Burglar Alarm Wiring Extension

Hi, I hope that someone can help me with these questions regarding burglar alarm systems.
 
I have an alarm that was professionally installed 15+ years ago and is maintained.   When I recently went to change flooring I found that the cable to one sensor (a door sensor) was stretched under the carpet with the less than adequate wire length and now we are moving to hard floor in one area I need to slightly re-route the cable.   All I need is a couple of extra inches free to enable me to take the cable around the edge of the floor but the stretched cable is not sufficient.   The cable in other places of the total route is now behind skirting etc and so to re run the whole sensor cable would be a pain.
  
I am hoping to be able to splice in an extra bit to enable the cable to be re-routed.   After some research I was proposing to use heat shrink solder sleeves for each core and then a heat shrink covering to wrap them all together as it appears that solder should be my first choice for connection on an alarm cable and I obviously want to protect the splice overall.   So the first question does the above look sensible?  Is there a better way without re-running the whole cable?... and any pointers of things to look out for on this method?
 
Separately I think and assume that there is a tamper circuit on the alarm.   I know on the alarm I have the ability to code out individual sensors out of the circuit, something we have done before when having building work done to avoid false alarms.   If I do this for the sensor concerned will it avoid tripping the tamper circuit when I cut the existing cable to splice in the extension?
 
I am comfortable doing the work but the intricacies of alarm wiring are a little beyond me!
 
Thanks for any and all help.    
 

solder / heatshrink should work OK. i doubt you can disable the tamper without engineer code though. but it may be possible to just silence the alarm after and re-set it once your done. just dont cut through the cable in 1 go or you will get problems

of course, a new cable is best but not always practical

yes solder then sleeve.

 As it will be at least a 4 core cable, I suggest you "stagger" the joints so you do not end up with one huge "lump" on the cable.

As Andy said, the customer code can not disable the tamper, you will just have to enter your code to silence it when it goes off, then enter your code again and ? to clear it when you have done.

Its probably a 6 core Jayboy.......... the colours will mean nothing as fitters choose what they use  but common usage is :-

Red/black........... pos & neg  12v power to a sensor

Blu/ Yell    .......... zone  (alarm trigger)

Gn/ whi  ............   Tamper

That sort of thing .

As Andy says , if you cut cable straight through you will  (a) blow the panel fuse for Power supplies.......(b)  trigger the tamper alert .  

Do you have the Engineer code  ?    If so you could enter it ,  open panel , remove Aux Power fuse  ....Tamper should  be isolated in Engineer. and cut the cable with gay abandon to do your joint .   

You can peel the outer sheath back  & cut them one at a time  but not knowing which is which  , you don't want to short any of them out or the above will occur .     Tamper will be sounding anyway  ..unless they havn't bothered to connect it , as some do. 

Make your joints one at a time ..keeping the panel end cores seperated  , don't let them touch each other ...insulate each joint so they can't touch the others then as you say ...heat shrink overall.     Voltage is only 12v so you are safe ....don't try this with a socket cable!!   

If it goes tets up  phone Andy  on 07****8******

As above. Stagger the joints. Similar to what I've shown here in post #8 but obviously you'll be soldering the cores together as opposed to crimping but the principles the same:

http://talk.electricianforum.co.uk/topic/25191-plastering-over-wagos-or-crimps-or-ashly-or-line/

Do you have the kit? Soldering iron, solder, heat shrink of two sizes etc? Whereabouts are you in London?

Gents

Thanks for the really swift response and great pointers.  I don't think I have the engineer code so I will have a dig around to see if I can find it before charging in.   I was planning to use the heat shrink butts (probably the smallest 0.5mm - 1.5mm diameter) which I think are pretty easy to find, with low temperature solder inside and so shouldn't need a soldering iron (although I do have one).   

I note the points about staggering the cuts and new joints and... no... whilst I am comfortable with this low voltage work and changing switches/wall sockets etc (with the fuse out/circuit off)  - I never touch mains wiring - I leave that to you guys!

Thanks again.

those crimps are probably no use. alarm cable is just too thin to use properly. they are also bulky for what you want

ive used gel crimps in the past.

or simply solder them and some heatshrink

A single red crimp would be larger in diameter than the whole cable!

Solder each core and shrink individually, then shrink the lot.

however, still stagger the connections, and don't be shy with the length of outer you strip, as it will make life easier, if you are worried you can always double shrink the sheath.

Again thanks for the great advice.   I was going to use the heat shrink solder sleeves to try to ensure a good joint; i can solder but as I don't do it for a living i hoped that the pre filled solder heat shrink solder sleeves would ensure a more consistent result, but after thinking about the comments above I will traditionally solder and heat shrink each core, and then heat shrink the lot.   I guess this will allow me to inspect each solder joint and if necessary re-do before I heat shrink it ( i suspect the prefilled sleeves won't allow me this option) and even not being shy with the length of cable as The Snake suggests, a using traditionally solders and heat shrunk joints will probably be a shorter overall staggered splice than allowing for a stagger using the solder filled shrink butts.

I thought i would have to splice a piece into the middle of the cable but i have now worked out a way in which i can free up the end of the cable going into the box, re-route and extend the box end of the cable which would mean only one set of joints for the extension.   I am now on a mission to track down the engineer code and if I can get it i will remove the sensor wire from the box (after first turning off the mains juice, carefully noting all the wiring (I have a copy of the installation guide and so the board, and only touching the 12V side of things) . extending the cable and reconnecting.

I assume that the programming is non volatile in that if i connect the sensor wires in engineer mode then i will not need to reprogramme the sensor or the board after connection - does that sound right?   it is a Veritas R8 if that helps.   Anything else i need to be aware of?

Thanks