Kitchen Hood & FA Contacts

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Alwayslearningelec

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NJ
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Estimator
Have a kitchen hood master PLC and they are showing 2- 24v wires to normally open contacts of fore alarm system.
Where would that tie in happen? Where would there be NO contacts in a fire alarm system? The FACP? Thanks.
 

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hillbilly1 said:
Can be an addressable relay, or an actual set of contacts at the FACP, but most likely they will set a supervised relay set near the hood.
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All the players for kitchen suppression systems have micro switches in their control heads that will change state when the head activates.
 
gadfly56 said:
All the players for kitchen suppression systems have micro switches in their control heads that will change state when the head activates.
Click to expand...
I think the op is talking about an input from the fire alarm system, that the hood controller PLC sees and takes action, such as shutting down the make up air and turning on the exhaust for smoke removal. Sounds like one of those fancy self contained systems that the fire suppression is built in.
 
hillbilly1 said:
I think the op is talking about an input from the fire alarm system, that the hood controller PLC sees and takes action, such as shutting down the make up air and turning on the exhaust for smoke removal. Sounds like one of those fancy self contained systems that the fire suppression is built in.
Click to expand...
Correct.
 
hillbilly1 said:
I think the op is talking about an input from the fire alarm system, that the hood controller PLC sees and takes action, such as shutting down the make up air and turning on the exhaust for smoke removal. Sounds like one of those fancy self contained systems that the fire suppression is built in.
Click to expand...
The next hood controller I see for kitchen hood suppression that's PLC based will be my first one. There is no reason for a fire alarm system to be activating a suppression system (see exception below). The vast majority of kitchen hoods out there have mechanically activated suppression systems. There is a pull station attached to a cable that runs back to the control head and there are fusible links above the appliances and in the exhaust plenum that are in a tensioned cable. If a link in the cable goes slack or the pull station cable is yanked the system is activated. The system flips the state of the micro switches via a rotating cam. You can use a fire alarm control panel that's linked to heat detectors such as the Fenwal Detect-A-Fire, but that's a pretty uneconomic choice since you still need the suppression system control head. The micro switches are all rated for 20 amps at 250 volts, so you could directly control the makeup air and lights depending on the load, otherwise use contactors.
 
gadfly56 said:
The next hood controller I see for kitchen hood suppression that's PLC based will be my first one. There is no reason for a fire alarm system to be activating a suppression system (see exception below). The vast majority of kitchen hoods out there have mechanically activated suppression systems. There is a pull station attached to a cable that runs back to the control head and there are fusible links above the appliances and in the exhaust plenum that are in a tensioned cable. If a link in the cable goes slack or the pull station cable is yanked the system is activated. The system flips the state of the micro switches via a rotating cam. You can use a fire alarm control panel that's linked to heat detectors such as the Fenwal Detect-A-Fire, but that's a pretty uneconomic choice since you still need the suppression system control head. The micro switches are all rated for 20 amps at 250 volts, so you could directly control the makeup air and lights depending on the load, otherwise use contactors.
Click to expand...
It doesn’t activate the fire suppression system, it only controls the fans. The fire suppression is built into the hood, (canisters and all), and works separately from electrical. The controls are tied into the micro switches on the activation head. I’ve seen them in Publix, and Longhorn Steakhouses.
 
gadfly56 said:
The next hood controller I see for kitchen hood suppression that's PLC based will be my first one. There is no reason for a fire alarm system to be activating a suppression system (see exception below). The vast majority of kitchen hoods out there have mechanically activated suppression systems. There is a pull station attached to a cable that runs back to the control head and there are fusible links above the appliances and in the exhaust plenum that are in a tensioned cable. If a link in the cable goes slack or the pull station cable is yanked the system is activated. The system flips the state of the micro switches via a rotating cam. You can use a fire alarm control panel that's linked to heat detectors such as the Fenwal Detect-A-Fire, but that's a pretty uneconomic choice since you still need the suppression system control head. The micro switches are all rated for 20 amps at 250 volts, so you could directly control the makeup air and lights depending on the load, otherwise use contactors.
Click to expand...

