Help with 521BXT smoke detector circuit

We moved into an older building. There are several Interlogix (Sentrol) 521BXT detectors. Detectors are not working so I traced the wire back to the control box and found the chained wire disconnected laying in the bottom of the box.

Is there a cheaper/simple control box I can hook these to? Local alarm?

I am not sure if there is a fault and that is why they were disconnected? Or box modified so no room for them. If they worked, a control box that would be set up for some kind of WIFI to contact someone if there is any trouble.

Or… I did get a couple poor pictures of the control box. Not sure if I have the correct model numbers. It shows on the door, Concord 4 Series system 600-1021-95r, 1022, 1040, 1042

The diagram shows smoke detectors to be hooked to Zone 8 but something is hooked to that terminal. Not sure if they hooked up another sensor to that. (non Fire)

Well the manager got a local alarm guy in. Asked about hooking the smokes up and got a lot of Ida knows.

I checked the wire and got infinity reading. So either a damaged wire or no termination resistor.

I did get a better look at the control board and it has a secondary board with 2 smoke circuits. I will run a trace on the wires when the place is not as active.

This is the secondary board.
Will see if I can post a picture.

It seems like you have a deactivated security system with smoke detectors

That is the model of the security system and the manufacture is GE/Interlogix
That blue circuit board appears to be a zone expander or a 2 wire smoke module. As to getting the smoke detectors to work your best bet is to get someone that can program and get the system to a working state. This may be a big challenge as it seems that the companies have stopped supporting as well as producing parts for this system. However this may be more costly and difficult than just using wireless interconnected smoke alarms. If you want a security system you may want to consider upgrading.

Though it sounds like you don’t own the system or building/apartment/unit which would mean it is there responsibility to get you proper fire safety.

BTW I did say manager, Maybe a misswording. It would be the owner. I don’t have ownership, but do repairs.

A family member owns it. It is a commercial building. The burglary system is working. We just did a smoke can test to verify the smokes and they are not working. I traced it down to the wire not connected to the control box. PO may have disconnected because of open loop??

The contracted alarm company is not very helpful.

I am fluent in electronics but not familiar with the alarm circuits. But am doing some research and learning quick. I am familiar with N/O N/C circuits.

The smoke circuit is showing infinity. Not showing an EOL resistor. With the line disconnected at the control box, I was thinking of shorting each smoke to see if the line is intact at that point. It may be easier to power the line with a fused 12 volt supply. Then look for lights on the smokes? Does that sound reasonable? (temporarily for testing.) How much resistance should each smoke have? I am thinking I should be getting some kind of resistance on the line.

Other than that possible set the meter at the box and keep shorting each smoke and using that to check the line. Or put a resistor at the line near the control box and working backward.

Everyone else was wanting to use battery operated units. Hardwired 120V units would be quite a hassle. With as many rooms there are. I would rather get this system repaired.

Appreciate the replies.

A 4.7K resistor on the last smoke and reconnecting the negative and positive wires should make it work again. The challenge might be finding the last detector on the circuit, by removing the detectors and looking if there are only two wires going into the detector instead of two more going to the next one.

Thinking it may be a break somewhere. Some of these units are 20 feet off the ground. The control box is in the middle of the circle of them. I think I will give it a try Saturday. Thanks

Appreciate it… Spent some time there today tracing them all out. There were several circuits. They were disconnected and no EOL resistors. A few 2k resistors sitting on top of the box. (What the box called for) Got me moving.

I have them hooked up on the secondary control board in the control box. They do work. I just need to figure out how to program the control box to accept them. Supposed to have the alarm company guy come out on Monday and maybe he can take care of that.

There were 2 runs laying in the bottom of the box. Wondering if the old system was replaced years before we moved in. Then they could not figure out why it would not work. Or just didn’t care and left them disconnected.

Ok, Passing on info. The expansion board has 2 smoke circuits. I have 10 smokes on one, 4 on the other. Does that sound ok? I know there is only so many on one circuit.

I talked to the local alarm company. The company whose sticker is on the box. Put it nice, he is not too friendly and not too helpful. He thinks the expansion board is bad and wants to replace it. (from his computer?) He said he knew the smoke detectors have been disconnected for many years. He thinks the old company that worked there knew that. He does not know if the smokes are compatible with this system. He said I should not put the resistor on the end of the loop, it should be in the control box at the terminals because it would be a lot easier to find. I asked if he knew why the smokes were disconnected. I got a large sigh and a I don’t know. He did not seem to happy with me looking over he system. (I can understand, DIY guys can make a mess.) But I asked him if he could give me an estimate to get them working. Another large sigh and an I guess when I come out. I also told him when testing the control panel the siren did not go off. He sighed again and said I test that when I look over the system.

We have never been told how to silence the system, or how to reset the smokes when there is a problem. If they would work.

I really hate to step on his toes on this but he is not very friendly/willing to work on it.

There are wireless battery smoke alarms available as a last resort.

I think the smoke detectors and or some security zones were intentionally disconnected, possibly because they couldn’t figure out why they weren’t working.

They appear to be conventional so they most likely should work with the system. Putting the resistor in the panel is generally not a good idea as if there is a break in the wire the panel won’t know.

The alarm company doesn’t sound that great, as they are not willing to help and don’t want to deal with the issue.

This also shows that there are potentially larger and or more issues with the system, however it could be another disconnected wire or the siren itself broke and just needs to be replaced.

I would just make sure the wires aren’t disconnected for the siren. Also wouldn’t hurt to get another opinion. Maybe try reaching out to a nicer alarm company and see what they say?

That was my opinion too. On both. But I am the guy learning.

BTW I have heard 10 smokes max… Correct?.. Would that be 10 on each circuit? Or 10 total for the expansion board?

The wires were attached at the control panel and found them run to an indoor siren. That was where I left it.

As far as another alarm company. Not sure on what is proper? You have 2 companies… One is the one that monitors and calls you when there is a problem. The other is the company with the name (sticker) on the control box. They are the ones that do the repairs. Are they associated with each other or are they separate? My Daughter set it up, but I am the one she calls when something is not working.

Nice would be a plus… But I would like a company that would help instead of being a hassle to deal with. Kind of like a place you dread having to call. How do you look for a local company? We are Northern Indiana. South Bend area. We don’t need anyone fancy or expensive. Small company is fine.

So does it work like we own the whole system and are just calling up a guy to work on it. Then another company to monitor the system?

Thanks for the help!!

Just like a tech to fix the system, not monitoring company.