Kitchen hood - shunt trip breakers required.

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anbm

Senior Member
Circuits serving equipments (electric consumed equipment, for example: grill, range, etc) under kitchen hood need to be protected by shunt-trip breakers.

If the above equipments utilize gas instead of electricity and need only 120V circuits for control.
Will these 120V control circuits need to be protected by shunt-trip breakers as well?
 

templdl

Senior Member
Location
Wisconsin
Remember that a breaker equiped with a shunt trip option provides a means to trip the breaker remotely shunting of power to whatever the breaker is supplying.
The shunt trip itself actually does not provide protection then.
That said, what is actuating the shunt trip? You need a contact closure somewhere to provide usually 120v to the shunt trip connection of the breaker. In most cases the shunt trip has a cutoff switch which immediately disconnects the 120v power from the shunt trip after the shunt trip is energized and breaker opens. The remote contact really doesn't have to be a momentary contact then.
What you need to know is the local code requirements which you will have to find out then. You will have to know what event should open the breaker and what items that are powered by the breaker need to be de-energized.
 

normbac

Senior Member
Every job I have done required all electrical under hood to shutdown. Easiest way I have found is to take all circuits to relays and shut them down with ansul system.
 

iwire

Moderator
Staff member
Location
Massachusetts
Every job I have done required all electrical under hood to shutdown. Easiest way I have found is to take all circuits to relays and shut them down with ansul system.

The least costly and least work way is almost always shunt trip breakers.
 

HoosierSparky

Senior Member
Location
Scottsdale AZ
In olden days you would just use an inexpensive relay in a NEMA 1 box connected to a limit switch in the ANSUL system. NOW, per the 2006 IMC 507.2.1.1:

507.2.1.1 Operation.
Type I hood systems shall be designed and installed to automatically activate the exhaust fan whenever cooking operations occur. The activation of the exhaust fan shall occur through an interlock with the cooking appliances, by means of heat sensors or by means of other approved methods.

Most Type 1 hoods now have an ANSUL CONTROL SYSTEM that has the necessary relays built in that will keep the exhaust fan running when the system is activated and turns off the make-up air. The point being to exhaust the smoke and not feed the fire. The system also will include the relay connected to the gas line solenoid that would shut off gas to all appliances and gas lines under the hood. The control panel is usually supplied by the mechanical company installing the hood. The EC would be responsible for all the electrical connections.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
In our jurisdiction, the Fire Marshall only requires circuits that actually power a source of heat to be disconnected on "dry" type systems.
On "wet" system they required all power to be removed. (I don't think they approve "wet" systems, now).
90% of the systems I inspect now have a factory supplied listed control panel that takes care of the exhaust fan start-up.
 

hillbilly1

Senior Member
Location
Atlanta,Ga
Occupation
Field coordinator/ technical support
On the gas ones, I have seen electric gas valves and some mechanical gas valves tied to the fire suppression system.
 

normbac

Senior Member
The least costly and least work way is almost always shunt trip breakers.

I figured the relays to be more cost efective. Example I just wired a job that required five. 208 v circuits and four 120 v circuits to shutdown I brought them all to a j box with relays approx 180.00 for relays and box 2 pole relay 18.00 seemed to be easiest way. i will try shunt next time to compare.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
In olden days you would just use an inexpensive relay in a NEMA 1 box connected to a limit switch in the ANSUL system. NOW, per the 2006 IMC 507.2.1.1:

507.2.1.1 Operation.
Type I hood systems shall be designed and installed to automatically activate the exhaust fan whenever cooking operations occur. The activation of the exhaust fan shall occur through an interlock with the cooking appliances, by means of heat sensors or by means of other approved methods.

Most Type 1 hoods now have an ANSUL CONTROL SYSTEM that has the necessary relays built in that will keep the exhaust fan running when the system is activated and turns off the make-up air. The point being to exhaust the smoke and not feed the fire. The system also will include the relay connected to the gas line solenoid that would shut off gas to all appliances and gas lines under the hood. The control panel is usually supplied by the mechanical company installing the hood. The EC would be responsible for all the electrical connections.

The Ansul system is unlikely to have anything to do with the required automatic activation means. CaptiveAire, which uses Ansul products in their hoods, may have other control means (e.g. heat detector) to start the the exhaust fan, but it is not directly related to the suppression system.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
Circuits serving equipments (electric consumed equipment, for example: grill, range, etc) under kitchen hood need to be protected by shunt-trip breakers.

If the above equipments utilize gas instead of electricity and need only 120V circuits for control.
Will these 120V control circuits need to be protected by shunt-trip breakers as well?

If your jurisdiction uses the IBC or the model Mechanical Code then the answer is "yes".

As a side note, I prefer contactors for reliability.
 

hillbilly1

Senior Member
Location
Atlanta,Ga
Occupation
Field coordinator/ technical support
Both are pretty reliable ways to shut down the equipment, but one the drawbacks of shunt trip breakers is many manufactures take up an extra pole space on smaller sizes which can be a problem on a remodel if the panel does not have enough pole spaces left, or circuiting has to be moved around to accommodate the extra width of the breakers.
 

kwired

Electron manager
Location
NE Nebraska
The least costly and least work way is almost always shunt trip breakers.

