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Joined: Dec 2000
Posts: 4,294
This install made me wonder....Do we really want it to be possible for a sprinkler head to spray directly into the open sides of bus-duct?


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Joined: May 2003
Posts: 2,876
e57 Offline
Emormous shunt trip CB connected to flow switch?

Mark Heller
"Well - I oughta....." -Jackie Gleason
Joined: Jan 2005
Posts: 5,460
Likes: 3
Cat Servant
The disconnects serve assortes electrical panels located directly underneath. This is actually the main service for an older shopping center

As a side note, this place has been remodeled and expanded so many times that the panel directories contain numerous "identifications" as "Unknown" and "if anyone knows what this is for, please let maintenance know."

Joined: Apr 2004
Posts: 156
I would have thought that Halon or CO2 would have been required there.

Personally I would have set aside some maintenance time so that the buss could be deenergized and that sprinkler head capped.

Scenario: Electrical fire in the fry-daddy aisle, sprinklers go off.

Supervisor; "Johnny go turn off the electrical power, it's by the wall over there."

Now there are two fry-daddy aisles with electrical fires in them.

Joined: Mar 2004
Posts: 391
What's the average activation temperature of these sprinkler heads? I was under the impression that the fusible link/glass bulb in most heads wouldn't fail unless the fire was just about directly under them. That is, they needed a whole lot of heat. If it gets to that point, isn't that bus duct already gonna be compromised?


Joined: Mar 2005
Posts: 12
I have seen a glass-bulb type trigger point as low as 155 F.

Joined: Jul 2003
Posts: 394
Ceiling temperatures skyrocket rapidly in the event of a fire. I've seen demonstrations where they were over several hundred degrees in minutes. Unless there was a large amount of ventilation in that room, the sprinkler would soon go off in the event of any real fire.

Joined: Oct 2004
Posts: 265
Don't know about old buildings, but the ones we do with backflows and PIVs are designed so that when the fire department shows up they select the building on fire and pressurize it up to 200 PSI. This results in all the sprinkler heads in the building going off. They might get a nice secondary explosion here =\

Though they are supposed to turn off the main when they show up, just don’t know if they do it before or after they set off the whole sprinkler system.

Joined: Jan 2003
Posts: 4,391
but the ones we do with backflows and PIVs are designed so that when the fire department shows up they select the building on fire and pressurize it up to 200 PSI. This results in all the sprinkler heads in the building going off

I am sorry I really have to question that, I think you may have been given incorrect info or misunderstood the info.

That is what happens in the movies, I have worked a lot of commercial buildings and have never seen a sprinkler system operate in that way.

The FD may very well turn on fire pumps but I doubt highly that causes all sprinkler heads to let go.

Two problems with that.

1)You would be basically 'wasting' your water supply and your main would have to be sized to run all heads at the same time.

I doubt a sprinkler main can support all heads open any more than our service main can handle all circuits fully loaded.

2)Insurance Companies. As much as the insurance company wants the fire out they definitely do not want water damage in the entire building for a localized fire.

Bob Badger
Construction & Maintenance Electrician
Joined: Oct 2004
Posts: 265
I've never seen em do that in the movies, this is how I've been told they do it by the sprinkler guys.

I do a lot of multi building tilt ups. There is a main sprinkler line that goes onto the property to the backflow, from there it splits off to a PIV (Post indicator valve) for each building. What I have been told is that when the fire department shows up, they shut off the PIVs to all other buildings on the property and then hook their engine up to the system. The backflow prevents the pressure from going back to the main feed off the property. This then results in the heads of the buildings going off.

From what I have been told, the fire department's lowest priority are the contents of the building. Saving lives, preventing spread to other buildings is their primary concern, followed by saving the structure currently on fire.

As I am sure you have seen, even one sprinkler head going off can basically destroy the contents of a small-medium size building. Let alone what the smoke and fire will do.

I am sure other buildings are different, but this is how I've been told it works for tiltups.

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