Okay, it would have been obvious to most of you but it just didn't occur to me before.

I'm near finishing my shed repairs. I have about 3 feet to go on sill plate, but needed to take electrical outlet boxes off studs, and I cut the power just to be extra safe. I'm glad they used sturdy steel boxes, I'll be able to reuse.

The only way to cut power here is to pull the main fuse block. When I put it back in, I got a good jolt. Not just a tingle. WTF? It's plastic, or bakelite or whatever you call it. Yeah the handle is steel, that little wire bail thing, but it didn't hurt when I pulled it out.

So when I had a moment I went back with better light and a meter. Oh hey, there are large brass screws on the front of the fuse block, just below the level of the plastic, and the holes are big enough to have your finger slip in there when you push the block in firmly. Nothing else was hot. So obviously I slipped a finger or thumb or even both onto a screw and got shocked. Damp day, concrete floor, sneakers but they're on the damp side, so I was probably at ground, or maybe even hit both screws and got 220.

It still might be a good idea to ask the service people to come out and look the interface over. And be sure to ask if their fuses are late-model current limiting fuses or not.

On 8/15/2020 9:14 AM, TimR wrote:
Okay, it would have been obvious to most of you but it just didn't occur to me before.

I'm near finishing my shed repairs. I have about 3 feet to go on sill plate, but needed to take electrical outlet boxes off studs, and I cut the power just to be extra safe. I'm glad they used sturdy steel boxes, I'll be able to reuse.

The only way to cut power here is to pull the main fuse block. When
I put it back in, I got a good jolt. Not just a tingle. WTF? It's
plastic, or bakelite or whatever you call it. Yeah the handle is
steel, that little wire bail thing, but it didn't hurt when I pulled
it out.
So when I had a moment I went back with better light and a meter. Oh
hey, there are large brass screws on the front of the fuse block,
just below the level of the plastic, and the holes are big enough to
have your finger slip in there when you push the block in firmly.
Nothing else was hot. So obviously I slipped a finger or thumb or
even both onto a screw and got shocked. Damp day, concrete floor,
sneakers but they're on the damp side, so I was probably at ground,
or maybe even hit both screws and got 220.

So, now you know better for next time!

If you wanted, stick a rubber plug in the holes or just tape over them,
but now you know they're there, you'll remember to keep hands on the
nonconductive parts, so I'd not worry about it.

--

On 08/15/2020 08:53 AM, wrote:
It still might be a good idea to ask the service people to come out and look the interface over. And be sure to ask if their fuses are late-model current limiting fuses or not.


In my experience that can lead to an expensive retrofit.

On Sat, 15 Aug 2020 12:44:21 -0600, lowbrowwoman, the endlessly driveling,
troll-feeding, senile idiot, blabbered again:


In my experience that can lead to an expensive retrofit.

Your entire existence needs retrofitting, you useless senile blabbermouth!

In alt.home.repair, on Sat, 15 Aug 2020 07:14:18 -0700 (PDT), TimR
wrote:

Okay, it would have been obvious to most of you but it just didn't occur to me before.

I'm near finishing my shed repairs. I have about 3 feet to go on sill plate, but needed to take electrical outlet boxes off studs, and I cut the power just to be extra safe. I'm glad they used sturdy steel boxes, I'll be able to reuse.

The only way to cut power here is to pull the main fuse block. When I put it back in, I got a good jolt. Not just a tingle. WTF? It's plastic, or bakelite or whatever you call it. Yeah the handle is steel, that little wire bail thing, but it didn't hurt when I pulled it out.

So when I had a moment I went back with better light and a meter. Oh hey, there are large brass screws on the front of the fuse block, just below the level of the plastic, and the holes are big enough to have your finger slip in there when you push the block in firmly. Nothing else was hot. So obviously I slipped a finger or thumb or even both onto a screw and got shocked. Damp day, concrete floor, sneakers but they're on the damp side, so I was probably at ground, or maybe even hit both screws and got 220.

Welcome back to the living.

And I'm warned.

In alt.home.repair, on Sat, 15 Aug 2020 11:15:18 -0500, dpb
wrote:

On 8/15/2020 9:14 AM, TimR wrote:
Okay, it would have been obvious to most of you but it just didn't occur to me before.

I'm near finishing my shed repairs. I have about 3 feet to go on sill plate, but needed to take electrical outlet boxes off studs, and I cut the power just to be extra safe. I'm glad they used sturdy steel boxes, I'll be able to reuse.

The only way to cut power here is to pull the main fuse block. When
I put it back in, I got a good jolt. Not just a tingle. WTF? It's
plastic, or bakelite or whatever you call it. Yeah the handle is
steel, that little wire bail thing, but it didn't hurt when I pulled
it out.
So when I had a moment I went back with better light and a meter. Oh
hey, there are large brass screws on the front of the fuse block,
just below the level of the plastic, and the holes are big enough to
have your finger slip in there when you push the block in firmly.
Nothing else was hot. So obviously I slipped a finger or thumb or
even both onto a screw and got shocked. Damp day, concrete floor,
sneakers but they're on the damp side, so I was probably at ground,
or maybe even hit both screws and got 220.

So, now you know better for next time!

If you wanted, stick a rubber plug in the holes or just tape over them,
but now you know they're there, you'll remember to keep hands on the
nonconductive parts, so I'd not worry about it.

You were right the first time. He should plug or cover the holes.
He's not the only one who will use the box, now or the next owner's
family.

In alt.home.repair, on Sat, 15 Aug 2020 07:53:01 -0700 (PDT),
wrote:

It still might be a good idea to ask the service people to come out and look the interface over. And be sure to ask if their fuses are late-model current limiting fuses or not.

What are current limiting fuses. I looked at a couple webpages and it
didn't say. I thought all fuses were current limiting.

On 8/15/2020 4:12 PM, micky wrote:
In alt.home.repair, on Sat, 15 Aug 2020 07:53:01 -0700 (PDT),
wrote:

It still might be a good idea to ask the service people to come out and look the interface over. And be sure to ask if their fuses are late-model current limiting fuses or not.

What are current limiting fuses. I looked at a couple webpages and it
didn't say. I thought all fuses were current limiting.

https://www.eaton.com/Eaton/ProductsServices/Electrical/ProductsandServices/Bussmann/MediumVoltageFuses/CurrentLimiting/index.htm

"A current limiting fuse is a fuse that, when its current responsive
element is melted by a current within the fuses specified current
limiting range, abruptly introduces a high resistance to reduce current
magnitude and duration, resulting in subsequent current interruption."

For ordinary distribution panel there's no point. The fuse will open
and protect what it's there to protect.

They're useful for motor starters, etc., ...

--

In alt.home.repair, on Sat, 15 Aug 2020 17:07:08 -0500, dpb
wrote:

On 8/15/2020 4:12 PM, micky wrote:
In alt.home.repair, on Sat, 15 Aug 2020 07:53:01 -0700 (PDT),
wrote:

It still might be a good idea to ask the service people to come out and look the interface over. And be sure to ask if their fuses are late-model current limiting fuses or not.

