Lab Bench: Gas/Electric Shutoff Switch

[Keri_WW]

I have a requirement for an owner to shutoff the gas and electricity to a lab bench via a mushroom button. There are four circuits feeding the receptacles at the lab bench. How do you design a system that can shut off all of these circuits and the main gas coming into the bench?

Thanks,
Keri :grin::grin:

 

[Buck Parrish]

Would a shunt trip breaker feeding a 4 circuit relay work for the outlets? This could also feed a LV relay that closes a valve on the gas.

 

[USMC1302]

What I'm familiar with is the panels used have a contactor built-in and the upper section panel spaces are off the contactor. Each classroom has a mushroom button or a push-button with a key operated reset. The gas and in our case water also, use a solenoid valve on the branch piping feeding the room. Works great. Otherwise, a multi-pole contactor and some solenoid valves should do the same thing?

steve

 

[kwired]

What I'm familiar with is the panels used have a contactor built-in and the upper section panel spaces are off the contactor. Each classroom has a mushroom button or a push-button with a key operated reset. The gas and in our case water also, use a solenoid valve on the branch piping feeding the room. Works great. Otherwise, a multi-pole contactor and some solenoid valves should do the same thing?

steve

Arent you describing basically the same thing in both scenarios?

 

[USMC1302]

Yeah, same thing. But, if you starting from scratch, you might want to consider the panel route if it is cheaper.

 

[Keri_WW]

Thanks guys.

Buck,
Why would I need to use a shunt trip breaker? Is that for a possible shut-off due to the fire alarm going off?

 

[LarryFine]

Keri, the receptacles can be controlled by something as simple as a 4-pole contactor, or four poles' worth of the aforementioned shunt-trip breakers.

A shunt-trip breaker is merely one that can be tripped remotely by feeding its coil wire with power momentarily.

If the gas valve is an electric one, that's as easy to control as a contactor. They may or may not want a gas-valve reset-box like we use in kitchens.

 

[hurk27]

Ones I have done in the past, was nothing but a simple start stop circuit controlling a small contactor with as many poles as circuits it controls, the start switch is a keyed momentary N/O contact, with a red mushroom stop button, the gas valve is a N/C gas valve meaning it has to have power to be open, we just powered the gas valve off one of the contacts.

 

[kwired]

If you have several circuits you need to shut off use a shunt trip as a feeder breaker to the panel supplying everything that needs shut off, fire alarm could easily operate the shunt trip if needed also. Shunt trip probably cost at least the same or even less than a 4 pole contactor and a magnetic contactor is something that will eventually get noisy as it gets older and will likely have coil failure at some time also because it will usually be energized 24/7.

 

[George Stolz]

...the start switch is a keyed momentary N/O contact...

I like this - No need to go find the panel(s) after an event, just start it back up.

 

[hurk27]

I like this - No need to go find the panel(s) after an event, just start it back up.

The reason the above circuit was chosen, was because if a power event was to happen, the gas would shut off, and would not come back on until the key switch was used, I would label the key switch as a "off/reset"

That was the main reason behind it, the convenience is just a plus:grin:

also we retro fitted these lab classrooms for very little money, placing the contactor in a small cabinet close to the panel feeding the receipts and using 24 volts class 2 for the control circuit, and a 24 volt gas valve which we had the plumbers install in a convenient location, and 4 mushroom stop switches, one on each wall in the room, and one key switch by the door that would also act as a shut off when turned the other way, so the teacher could shut off the system as he/she was leaving the room.

 

[cbishop7]

Been awhile on this post, but I am trying to find out the code requirements for a similar situation.

Is it just the lab bench power/receps that need to be tied into the shut off or would it be all the general power/receps in that laboratory/classroom?

 

[stevebea]

Ones I have done in the past, was nothing but a simple start stop circuit controlling a small contactor with as many poles as circuits it controls, the start switch is a keyed momentary N/O contact, with a red mushroom stop button, the gas valve is a N/C gas valve meaning it has to have power to be open, we just powered the gas valve off one of the contacts.

I used this setup in the past in a science classroom with a Square D lighting contactor because of the number of circuits. Also had an E-Stop at all three exits with a key reset and N/C gas solenoids like you described.