Hi all, we've some single phase fans that need to deenergize in some emergency conditions. Is practical to use Emergency Power Off button like regular switch without any relay or contactor to disconnect the fan? If possible under what conditions?Thanks for any advice and help
Use EPO button like a regular switch
- Thread starter marcosgue
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What is the environment and where are those fans installed or part of it (Air handling units, kitchen hood, or a unique set up etc.)? Also the size of the fans, what is the HP?
Usually, emergency conditions require automatic/semi-auto shut off and must meet certain requirements. Utilizing a "push button" is no different than a "stop" button which does not fall under emergency shut off and it is a manual control.
E-stop push button is a locking type and a little different, still needs to be part of an E-stop circuit and controls.
Would you please provide more information? Thank you.
Usually, emergency conditions require automatic/semi-auto shut off and must meet certain requirements. Utilizing a "push button" is no different than a "stop" button which does not fall under emergency shut off and it is a manual control.
E-stop push button is a locking type and a little different, still needs to be part of an E-stop circuit and controls.
Would you please provide more information? Thank you.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Yes, you can use mushroom head buttons any place you want. They can be momentary or locking type. The NEC does not address the color choice of these buttons.
The use of safety relays is an independent issue and is normally covered by OSHA or other safety standards such as NFPA79.
The use of safety relays is an independent issue and is normally covered by OSHA or other safety standards such as NFPA79.
hillbilly1
Senior Member
- Location
- North Georgia mountains
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- Owner/electrical contractor
Usually EStop button contacts are not rated for a lot of amps, not sure they are even HP rated. Probably only good for a fractional HP motor. Twist lock or maintained position.
This are fans installed in AC duct system as a part of AHU in science classroom that in case of emergency they've to operate and the receptacles circuits have to shutdown so the epo button will've NO and NC contacts. The receptacles circuits are part of contactors panel located in Electrical room but not the fans which they want to add NO contacts in the mushroom EPO button to operate theses fans
The fans are rated 1hp-1.5hp, 120V
The fans are rated 1hp-1.5hp, 120V
hillbilly1
Senior Member
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- North Georgia mountains
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- Owner/electrical contractor
Bite the bullet and put in a contactor or RIB relay controlled by the E-Stop. The standard contact rating is 10 amps, and not hp rated. Does the E-Stop enclosure even have enough room for all those wires?
Thank you for the additional information. Because of its criticality, I would take NFPA 72 Chapter 21, NFPA 90A, 92 and 101 into consideration. It makes a difference whether this is a stand-alone system, part of a supervisory system, AHU with smoke detectors etc. because I would question whether this should be an automatic shut off etc. It is important to understand the requirements
As it is mentioned, I have used RIB relays which are controlled by duct smoke detectors "dry contacts" as part of the emergency stop circuit. Turning off the control signal to motor's VFD, magnetic starter etc.
For example: 6.4.3.1 Smoke detectors provided as required by 6.4.2 shall automatically stop their respective
fan(s) on detecting the presence of smoke.
"Where duct smoke detectors are installed to shut down associated HVAC air-handling units and
the building does not contain a fire alarm and signaling system, 6.4.4.3 of NFPA 90A requires that duct
smoke detector activation cause a visual signal and an audible signal in a normally occupied area, and
that duct smoke detector trouble conditions be indicated visually or audibly in a normally occupied
area and identified as air duct detector trouble."
If you are not using smoke detectors and the manual control to shut down the fans is "approved" by authorities, I would go with what @hillbilly1 suggested.
gadfly56
Senior Member
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- New Jersey
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- Professional Engineer, Fire & Life Safety
As I read it, this "EPO" is actually turning ON the power to the fans to keep them running. It all sounds very jury-rigged.
@gadfly56, based on your professional title and experience, you know how it should be done. Since there is a concern with the liability of the overall system, what could go wrong etc., I would personally make sure that it is implemented correctly and make it an automatically shut down design of the fans. I don't rely or trust people shutting the fans off especially during the emergency situations. Everyone will run outside during the fire/ evacuation.
I understand that there is always a concern with how much things cost, labor, feasibility, however, safety comes first.
"Just because it works, it does not mean that it is right" phrase come to mind.
gadfly56
Senior Member
- Location
- New Jersey
- Occupation
- Professional Engineer, Fire & Life Safety
If you think I approve of this design, I'm not sure how you got that impression. I was simply commenting that you appeared to have misinterpreted the intent of the button. It sounds like it is shunting the emergency power from the "orange" outlets to the (exhaust?) fans for the room, although it seems that posts #1 and #5 contradict each other.
No, it is opposite; I was agreeing with your assessment of "It all sounds very jury-rigged". Also, since you are a PE, in Life and Safety field, I was actually trying to compliment you. I guess it back-fired on me
If I totally misunderstood the post, it is my bad. I have answered it based on how I understood it. Have a good evening Jersey guy. I left NJ back in 2006. I still have relatives and friends there and visit NJ frequently .
gadfly56
Senior Member
- Location
- New Jersey
- Occupation
- Professional Engineer, Fire & Life Safety
Is this smoke control automatic, or does it depend on someone hitting that button?
gadfly56
Senior Member
- Location
- New Jersey
- Occupation
- Professional Engineer, Fire & Life Safety
Sorry for misunderstanding your post.No, it is opposite; I was agreeing with your assessment of "It all sounds very jury-rigged". Also, since you are a PE, in Life and Safety field, I was actually trying to compliment you. I guess it back-fired on me
If I totally misunderstood the post, it is my bad. I have answered it based on how I understood it. Have a good evening Jersey guy. I left NJ back in 2006. I still have relatives and friends there and visit NJ frequently .
No problem at all. It is sometimes hard to understand and describe things based on how and what is written. We are doing our bestSorry for misunderstanding your post.
Have a great day sir.
gadfly56
Senior Member
- Location
- New Jersey
- Occupation
- Professional Engineer, Fire & Life Safety
If it is anticipated that there could be a smoke condition in an occupiable space that is more than might be considered normal (a trash can fire in an office is normal, a 5-foot stack of pallets in the same office catching fire is not) then smoke control should be automatic, not dependent on the clear-headed actions of those occupying the space. That's a whole 'nother level of fire alarm system design.
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