What are current limiting fuses. I looked at a couple webpages and it
didn't say. I thought all fuses were current limiting.

https://www.eaton.com/Eaton/ProductsServices/Electrical/ProductsandServices/Bussmann/MediumVoltageFuses/CurrentLimiting/index.htm

"A current limiting fuse is a fuse that, when its current responsive
element is melted by a current within the fuse’s specified current
limiting range, abruptly introduces a high resistance to reduce current
magnitude and duration, resulting in subsequent current interruption."

I had read that and didn't understand it.

For ordinary distribution panel there's no point. The fuse will open
and protect what it's there to protect.

They're useful for motor starters, etc., ...

So there will still be some current to the motor starter. What's a
motor starter? ;-)

On Saturday, August 15, 2020 at 2:44:24 PM UTC-4, rbowman wrote:
On 08/15/2020 08:53 AM, wrote:
It still might be a good idea to ask the service people to come out and look the interface over. And be sure to ask if their fuses are late-model current limiting fuses or not.


In my experience that can lead to an expensive retrofit.

IDK what service people those would be, since what he's dealing with appears
to be customer eqpt, not the utility's side.

On Sat, 15 Aug 2020 19:47:38 -0400, micky
wrote:

In alt.home.repair, on Sat, 15 Aug 2020 17:07:08 -0500, dpb
wrote:

On 8/15/2020 4:12 PM, micky wrote:
In alt.home.repair, on Sat, 15 Aug 2020 07:53:01 -0700 (PDT),
wrote:

It still might be a good idea to ask the service people to come out and look the interface over. And be sure to ask if their fuses are late-model current limiting fuses or not.

What are current limiting fuses. I looked at a couple webpages and it
didn't say. I thought all fuses were current limiting.

https://www.eaton.com/Eaton/ProductsServices/Electrical/ProductsandServices/Bussmann/MediumVoltageFuses/CurrentLimiting/index.htm

"A current limiting fuse is a fuse that, when its current responsive
element is melted by a current within the fuses specified current
limiting range, abruptly introduces a high resistance to reduce current
magnitude and duration, resulting in subsequent current interruption."

I had read that and didn't understand it.

For ordinary distribution panel there's no point. The fuse will open
and protect what it's there to protect.

They're useful for motor starters, etc., ...

So there will still be some current to the motor starter. What's a
motor starter? ;-)

Typically a relay but it can be anything that gets a motor going and
may have some protection built in. A lot depends on what kind of motor
you are talking about and the application. Some 3p starters are pretty
sophisticated electronic circuits that bring them up slowly.

In alt.home.repair, on Sun, 16 Aug 2020 16:47:58 -0400,
wrote:

On Sat, 15 Aug 2020 19:47:38 -0400, micky
wrote:

In alt.home.repair, on Sat, 15 Aug 2020 17:07:08 -0500, dpb
wrote:

On 8/15/2020 4:12 PM, micky wrote:
In alt.home.repair, on Sat, 15 Aug 2020 07:53:01 -0700 (PDT),
wrote:

It still might be a good idea to ask the service people to come out and look the interface over. And be sure to ask if their fuses are late-model current limiting fuses or not.

What are current limiting fuses. I looked at a couple webpages and it
didn't say. I thought all fuses were current limiting.

https://www.eaton.com/Eaton/ProductsServices/Electrical/ProductsandServices/Bussmann/MediumVoltageFuses/CurrentLimiting/index.htm

"A current limiting fuse is a fuse that, when its current responsive
element is melted by a current within the fuse’s specified current
limiting range, abruptly introduces a high resistance to reduce current
magnitude and duration, resulting in subsequent current interruption."

I had read that and didn't understand it.

For ordinary distribution panel there's no point. The fuse will open
and protect what it's there to protect.

They're useful for motor starters, etc., ...

So there will still be some current to the motor starter. What's a
motor starter? ;-)

Typically a relay but it can be anything that gets a motor going and
may have some protection built in. A lot depends on what kind of motor
you are talking about and the application.

So why would you want some current to be still going through it if there
had been enough to blow the fuse? There must be a short circuit so even
the small amount of current will be going through the short circuit and
it won't be enough to close the relay.

Some 3p starters are pretty
sophisticated electronic circuits that bring them up slowly.

The same question for a starter like this.

On 8/16/20 6:35 PM, micky wrote:
In alt.home.repair, on Sun, 16 Aug 2020 16:47:58 -0400,
wrote:

On Sat, 15 Aug 2020 19:47:38 -0400, micky
wrote:

In alt.home.repair, on Sat, 15 Aug 2020 17:07:08 -0500, dpb
wrote:

On 8/15/2020 4:12 PM, micky wrote:
In alt.home.repair, on Sat, 15 Aug 2020 07:53:01 -0700 (PDT),
wrote:

It still might be a good idea to ask the service people to come out and look the interface over. And be sure to ask if their fuses are late-model current limiting fuses or not.

What are current limiting fuses. I looked at a couple webpages and it
didn't say. I thought all fuses were current limiting.

https://www.eaton.com/Eaton/ProductsServices/Electrical/ProductsandServices/Bussmann/MediumVoltageFuses/CurrentLimiting/index.htm

"A current limiting fuse is a fuse that, when its current responsive
element is melted by a current within the fuses specified current
limiting range, abruptly introduces a high resistance to reduce current
magnitude and duration, resulting in subsequent current interruption."

I had read that and didn't understand it.

For ordinary distribution panel there's no point. The fuse will open
and protect what it's there to protect.

They're useful for motor starters, etc., ...

So there will still be some current to the motor starter. What's a
motor starter? ;-)

Typically a relay but it can be anything that gets a motor going and
may have some protection built in. A lot depends on what kind of motor
you are talking about and the application.

So why would you want some current to be still going through it if there
had been enough to blow the fuse? There must be a short circuit so even
the small amount of current will be going through the short circuit and
it won't be enough to close the relay.

Some 3p starters are pretty
sophisticated electronic circuits that bring them up slowly.

The same question for a starter like this.

This might be more than you want to know about time delay fuses. A
motor pulls several times the normal current load while it's starting. A
time delay fuse lets that extra current go through for a short period of
time before it blows. But it cuts the current completely when it does
blow.

https://blog.usesi.com/2018/01/15/electrical-supply-what-is-a-time-delay-fuse-2/

On Saturday, Aug 15, 2020 7:47:38 p.m., -0400, micky wrote:
In alt.home.repair, on Sat, 15 Aug 2020 17:07:08 -0500, dpb
wrote:

On 8/15/2020 4:12 PM, micky wrote:
In alt.home.repair, on Sat, 15 Aug 2020 07:53:01 -0700 (PDT),
wrote:

It still might be a good idea to ask the service people to come out and look the interface over. And be sure to ask if their fuses are late-model current limiting fuses or not.

What are current limiting fuses. I looked at a couple webpages and it
didn't say. I thought all fuses were current limiting.

https://www.eaton.com/Eaton/ProductsServices/Electrical/ProductsandServices/Bussmann/MediumVoltageFuses/CurrentLimiting/index.htm

"A current limiting fuse is a fuse that, when its current responsive
element is melted by a current within the fuses specified current
limiting range, abruptly introduces a high resistance to reduce current
magnitude and duration, resulting in subsequent current interruption."

