Must you automatically de-energize electrical equipment in an area containing a fire?

[nukem2k5]

The background of my question is from an offshore industrial (IEC) perspective, but I welcome feedback based on commercial and/or NEC/ANSI/NEMA design.

In order to remove the shock hazard for people present in a space where a fire starts and activates the water-based fire protection (water mist or sprinkler/deluge): is the fire (& gas) system typically designed to automatically trip all breakers which are feeding power to equipment in that space? If so, does that include de-energizing receptacles, light fixtures, etc., which would also pose a hazard (unless they have suitable IP rating to remain energized)?

We're evaluating different types of fire suppression (e.g. watermist, gaseous, etc.) for an emergency switchgear/generator room, as well as proper IP rating of the switchgear. There's a push to go with watermist due to lower cost, but our switchgear Mfr has not tested the equipment (IP42) with mist, only dripping water. Hence, I'm concerned that the mist will maneuver into the gear in a way that could cause unintended components to become energized. I realize this is why we bond/earth, but trying to understand whether this is a credible concern (e.g. if the switchgear is disconnected via the FGS system upon fire detection, the hazard is removed, so IP rating isn't an issue).

 

[iwire]

The only place I run into anything like that is in commercial kitchens. If the exhaust hood fire suppression system activates the power feeding heat producing equipment under that hood must be removed.

 

[nukem2k5]

The only place I run into anything like that is in commercial kitchens. If the exhaust hood fire suppression system activates the power feeding heat producing equipment under that hood must be removed.

Thanks for the feedback. What's the forum rule for re-posting the same question in multiple sub-forums? Best to post a link, or to re-post the same subject/body?

 

[hbiss]

No need to. The same people read all the forums.

-Hal

 

[petersonra]

The background of my question is from an offshore industrial (IEC) perspective, but I welcome feedback based on commercial and/or NEC/ANSI/NEMA design.

In order to remove the shock hazard for people present in a space where a fire starts and activates the water-based fire protection (water mist or sprinkler/deluge): is the fire (& gas) system typically designed to automatically trip all breakers which are feeding power to equipment in that space? If so, does that include de-energizing receptacles, light fixtures, etc., which would also pose a hazard (unless they have suitable IP rating to remain energized)?

We're evaluating different types of fire suppression (e.g. watermist, gaseous, etc.) for an emergency switchgear/generator room, as well as proper IP rating of the switchgear. There's a push to go with watermist due to lower cost, but our switchgear Mfr has not tested the equipment (IP42) with mist, only dripping water. Hence, I'm concerned that the mist will maneuver into the gear in a way that could cause unintended components to become energized. I realize this is why we bond/earth, but trying to understand whether this is a credible concern (e.g. if the switchgear is disconnected via the FGS system upon fire detection, the hazard is removed, so IP rating isn't an issue).

there is no general rule about this. think about all the locations with sprinklers overhead that can open up and there is no power cutoff. The reason you cut off power is where there are special hazards present. One of them that is common is where there are ventilation systems that might fan the flames or actually limit the effectiveness of the extinguishing agent. in those cases it is appropriate to turn off the ventilation.

personally, I would not be real worried about the emergency switchgear getting wet if there is a fire in the room. This room should be essentially fireproof anyway. so if there is a fire in there it is likely because the rest of the building is also on fire and really the best thing you can do is worry about putting out the fire.

 

[Jraef]

there is no general rule about this. think about all the locations with sprinklers overhead that can open up and there is no power cutoff. The reason you cut off power is where there are special hazards present. One of them that is common is where there are ventilation systems that might fan the flames or actually limit the effectiveness of the extinguishing agent. in those cases it is appropriate to turn off the ventilation.

personally, I would not be real worried about the emergency switchgear getting wet if there is a fire in the room. This room should be essentially fireproof anyway. so if there is a fire in there it is likely because the rest of the building is also on fire and really the best thing you can do is worry about putting out the fire.

Yeah, I call that the "least of your worries at that point" factor. I just got into a debate on that recently with regard to sprinklers in an MCC room. Separate room, controlled access by qualified personnel only, two egress points with panic bars etc.. I made the argument that sprinklers were likely MORE dangerous than not having sprinklers and besides, pointless because by the time THAT room caught on fire in a general fire, you were not going to be saving anything or any one. if the fire STARTED in the MCC, sprinklers were pointless too. It would ALREADY be toast.

 

[don_resqcapt19]

Yeah, I call that the "least of your worries at that point" factor. I just got into a debate on that recently with regard to sprinklers in an MCC room. Separate room, controlled access by qualified personnel only, two egress points with panic bars etc.. I made the argument that sprinklers were likely MORE dangerous than not having sprinklers and besides, pointless because by the time THAT room caught on fire in a general fire, you were not going to be saving anything or any one. if the fire STARTED in the MCC, sprinklers were pointless too. It would ALREADY be toast.

The purpose of fire sprinklers in electrical rooms is not to protect the electrical equipment...their purpose is to protect the rest of the building from a fire that originated in the electrical equipment.

 

[nukem2k5]

The reason you cut off power is where there are special hazards present.

[...]

if there is a fire in there it is likely because the rest of the building is also on fire and really the best thing you can do is worry about putting out the fire.

Yeah, in this case, the room comprises a 2.5 MW emergency diesel generator, 24-hr diesel day tank, and the Emergency switchgear (690v)

 

[gadfly56]

The purpose of fire sprinklers in electrical rooms is not to protect the electrical equipment...their purpose is to protect the rest of the building from a fire that originated in the electrical equipment.

That's precisely right. You don't care about water hitting the gear, you want to keep the fire in the room.

 

[gadfly56]

The background of my question is from an offshore industrial (IEC) perspective, but I welcome feedback based on commercial and/or NEC/ANSI/NEMA design.

In order to remove the shock hazard for people present in a space where a fire starts and activates the water-based fire protection (water mist or sprinkler/deluge): is the fire (& gas) system typically designed to automatically trip all breakers which are feeding power to equipment in that space? If so, does that include de-energizing receptacles, light fixtures, etc., which would also pose a hazard (unless they have suitable IP rating to remain energized)?

We're evaluating different types of fire suppression (e.g. watermist, gaseous, etc.) for an emergency switchgear/generator room, as well as proper IP rating of the switchgear. There's a push to go with watermist due to lower cost, but our switchgear Mfr has not tested the equipment (IP42) with mist, only dripping water. Hence, I'm concerned that the mist will maneuver into the gear in a way that could cause unintended components to become energized. I realize this is why we bond/earth, but trying to understand whether this is a credible concern (e.g. if the switchgear is disconnected via the FGS system upon fire detection, the hazard is removed, so IP rating isn't an issue).

The actual quantity of water that will enter the gear is likely very low, even if it's fan ventilated. The operating principal of water-mist systems is to use the fire dynamics to deliver the mist to the fire point. The convection currents created by the fire draw the mist into the fire, thereby cooling the fuel and surrounding area and eventually quenching the fire.