DC switch burned out

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

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

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.

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

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

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

mac

Please remove splinters before emailing

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

mac

Please remove splinters before emailing

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

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

mac

Please remove splinters before emailing