I had read that and didn't understand it.

For ordinary distribution panel there's no point. The fuse will open
and protect what it's there to protect.

They're useful for motor starters, etc., ...

So there will still be some current to the motor starter. What's a
motor starter? ;-)

It's used residentially and commercially for starting "stopping, reversing and protecting electric motor" devices, supports and disconnects, etc. You could have a pool on the premesis. An upstairs whirlpool? And you have a lot of welding equipment in your garage? Plus a sauna? You just got a steam bath installed. The Mrs. has the kitchen expanded for the catering service. This may all call for a 60 amp breaker.

In article , NONONOmisc07
@bigfoot.com says...

Some 3p starters are pretty
sophisticated electronic circuits that bring them up slowly.

The same question for a starter like this.



While not technically correct, I refer to it as a one shot inverter or
speed control. In the AC line are some SCRs or Triacs and a control
circuit to drive them. They ramp the speed of the motor up slow and when
it gets near full speed a relay usually pulls in to put the full voltage
to it. Most often used in motors of 50 HP and up. We had them on some
200 hp motors where I worked. Big motors are like a dead short on the
lines so in order to keep the inrush current down, the ramp up starters
are used.

On 8/15/2020 4:07 PM, dpb wrote:
On 8/15/2020 4:12 PM, micky wrote:
In alt.home.repair, on Sat, 15 Aug 2020 07:53:01 -0700 (PDT),
wrote:

It still might be a good idea to ask the service people to come out
and look the interface over.Â* And be sure to ask if their fuses are
late-model current limiting fuses or not.

What are current limiting fuses.Â* I looked at a couple webpages and it
didn't say.Â*Â*Â* I thought all fuses were current limiting.

https://www.eaton.com/Eaton/ProductsServices/Electrical/ProductsandServices/Bussmann/MediumVoltageFuses/CurrentLimiting/index.htm


"A current limiting fuse is a fuse that, when its current responsive
element is melted by a current within the fuses specified current
limiting range, abruptly introduces a high resistance to reduce current
magnitude and duration, resulting in subsequent current interruption."

For ordinary distribution panel there's no point.Â* The fuse will open
and protect what it's there to protect.

They're useful for motor starters, etc., ...


The definition is really awful.

http://www.cooperindustries.com/cont...-fuseology.pdf
at page 17 has useful information
"Current-Limiting Overcurrent Protective Device:
A device that, when interrupting currents in its current-limiting
range, reduces the current flowing in the faulted circuit to a magnitude
substantially less than that obtainable in the same circuit if the
device were replaced with a solid conductor having comparable impedance."

Current-limiting fuses can be particularly useful on circuits that can
have high available-fault-currents. The fuse melts _and clears_ in less
than 1/4 cycle (before the fault current rises to its peak). The peak
fault current that gets through the fuse will be significantly less than
for a fuse that takes a cycle to clear. The fuse will, indeed, limit the
peak current when compared to a slower fuse. Nice diagram on page 17

Why is that important?
1 - Magnetic effects that can rip bus bars loose are proportional to
the fault current (or squared?). Switchgear is designed for the magnetic
effects that may occur. Replacing a current-limiting fuse with a slower
acing one can have disastrous effects. Fuse holders for current-limiting
fuses have a "rejection" feature that prevent other fuses from being used.
2 - Heat energy produced by a fault is proportional to the current
squared and time (I squared t). Current-limiting fuses may make the
difference, for a worker involved in an "arc-flash" event, between
little or no injury and being dead. Both OSHA and the NEC have
discovered arc-flash and protection has been added to the codes (and is
still being added).
3 - Commonly available fuses, including Bussmann FRN, are available with
available-fault-current ratings of 200,000 A. How do you make a 15A fuse
that is safe on a 200,000 A available fault circuit? You interrupt the
current before it can get anywhere near 200kA. Note that a 100A fuse
will not be current limiting at a 200A fault, but will be with a 10,000
A fault.

IMHO there is seldom a reason to not use a current-limiting fuse on
power circuits.

====================================
A motor starter is very likely to have motor overload protection. In the
good old days this was overload "heaters" that caused the starter to
open on an overload. The "heaters" are available in a large number of
sizes to tailor the protection to the specific motor current. The
overload system is also designed for motor protection. Fuses aren't
designed for motor overload protection.

Motor starters now may have electronic adjustable motor current settings.
====================================
IMHO the fuse pull-out originally had insulating plugs in the holes over
the brass screws. That is why the screws are recessed. Even an
incompetent manufacturer would not make pullouts without insulating plugs.

On Sun, 16 Aug 2020 12:01:51 -0700 (PDT), trader_4 posted for all of us to
digest...


On Saturday, August 15, 2020 at 2:44:24 PM UTC-4, rbowman wrote:
On 08/15/2020 08:53 AM, wrote:
It still might be a good idea to ask the service people to come out and look the interface over. And be sure to ask if their fuses are late-model current limiting fuses or not.


In my experience that can lead to an expensive retrofit.

IDK what service people those would be, since what he's dealing with appears
to be customer eqpt, not the utility's side.

Any disconnect I ever saw had some kind of protective panel over the line side.
It might be old and have fallen out or disintegrated. I saw a piece of
cardboard shoved in one once. I'm sure Greg & Clare have other stories to tell.

--
Tekkie

On 8/15/20 6:47 PM, micky wrote:
In alt.home.repair, on Sat, 15 Aug 2020 17:07:08 -0500, dpb
wrote:

On 8/15/2020 4:12 PM, micky wrote:
In alt.home.repair, on Sat, 15 Aug 2020 07:53:01 -0700 (PDT),
wrote:

It still might be a good idea to ask the service people to come out and look the interface over. And be sure to ask if their fuses are late-model current limiting fuses or not.

What are current limiting fuses. I looked at a couple webpages and it
didn't say. I thought all fuses were current limiting.

https://www.eaton.com/Eaton/ProductsServices/Electrical/ProductsandServices/Bussmann/MediumVoltageFuses/CurrentLimiting/index.htm

"A current limiting fuse is a fuse that, when its current responsive
element is melted by a current within the fuses specified current
limiting range, abruptly introduces a high resistance to reduce current
magnitude and duration, resulting in subsequent current interruption."

I had read that and didn't understand it.

For ordinary distribution panel there's no point. The fuse will open
and protect what it's there to protect.

They're useful for motor starters, etc., ...

So there will still be some current to the motor starter. What's a
motor starter? ;-)

It's a contactor with some added stuff.
https://www.youtube.com/watch?v=cpnnXGwDaBE

On Monday, August 17, 2020 at 4:44:27 PM UTC-4, Tekkie® wrote:
Any disconnect I ever saw had some kind of protective panel over the line side.
It might be old and have fallen out or disintegrated. I saw a piece of
cardboard shoved in one once. I'm sure Greg & Clare have other stories to tell.

--
Tekkie

The safety panel is in place.

