# Shutting Down Main Breaker Panel via Shunt Trip



## Hoons (Feb 6, 2014)

Hello,

Upon duct smoke detection, a main breaker panel is wired to trip which serves other equipments such as split systems, and exhaust fans rather than tripping the individual breaker that serves the HVAC unit. I think this is wrong because NFPA 90A says to shut down the respective unit associated with the duct detector. However, I see no harm in doing it this way. What are some of your thoughts on this?

Hoons


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## Hoons (Feb 6, 2014)

Does it violate any electrical code?


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## Gregg Harris (Feb 6, 2014)

Hoons said:
			
		

> Hello,Upon duct smoke detection, a main breaker panel is wired to trip which serves other equipments such as split systems, and exhaust fans rather than tripping the individual breaker that serves the HVAC unit. I think this is wrong because NFPA 90A says to shut down the respective unit associated with the duct detector. However, I see no harm in doing it this way. What are some of your thoughts on this?
> 
> Hoons


An expensive way to shut units down when the duct detector will do the same thing


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## cda (Feb 6, 2014)

Hoons said:
			
		

> Hello,Upon duct smoke detection, a main breaker panel is wired to trip which serves other equipments such as split systems, and exhaust fans rather than tripping the individual breaker that serves the HVAC unit. I think this is wrong because NFPA 90A says to shut down the respective unit associated with the duct detector. However, I see no harm in doing it this way. What are some of your thoughts on this?
> 
> Hoons


as stated if no violation of electrical code

now some units now adays do not tolerate sudden shutdown, some have to wind down, which is not a code related problem

as long as you meet the intent of the code to shut down the offending unit, you are good. Like said before, I do see some set up to shut all units down off of one duct in one unit going sensing something


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## steveray (Feb 6, 2014)

You would certainly want to make sure you are not shutting down anything that should stay running like the fire alarm or kitchen exhaust hood fans and such, but no electrical code that I can think of....


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## Hoons (Feb 7, 2014)

Upon further consideration with fellow inspectors/engineers, we will not have the contractor re-wire the system. Because it is a relatively small, one level building and smoke can propagate quickly in this configuration. And it seems they are going beyond the code requirement by shutting down all air moving equipments in the area. Also, all the code books I've checked refers to NFPA 72 for wiring but 72 doesn't prescribe any method for shutting down the units. I am assuming the code is silent in this regard so that the designer has some flexibility. In the end, as long as the fans shutdown that's all that matters. Thanks for all the responses, I appreciate it.


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## ICE (Feb 7, 2014)

Well I suppose it wouldn't be a big deal to lose all power during daylight.  It could create a problem at night.

Considering that there is no way to predict the unintended consequences of shutting off all of the power, I would recommend that they wire it correctly.


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