ magnetic or physical barrier arc quenching whenever contacts open.

Not so much quenching, as sacrificial absorption....


** Hello to the smug troll calling itself \" legg\" .

The term \"quenching\" here clearly refers to physically breaking an arc by extending it.
Rest of your pedantic, tedious, self aggrandizing, spew inducing BULLSHIT snipped.
Have a really rotten day.

.... Phil
Click to expand...

G\'daye.

RL
 
On Sunday, June 4, 2023 at 9:50:55 PM UTC-4, bob prohaska wrote:
I\'ve been given a collection of residential service panel breakers
and would like to check them to see if they trip correctly. They
were in use before I got them, so they certainly close correctly,
but it\'s unknown if they trip correctly.
Click to expand...

If they\'re thermal breakers, the only part that can fail while retaining
the on/off function is a heater. A welder intended to melt metal
applied to a heater is... maybe not a test that should be applied.

The heater, if it fails open, won\'t let the breaker pass current.
If it fails closed circuit... there\'s extra metal inside the breaker?

Circuit breakers should, and generally do, fail in safe ways.
Go ahead and use them without applying a stress test beyond normal
currents and voltages.
 
On 6/10/2023 5:52 AM, whit3rd wrote:
On Sunday, June 4, 2023 at 9:50:55 PM UTC-4, bob prohaska wrote:
I\'ve been given a collection of residential service panel breakers
and would like to check them to see if they trip correctly. They
were in use before I got them, so they certainly close correctly,
but it\'s unknown if they trip correctly.


If they\'re thermal breakers, the only part that can fail while retaining
the on/off function is a heater. A welder intended to melt metal
applied to a heater is... maybe not a test that should be applied.

The heater, if it fails open, won\'t let the breaker pass current.
If it fails closed circuit... there\'s extra metal inside the breaker?

Circuit breakers should, and generally do, fail in safe ways.
Go ahead and use them without applying a stress test beyond normal
currents and voltages.
Click to expand...

If the breakers trip using a heater, then the setting of the welder (AC)
output current will not represent the current that the breaker actually
would trip at on line voltage, because the welder voltage likely will be
lower
 
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