The fuse block holds two cylindrical fuses, looking something like fat AA batteries. The fuse block pulls completely out if you need to change fuses or cut power completely - you insert it rotated while power is out. The fuses are hidden on the back side of the fuse block when it is inserted. There is no obvious way to do Lockout/Tagout or ZeroEnergyState or whatever OSHA calls it lately.

The fuses are held in copper clamps. The clamps are secured to the fuse block with large brass screws from the front side; the holes are a good half inch across and a finger can slip in.

I suppose it is possible there are little plastic caps made to fit those holes.

Here's an image online. It looks like the upper screw holes are sealed, which is a good idea because his thumb is in a risky spot otherwise:
https://www.bhg.com/home-improvement...ower-fuse-box/

Grainger advertises "finger safe" fuse blocks so apparently it is a known problem.

On Tuesday, August 18, 2020 at 8:35:01 AM UTC-4, TimR wrote:
On Monday, August 17, 2020 at 4:44:27 PM UTC-4, Tekkie® wrote:
Any disconnect I ever saw had some kind of protective panel over the line side.
It might be old and have fallen out or disintegrated. I saw a piece of
cardboard shoved in one once. I'm sure Greg & Clare have other stories to tell.

--
Tekkie

The safety panel is in place.

The fuse block holds two cylindrical fuses, looking something like fat AA batteries. The fuse block pulls completely out if you need to change fuses or cut power completely - you insert it rotated while power is out. The fuses are hidden on the back side of the fuse block when it is inserted. There is no obvious way to do Lockout/Tagout or ZeroEnergyState or whatever OSHA calls it lately.

You can take the block with you, hide it, etc. That prevents anyone
from putting the power back on and killing you. But it does still leave
the hole in the panel open and energized where some dummy could kill
themselves, so it's not totally safe.





The fuses are held in copper clamps. The clamps are secured to the fuse block with large brass screws from the front side; the holes are a good half inch across and a finger can slip in.

I suppose it is possible there are little plastic caps made to fit those holes.

You would hope so. Like Tekkie, I never saw a disconnect where any live
parts were exposed in anyway.



Here's an image online. It looks like the upper screw holes are sealed, which is a good idea because his thumb is in a risky spot otherwise:
https://www.bhg.com/home-improvement...ower-fuse-box/

It looks to me like they put a raised block across the upper part as a
comfortable spot for your thumb. You can't tell what's going on with the
bottom two holes, I'd be surprised if they are not covered/insulated.




Grainger advertises "finger safe" fuse blocks so apparently it is a known problem.

Interesting, but I wonder what that really means.

On Sunday, August 16, 2020 at 7:36:03 PM UTC-4, micky wrote:
In alt.home.repair, on Sun, 16 Aug 2020 16:47:58 -0400,
wrote:

On Sat, 15 Aug 2020 19:47:38 -0400, micky
wrote:

In alt.home.repair, on Sat, 15 Aug 2020 17:07:08 -0500, dpb
wrote:

On 8/15/2020 4:12 PM, micky wrote:
In alt.home.repair, on Sat, 15 Aug 2020 07:53:01 -0700 (PDT),
wrote:

It still might be a good idea to ask the service people to come out and look the interface over. And be sure to ask if their fuses are late-model current limiting fuses or not.

What are current limiting fuses. I looked at a couple webpages and it
didn't say. I thought all fuses were current limiting.

https://www.eaton.com/Eaton/ProductsServices/Electrical/ProductsandServices/Bussmann/MediumVoltageFuses/CurrentLimiting/index.htm

"A current limiting fuse is a fuse that, when its current responsive
element is melted by a current within the fuses specified current
limiting range, abruptly introduces a high resistance to reduce current
magnitude and duration, resulting in subsequent current interruption."

I had read that and didn't understand it.

For ordinary distribution panel there's no point. The fuse will open
and protect what it's there to protect.

They're useful for motor starters, etc., ...

So there will still be some current to the motor starter. What's a
motor starter? ;-)

Typically a relay but it can be anything that gets a motor going and
may have some protection built in. A lot depends on what kind of motor
you are talking about and the application.

So why would you want some current to be still going through it if there
had been enough to blow the fuse? There must be a short circuit so even
the small amount of current will be going through the short circuit and
it won't be enough to close the relay.

Some 3p starters are pretty
sophisticated electronic circuits that bring them up slowly.

The same question for a starter like this.

That's what I don't get either. Why would you want some current still going
to something that's part of the circuit? And isn't the load that caused the
trip still present and part of it?

trader_4 expressed precisely :
On Sunday, August 16, 2020 at 7:36:03 PM UTC-4, micky wrote:
In alt.home.repair, on Sun, 16 Aug 2020 16:47:58 -0400,
wrote:

On Sat, 15 Aug 2020 19:47:38 -0400, micky
wrote:

In alt.home.repair, on Sat, 15 Aug 2020 17:07:08 -0500, dpb
wrote:

On 8/15/2020 4:12 PM, micky wrote:
In alt.home.repair, on Sat, 15 Aug 2020 07:53:01 -0700 (PDT),
wrote:

It still might be a good idea to ask the service people to come out and
look the interface over. And be sure to ask if their fuses are
late-model current limiting fuses or not.

What are current limiting fuses. I looked at a couple webpages and it
didn't say. I thought all fuses were current limiting.

https://www.eaton.com/Eaton/ProductsServices/Electrical/ProductsandServices/Bussmann/MediumVoltageFuses/CurrentLimiting/index.htm

"A current limiting fuse is a fuse that, when its current responsive
element is melted by a current within the fuses specified current
limiting range, abruptly introduces a high resistance to reduce current
magnitude and duration, resulting in subsequent current interruption."

I had read that and didn't understand it.

For ordinary distribution panel there's no point. The fuse will open
and protect what it's there to protect.

They're useful for motor starters, etc., ...

So there will still be some current to the motor starter. What's a
motor starter? ;-)

Typically a relay but it can be anything that gets a motor going and
may have some protection built in. A lot depends on what kind of motor
you are talking about and the application.

So why would you want some current to be still going through it if there
had been enough to blow the fuse? There must be a short circuit so even
the small amount of current will be going through the short circuit and
it won't be enough to close the relay.

Some 3p starters are pretty
sophisticated electronic circuits that bring them up slowly.

The same question for a starter like this.

That's what I don't get either. Why would you want some current still going
to something that's part of the circuit? And isn't the load that caused the
trip still present and part of it?

It is more about being fast-acting than it is about the current it
allows while resisting.

On 8/18/20 9:12 AM, trader_4 wrote:
On Sunday, August 16, 2020 at 7:36:03 PM UTC-4, micky wrote:
In alt.home.repair, on Sun, 16 Aug 2020 16:47:58 -0400,
wrote:

On Sat, 15 Aug 2020 19:47:38 -0400, micky
wrote:

In alt.home.repair, on Sat, 15 Aug 2020 17:07:08 -0500, dpb
wrote:

On 8/15/2020 4:12 PM, micky wrote:
In alt.home.repair, on Sat, 15 Aug 2020 07:53:01 -0700 (PDT),
wrote:

It still might be a good idea to ask the service people to come out and look the interface over. And be sure to ask if their fuses are late-model current limiting fuses or not.

