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 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!

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 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 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.

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 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.

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.

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 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 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.

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.

--

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 07:14:18 -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.