FOS 6117-N

Hi all,
I’m a homeowner whose fire alarm/strobe is malfunctioning. I believe we have the FOS 6117-N. It randomly went off when there was no fire and it won’t stop sounding the alarm unless I cut off power from the main electric panel. I don’t know how to fix the alarm or how to disconnect it so at least I can use the other appliances/outlets on the same electric switch. Is it just a matter of unscrewing the face plate and disconnecting any wiring? Any help would be greatly appreciated. Thanks.

A picture of the fire alarm can be seen here. https://imgur.com/a/lzxRE

Allen

Hello, welcome to the forums! If you have any questions or concerns relating to the site, please contact me or another member of the forum staff.

The device in question is simply what is known as a notification appliance in this industry - it contains only the circuity to produce sound and light to indicate an alarm. This means that the device does not have the capability to detect a fire condition or activate itself, therefore there must be a fault elsewhere in the system that is causing the alarm horn to sound, so disconnecting this device only will not solve the root issue at hand.

The label on the device reads 120V (mains voltage), so that would suggest there is no traditional fire alarm panel controlling this device. If you are aware of them, what other devices, such as smoke/heat detectors or manual stations, are known to be connected to this system?

Being that this is a 120V appliance, I do not recommend you attempt to disconnect the wiring to the device. In doing so, you risk an electric shock should the circuit still be energized during removal, and the presence of abandoned live wiring at the device location, in addition to whatever electrical short or faulty initiating device is the root cause of this issue.

Do you have a service or monitoring company you are able to contact in relation to this system? I assume not, given that this system seems rather simple. In that case, you will want to look into contacting an electrician who can resolve the issue, or safely remove/abandon-in-place the system in its entirety.

Hi Nick,
Thanks so much for the quick reply and thorough answer. We do have smoke detectors, but I don’t think it’s connected to the system. I am no expert, but my guess is it’s a stand alone. I noticed most of the houses in my community have this setup as there’s also a circular fire alarm mounted on the first floor outside. I’m assuming this is what the developers planned for all these houses.

I don’t use a monitoring system, so I will probably have to contact an electrician. From what you can tell, you think it’s something faulty in the electrical circuit/wiring? Thanks so much.

Allen

Either a wiring fault, or an initiating device somewhere on the circuit that has gone bad. There has to be some device on the circuit that serves to activate the FOS device, but if your smoke detectors appear to be behaving normally they can likely be ruled out as being connected to this system. There may be another heat or smoke detector concealed somewhere that is causing an issue.

See the image below - this is the horn mechanism to a device in the same series of the one you have pictured. You will see there is only the electromagnet assembly to sound the audible portion of the device, and no means internally to activate the device. Applying power to the input leads will cause the device to sound irregardless of the surrounding environment - this is where I base my statements that there must be an external device that permits power to reach the horn and sound the alarm. This device may have failed and is allowing power to reach the horn, or an electrical wiring fault is making the connection elsewhere to complete the circuit.

Thanks again Nick. What’s the possibility that this is a result of a faulty/malfunctioning smoke detector? We’ve lived in this house for three years and never had an issue with our smoke detectors aside from low batteries. On those occasions, I’ve swapped out the battery, but we’ve never had this fire alarm issue until yesterday. I’m not even sure if they’re linked.

Do the smoke detectors appear to switch over to battery power when you shut down the circuit that the FOS horn is on? Whether or not they are in the same branch circuit will be a pretty good indicator of whether or not they are related.

There is a chance that the detectors could trip in a relay and sound the horn depending on the model. Can we see an image of one of the detectors to get an idea of their type?

The picture of the smoke detector can be found at the url below.

https://imgur.com/a/qIhKL

I’ll test the circuit when my family leaves the house later on. How would I determine if it switches to battery power? If it still is on? Thanks.

The green light on the detectors will most likely extinguish when AC power is removed. It may be replaced with intermittent blinking to conserve battery power.

If you still can’t tell, power down the circuit and pull the backup battery from the detector. Try to activate it via the test button - if it fails to sound, you can confirm that AC power is no longer present at the unit. If it still activates with the FOS horn circuit powered down and no backup battery, it is drawing power from a different circuit.

I also called an alarm company and they suggested using a blow dryer to blow air into each smoke detector to remove any dust. They said this is usually the culprit of disrupting the smoke detector and therefore setting off the fire alarm? It sounds like if the systems are linked then this could be the issue?

Sorry, another thing. If it is a smoke detector issue, wouldn’t there be some sort of signal from the smoke detector itself? Or is it because it’s broken the fire alarm is going off? Thanks so much for all your help. I truly appreciate it.