What are current limiting fuses. I looked at a couple webpages and it
didn't say. I thought all fuses were current limiting.

https://www.eaton.com/Eaton/ProductsServices/Electrical/ProductsandServices/Bussmann/MediumVoltageFuses/CurrentLimiting/index.htm

"A current limiting fuse is a fuse that, when its current responsive
element is melted by a current within the fuses specified current
limiting range, abruptly introduces a high resistance to reduce current
magnitude and duration, resulting in subsequent current interruption."

I had read that and didn't understand it.

For ordinary distribution panel there's no point. The fuse will open
and protect what it's there to protect.

They're useful for motor starters, etc., ...

So there will still be some current to the motor starter. What's a
motor starter? ;-)

Typically a relay but it can be anything that gets a motor going and
may have some protection built in. A lot depends on what kind of motor
you are talking about and the application.

So why would you want some current to be still going through it if there
had been enough to blow the fuse? There must be a short circuit so even
the small amount of current will be going through the short circuit and
it won't be enough to close the relay.

Some 3p starters are pretty
sophisticated electronic circuits that bring them up slowly.

The same question for a starter like this.

That's what I don't get either. Why would you want some current still goinghe
to something that's part of the circuit? And isn't the load that caused the
trip still present and part of it?

This isn't the best picture in the world but might serve the purpose.
http://assets.suredone.com/1599/media-photo/jf06170-allen-bradley-480v-size-1-combination-motor-starter-512-bab-24-4.jpg
Power comes in way at the top, goes through the disconnect, then the
fuses. Everything else is after that.
The starters have 480 volt coils so need power from two lines to keep
them engaged. A fuse blowing on either of those two lines will
immediately kick the starter out. A fuse blowing on the third line
will overload the other two circuits which will cause the motor starter
to kick out.
The motor will be disconnected in either case.

On Tuesday, August 18, 2020 at 9:26:54 AM UTC-4, bud-- wrote:
IMHO the fuse pull-out originally had insulating plugs in the holes over
the brass screws. That is why the screws are recessed. Even an
incompetent manufacturer would not make pullouts without insulating plugs.

That does make sense. I'll see if I can get a photo.

There was one curious thing.

This is the same shed I posted about before, where I pulled the disconnect lever, and still had hot outlets, so I had to pull the fuse block also.

Well, this time I didn't bother pulling the lever, I just pulled the fuse block, knowing that cut all the power.

Only it didn't. One of the lights stayed on. I guess I really should figure out how this thing is wired.

In article , says...

If others are deciphering the picture, the fuses are not installed an go
in the open space toward the middle. The fuses are long because they are
for 480V.



You were doing well up to this point. The fuses are not long because of
480 volts. They are long as when they open up there is a long enough
path that an arc can not form and keep current flowing.

Most of the motor contactors are designed to have a way of 'blowing
out' the arc when the contacts open as opposed to some similar looking
relays (contactors) that are designed for resistance only loads.

In the same type of motor starter, many contactors will have a
transformer across 2 legs before the contactor that converts the 480 to
120 volts and the coil will be 120 volts. That is usually for long runs
to switches. The fuses for that transformer are not long at all.

On 8/18/2020 8:52 AM, Dean Hoffman wrote:
On 8/18/20 9:12 AM, trader_4 wrote:
On Sunday, August 16, 2020 at 7:36:03 PM UTC-4, micky wrote:
In alt.home.repair, on Sun, 16 Aug 2020 16:47:58 -0400,
wrote:

On Sat, 15 Aug 2020 19:47:38 -0400, micky
wrote:

In alt.home.repair, on Sat, 15 Aug 2020 17:07:08 -0500, dpb
wrote:

On 8/15/2020 4:12 PM, micky wrote:
In alt.home.repair, on Sat, 15 Aug 2020 07:53:01 -0700 (PDT),
wrote:

It still might be a good idea to ask the service people to come
out and look the interface over.Â* And be sure to ask if their
fuses are late-model current limiting fuses or not.

What are current limiting fuses.Â* I looked at a couple webpages
and it
didn't say.Â*Â*Â* I thought all fuses were current limiting.

https://www.eaton.com/Eaton/ProductsServices/Electrical/ProductsandServices/Bussmann/MediumVoltageFuses/CurrentLimiting/index.htm


"A current limiting fuse is a fuse that, when its current responsive
element is melted by a current within the fuses specified current
limiting range, abruptly introduces a high resistance to reduce
current
magnitude and duration, resulting in subsequent current
interruption."

I had read that and didn't understand it.

For ordinary distribution panel there's no point.Â* The fuse will open
and protect what it's there to protect.

They're useful for motor starters, etc., ...

So there will still be some current to the motor starter.Â* What's a
motor starter?Â*Â* ;-)

Typically a relay but it can be anything that gets a motor going and
may have some protection built in. A lot depends on what kind of motor
you are talking about and the application.

So why would you want some current to be still going through it if there
had been enough to blow the fuse?Â* There must be a short circuit so even
the small amount of current will be going throughÂ* the short circuit and
it won't be enough to close the relay.

The large relay in a motor starter is called a contactor.

Some 3p starters are pretty
sophisticated electronic circuits that bring them up slowly.

The same question for a starter like this.

That's what I don't get either.Â* Why would you want some current still
goinghe
to something that's part of the circuit?Â* And isn't the load that
caused the
trip still present and part of it?

If you are referring to the "high resistance" in the fuse definition,
the definition is incredibly bad. CL fuses do not any intentional
resistance other than the resistance of the fusible elements (which may
be silver).
See the definition in my other post.

The defining characteristic of a current-limiting fuse is that it melts
and clears in a shorter time than 'ordinary' fuses - less than 1/4 cycle
when the fault current is high enough to cause the fuse to current limit.

Â*Â*Â*Â* This isn't the best picture in the world but might serve the purpose.
http://assets.suredone.com/1599/media-photo/jf06170-allen-bradley-480v-size-1-combination-motor-starter-512-bab-24-4.jpg

Â* Power comes in way at the top, goes through the disconnect, then the
fuses.Â* Everything else is after that.
The starters have 480 volt coils so need power from two lines to keep
them engaged.Â* A fuse blowing on either of those two lines will
immediately kick the starter out.Â*Â* A fuse blowing on the third line
will overload the other two circuits which will cause the motor starter
to kick out.
Â* The motor will be disconnected in either case.

If others are deciphering the picture, the fuses are not installed an go
in the open space toward the middle. The fuses are long because they are
for 480V.

"Motor starters" almost always have an "overload" unit that trips the
starter off (by opening the control circuit that powers the coil). The
overload is at the bottom of the black blob (contactor) at the bottom.
This overload uses "heaters" - one in each phase. There is probably a
table on the door label for selecting the size of the heaters using the
motor current. The black disc toward the bottom of the door pushes a
post on the overload to reset it.

