Remotely-triggerable 3 phase power switch - Electrician Talk - Professional Electrical Contractors Forum
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Old 10-09-2019, 04:58 PM   #1
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Default Remotely-triggerable 3 phase power switch

Hi,

I am looking for a way to cut power to an instrument operating on 208V 3phase <=24 Amps.

I was going to use a watchdog relay to trigger a switch, but I am not finding a UL certified switch available. Does anyone know of such a device?
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Old 10-09-2019, 05:58 PM   #2
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If by 'switch' you mean 'relay', there are tons of them that are UL listed and will handle a 208 3Ø 24 amp load.

Just about any motor starter comes to mind but there are others as well.
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Old 10-09-2019, 06:11 PM   #3
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That watchdog relay is a specialized thing, do you have a means of generating the pulse it looks for?
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Old 10-09-2019, 06:11 PM   #4
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Are you wanting to trip it on an over current? Or am I reading this wrong? As @micromind said, a NEMA 1 starter of your brand choice is ready and willing to take on the task. If silent operation is required, DC coils are available.
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Old 10-09-2019, 07:53 PM   #5
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Shunt trip breaker?
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Old 10-09-2019, 08:12 PM   #6
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Three phase disconnect. Hire a guy to stand beside it with a pager. Every time you want the disconnect activated (either on or off), page him, and he flips the switch on the disconnect.

This is by far the easiest way to go.

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Old 10-09-2019, 08:21 PM   #7
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Quote:
Originally Posted by dangordon View Post
Hi,

I am looking for a way to cut power to an instrument operating on 208V 3phase <=24 Amps.

I was going to use a watchdog relay to trigger a switch, but I am not finding a UL certified switch available. Does anyone know of such a device?
First time i read that im trying to picture a pressure sensor or flow meter hooked to 208.

Then he mentioned watchdog which a plc term for checking if a processor has frozen which it probably would if you put 208 to a analog card so im just posting to get my post count higher so i can donate it to what ever that thing is they do once a year.

Guessing i would say this is a e-stop question using all the wrong words.
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Old 10-09-2019, 08:30 PM   #8
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Quote:
Originally Posted by gpop View Post
First time i read that im trying to picture a pressure sensor or flow meter hooked to 208.

Then he mentioned watchdog which a plc term for checking if a processor has frozen which it probably would if you put 208 to a analog card so im just posting to get my post count higher so i can donate it to what ever that thing is they do once a year.

Guessing i would say this is a e-stop question using all the wrong words.
Seems to me that watchdog was a term that Westinghouse or GE used for the Klixon imbedded in the windings in motors and xformers to signal an over temp situation. Maybe this is what he’s speaking of.
And + two points. But I’m keeping mine!
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Old 10-09-2019, 09:10 PM   #9
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Quote:
Originally Posted by 460 Delta View Post
Seems to me that watchdog was a term that Westinghouse or GE used for the Klixon imbedded in the windings in motors and xformers to signal an over temp situation. Maybe this is what he’s speaking of.
And + two points. But I’m keeping mine!
I had to google Klixon. I learnt a cool sounding new word today so that's worth 2 points. Ive always referred to them as thermal switch's.
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Old 10-09-2019, 09:32 PM   #10
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I've known them as Klixons for 45 years.......
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Old 10-09-2019, 09:50 PM   #11
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Red Lion makes a watchdog relay, which looks for a heartbeat pulse from the PLC. A high or low signal may continue if the PLC hangs, but a flip flop / heartbeat means the program must still be running.

https://www.redlion.net/sites/defaul...ta%20Sheet.pdf
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Old 10-09-2019, 10:57 PM   #12
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Quote:
Originally Posted by Kevin_Essiambre View Post
Three phase disconnect. Hire a guy to stand beside it with a pager. Every time you want the disconnect activated (either on or off), page him, and he flips the switch on the disconnect.

This is by far the easiest way to go.

P.S., please fill out your profile.

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Old 10-10-2019, 05:04 AM   #13
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Quote:
Originally Posted by micromind View Post
I've known them as Klixons for 45 years.......
Yeah but we are like old and stuff so.......
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Old 10-10-2019, 06:25 AM   #14
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Isn’t it just a timer delay relay with normally closed contacts? I know AB has a universal one and I’m sure Macromatic does too.

The Klixon brand covers a huge variety of let’s just say motor accessories. Thermistors, thermal switches, centrifugal switches. Mostly stuff the motor shop epoxies or bolts inside then runs extra wires out to the peckerhead. It’s all chintzy looking but for whatever reason holds up, except RTDs. Why anyone builds anything to protect something that isn’t far more reliable than the thing it protects is beyond me. Motor RTD designers should be ashamed of themselves. Their solution is that they’re cheap so buy lots and buy an RTD reader with a dozen inputs so you can trip by majority voting logic. Oh that makes sense. Kind of like let’s install 6 breakers for one circuit because well you know, one or two will go bad.


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Old 10-10-2019, 09:11 PM   #15
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Square D used to make a load shedding system called a "Watchdog"...


I think until the OP checks back in and defines what he/she meant by "watchdog relay", we can go on guessing for days, maybe weeks.
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