Does anyone need a high voltage switch

[bschwartz]

http://www.wimp.com/switchopening/

[WStayton]

Hi!

  No, but I do need a couple of 240 volt switches capable of handling 24 kW - one in three phase (hmm, better make that one 36 kw! <grin>)  and one in two-phase.

  The three phase is to completly unhook everything, including the neutral,  from the net, when I don't need it, and the two phase is to completely unhook everything from the generator for shut-down/start-up.

  If anybody sees such animals, for a "good" price, (remember, I'm cheap! <grin>), please, please, scream!

Regardz,

Wayne Stayton

[BioHazard]

No, but I do need a couple of 240 volt switches capable of handling 24 kW - one in three phase (hmm, better make that one 36 kw! <grin>)  and one in two-phase.

Square D makes high amp circuit shutoffs that look just like their normal circuit breakers but they don't actually have a breaker inside.

Otherwise just use a normal circuit breaker? Or an A/C disconnect?

[WStayton]

BioHazard

  I've personally avoided using circuit breakers as switches because I had a couple of very experienced electricians both tell me that switching circuit breakers off and on, especally under load, degrades the trip point, so that eventually, they start tripping at significantly lower current than their rating.  This WAS some years back, so I don't know if this was something that was previously true, or if it still is, but I have avoided using circuit breakers for switches for that reason.

  What I really would like (but I'm not sure I can afford!) is a couple of knife switches designed for circuit disconnects - one three pole and one two pole.  I THINK that an AC disconnect fits this category but any that I have seen in the capacity that I require are VERY dear - and, being cheap, I was/am hoping to do better, cost wise!  <grin>

  24 kW is 100 amps per contact, and 36 kW three phase is again 100 amps per contact - and it seems that ANYTHING rated for 100 amps per leg is strictly industrial and pricey, hence I continuing to turn over rocks, hoping something good will crawl out!  <smile>

Regardz,

Wayne Stayton

[Lloyd]

BioHazard

  I've personally avoided using circuit breakers as switches because I had a couple of very experienced electricians both tell me that switching circuit breakers off and on, especally under load, degrades the trip point, so that eventually, they start tripping at significantly lower current than their rating.  This WAS some years back, so I don't know if this was something that was previously true, or if it still is, but I have avoided using circuit breakers for switches for that reason.

 Wayne Stayton

Wayne,

Look at marine rated circuit breakers, they are by design switching-circuit breakers, made by Air-Pax, Carling, and a couple others BlueSeas sells their label, but they are made by one of the above. They come in AC, or DC variety.

Most breakers that you buy at Home Crapo for Sq-d and the various home supply manu...'s are not switching CB's

Lloyd

[BioHazard]

Whether designed for it or not, I hit the (Cuttler Hammer) breaker to my water heater at the shop every day. That's about 700 switches so far in the last 2 years. And it's about 15 years old. Still works just fine. Maybe it will only last 10,000 cycles instead of 1,000,000, but really, how many times do you need to use the switch?

I *THINK* the "QO" circuit breakers by Square D are fine for switching, as this is the same type of breaker they make DISCONNECT SWITCHES out of. There's just no breaker. The shell and the switch mechanism they make them out of are physically the same.

But hell if it was me, I'd probably make my own big-ass knife switches.  To hell with OSHA! 

[Lloyd]

Whether designed for it or not, I hit the (Cuttler Hammer) breaker to my water heater at the shop every day. That's about 700 switches so far in the last 2 years. And it's about 15 years old. Still works just fine. Maybe it will only last 10,000 cycles instead of 1,000,000, but really, how many times do you need to use the switch?

I *THINK* the "QO" circuit breakers by Square D are fine for switching, as this is the same type of breaker they make DISCONNECT SWITCHES out of. There's just no breaker. The shell and the switch mechanism they make them out of are physically the same.

But hell if it was me, I'd probably make my own big-ass knife switches.  To hell with OSHA! 

Bio...

have you ever considered make bf break, or break  bf make, then there is is always "Hydraulic/Magnetic CBs", Thermal CB's , Equipment Leakage CB's...plus a mired of other  technologies.