Fuses/circuit breakers don't provide overload protection - they provide
short circuit protection. g posted an example years ago where a
circuit breaker at the source of a motor circuit could be twice the wire
amp rating (and the wire rating is higher than the motor full-load
current). (Fuses sometimes are used - i.e. a 6 1/4 amp fuse may be used
on some small motors.)

You really don't want single fuses to blow in a 3 phase set.

On 8/18/20 5:10 PM, bud-- wrote:
On 8/18/2020 11:30 AM, Ralph Mowery wrote:
In article , says...

If others are deciphering the picture, the fuses are not installed an go
in the open space toward the middle. The fuses are long because they are
for 480V.



You were doing well up to this point.Â* The fuses are not long because of
480 volts.Â* They are long as when they open up there is a long enough
path that an arc can not form and keep current flowing.

IMHO that is saying the same thing (with more detail).

Most of the motor contactors are designed to have a way of 'blowing
out' the arc when the contacts open as opposed to some similar looking
relays (contactors) that are designed for resistance only loads.

Motor contactors have to be rated for the locked-rotor current, which is
about 6 x the run current.
Circuit breakers have to be rated for the available-fault-current.

I have seen pictures of high rated circuit breaker contacts with
arc-chutes and magnetic blowouts. I haven't see that on contactors, but
you likely had some real big motors where you worked.
[you picked a great time to retire.]


In the same type of motor starter, many contactors will have a
transformer across 2 legs before the contactor that converts the 480 toh
120 volts and the coil will be 120 volts.Â* That is usually for long runs
to switches.Â* The fuses for that transformer are not long at all.

Seems a little surprising there are not even start/stop buttons on the
door in the picture. The only motor control is the disconnect.

Wouldn't work so well to run 480 coil voltage outside the controller
(switches and sensors would have to be rated 480), and it would have to
be fused. in both legs.

Everything I remember was 120V control like you describe.

Most of the pump panels I've seen had a "Hand-Off-Auto" switch
under the disconnect switch handle. Others had it on the right side of
the panel. They all had some sort of switch for the contactor though.
Do you suppose this one's switch is on the left hand side of the
panel? I can't see the picture well enough to tell where the little red
wires are going.

On 8/18/2020 4:30 PM, Dean Hoffman wrote:
On 8/18/20 5:10 PM, bud-- wrote:
....

Seems a little surprising there are not even start/stop buttons on the
door in the picture. The only motor control is the disconnect.

Wouldn't work so well to run 480 coil voltage outside the controller
(switches and sensors would have to be rated 480), and it would have
to be fused. in both legs.

Everything I remember was 120V control like you describe.

Â*Â* Most of the pump panels I've seen had a "Hand-Off-Auto"Â* switch
under the disconnect switch handle.Â*Â* Others had it on the right side of
the panel.Â*Â* They all had some sort of switch for the contactor though.
Â* Do you suppose this one's switch is on the left hand side of the
panel?Â* I can't see the picture well enough to tell where the little red
wires are going.

The red/green buttons are start/stop; the round plunger in the door is
reset...had hundreds of these and just a few years earlier versions in
power plants -- have about three of them salvaged from the scrap heap
when a retrofit went on but haven't found anything large enough yet to
use them for -- the versions a few years earlier did have to separate
start/stop buttons towards the bottom on the case; not sure just when
they went to the integrated ones like this.

The contactor just isn't wired to the buttons in this picture...

--

On 8/18/2020 4:58 PM, dpb wrote:
On 8/18/2020 4:30 PM, Dean Hoffman wrote:
On 8/18/20 5:10 PM, bud-- wrote:
...

Seems a little surprising there are not even start/stop buttons on
the door in the picture. The only motor control is the disconnect.

Wouldn't work so well to run 480 coil voltage outside the controller
(switches and sensors would have to be rated 480), and it would have
to be fused. in both legs.

Everything I remember was 120V control like you describe.

Â*Â*Â* Most of the pump panels I've seen had a "Hand-Off-Auto"Â* switch
under the disconnect switch handle.Â*Â* Others had it on the right side
of the panel.Â*Â* They all had some sort of switch for the contactor
though. Â*Â* Do you suppose this one's switch is on the left hand side
of the panel?Â* I can't see the picture well enough to tell where the
little red wires are going.

The red/green buttons are start/stop; the round plunger in the door is
reset...had hundreds of these and just a few years earlier versions in
power plants -- have about three of them salvaged from the scrap heap
when a retrofit went on but haven't found anything large enough yet to
use them for -- the versions a few years earlier did have to separate
start/stop buttons towards the bottom on the case; not sure just when
they went to the integrated ones like this.

The contactor just isn't wired to the buttons in this picture...

--

Oh. Here's link to a bunch more pitchures...
https://fazziosurplus.com/allen-bradley-480v-size-1-combination-motor-starter-512-bab-24-jf06170

--

On 8/18/2020 11:30 AM, Ralph Mowery wrote:
In article , says...

If others are deciphering the picture, the fuses are not installed an go
in the open space toward the middle. The fuses are long because they are
for 480V.



You were doing well up to this point. The fuses are not long because of
480 volts. They are long as when they open up there is a long enough
path that an arc can not form and keep current flowing.

IMHO that is saying the same thing (with more detail).

Most of the motor contactors are designed to have a way of 'blowing
out' the arc when the contacts open as opposed to some similar looking
relays (contactors) that are designed for resistance only loads.

Motor contactors have to be rated for the locked-rotor current, which is
about 6 x the run current.
Circuit breakers have to be rated for the available-fault-current.

I have seen pictures of high rated circuit breaker contacts with
arc-chutes and magnetic blowouts. I haven't see that on contactors, but
you likely had some real big motors where you worked.
[you picked a great time to retire.]


In the same type of motor starter, many contactors will have a
transformer across 2 legs before the contactor that converts the 480 to
120 volts and the coil will be 120 volts. That is usually for long runs
to switches. The fuses for that transformer are not long at all.

Seems a little surprising there are not even start/stop buttons on the
door in the picture. The only motor control is the disconnect.

Wouldn't work so well to run 480 coil voltage outside the controller
(switches and sensors would have to be rated 480), and it would have to
be fused. in both legs.

Everything I remember was 120V control like you describe.

On 8/18/2020 9:51 AM, TimR wrote:
On Tuesday, August 18, 2020 at 9:26:54 AM UTC-4, bud-- wrote:
IMHO the fuse pull-out originally had insulating plugs in the holes over
the brass screws. That is why the screws are recessed. Even an
incompetent manufacturer would not make pullouts without insulating plugs.

That does make sense. I'll see if I can get a photo.

There was one curious thing.

This is the same shed I posted about before, where I pulled the disconnect lever, and still had hot outlets, so I had to pull the fuse block also.

Well, this time I didn't bother pulling the lever, I just pulled the fuse block, knowing that cut all the power.

Only it didn't. One of the lights stayed on. I guess I really should figure out how this thing is wired.


(Sorry if this is a duplicate)

Not clear what you have.

A "main and range" 60A service used to be common. There were 2 - 60A
pullouts, both were service disconnects. One was for an optional range
(or anything else), and the other pullout fed the plug fuses (the rest
of the panel).

