Fire fighting query

[JDgreen227]

Is it really safe to use water to fight fires in buildings that have live electrical wiring without having to concern yourself about a possible shock hazard? Seems to me since water from the hose will conduct electricity, and you are grounded and quite possibly standing on a wet surface....??

Or will water spraying into an outlet or switch simply short it out and trip the breaker, therefore eliminating the hazard? What about water hitting the main service panel?

 

[Gary Fowler]

Pure water is not conductive enough to do any of the things you stated. It does help with grounding if you touch a live wire while standing in it, but you can dump a power cord in a bucket of water and it wont trip a breaker. It may trip a GFI but not a regular breaker. I dont think you have to worry about electricity running back down a hose and shocking you. Try it with a bucket of water and one of your cords if you dont believe me.

In salt water, this is not the case. Even using salt water in your hose wont shock you unless you are within millimeters of the current. Salt will conduct enough current to actually dissolve the copper wire in a cord given enough time. For this reason, never buy any "deal" on a piece of equipment with electrical system that has been in salt water immersion. The electrical grimlins will be with you for as long as you have the equipment since it is almost impossible to get all the salt removed from the nooks and crannies, corrosion will continue till all the copper is gone.

 

[firedog]

There is really not an issue with the use of water and live circuits in a typical building. There are some numbers out there (can't think of them offhand) that give distances for water application vs line voltage (it's close to 20' minimum distance for an 1 1/2" straight stream to a 138K line.)
The typical 120/240 exposure however is of great concern for direct personal contact, where the insulation is damaged or burnt off and the circuit is still live. I'm a lot more concerned about coming in bodily contact with live wiring than i am about any part of the water application.
We had a mobile home fire once where the meter was located on a service pole about 3' from the home. The service wires burnt inside the riser, but since it was improperly grounded the entire frame of the mobile home became electrified.

BUT STILL, we'll kill the power before making entry if it is accessible. Better safe than sorry.

 

[JDgreen227]

Thanks much for the detailed and helpful replies, I have been wondering about the issue for some time...:thumbsup:

 

[ultrarunner]

Don't know if this is too far off topic?

Last year my tenant came home to a garage full of smoke, foul smelling and sizzling.

The hot water supply hose on the washing machine had a pin hole leak that directed water to the 220v dryer receptacle...

This resulted in a charred wall and the cord and outlet were toast with all the insulation burned from the plug end of the dryer cord...

I saw the leak from the hose and it was a true pinhole directed exactly at the outlet.

 

[firedog]

Don't know if this is too far off topic?

Last year my tenant came home to a garage full of smoke, foul smelling and sizzling.

The hot water supply hose on the washing machine had a pin hole leak that directed water to the 220v dryer receptacle...

This resulted in a charred wall and the cord and outlet were toast with all the insulation burned from the plug end of the dryer cord...

I saw the leak from the hose and it was a true pinhole directed exactly at the outlet.

Not off topic to me.
No doubt that a water saturated outlet can short. Considering the inpurities that can be encountered (dust, insulation, construction debris, etc) that will significantly increase the electrical conductivity of the water and create a short condition.
The same thing can and does happen in a fire situation as the OP described with water application. I was speaking more in reference to firefighter safety in my previous post. Much more likey to short a circuit across bare wires or an oulet than conduct electricity back to the firefighter.

 

[tommu56]

The fire fighters nozzles are now a days are fog nozzles if you look at the stream it is droplets in a stream which helps with the conductivity issue.
It is suppose to help prevent electrocution and at out local electric / fire training school they have a demo set up spraying water on a piece of fence charged with 7,000 volts the old straight bore or pipes as they were called would kill a fire fighter but the fog nozzle in the same test not even a tingle.

tom

 

[CompactTractorFan]

Usually this is not a really big concern for firefighters fighting house fires. With that said, if we have a fire at an electric sub station or the like, we won't just go running up with a hose...

 

[firedog]

if we have a fire at an electric sub station or the like, we won't just go running up with a hose...

That's no joke! I saw where a 4160V feeder shorted and blew a hole thru a double wall into the next cube and fried the PT. What a mess!

 

[JDgreen227]

Usually this is not a really big concern for firefighters fighting house fires. With that said, if we have a fire at an electric sub station or the like, we won't just go running up with a hose...

CTF, was wondering if you would chime in on this. I bailed from LMF partly because threads like this one I started here would be wasted over there, doubtful if anyone on that forum would know what I was talking about.