Sure you can wing it and hope that no failure happens.   BuTTTTTTTTTTTTTTT, I can tell you this story that happened across the dock today...an engine room fire as a result of an improper breaker, it could have burnt down the whole marina.

Now you may say that's what insurance is for...but in today's world, that is a big risk... you say no worries it's their loss...well guess what you just burnt down your neighbor...and all their belongings.

HOW WOULD YOU LIKE A NEIGHBOR LIKE THAT???

dude.

lloyd

[BioHazard]

Lloyd, I do not think I am suggesting anything unsafe and would not do so. The worst that is going to happen if you use a breaker for a switch is that it's going to end up tripping more often than it should. It is very, very, very common for breakers to be used as switches. I've never actually seen anything happen as a result of that. They are designed to break into the "safe" mode.

As to whether it's break-before-make, or make-before-break, or take-a-beer-break that's for WStayton to decide what is needed.

Think of it like pulling a plug from an outlet while it is drawing power. You are not supposed to do that. Most appliance manuals tell you not to. You'll usually see a big blue spark, and if you do it enough, it will wear away the blades on the plug and your wall socket. Then again, we've all probably done it hundreds of times and lived. The only "bad" thing that happens is your plug/socket wears out, not your house burns down.

[Lloyd]

Lloyd, I do not think I am suggesting anything unsafe and would not do so. The worst that is going to happen if you use a breaker for a switch is that it's going to end up tripping more often than it should. It is very, very, very common for breakers to be used as switches. I've never actually seen anything happen as a result of that. They are designed to break into the "safe" mode.

As to whether it's brake-before-make, or make-before-brake, or take-a-beer-break that's for WStayton to decide what is needed.

Think of it like pulling a plug from an outlet while it is drawing power. You are not supposed to do that. Most appliance manuals tell you not to. You'll usually see a big blue spark, and if you do it enough, it will wear away the blades on the plug and your wall socket. Then again, we've all probably done it hundreds of times and lived. The only "bad" thing that happens is your plug/socket wears out, not your house burns down.

Bio,

Don't take this personally...but you are the last person that should give advise in re electricity on a public forum....just look at you last 663 post....

BC someone may take to heart what you say.

dude.

lloyd

[BioHazard]

Bio,

Don't take this personally...but you are the last person that should give advise in re electricity on a public forum....just look at you last 663 post....

Well, I could say the same about you, but I won't.  Just because I might ask a funny question here means nothing, that is NOTHING, to do with what I know about electricity. You haven't got a clue what I know. I'll have you know I am quite experienced with electricity. No, I'm not an electrician, I never claimed to be. And no, I am not, nor have I ever, given advice to somebody that is dangerous.

[Lloyd]

 >:(hehehehe

lloyd

this could happen to some unsuspecting person http://www.wimp.com/switchopening/  then what would yor advice be??

[BioHazard]

WStayton - for some usefull advice besides "don't do that!"....

You might try a couple of these:
http://www.surpluscenter.com/item.asp?item=11-2485&catname=electric

Probably your cheapest solution. Pull the fuse, circuit is dead. No questioning it. Keep some spare fuses.

[BioHazard]

>:(hehehehe

lloyd

this could happen to some unsuspecting person http://www.wimp.com/switchopening/  then what would yor advice be??

Tell me how that could happen without a 500kv power supply?  

You need to read your own signature, Lloyd.

[Lloyd]

Switching unrated CB' on and of during a load causes an arcing, arcing causes burned contacts or welded contacts. Welded contacts can result in the CB not opening.

I have seen light bulbs that shorted the tungsten filament, which caused a continued short circuit...lacking a functioning cb/fuse...heat develops...and then fire.

lloyd

[BioHazard]

Well, in that case we should all remove the circuit breakers from our homes to be safe. 

Are you *actually* an electrician, Lloyd? I know you work on boat electronics but that requires no liscense.....

As for me, I own a factory that makes and sells electrical products, mostly various types of cord sets. What do you think I do at the "shop" I'm always talking about? Yes, I invented those products, and got them UL approved too. You can find them in a Northern Tool catalog, among other places.