My mother had a 100A service with 4 pullouts - all service disconnects.
One 60A pullout fed the plug fuses. The other 3 pullouts (30, 30, 60)
fed whatever.

If you have multiple service disconnect pullouts, some of the loads may
be fed from a pullout other than the one for the plug fuses. A 15A
cartridge fuse could be in a 30A pullout, or could be in a 60A pullout
using fuse reducers.

These are versions of a "split-bus" panel. Note that with multiple
service disconnects the service fuses may total more than the service
rating. The minimum required service size is determined by a "load
calculation"

========================
If I had a pullout with exposed screws, I would make sure the screws
were tight and cover them with epoxy, preferably black.

In article , says...

Motor contactors have to be rated for the locked-rotor current, which is
about 6 x the run current.
Circuit breakers have to be rated for the available-fault-current.

I have seen pictures of high rated circuit breaker contacts with
arc-chutes and magnetic blowouts. I haven't see that on contactors, but
you likely had some real big motors where you worked.
[you picked a great time to retire.]


In the same type of motor starter, many contactors will have a
transformer across 2 legs before the contactor that converts the 480 to
120 volts and the coil will be 120 volts. That is usually for long runs
to switches. The fuses for that transformer are not long at all.

Seems a little surprising there are not even start/stop buttons on the
door in the picture. The only motor control is the disconnect.

Wouldn't work so well to run 480 coil voltage outside the controller
(switches and sensors would have to be rated 480), and it would have to
be fused. in both legs.

Everything I remember was 120V control like you describe.



I retired about 7 years ago from a small plant that had about 40 acers
under roof and had over 3000 people there at one time.


Dealt with many things. From small motors you could hold in one hand to
some around 300 HP. Not sure how how the big compressor motors were as
I dealt very little with them. They operated on 4160 volts. They had
fuses that were about 6 inches across and 2 feet long. The fuse in the
primary of the control circuit that dropped the 4160 to 120 volts was
about 2 inches in diameter and almost a foot long. Rated for only 1
amp,but 6000 volts.

Some of the big contactors that I dealt with were rated around 300 amps
at 480 3 phase had 480 volt coils but there was an interposing relay
that was fed with 120 volts to run outside the cabinet.

Some of the big resistance heaters that had 300 amp fuses and 480 volts
had 3 contactors in series. One would pull in and about 10 seconds
later the other would pull in. This was a safety so that if one
contactors contacts welded together, the one that pulled in first not
under load should release. They were both wired to seperate
thermocouple safety switches to if it got too hot they would release and
not have a thermo meltdown. We made ployester out of raw materials, so
it could be a really bad thing if it all melted or caught fire.

In article , says...
--

Oh. Here's link to a bunch more pitchures...
https://fazziosurplus.com/allen-bradley-480v-size-1-combination-motor-starter-512-bab-24-jf06170

--




That is a newer one. Notice how the switch that disconnects the power
is red for on and green for off. Some asshole about 20 years ago
decided that the green should stand for safe to open the cabinet and the
red was danger the power is on and it is not safe to enter the cabinet.

I am not sure, but believe that backwards red and green came from a
foreign country as the first time I remember seeing that was some
foreign made equipment. Confusing as hell when you have a room that is
about 20 feet wide and 75 feet long and there is a mix of the old and
new. I got to the point that I did not pay the colors any attention.

Can not remember is any of the disconnects were up for off and down for
on.

On 8/18/2020 3:30 PM, Dean Hoffman wrote:
On 8/18/20 5:10 PM, bud-- wrote:
On 8/18/2020 11:30 AM, Ralph Mowery wrote:
In article , says...

If others are deciphering the picture, the fuses are not installed
an go
in the open space toward the middle. The fuses are long because they
are
for 480V.



You were doing well up to this point.Â* The fuses are not long because of
480 volts.Â* They are long as when they open up there is a long enough
path that an arc can not form and keep current flowing.

IMHO that is saying the same thing (with more detail).

Most of the motor contactors are designed to have a way of 'blowing
out' the arc when the contacts open as opposed to some similar looking
relays (contactors) that are designed for resistance only loads.

Motor contactors have to be rated for the locked-rotor current, which
is about 6 x the run current.
Circuit breakers have to be rated for the available-fault-current.

I have seen pictures of high rated circuit breaker contacts with
arc-chutes and magnetic blowouts. I haven't see that on contactors,
but you likely had some real big motors where you worked.
[you picked a great time to retire.]


In the same type of motor starter, many contactors will have a
transformer across 2 legs before the contactor that converts the 480 toh
120 volts and the coil will be 120 volts.Â* That is usually for long runs
to switches.Â* The fuses for that transformer are not long at all.

Seems a little surprising there are not even start/stop buttons on the
door in the picture. The only motor control is the disconnect.

Wouldn't work so well to run 480 coil voltage outside the controller
(switches and sensors would have to be rated 480), and it would have
to be fused. in both legs.

Everything I remember was 120V control like you describe.

Â*Â* Most of the pump panels I've seen had a "Hand-Off-Auto"Â* switch
under the disconnect switch handle.Â*Â* Others had it on the right side of
the panel.Â*Â* They all had some sort of switch for the contactor though.
Â* Do you suppose this one's switch is on the left hand side of the
panel?Â* I can't see the picture well enough to tell where the little red
wires are going.

You can download the picture and change the brightness and contrast and
see better. I don't see wires going anywhere but to terminals on the
contactor.
Putting a switch on the side would be dumb.

Looks like a stock motor control center that is to be modified by the
buyer - maybe that is why there are no switches.

On 8/18/20 6:00 PM, bud-- wrote:
On 8/18/2020 3:30 PM, Dean Hoffman wrote:
On 8/18/20 5:10 PM, bud-- wrote:
On 8/18/2020 11:30 AM, Ralph Mowery wrote:
In article , says...

If others are deciphering the picture, the fuses are not installed
an go
in the open space toward the middle. The fuses are long because
they are
for 480V.



You were doing well up to this point.Â* The fuses are not long
because of
480 volts.Â* They are long as when they open up there is a long enough
path that an arc can not form and keep current flowing.

IMHO that is saying the same thing (with more detail).

Most of the motor contactors are designed to have a way of 'blowing
out' the arc when the contacts open as opposed to some similar looking
relays (contactors) that are designed for resistance only loads.

Motor contactors have to be rated for the locked-rotor current, which
is about 6 x the run current.
Circuit breakers have to be rated for the available-fault-current.

I have seen pictures of high rated circuit breaker contacts with
arc-chutes and magnetic blowouts. I haven't see that on contactors,
but you likely had some real big motors where you worked.
[you picked a great time to retire.]


In the same type of motor starter, many contactors will have a
transformer across 2 legs before the contactor that converts the 480
toh
120 volts and the coil will be 120 volts.Â* That is usually for long
runs
to switches.Â* The fuses for that transformer are not long at all.

Seems a little surprising there are not even start/stop buttons on
the door in the picture. The only motor control is the disconnect.

Wouldn't work so well to run 480 coil voltage outside the controller
(switches and sensors would have to be rated 480), and it would have
to be fused. in both legs.