 

[CompactTractorFan]

I bailed from LMF partly because threads like this one I started here would be wasted over there, doubtful if anyone on that forum would know what I was talking about.

What? Did I miss something???

 

[JDgreen227]

What? Did I miss something???

Perhaps you did...but I am THROUGH with LMF.

 

[farmfun]

Perhaps you did...but I am THROUGH with LMF.

What's the LMF - Lemmings Making Futures?:confused2:

 

[CompactTractorFan]

Perhaps you did...but I am THROUGH with LMF.

OK.................................

 

[grsthegreat]

I was talking to a fire chief on a recent inspection of a restaurant i wired, and he told me that the main reason that they shut off the main power is to silence the smoke detectors . He said it drives them nuts.

 

[grsthegreat]

hehe.. i just typed LMF on wiki..... very funny. A hip hop band from hong kong.cant post it here though.... wouldn't pass the censors.

 

[grnspot110]

Been there, done that, makes a purty BLUE flame! Was working a house fire years ago that had the fuel oil tank in the basement (full). I was working through a basement window & hit the fuse/breaker box with a fog stream, exiting, but no shock! After that, pulling the meter was one of my first priorities. Note, pulling the meter does not guaranty dis-connection of power, but usually does in residential construction! ~~ grnspot

 

[schmism]

I cant say for certain what the probability of getting shocked while useing a hose line is.

but i can say for shure that if you do hit live power wires that have had there insulation burnt off of them with a hose stream, they make all sorts of fun noises and colorful lights. IT was at that point that we shut down and pulled the "other" meter on the side of the barn. (cause the first one we pulled i guess only ran the house)

 

[Sackett2]

This thread answered a question that has been bugging me for 12 years.

I was a Facility Manager (FM) at a ICBM Minuteman III Missile site. The job of the FM was every little job needed for daily operation, from Fire Protection, First aid, snow removal lawn mowing etc....
6 months after I had moved on from that job, one of the sites burned down. I knew one of the individuals on the site, I had trained him as a FM but he was now back in the chef career field.

So late in the evening they noticed smoke; and a small room on the corner of the building was on fire; this was the diesel generator room, a generator set up to provide the building with AC power during power loss. About 10' x 20'. After opening up the door and getting blown back by the fire, they closed the door and evacuated the building.

Not 20 feet away was a fire hose with 3500-7000 gallons of water ready. As a FM, a daily job was inspecting the water room and insuring the water availability for emergencies. The Missile crew Locked themselves into their area and waited for 24 hours until the all clear was sounded and came up the ladder to no building.

Also available to the FM was a Case FE loader, and the room next to the generator room could have been separated from the Gen room and the fire couldn't have crawled thru the attic into the rest of the building.

I always wondered why they didn't do anything, and the only thing I came up with was the big power box on the wall. It wouldn't have stopped me; 7000 gallons of water would have been put into that room. Afterwards, someone tried to give the two guys a medal... it was turned down....

 

[ericher69]

Is it really safe to use water to fight fires in buildings that have live electrical wiring without having to concern yourself about a possible shock hazard? Seems to me since water from the hose will conduct electricity, and you are grounded and quite possibly standing on a wet surface....??

Or will water spraying into an outlet or switch simply short it out and trip the breaker, therefore eliminating the hazard? What about water hitting the main service panel?

When making an interior attack on a residential occupancy we use combination fog/straight stream nozzles.

This has many advantages such as;
1. providing fine droplets (fog) for
maximum heat absorption
2. Fine droplets provide less chance of
Electricity being transmitted back to
Firefighter
3. Straight stream for extinguishing the
Seat of the fire (penetration/reach)

In my 13 years of professional firefighting and many fires I have never received a shock (knock on wood) from interior attacks

We do usually shut off main breaker ASAP shut off natural gas ASAP. And back it up with getting hydro to cut power to the building.

We no longer pull meters as some firefighters have been electrocuted doing this! Also if the meter has been bypassed (aka grow-op) pulling the meter will give a false sense of security

Hydro disconnecting power at pole is the only %100 guarantee

Water hitting an outlet will usually NOT trip the breaker unless its a Arc Fault Interrupter (code in Ontario since 2006) for bedrooms

These breakers will trip when any arcing is detected

As for hitting the main panel usually not an issue with cover on and door closed

And as for shutting the power just to shut the smoke alarms off...most in older homes are battery powered and is not a valid reason to cut power

Hope this answers your question