If Nick doesn’t mind - I’ll chime in too, since my house used to have those sort of smoke detectors.
When you press the test button on the detector, does the FOS horn go off? Or has the horn ever gone off when the smoke detector is accidentally set off due to things like cooking smoke/burned food?
Also, I’m not sure if I’d recommend a blowdryer to dislodge the dust from the smoke alarm. A vaccuum cleaner usually tends to work better than a hairdryer.

Hey Robert. Thanks for chiming in. No, the FOS horn has never gone off. The only issue we’ve ever had with the smoke detector is when it’s low on battery and beeps as warning. II’ll try the vacuum cleaner thing when I get back from work, but I’m operating under the assumption the FOS horn and alarm are connected to the smoke detectors and there is some sort of issue there triggering the FOS horn.

The reason I asked is because those smoke alarms seem to be the 120VAC interconnect type, with the battery serving as a backup. When one smoke alarm beeps, does the whole house beep too? If they do but the horn doesn’t go off then I’m not sure the smoke alarms are connected to the horn.
The reason I say this is because the smoke alarms are powered by 120VAC all the time, but are only going off when either the test button is pushed or the detection chamber (thinks it) detects smoke. The horn, on the other hand, only goes off some of the time, which leads me to believe the circuit powering the horn isn’t energized the whole time, and is only being powered intermittently.
But in these interconnect smoke alarms, there’s a third wire that connects each smoke alarm to each other and allows the whole house to go off when one detector activates.

Something I have not seen mentioned is the possibility of there being some heat detectors. These would be in places that are not appropriate smoke detectors because of dirty conditions or temperatures too extreme for the electronics. That includes furnace closets, water heater closets, attics, basements near heating equipment, or garages.

Many mechanical heat detectors are quite small and can go unnoticed, especially because of where they are located. Mechanical heat detectors are chosen because they don’t have electronics in them. That also means they don’t have a LED to indicate alarm. They can be the thermodot type which are self restoring when the temperature decreases. There are also fixed temperature types that has an element that melt out, so are one shot devices. There are also fixed temperature devices that have a rate of rise section. The fixed temperature section is a one shot but the rate of rise section is self restoring.

The thermodot type is quite reliable because it is a bimetal element similar to an older heating thermostat. However, anything can go bad. The rate of rise types are based on air in a semi-sealed chamber and can drift in sensitivity. Below are a few examples of mechanical heat detectors. Might want to have a look around to see if any are installed.

No, the only time the smoke alarm has beeped is when it’s low on battery. When this happens, it’s only the smoke alarm in question.

In regards to the heat detectors, I don’t see any in our home.

It might not replicate battery alarms over the interconnect wire. If possible, use a humidifier, vape, fog machine, or essentially something that puts out a large cloud of opaque air to set off one smoke detector. If the rest respond (or the horn goes off) then there’s your answer.

Let’s bring this back to the issue at hand. I do not believe the smoke detectors themselves are the root of the problem. It is more than likely a heat detector or other concealed initiating device as Retired STR-SG has suggested.

In response to jelimoore’s post above, those methods will likely not activate the detectors as they do not produce particles of combustion. Carefully lighting and extinguishing a match near the deice will have a higher success rate if you are really interested in doing a smoke test.

You are correct that there would be a signal from the smoke detector if a valid alarm were being activated there. Based on your statement that the FOS horn has never activated with these detectors, I think we can begin to rule them out of the equation. There remains a small possibility that a relay is wired into the interconnect circuit, but based on the descriptions of this system being installed with the house as built, I believe that is probably unlikely as those interconnect devices technically violate electrical code if used with a 120V appliance such as this. Additionally, it was noted that other outlets and devices are de-activated when the FOS horn circuit is disabled. This further suggests that, if wired to code, this system is separate from the smoke detectors.

Bringing this back full circle, contacting an electrician will be your best course of action. They will be able to trace the wiring and find the exact system configuration, rather than having us speculate here on this forum. I’m sure that the information we have been able to provide thus far will be useful to present to them as the investigation into this issue begins.

Please let us know if you have any updates, or any results from the tests that have been suggested.

Thanks everyone. I just had an electrician disconnect the alarm.

A little late to this one, but it is possible that this was connected to a set of mechanical heat detectors or a fire sprinkler waterflow switch. These could be protecting an attic or crawlspace so you wouldn’t see devices in the living area. Both would be a good thing to have a working alarm for, if you do choose to investigate this a bit further, rather than leave it disconnected forever.