1930s school fire alarm

[James L]

Some circuit tracers can work by connecting to any hot wire in a pull, and a convenient ground. You should then be able to locate the overcurrent device feeding it.

For sure.

I was just wanting to make sure I'm on tbe right track thinking it's line voltage.

I know from working on old residential low voltage switching, tbose relay panels can be anywhere. And in this building there are a ton of corridors, crawl spaces, attics, and other places designed for access to various plumbing connections, etc.

 

[gadfly56]

Trying a couple more pictures. I appreciate the response so far...

The gist of this whole exercise is that they do a manual fire drill every so often. They pull at a station to sound the alarm, and it is supposed to shut off when the lever is pushed back in (momentary contact). However, one of the levers does not want to act right all the time, they have to push-pull-push several times to get it to turn back off.

They want to have the regular maintenance man change out this pull switch, but they want the whole system turned off before he messes with it

They simply asked me to help figure out how to turn it off, although it's entirely likely I'll be there at that time, just in case. My thought was/is that it is likely a line voltage system fed from a single pole breaker.

It appears that the break-glass station has a plunger switch that is held down (open) by the glass plate. When the glass is broken or someone opens the station, the spring closes the switch completing the circuit and activating the notification appliances. Do I have that right?

What kind of switch does the maintenance man propose to use? FWIW, I'd suggest this as a replacement. It can handle up to 10 amps at 125 vAC. If you replace the problematic station with one that is different, NFPA 72 will indicate you must replace all the stations. You can't have different model pull stations with different means of activation in the same protected space.

 

[James L]

It appears that the break-glass station has a plunger switch that is held down (open) by the glass plate. When the glass is broken or someone opens the station, the spring closes the switch completing the circuit and activating the notification appliances. Do I have that right?

What kind of switch does the maintenance man propose to use? FWIW, I'd suggest this as a replacement. It can handle up to 10 amps at 125 vAC. If you replace the problematic station with one that is different, NFPA 72 will indicate you must replace all the stations. You can't have different model pull stations with different means of activation in the same protected space.

I believe you're correct. They have a new pull station to install. And thanks for the advice about having like devices

 

[GrayHair]

<sup>Also, check the nameplate voltage on one of the audibles and count the devices; some old systems put line voltage to audibles in series. IE: 5 audibles at 24VAC or 10 audibles at 12VAC, usually with a big adjustable wire-wound resistor in series to drop "unused" voltage.

Never worked on one, but I remember old code allowing fire systems to get their power before the main disconnect.</sup>

 

[kwired]

^{Never worked on one, but I remember old code allowing fire systems to get their power before the main disconnect.}

I don't know if it was old code or not, but have commonly seen in 1960's and 1970's installations where they tapped ahead of main disconnect and supplied a separate disconnect for the FA, and often done similar with exit signs and maybe even emergency lights. There was still a disconnect with overcurrent protection that supplied the FA though.

I will also say that the mentioned tap was usually accomplished by landing a 12 or 10 AWG into the same hole in same main lug that the service entrance conductor landed in.:roll:

 

[James L]

I don't know if it was old code or not, but have commonly seen in 1960's and 1970's installations where they tapped ahead of main disconnect and supplied a separate disconnect for the FA, and often done similar with exit signs and maybe even emergency lights. There was still a disconnect with overcurrent protection that supplied the FA though.

I will also say that the mentioned tap was usually accomplished by landing a 12 or 10 AWG into the same hole in same main lug that the service entrance conductor landed in.:roll:

That there may be what I'm looking for. At the original service location (single phase), in the old boiler room, there are 4-5 fused disconnects. The original panel was re-fed as a subpanel back in the 80s when the service was upgraded and moved to the other corner of the building. Boilers were removed because each classroom got a thru-the-wall electric furnace/heat pump at that time.

I'm primarily looking for where to shut off the system so it's not sounding during removal of a device (have to open the device cover to remove screws)

The better I can understand the context (voltage, old wiring methods, etc) will help me find how to turn it off.

 

[James L]

^{...Never worked on one, but I remember old code allowing fire systems to get their power before the main disconnect.}

very pertinent info indeed. Thanks

 

[fmtjfw]

WARNING!

WARNING!

Does your state license fire alarm technicians? Does your liability insurance cover you for fire alarms? Do you know how they work?

I worked on them in public schools, because licensing requirements did not apply, I actually knew how they worked, and I had $2,000,000 in errors and omissions liability coverage.

A 120V system can be as simple as 0 to 2 relays assuming it has supervision. With no supervision, maybe it is just wiring connecting the pulls and the alarms.

 

[gadfly56]

I believe you're correct. They have a new pull station to install. And thanks for the advice about having like devices

I took a look at the cut sheet for the product you showed. It's basically the same, just branded for ESL.

You might want to run a test with one of the existing stations and measure voltage and current just to be sure that the new station is OK for this service.