Everything I remember was 120V control like you describe.

Â*Â*Â* Most of the pump panels I've seen had a "Hand-Off-Auto"Â* switch
under the disconnect switch handle.Â*Â* Others had it on the right side
of the panel.Â*Â* They all had some sort of switch for the contactor
though. Â*Â* Do you suppose this one's switch is on the left hand side
of the panel?Â* I can't see the picture well enough to tell where the
little red wires are going.

You can download the picture and change the brightness and contrast and
see better. I don't see wires going anywhere but to terminals on the
contactor.
Putting a switch on the side would be dumb.

Agreed. It makes handling it just a little tougher if for no
other reason. Some college boy with a tie tried to think. That old
saying "Common sense isn't" comes to mind.
https://www.springfieldelectric.com/d/Square-D-Schneider-8940SSE4050/2847970

Looks like a stock motor control center that is to be modified by the
buyer - maybe that is why there are no switches.

In article , says...

You can download the picture and change the brightness and contrast and
see better. I don't see wires going anywhere but to terminals on the
contactor.
Putting a switch on the side would be dumb.

Agreed. It makes handling it just a little tougher if for no
other reason. Some college boy with a tie tried to think. That old
saying "Common sense isn't" comes to mind.
https://www.springfieldelectric.com/d/Square-D-Schneider-8940SSE4050/2847970

Looks like a stock motor control center that is to be modified by the
buyer - maybe that is why there are no switches.




It sometims makes sense to have the start/stop buttons on the side.
Think of it this way. If you have to work inside the box with the power
on such as to check the current the motor is drawing you have the power
going to the switch on the door. The door is pulled closed by the
tension on the wire and hits your bare hand or face. Big shock hazzard.

It still burns me up that some asshole decided that the Green ment the
power is switched off and it is safe to go into the box. For many
years the green ment that the power was switched on and red ment it was
off. Maybe ok if all new in a building, but a big CF when an older
building is added to and you have some of each.

On 8/18/2020 4:34 PM, Ralph Mowery wrote:
In article , says...

Motor contactors have to be rated for the locked-rotor current, which is
about 6 x the run current.
Circuit breakers have to be rated for the available-fault-current.

I have seen pictures of high rated circuit breaker contacts with
arc-chutes and magnetic blowouts. I haven't see that on contactors, but
you likely had some real big motors where you worked.
[you picked a great time to retire.]


In the same type of motor starter, many contactors will have a
transformer across 2 legs before the contactor that converts the 480 to
120 volts and the coil will be 120 volts. That is usually for long runs
to switches. The fuses for that transformer are not long at all.

Seems a little surprising there are not even start/stop buttons on the
door in the picture. The only motor control is the disconnect.

Wouldn't work so well to run 480 coil voltage outside the controller
(switches and sensors would have to be rated 480), and it would have to
be fused. in both legs.

Everything I remember was 120V control like you describe.



I retired about 7 years ago from a small plant that had about 40 acers
under roof and had over 3000 people there at one time.

Yea - "small plant"
("You picked a great time to retire" is a delayed response to another
recent description of your place.)

I think I said before - it sounds like an interesting place. Sounds even
more interesting.



Dealt with many things. From small motors you could hold in one hand to
some around 300 HP. Not sure how how the big compressor motors were as
I dealt very little with them. They operated on 4160 volts. They had
fuses that were about 6 inches across and 2 feet long. The fuse in the
primary of the control circuit that dropped the 4160 to 120 volts was
about 2 inches in diameter and almost a foot long. Rated for only 1
amp,but 6000 volts.

Some of the big contactors that I dealt with were rated around 300 amps
at 480 3 phase had 480 volt coils but there was an interposing relay
that was fed with 120 volts to run outside the cabinet.

Some of the big resistance heaters that had 300 amp fuses and 480 volts
had 3 contactors in series. One would pull in and about 10 seconds
later the other would pull in. This was a safety so that if one
contactors contacts welded together, the one that pulled in first not
under load should release. They were both wired to seperate
thermocouple safety switches to if it got too hot they would release and
not have a thermo meltdown. We made ployester out of raw materials, so
it could be a really bad thing if it all melted or caught fire.

On 8/19/20 9:16 AM, Ralph Mowery wrote:
In article , says...

You can download the picture and change the brightness and contrast and
see better. I don't see wires going anywhere but to terminals on the
contactor.
Putting a switch on the side would be dumb.

Agreed. It makes handling it just a little tougher if for no
other reason. Some college boy with a tie tried to think. That old
saying "Common sense isn't" comes to mind.
https://www.springfieldelectric.com/d/Square-D-Schneider-8940SSE4050/2847970

Looks like a stock motor control center that is to be modified by the
buyer - maybe that is why there are no switches.




It sometims makes sense to have the start/stop buttons on the side.
Think of it this way. If you have to work inside the box with the power
on such as to check the current the motor is drawing you have the power
going to the switch on the door. The door is pulled closed by the
tension on the wire and hits your bare hand or face. Big shock hazzard.

It still burns me up that some asshole decided that the Green ment the
power is switched off and it is safe to go into the box. For many
years the green ment that the power was switched on and red ment it was
off. Maybe ok if all new in a building, but a big CF when an older
building is added to and you have some of each.

My experience is limited to irrigation wells and pivots. I can't
imagine working in a big manufacturing plant and such. It's bad enough
when someone gets creative in my world. They'd change something just to
get by without thinking it through.
I always thought the red and green was to mimic stop lights. Green
is go, safe: red is stop, danger. I'm the tender of 65 though, so
there's an awful lot I haven't seen.,

In article , says...
My experience is limited to irrigation wells and pivots. I can't
imagine working in a big manufacturing plant and such. It's bad enough
when someone gets creative in my world. They'd change something just to
get by without thinking it through.
I always thought the red and green was to mimic stop lights. Green
is go, safe: red is stop, danger. I'm the tender of 65 though, so
there's an awful lot I haven't seen.,




At one time there were around 70 electricians/instrument people in the
plant deviced into several shops of around 15 men each and responsiable
for a small area of the plant. There were around 100 mechanics devided
similar. As the company down sized there were around 20 electricians for
the same ammount of different equipment, but just not as much in each
area.

We did have some that would just move wires around and change things
just to get by. Then there was some major construction going onfrom time
to time. Interisting to have to go over a few hundred wires in a
cabinet to find out why things do not work correct. One of the more
interisting things to me was very simple. A small set of scales would
trip out a ground fault. It would work fine on another receptical in
the same room. After a few others had looked at it, I was called. I
discovered that anything plugged into that receptical would trip the
GFCI breaker. To make a long story short, after about an hour,I found
in a breaker box of about 20 breakers and some GFCIs that some nuckle
head had just picked out a neutral wire and ran it to the 'faulty'
receptical. Then took a while to find the correct neutral for that
circuit.

I enjoyed much of the work except in two areas. One was the waste
treatment area of the plant we had. Jut did not like working around
the crap and smell, but the equipment was simple. Another was greasy
and nasty.If I could have just worked on what I wanted to,I probably
would have stayed a few more years, but retired at 62 from there.