Just a question for the electrician types in the group:

I have a Harbor Fright "2 hp" Dc that's had a LOT of hours in the last 4 or 5
years..
A few days ago, it hiccupped a few times and quit.. I figured that it threw a
breaker, but that was fine..

Found that the switch was burned up.. was frozen in the ON position, but had a
semi-melted contact..

The weird thing is that I never USE the switch... The DC is plugged into a
switched plug and the DC switch has been in the ON position for years..

Any idea what would make the DC switch go, when nothing else did, including the
breaker or the 15 amp slo-blow fuse on the remote switch?

I should add that this $140 DC has really sucked over the years and I'd buy
another if I was looking for an inexpensive DC.. YMWV


mac

Please remove splinters before emailing

On Jul 3, 9:53 am, mac davis wrote:
Just a question for the electrician types in the group:

I have a Harbor Fright "2 hp" Dc that's had a LOT of hours in the last 4 or 5
years..
A few days ago, it hiccupped a few times and quit.. I figured that it threw a
breaker, but that was fine..

Found that the switch was burned up.. was frozen in the ON position, but had a
semi-melted contact..

Mac - as you know I am not an electrician. I am not particularly good
with it, so I have to ask any time anything unusual comes up.

Several years ago we were remodeling a small office that had lab
equipment in it. They had a burned out switch (not in our area of
work or contract) they asked us to look at for repair. It was a
vaccum pump that they used in their lab all day long, so they turned
it and several other machines on by the industrial surge protector
they kept all their machines plugged into.

The machine switch failed. I was baffled. If something isn't used,
how does it wear out?

My guy explained to me (take it for what it is worth) that the key is
the method of contact for the contact points in the switch. The
switch on their vacuum had tool type switch that had a very
distinctive *click* when it was thrown. According to him, this
indicated that the contacts were held together by spring pressure when
the switch was on.

But contact points do not seat perfectly. The may be a thousandth or
so of opening, and at that opening, there is an arc every time you use
the switch. The arc causes corrosion, and the corrosion causes the
short and resulting sizzled switch. According to him, that
infinitesimally small arc can also continue during the everyday use of
the switch for a long time.

He explained that for solid, permanent connections there were switches
for that purpose (think breakers, knife swiches, etc.) that were made
to be rarely used.

But the standard on/off switch is not constructed in that manner.

FWIW...

Robert

On Thu, 03 Jul 2008 07:53:15 -0700, mac davis
wrote:

Just a question for the electrician types in the group:

I have a Harbor Fright "2 hp" Dc that's had a LOT of hours in the last 4 or 5
years..
A few days ago, it hiccupped a few times and quit.. I figured that it threw a
breaker, but that was fine..

Found that the switch was burned up.. was frozen in the ON position, but had a
semi-melted contact..

The weird thing is that I never USE the switch... The DC is plugged into a
switched plug and the DC switch has been in the ON position for years..

Any idea what would make the DC switch go, when nothing else did, including the
breaker or the 15 amp slo-blow fuse on the remote switch?

I should add that this $140 DC has really sucked over the years and I'd buy
another if I was looking for an inexpensive DC.. YMWV


mac

Please remove splinters before emailing

The action of turning a switch on and off usually provides a little
cleaning as the contacts wipe across each other - something this
switch never received.

It's also possible that the geometry of the switch caused the spring
tension to relax over the years from always being in the on position,
thus leading to high contact resistance which caused overheating and
failure.

Conclusion - turn the DC's switch off once a month ;-)

John

wrote in message
...
On Jul 3, 9:53 am, mac davis wrote:
Just a question for the electrician types in the group:

I have a Harbor Fright "2 hp" Dc that's had a LOT of hours in the last 4
or 5
years..
A few days ago, it hiccupped a few times and quit.. I figured that it
threw a
breaker, but that was fine..

Found that the switch was burned up.. was frozen in the ON position, but
had a
semi-melted contact..

Mac - as you know I am not an electrician. I am not particularly good
with it, so I have to ask any time anything unusual comes up.

Several years ago we were remodeling a small office that had lab
equipment in it. They had a burned out switch (not in our area of
work or contract) they asked us to look at for repair. It was a
vaccum pump that they used in their lab all day long, so they turned
it and several other machines on by the industrial surge protector
they kept all their machines plugged into.

The machine switch failed. I was baffled. If something isn't used,
how does it wear out?

