I work in locations that have wet and dry sprinkler zones and a deluge system. I could see cases where a sprinkler could go and result in other heads going, not from heat.
Consider a dry zone near a garage door. The riser has an air over water flapper valve where a given air pressure on top will hold back 4 times (or more) the water pressure. If your compressor fails or you develop a leak that the compressor can't keep up with, the flapper will release. Weak sprinkler heads, perhaps the ones that were leaking air, would now be spraying water.
Some wet zones also have flappers to allow a lower water pressure to hold back a higher pressure water source.
Our deluge systems are usually fired by heat detectors and pull stations mixed on two zones, triggering a solenoid to release the deluge valve There are no sprinkler heads, just flow nozzles.
Any of these flow events drop the pressure in the system more than the low volume jockey pump can make up for. The Jockey pump start pressure is the highest, followed by the electric, and the diesel fire pump being the lowest. Once the electric or diesel fire pump kicks in, the pressure pulse can wreak havoc with weak links in the system. I have seen broken fittings and pressure relief and check valves fail.
Our Fire Department siamese connections are for the fire fighters to connect to our high pressure side as their source. We do use dry connections in the subway though.
Finally, we do periodic testing of portable generators on a load bank. This is usually done just outside a building. One day it started raining so they pulled the gen and load bank just inside the garage door. They didn't notice that they had positioned the load bank directly underneath a sprinkler head. They found out shortly.
Joe
[This message has been edited by JoeTestingEngr (edited 07-13-2006).]