The last few hoods I’ve seen no longer have micro switches or pull handles

They’re using PLC’s now and push-button controls for manual activation.

Also instead of fusible links they are using thermocouples connected to the plc to trigger the suppression, or to just keep the fan running.

Sent from my iPhone using Tapatalk
 
hillbilly1 said:
I think the op is talking about an input from the fire alarm system, that the hood controller PLC sees and takes action, such as shutting down the make up air and turning on the exhaust for smoke removal. Sounds like one of those fancy self contained systems that the fire suppression is built in.
Click to expand...
Makes sense to shut down both exhaust and make up air. Why feed more air to any potential fire that wasn't detected under the hood?

If detected under hood you leave the exhaust running, but are presuming the suppression system has quenched the fire or even possibly grease in the hood might still be on fire and by running exhaust you are likely to keep it contained in the hood.

Input to fire alarm system from the suppression system - doesn't seem too logical to do that. There should at very least be heat detectors in the kitchen if a problem should spread beyond the hood area that can trigger the fire alarm.
 
kwired said:
Makes sense to shut down both exhaust and make up air. Why feed more air to any potential fire that wasn't detected under the hood?

If detected under hood you leave the exhaust running, but are presuming the suppression system has quenched the fire or even possibly grease in the hood might still be on fire and by running exhaust you are likely to keep it contained in the hood.

Input to fire alarm system from the suppression system - doesn't seem too logical to do that. There should at very least be heat detectors in the kitchen if a problem should spread beyond the hood area that can trigger the fire alarm.
Click to expand...

When you connect it to the FACP, it will trigger a sequence the same as if a fire was detected within the hood. The fan will turn on, MUA off, and the appliances will turn off.
 
brantmacga said:
When you connect it to the FACP, it will trigger a sequence the same as if a fire was detected within the hood. The fan will turn on, MUA off, and the appliances will turn off.
Click to expand...
That I understand, but do you want it to trigger a general fire alarm as well?

Say this is in a hospital or nursing home kitchen - do you want it to make them evacuate all the patients for something that is likely under control? If it is not under control it still will end up setting off the FA via the heat detectors in the kitchen.
 
kwired said:
That I understand, but do you want it to trigger a general fire alarm as well?

Say this is in a hospital or nursing home kitchen - do you want it to make them evacuate all the patients for something that is likely under control? If it is not under control it still will end up setting off the FA via the heat detectors in the kitchen.
Click to expand...

My experience is in restaurants and daycares only, and it would trigger the entire FA system. I don't know how this would be configured in an institutional setting; I wonder if they can alert a localized zone and not the entire facility?

edit to say.... I think though when you connect to the N.O. contacts on the FACP, that is to trigger a shutdown of appliances at the hood. I think.... I will have to ask around about that. Our work ends at the hood, and I'm not the one usually on-site when the FA testing takes place. Whoever is job foreman handles that.
 
brantmacga said:
My experience is in restaurants and daycares only, and it would trigger the entire FA system. I don't know how this would be configured in an institutional setting; I wonder if they can alert a localized zone and not the entire facility?

edit to say.... I think though when you connect to the N.O. contacts on the FACP, that is to trigger a shutdown of appliances at the hood. I think.... I will have to ask around about that. Our work ends at the hood, and I'm not the one usually on-site when the FA testing takes place. Whoever is job foreman handles that.
Click to expand...
Makes sense to shut down appliances if there is fire alarm. In many ways no different than shutting down HVAC systems and closing dampers in ducts or dropping holding circuits for fire doors/partitions when there is a fire alarm.
 
brantmacga said:
The last few hoods I’ve seen no longer have micro switches or pull handles

They’re using PLC’s now and push-button controls for manual activation.

Also instead of fusible links they are using thermocouples connected to the plc to trigger the suppression, or to just keep the fan running.

Sent from my iPhone using Tapatalk
Click to expand...
Do you have links or model/brand names?
 
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