My guy explained to me (take it for what it is worth) that the key is
the method of contact for the contact points in the switch. The
switch on their vacuum had tool type switch that had a very
distinctive *click* when it was thrown. According to him, this
indicated that the contacts were held together by spring pressure when
the switch was on.

But contact points do not seat perfectly. The may be a thousandth or
so of opening, and at that opening, there is an arc every time you use
the switch. The arc causes corrosion, and the corrosion causes the
short and resulting sizzled switch. According to him, that
infinitesimally small arc can also continue during the everyday use of
the switch for a long time.

He explained that for solid, permanent connections there were switches
for that purpose (think breakers, knife swiches, etc.) that were made
to be rarely used.

But the standard on/off switch is not constructed in that manner.

That sound right. I have worked in a couple shops where all the switches
were replaced by heavy duty, industrial type of switches. I asked about
this at one place. I was told that was recommended to him by an electrician
that he trusted.

mac davis wrote:



I should add that this $140 DC has really sucked over the years and I'd
buy another if I was looking for an inexpensive DC.. YMWV

I thought that's what Dust Collectors were suppose to do. Really Suck!!


--
"You can lead them to LINUX
but you can't make them THINK"
Running Mandriva release 2008.0 free-i586 using KDE on i586

"mac davis" wrote:


Found that the switch was burned up.. was frozen in the ON position,
but had a
semi-melted contact..

The weird thing is that I never USE the switch... The DC is plugged
into a
switched plug and the DC switch has been in the ON position for
years..

With out boring you to death, the solution is simple.

Cut out the defective switch and twist the leads together, then tape.

Best insulation is some shrink tubing and a heat gun after soldering
the leads together.

Have fun.

Lew

On Thu, 3 Jul 2008 09:06:22 -0700 (PDT), "
wrote:

snip
My guy explained to me (take it for what it is worth) that the key is
the method of contact for the contact points in the switch. The
switch on their vacuum had tool type switch that had a very
distinctive *click* when it was thrown. According to him, this
indicated that the contacts were held together by spring pressure when
the switch was on.

But contact points do not seat perfectly. The may be a thousandth or
so of opening, and at that opening, there is an arc every time you use
the switch. The arc causes corrosion, and the corrosion causes the
short and resulting sizzled switch. According to him, that
infinitesimally small arc can also continue during the everyday use of
the switch for a long time.

He explained that for solid, permanent connections there were switches
for that purpose (think breakers, knife swiches, etc.) that were made
to be rarely used.

But the standard on/off switch is not constructed in that manner.

FWIW...

Robert

Thank you, sir.. makes sense to me...


mac

Please remove splinters before emailing

On Thu, 03 Jul 2008 12:09:21 -0400, John wrote:

snip
The action of turning a switch on and off usually provides a little
cleaning as the contacts wipe across each other - something this
switch never received.

It's also possible that the geometry of the switch caused the spring
tension to relax over the years from always being in the on position,
thus leading to high contact resistance which caused overheating and
failure.

Conclusion - turn the DC's switch off once a month ;-)

John

I went one better, John.. took the switch out and wired it direct..


mac

Please remove splinters before emailing

On Thu, 03 Jul 2008 10:52:35 -0700, evodawg wrote:

mac davis wrote:



I should add that this $140 DC has really sucked over the years and I'd
buy another if I was looking for an inexpensive DC.. YMWV

I thought that's what Dust Collectors were suppose to do. Really Suck!!

Yep.. and it's been doing just that...
With the Mickey Mouse setup I have with the trash can collector and hoses
running all over, I'm really surprised that it works as well as it does...

I will add, though, that before I put a muffler on it, it was VERY loud..
Ya get what ya pay for, I guess.. ;-]


mac

Please remove splinters before emailing

On Thu, 03 Jul 2008 23:33:58 GMT, "Lew Hodgett" wrote:


"mac davis" wrote:


Found that the switch was burned up.. was frozen in the ON position,
but had a
semi-melted contact..

The weird thing is that I never USE the switch... The DC is plugged
into a
switched plug and the DC switch has been in the ON position for
years..

With out boring you to death, the solution is simple.

Cut out the defective switch and twist the leads together, then tape.

Best insulation is some shrink tubing and a heat gun after soldering
the leads together.

Have fun.

Lew

Great minds think alike, Lew..
I used wire nuts and tape..


mac

Please remove splinters before emailing