# Whole Shop Kill Switch



## ste6168 (Mar 12, 2015)

Like the kind you would find in a woodshop classroom, specifically in the high school setting, buttons in strategically placed positions around the room to cut power to the machines… Where do you get this kind of system? I am guessing it runs on a relay system of some type? More or less just interested in how it works, what a similar system costs, etc. Not so much interested in installing a system in my garage/hobby/one man shop.

I just did a little searching, and couldn't seem to find anything. Doesn't seem feasible that every high school had this system custom designed?


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## Mahdeew (Jul 24, 2013)

It has to run to the circut breaker. I have been thinking to turn of the circuit breaker to my shop when it is not used. It would be a good idea to have a alternate switch since circuit breakers where not designed for frequent use.


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## ste6168 (Mar 12, 2015)

> It has to run to the circut breaker. I have been thinking to turn of the circuit breaker to my shop when it is not used. It would be a good idea to have a alternate switch since circuit breakers where not designed for frequent use.
> 
> - mahdee


Correct. But certainly you don't just have 40, 60, 100+ amp service running through the safety kill switches? Doesn't seem very feasible, nor safe, to set up the system as such.

When I was teaching, the system in my classroom even had a key lock out, located on the wall behind my desk. If any one of the 6 e-stop buttons where pressed, they would need to be reset and the key would need to be used to "unlock" or turn the power back one. Presumably after I (the teacher) attended to the safety violation (or worse, injury) which required the stop, and then checked each machine to ensure the power switch was off before starting again. This system would work even better, if each machine were equipped with a mag-switch.


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## MrUnix (May 18, 2012)

Google shunt-trip breakers. Another alternative would be to look at the e-stop systems normally used in data centers. Keep in mind, they are not emergency stops, but simply cut power. Some machines will continue to run due to inertia for a bit after power is removed. So while cutting power may be good in a fire or similar type situation, they might not be ideal when someone is getting pulled into a machine (although it would be better than doing nothing at all).

As for the switches… usually they are low voltage NC type push buttons wired in series to a relay or other logic type device, so pushing any one of them will break the connection.

Cheers,
Brad


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## ste6168 (Mar 12, 2015)

> Google shunt-trip breakers. Another alternative would be to look at the e-stop systems normally used in data centers. Keep in mind, they are not emergency stops, but simply cut power. Some machines will continue to run due to inertia for a bit after power is removed. So while cutting power may be good in a fire or similar type situation, they might not be ideal when someone is getting pulled into a machine (although it would be better than doing nothing at all).
> 
> As for the switches… usually they are low voltage NC type push buttons wired in series to a relay or other logic type device, so pushing any one of them will break the connection.
> 
> ...


Right, not exactly "emergency stop" buttons, but they do kill power to the shop. Pushing the button does not cause a "hot dog in blade" reaction at each machine.

I will look into "shunt-trip breakers" - That is a new term to me. As I stated, not really interested in purchasing or installing such system in my shop, but I thoroughly enjoy the process of learning, and understanding how things work.


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## ste6168 (Mar 12, 2015)

> Google shunt-trip breakers. Another alternative would be to look at the e-stop systems normally used in data centers. Keep in mind, they are not emergency stops, but simply cut power. Some machines will continue to run due to inertia for a bit after power is removed. So while cutting power may be good in a fire or similar type situation, they might not be ideal when someone is getting pulled into a machine (although it would be better than doing nothing at all).
> 
> As for the switches… usually they are low voltage NC type push buttons wired in series to a relay or other logic type device, so pushing any one of them will break the connection.
> 
> ...


Right, not exactly "emergency stop" buttons, but they do kill power to the machines. Pushing the button does not cause a "hot dog in blade" reaction at each machine.

I will look into "shunt-trip breakers" - That is a new term to me. As I stated, not really interested in purchasing or installing such system in my shop, but I thoroughly enjoy the process of learning, and understanding how things work.

- ste6168


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## Tennessee (Jul 8, 2011)

When I was an electrician in the Navy I saw a couple of these when I was in repair facilities, especially on shore.
Usually the area would be controlled by a three phase contactor, of the correct amperage. (Some could go into the hundreds of amps)
When an E-stop was hit in any location where one was located, and some were actually remotely controlled, it would kill the coil voltage to the main contactor, and thus kill everything on the circuit. Used them in some fire control safety circuits, and there were some on ships in remote positions, especially on the bridge.

Never could say that I saw one in a factory, or in any kind of manufacturing or craft setting. I can see them being used in schools.


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## MPMaint (Dec 22, 2015)

I installed something like this back yrs ago in a mfg plant I use to work at. The insurance co wanted every machine to shut down in case of a fire. All the machines were hydraulic molding machines so if one sprung a leak and was spraying hydraulic oil onto another machines heaters it would be like a torch.

A heat detector was installed on every machine all in series back to a coil on a relay. Then, 120v power was connected to a NO contact on the relay and fed back to every machine. Every machine had another relay which was fed from the primary relay. Took the wire from the coil on the motor starter and went thru the NO contact. 
One heat detector went off, dropped out the system relay which cut power to all the relays on each machine which cut the power to every motor starter. All motor starters opened up and all motors stopped.


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## hhhopks (Nov 22, 2011)

If such a device is needed in my shop I would have a dedicated subpanel for power feed to the machines. The main breaker would be shunt-trip type or a contactor would be place ahead of the subpanel to shut off power. I definitely don't to my lights to turn off or other critical loads to turn off if the panic switch/e-stop is activated.


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