Fire alarm fault

[nvhelectrical]

hi got called to a hotel other day regarding a fire alarm sounder bell old school type 24v. maintenance guy had removed the wire and put them in to terminal blocks brown to brown blue to blue. guy said they had a revenonations done few month ago. when testing alarm sounder failed to ring this test (had been ringing when tested prior). i put the bell back together browns to + blue to - bell then immediately rang (not in test mode at this point). one new smoke detector head had also been installed (after renovations) as water damage or debris had caused the alarm to fault often. question why is the bell sounding when it should not be
could a incorrect head cause the fault to occur
need some ideas as i could not performs test 1st visit due to a wedding going on and i only have a 30 minute window tomorrow between appointments and conferences etc

 

[DaftPunk]

You need to employ a competent fire alarm engineer. This is a life protection system, not something to have a go at and leave not working properly.

 

[Lectrician]

It depends on the panel.

There were some "single pair" panels which would allow normal bells/sounders and detectors to be connected to the same single 2 core cable, rather than having separate wiring for the bells and detectors. The panel would reverse the polarity during a fire condition, and so polarised bells were used, connected in reverse polarity (red to - and black to +). The bells would not sound during normal conditions due to the polarising diode, but would once the panel reverse polarity. If you connected a bell the "right" way around, it would sound during normal conditions, and stop during a fire condition.

Fairly rare panels though, and not used these days.

 

[nvhelectrical]

fire system is still 2working bells within 8 meters.
tis a very old board

 

[Adam_151]

It depends on the panel.

There were some "single pair" panels which would allow normal bells/sounders and detectors to be connected to the same single 2 core cable, rather than having separate wiring for the bells and detectors. .......

Fairly rare panels though, and not used these days.

Perhaps its a regional thing, but bi-wire systems are quite common here, even on new installs.

A rarey is finding an old three-wire system still in use

 

[Lectrician]

Bi-wire systems are very common, assuming you mean any system which places detection, sounders, beacons on a single circuit. Most bi-wire use their own devices, the devices being designed to work with the panel.

The panel I was talking about can use any traditional detectors, and any traditional sounders, as long as they're polarised. They are deliberately wired in reverse polarity.

I haven't seen a panel like this for around 15 years. Bi-wire panels, yes, but not this particular type. They were the for front of what we have today as bi-wire.

 

[nvhelectrical]

hi
so the fault was a bell installed on the sounder circuit. simple in the end.
yes it was a old panel with the polerised circuit as described above. thanks for the help