Galaxy alarm cable cut and rejoined but tamper still evident

[BintyandtheBeast]

Hi all,

We are in the process of getting our attic converted and I had to cut the alarm cable between the main box and the external bell in order to get new trusses installed. I have since rejoined the cable using telephone wire jelly connectors, but I am still showing a tamper to the bell.

I have gone over the connectors and they are fine, I have also opened up the bell box outside to check whether the cable may have been tugged and worked loose of it's connection, but they are all good.

I have managed to get the engineer code for the alarm and it will now not let me exit engineer mode as it is picking up a tamper in the bell circuit.

I have thought about cutting off the jelly connectors and trying again, but the cable has no slack. Also, with the location of the cable there's no way to replace (3m to the bell and then around 9m to the unit through numerous partitions and dwangs) or to solder the cables (the join is around 2m in to the eaves, in the very bottom edge of the truss.

Is there a way of checking definitively that it is the join, or can I be safe in the assumption?

Thanks,
The Beast

 

[JohnW2]

Do I take it that you have tried completely powering-down the system (including disconnecting batteries) and then 'starting again from scratch' - in case it is just 'remembering' a tamper? I once had that problem with an alarm system.

Kind Regards, John

 

[BintyandtheBeast]

Hi John,

I had the alarm powered off for 4 weeks while the worst of the work was being carried out, so yes. I reconnected yesterday and it showed the tamper when I powered up again. I thought it may have been because the batteries had discharged, but they will be fully charged again by now. I also have a pair of flashing LEDs on the bell box which are showing, so power is definitely getting there.

I killed the power for half an hour again (switch off the breaker and pulled the battery back up) and when reconnected it showed the bell tamper again.

 

[JohnW2]

Hi John, I had the alarm powered off for 4 weeks while the worst of the work was being carried out, so yes. I reconnected yesterday and it showed the tamper when I powered up again. I thought it may have been because the batteries had discharged, but they will be fully charged again by now. I also have a pair of flashing LEDs on the bell box which are showing, so power is definitely getting there. ... I killed the power for half an hour again (switch off the breaker and pulled the battery back up) and when reconnected it showed the bell tamper again.

Fair enough - it was just a thought, given that I had experienced such a 'tamper memory' myself in the past!

It therefore sounds as if there is either something wrong with your 'join', or else that the cable has been otherwise damaged during the work.

Kind Regards, John

 

[BintyandtheBeast]

I was really hoping that wouldn't be the answer! The join appears to be good, so that indicates a problem somewhere else. Not sure how I test it, and really don't want to be paying to get someone out to fix it!

I really need to get this fixed over the next week or so before the area is sheeted out and access is lost.

 

[JohnW2]

I was really hoping that wouldn't be the answer! The join appears to be good, so that indicates a problem somewhere else. Not sure how I test it, and really don't want to be paying to get someone out to fix it! I really need to get this fixed over the next week or so before the area is sheeted out and access is lost.

I understand your problem. Although you say that a lot of the cable run is not easily accessible for replacement, I would presume that any damage to the cable would be most likely to have occurred in that which is exposed/accessible, so I suppose you could try replacing just that bit (which, of course, would require a new 'join').

Kind Regards, John

 

[BintyandtheBeast]

And that is why you are paid the big bucks!

I'll look to source a 5m length of cable which is what is visible in the eaves and cut and replace the visible section.

Are phone cable jelly connectors suitable? As I said, there's no chance of getting a solder carried out due to space and access, especially as the existing cut is so close to where the cable gets fed through a partition.

 

[JohnW2]

And that is why you are paid the big bucks! ... I'll look to source a 5m length of cable which is what is visible in the eaves and cut and replace the visible section.

Under the circumstances, I reckon that's probably worth a try - but, of course, it's very speculative and by no means guaranteed to solve the problem!

Are phone cable jelly connectors suitable? As I said, there's no chance of getting a solder carried out due to space and access, especially as the existing cut is so close to where the cable gets fed through a partition.

Anything which results in satisfactory electrical connection would suffice. However, IIRC, those 'jelly connectors' are specifically designed for use on solid conductors (i.e. just a single, solid, 'wire' for each conductor), and I'm not sure how well they work with stranded conductors. I suspect that the cable you're joining may well have stranded conductors - is that the case? (and how many cores are there that you're joining?).

Kind Regards, John

 

[alan333]

I'm not an alarm expert but have a fair knowledge from fitting my own Galaxy. I also haven't used jelly connectors, but from a quick google they seem to have some gel inside them. The tamper detection works by changing resistance across the circuit, so perhaps one of the connections hasn't connected properly due to contacting the gel, thus changing the resistance.

If it was mine I'd cut off the jelly connectors, and join again using terminal strip. If the cable is too tight then splice in a new piece of alarm cable using terminal connectors, and see if it cures it.

 

[JohnW2]

... The tamper detection works by changing resistance across the circuit, so perhaps one of the connections hasn't connected properly due to contacting the gel, thus changing the resistance. ... If it was mine I'd cut off the jelly connectors, and join again using terminal strip. If the cable is too tight then splice in a new piece of alarm cable using terminal connectors, and see if it cures it.

Good point - and, as I've just said, the gel connectors might not be too good with stranded conductors, if that's what the OP has. Assuming that there is space to do it, it would certainly be worthwhile to change the gel connectors to a connector block, even if only temporarily, to determine if the gel connectors are the problem.

Kind Regards, John

 

[bernardgreen]

The "jelly" connectors are IDC ( insulation displacement connector ) and rely on the diameter of solid copper strand being large than the gap between the "teeth" of the connector. Otherwise the insulation is not cut and the connection fails.

Bootlace ferrules and sleeving make ideal connectors for repairing stranded alarm cable.

 

[JohnW2]

The "jelly" connectors are IDC ( insulation displacement connector ) and rely on the diameter of solid copper strand being large than the gap between the "teeth" of the connector. Otherwise the insulation is not cut and the connection fails.

Thanks. If they are IDC connectors, being used on stranded conductors (quite possible of a different size from phone cable conductors, anyway), then that easily could be the OP's problem. As I said, at least a temporary change to some other form of joining the conductors would serve to demonstrate whether the gel connectors are the problem.

Kind Regards, John

 

[BintyandtheBeast]

Thanks guys for all the input.

I think you may have a point. The cable is really thin, maybe less than the 0.5mm2 which the jelly connectors I have used are designed for (telephone cable), so could be that there is a wire which has not been fully stripped to make the connection, but visually they look as though they have.

Also, the cable is 8 core with single wires, not strands.

 

[sparkymarka]

Silicon crimps work fine if you strip to conductor twist together then crimp, if it's an 8 core there will be spare cores, double up the 0volt and tamper return cores and see if this clears the fault.