I figured the relays to be more cost efective. Example I just wired a job that required five. 208 v circuits and four 120 v circuits to shutdown I brought them all to a j box with relays approx 180.00 for relays and box 2 pole relay 18.00 seemed to be easiest way. i will try shunt next time to compare.

Relays require something to put them in, time to install enclosure, relay(s) and make connections, they also require additional space somewhere to put them.

Shunt trip breakers just bolt or plug in panel (which you were going to do anyway) and then connect leads to shunt trip- often one lead just goes to the neutral bus in the panel where the breaker is located. The fact that the shunt trip makes for an unusable space in the panel is one disadvantage.

A continuously energized contactor is going to have coil failure at some time. If a mechanically held type of relay were to be used it will have a cost. Shunt trip is not immune to failure but the chance of failure is not that great - periodic testing of any method used is probably a good idea.

Just some food for thought.

As a side note, I prefer breakers for reliability.
I second that.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
Relays require something to put them in, time to install enclosure, relay(s) and make connections, they also require additional space somewhere to put them.

Shunt trip breakers just bolt or plug in panel (which you were going to do anyway) and then connect leads to shunt trip- often one lead just goes to the neutral bus in the panel where the breaker is located. The fact that the shunt trip makes for an unusable space in the panel is one disadvantage.

A continuously energized contactor is going to have coil failure at some time. If a mechanically held type of relay were to be used it will have a cost. Shunt trip is not immune to failure but the chance of failure is not that great - periodic testing of any method used is probably a good idea.

Just some food for thought.

I second that.

Your labor to wire from the shunt trip to the suppression system control head is likely to be the same or greater than the labor to install the enclosure and wire up the contactor, based on our experience. You won't save a lot of man-hours, overall.

The cost of the contactor and enclosure is half the cost of a shunt trip breaker, based on our inventory.

When I say "reliable", I mean "shuts down when it has to", not "stays on when you want it". If there is a failure in the leg going from the shunt coil to the control head, you won't know about it until the next inspection or fire, whichever comes first. And before you say how unlikely it is you'll have that fire, the number one cause of claims, in dollar value, for restaurants is fires that start in the range hood.
 

nhfire77

Senior Member
Location
NH
Your labor to wire from the shunt trip to the suppression system control head is likely to be the same or greater than the labor to install the enclosure and wire up the contactor, based on our experience. You won't save a lot of man-hours, overall.

The cost of the contactor and enclosure is half the cost of a shunt trip breaker, based on our inventory.

When I say "reliable", I mean "shuts down when it has to", not "stays on when you want it". If there is a failure in the leg going from the shunt coil to the control head, you won't know about it until the next inspection or fire, whichever comes first. And before you say how unlikely it is you'll have that fire, the number one cause of claims, in dollar value, for restaurants is fires that start in the range hood.

Sounds like an argument for fail safe design. I get it. You want to have safety designed into every step, and remove the human factor that can lead to a system being impaired without supervision.

I guess my propensity for a shunt would be akin to the way elevator shunt trips are set up in fire alarms. The shunt trip control voltage is monitored by a monitor module via a relay powered off that circuit. It goes out, you get a supervisory alarm. That would be a good idea for a hood system. Of course, that adds to costs. The business side of me says the bigger the system, the bigger the profit, plus you get true supervision. With a contactor, there would be no safety reason to monitor it. The customer advocate side of me says, maybe the contactor is cheaper, maybe not.

It can be simpler in terms of materials for some of us. The shunt trip is just another space in the panel as was already pointed out. You will find that most of the system control heads with a shunt trip get fed with MC from the panel, which can be quicker that setting up the contactor and enclosure, because there normally isn't an easy or good spot for it in a crowded electrical space in a crowded restaurant. (not always of course, i would advocate for more space) If its mounted at eye level and you can't nipple off the panel, you will probably put in pipe. A shunt trip is the predominant set up you find around here, maybe I'm biased. I'm not arguing against the contactor, just for the shunt breaker.
 

normbac

Senior Member
I also make sure the cook can not shut off the exhaust after pulling ansul
single MUA large enough to handle two exhaust hoods
 

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hillbilly1

Senior Member
Location
Atlanta,Ga
Occupation
Field coordinator/ technical support
I also make sure the cook can not shut off the exhaust after pulling ansul
single MUA large enough to handle two exhaust hoods

The problem with the diagram is most fire suppression systems have only two micro switches on the head, one set is almost always used by the fire alarm system, and the other set is for the shut down. You are showing three micro switches in the diagram. ;)
 

kwired

Electron manager
Location
NE Nebraska
The problem with the diagram is most fire suppression systems have only two micro switches on the head, one set is almost always used by the fire alarm system, and the other set is for the shut down. You are showing three micro switches in the diagram. ;)
Additional relay(s) can make up for that.
 
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