Dry type Fire protection

[Mike01]

Where a dry pipe system is installed is the compressor that charges the system required to be on emergency power when available I could not find anything in the NEC or NFPA 20 regarding this and just wondering if anyone else has come across this?

 

[cosmos]

I don't think that a compressor or fire pump is required to be on emergency power. Maybe the thinking is that if you lose power, everyone will evacuate the building.

 

[ron]

It does not have to be on emergency power. The air pressure is supervised, so that if the compressor doesn't come on as needed to maintain supervisory air pressure in the pipe, the fire alarm system will go into a trouble condition.

 

[nhfire77]

It does not have to be on emergency power. The air pressure is supervised, so that if the compressor doesn't come on as needed to maintain supervisory air pressure in the pipe, the fire alarm system will go into a trouble condition.

And in some places (Local AHJ requirement) low pressure is an alarm. Or low water pressure on a wet system as well.

It's annoying for the sprinkler and alarm guy.

 

[rcwilson]

Our large 240 MVA 230 kV transformers have deluge sprinkler systems in case of a transformer fire. One means for releasing the deluge is a pressurized dry system with melting alloy sprinkler heads acting as heat detectors around and on top of the transformer. When a sprinkler head gets overheated and melts, it releases the sensing line air pressure that holds the deluge valve closed. The valve opens and floods the transformer. The 400HP fire pump comes on to keep pouring water on an energized transformer and fill up the oil water separator sumps. The same thing happens if the compressor doesn't run and the detection line has an air leak. Lots of water and unhappy operators.

The same results occurred on an indoor 400 MW steam turbine deluge system.

In both cases the small air compressors provided by the fire alarm contractors were not on essential power and the plant operators did not properly respond to the trouble alarm during a partial plant outage.

Our design was to backup the detection air supply with the power plant's compressed air system that had large air receivers and two 400 HP air compressors powered off the essential power. But that redundant system was not certified by the AHJ for fire service so the air line was never connected. (Did I mention that it was about -10F outside when the transformer was coated in ice. At least it ran cool.)

I moved the dinky compressors to the essential services bus.

So my answer as to whether fire alarm air compressors need to be on essential power?

It depends.