Water flow 120 VAC bell

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NFPA 72 requires only that a waterflow alarm device be provided. The kicker comes from NFPA 13 which requires an alarm device be provided and that it continue to sound until the waterflow stops (3-10.1) If someone silences the panel and the NAC the waterflow alarm device is on isn't or can't be set as non-silenceable, you would violate the requirements of NFPA 13. Easier to grab a handy 120 VAC line and wire it up.

Oddly enough, on a quick look, it doesn't appear that this device is required to be supervised in either NFPA 13 or 72. In fact, if the waterflow alarm device is electrically operated and is NOT part of a required protective signaling system, it shall not be supervised per 3-10.5.1 and shall be installed per NFPA 70 article 760. It is possible that "supervised" in this context means sending a signal to a "contstantly attended location" but I wouldn't swear to that.
 
Interesting look at it Gadfly, I guess that kinda explains the separation.

I guess I've just always seen them separated and didn't really check into why - thanks...


That is like todays debate I had with the HVAC guys - two factory installed duct detectors on roof mounted units - we pulled our 2 conductor to the detector alarm screws, then through the supervisory screws and resistor - like we have done a hundred times.

HVAC guy asks me where "I" put "my" 24V to power the detector... :confused:

I tried to explain that he does that from power derived in the HVAC unit - he exploded and couldn't understand why we didn't do that and why he has to figure out how to shut down all the systems -

dang?? :roll:


Jim
 
The Duct Detector requires a back up power supply so it typically is supplied by a fire rated device. This is because the RTU may be off in the main power is out, but the duct will still detect smoke without the power supply. This assumes smoke enters the Duct Work and is moving fast enough to enter the smoke head of course. Also, the 24 VAC transformer on the RTU is not UL listed for fire alarm service.
 
OK, but if the RTU is off (power loss etc) then the air's not moving and then there's no need to shut it down - right?

As for detection of smoke and initiating an alarm, with no air flow the smoke wouldn't enter the duct detector tube with enough pressure (reliably anyway) to trip it...

Jim
 
Security101 said:
OK, but if the RTU is off (power loss etc) then the air's not moving and then there's no need to shut it down - right?

As for detection of smoke and initiating an alarm, with no air flow the smoke wouldn't enter the duct detector tube with enough pressure (reliably anyway) to trip it...

Jim
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Yes that is true, but it should be powered by a UL listed fire rated power supply because its part of the fire alarm system. Again I agree with you in principle.
 
gadfly56 said:
NFPA 72 requires only that a waterflow alarm device be provided. The kicker comes from NFPA 13 which requires an alarm device be provided and that it continue to sound until the waterflow stops (3-10.1) If someone silences the panel and the NAC the waterflow alarm device is on isn't or can't be set as non-silenceable, you would violate the requirements of NFPA 13. Easier to grab a handy 120 VAC line and wire it up.

Oddly enough, on a quick look, it doesn't appear that this device is required to be supervised in either NFPA 13 or 72. In fact, if the waterflow alarm device is electrically operated and is NOT part of a required protective signaling system, it shall not be supervised per 3-10.5.1 and shall be installed per NFPA 70 article 760. It is possible that "supervised" in this context means sending a signal to a "contstantly attended location" but I wouldn't swear to that.
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Its not just "waterflow alarm device." It is a "audible notification appliance" (72- 3.3.113.1).

It is deigned to be connected to a fire alarm control unit (system sensor installation instruction)

The connections are monitored for integrity (supervised) 72- 7.3.6

Also its power supply must be monitored 72- 4.4.7.3.1.1.

All bells 24 or 120 I've ever installed are not supplementary, the AHJ requires them.
 
Security101 said:
Oh I see what you meant ;) I agree, but I doubt it's that way.

I havent looked at the power supply but I'll bet it's just a standard UL listed unit...

Jim
Click to expand...

I guess so

UL 268A:

A detector shall be powered from a commercial power source, separate power supply, or be connected to a control unit as part of a fire protection signaling system. Duct detectors are not intended as a substitute for open area protection.
 
nhfire77 said:
I guess so

UL 268A:

A detector shall be powered from a commercial power source, separate power supply, or be connected to a control unit as part of a fire protection signaling system. Duct detectors are not intended as a substitute for open area protection.
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The Duct detectors we have been using are a simple unit, they are self powered by an internal transformer, they have two or more sets of contacts that shut down the RTU's 24 volt side but the RTU's don't supply 24 volts to the duct detectors. they just have dry contacts to shut them down, and we wire them so that if one detector goes off all RTU's shut down, each unit also comes with a buzzer/test/silence key switch pad with operational LEDs. so the FM can test them. if the building is monitored then the alarm guys will use a set of contacts into their system. But in most cases the building is not monitored. so they just get local power from a lighting circuit that would be noticed if turned off.
 
hurk27 said:
The Duct detectors we have been using are a simple unit, they are self powered by an internal transformer, they have two or more sets of contacts that shut down the RTU's 24 volt side but the RTU's don't supply 24 volts to the duct detectors. they just have dry contacts to shut them down, and we wire them so that if one detector goes off all RTU's shut down, each unit also comes with a buzzer/test/silence key switch pad with operational LEDs. so the FM can test them. if the building is monitored then the alarm guys will use a set of contacts into their system. But in most cases the building is not monitored. so they just get local power from a lighting circuit that would be noticed if turned off.
Click to expand...

Sure, I get it. That is a stand alone situation and that is fine.
 
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