Interconnected smoke alarm - troubleshooting

[Neptune]

Hi,

I have an aico alarm system which was mains powered and interconnected when installed 3 years ago. It's not been maintained and when I took a look recently, a couple of the detectors are missing. Only the ceiling plate is on the ceiling. Also, the interconnect isn't working. When I test any smoke detector, only that beeps and - none of the others.

I need to ensure that they are all still mains powered and restore the interconnection between them. They have a 3 core and earth cable for the interconnect.

I am pretty handy with electrics and own various tools including a fluke 2 pole tester.

I have 8 detectors. Can you please suggest a logical approach for this. Does the indicator on the detectors have any significance?

Look forward to receiving your advice. Thanks in advance.

 

[Mike Johnson]

Test each alarm in turn, if two sound then they are interconnected, then do the same with one of those and the next one, when you get to one that does not sound with the previously sounding others then the interconnect between it and the others is suspect, this way you could narrow it down to one of two legs, test between each cable at the alarm for shorting, a continuity tester and a long lead would make it easier between alarms.

Another but messy check is to temporarily disconnect each alarm from the existing interconnect cable and then connect each alarm with some 0.75 multi stand, cheap and easily obtainable.

Or disconnect the interconnect from all the alarms and put in the radio base's probably easier in the long run.

 

[Neptune]

Test each alarm in turn, if two sound then they are interconnected, then do the same with one of those and the next one, when you get to one that does not sound with the previously sounding others then the interconnect between it and the others is suspect, this way you could narrow it down to one of two legs, test between each cable at the alarm for shorting, a continuity tester and a long lead would make it easier between alarms.

Another but messy check is to temporarily disconnect each alarm from the existing interconnect cable and then connect each alarm with some 0.75 multi stand, cheap and easily obtainable.

Or disconnect the interconnect from all the alarms and put in the radio base's probably easier in the long run.

When I tested these earlier today, I removed all the heads and then fitted the first one (where the mains power was supplied). I then fitted what I think is the next one in the chain. I then tested, they only beeped individually. I then added the next one and tested as I went along. Each time, there were no multiple alarms beeping.

My confusion: even if some of the inter links are broken, surely not all of them are and therefore some (and probably most) alarms should have worked - I felt.

In my case, none of them have the interlink working. I can do continuity tests across the interlink wire but it just feels that there is something more fundamental as none of the interlinks are working.

Am I missing something?

Also, forgot to mention that there is a call point installed on this system too. I didn’t check the wiring for this.

 

[Neptune]

I was about to suggest is it being tried with the faulty detectors not in place.

I’ve tried it with and without he faulty detectors. Not had any effect.

I assumed that having the faulty heads doesn’t matter as the continuity is within the wiring of the base and I can see that the mains current is being carried across to all bases - and presumably the continuity of the interconnect wire too

 

[Neptune]

Rather than a continuity problem, it's more likely to be that the interconnect wire is shorted out, either by a wiring fault or a faulty detector.

But would every leg of the interconnect short as none of them are working?

I could get a wonder lead and test continuity across one of the legs with my two pole tester as this has a continuity function.

 

[Mike Johnson]

Does the call point work?
Are you testing from the same sender unit each time? if so test from a different sender unit.
Do these alarms work individually?
If none of the above work, I would suggest making up a test panel removing the alarms and base's and testing on that you could then eliminate the rogue element of the interlinks in the alarms being the malfunction.

 

[littlespark]

Is there power at each base?
Is there two x 3 cores at each base?

I’m thinking, if you test at various bases, and there’s no interlinking… maybe there’s a central jointbox and the interlink cable is loose?

I see the first photo they used the wrong colour for the neutral (no discussion… it’s just wrong!?)
Is that the same all the way through?
Neutral and interlink mixed up can cause damage.

 

[Neptune]

Does the call point work?
Are you testing from the same sender unit each time? if so test from a different sender unit.
Do these alarms work individually?
If none of the above work, I would suggest making up a test panel removing the alarms and base's and testing on that you could then eliminate the rogue element of the interlinks in the alarms being the malfunction.

I couldn’t test from the call point as I don’t have a key.
I have tested from each individual unit and in every case (apart from two faulty heads) that individual unit beeps but none of the others.

The test rig sounds like the way to go…
Does the interconnect work without mains power I.e. using batteries
Could I remove a couple of units from the ceiling, link them together with 3 core and earth (or interconnect only?) and test them like this?

 

[westward10]

Provided the batteries are good yes they will function with no mains supply.

 

[Neptune]

Is there power at each base?
Is there two x 3 cores at each base?

I’m thinking, if you test at various bases, and there’s no interlinking… maybe there’s a central jointbox and the interlink cable is loose?

I see the first photo they used the wrong colour for the neutral (no discussion… it’s just wrong!?)
Is that the same all the way through?
Neutral and interlink mixed up can cause damage.

Yes, power at every base.
The same coloured cables are being used throughout.
Every base has 2 sets of 3 core and earth apart from two:

• The first one has 1 3 core and earth and another twin and earth (mains power)
• another base has 3 sets of 3 core and earth. That’s because I spurred an additional detector off this one a few years ago.

 

[brianmoooore]

If you an get three x 3&E cable connected and fully enclosed within the terminal box of an Aico smoke alarm base, then you have my respect!

 

[HappyHippyDad]

If you an get three x 3&E cable connected and fully enclosed within the terminal box of an Aico smoke alarm base, then you have my respect!

They are horribly fiddly aren't they!

 

[Neptune]

They are horribly fiddly aren't they!

My long nose pliers are magic!

 

[Neptune]

Is there a circumstance that can cause the whole interconnect cable across all devices to be damaged? Would a continuity test across each leg of the interconnect wire substantiate this?

Also, could this same situation have damaged all the interconnect functionality on the heads/base?

 

[Neptune]

If the devices work on the ground with a fresh 3 core and earth connected between them, I would conclude a damaged interconnect cable.

If the devices don’t work on the ground, do I assume that the base and/or heads are damaged - or at least the interconnect part of them?

Are these reasonable assumptions?

 

[westward10]

This really is a process of elimination. What I would do is check all connections and then confirm conductor continuity.