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.