Life span of fire alarm cable.

[Dinnertime Dave]

We are obtaining quotes for a new fire warning system in a residential care home, the parts for existing one are obsolete and we are at risk if it should fail. One quote indicates that we can reuse the cabling to keep costs down.

Could anyone advise me of the potential life span of cabling and any problem of doing this.

[SeaBass]

I?ve been involved in jobs in the past where the existing cabling was reused.  To facilitate this we had every cable individually tested and inspected to ensure, so far as was practical, that there was no mechanical damage or deterioration of the insulation. Generally mineral insulated cables live forever (unless the outer sheath is polished away by over zealous house keepers)  P.V.C (Plastic) insulated cables also have a very long life span, twenty five years is the accepted norm but I?ve seen much older PVC cables that are still in perfect condition. The main problem with plastic insulation is the degradation that can come about due to environmental/atmospheric  conditions such as higher or lower temperatures, fumes from process?s, UV light, movement in the cable, containment or building, to name a few.
The problems that we encountered included:
?   Older cables being fully serviceable and in good condition, but not compliant with current BS / EN standards.
?   Inability to physically inspect or reach some cable runs
?   Requirement to upgrade cable containment to meet guidance of BS 5839.
?   Installers guarantees being heavily caveated and not covering any faults that could be attributed to issues arising from the cabling.
?   Existing cables being replaced because the installers break one of the cores and there is no slack in the cable run.     

[Fishy]

CIBSE Guide M (Maintenance engineering and management) is the most often-used bible.  Quoted economic lifespans for cables are 35 years for MI & Thermoset cables; 30 years for thermoplastic.  The same document quotes an economic life for the fire alarm panels themselves as 15 years, so entirely feasible that you could use cable existing that's half-way through its economic life, in good functional and physical condition, fixed and positioned compliant with BS 5839-1 and reasonably expect it to last the life of the new panel.

As Basco says, environmental conditions can have a huge impact (e.g. UV degradation, oil & chemical contamination, movement/vibration etc, etc), so (for example) be very critical about retaining cable exposed to external conditions.

With a modern, compliant fire alarm system it should fail safe (to a reasonable extent), so the risk with non-replacement is reduced reliability & availability until an offending cable fault can be identified, traced & rectified.  How manageable that might be will vary from premises to premises.

[kurnal]

Presumably you will be replacing a conventional system with an addressable system. The wiring configurations can be very different and you should confirm that there are no interference issues likely to arise through a lack of screening or adjacent power cables etc.  With old MICC systems damp ingress can be a problem especially if it is a site with buildings linked together. I have seen it work, but have also a couple of horror stories from doing this.

On another front, how will you maintain the availability of the system during the installation if re-using the cable?

[Dinnertime Dave]

Thanks everyone for the advice, a few things to think about and confirm with the companies tendering.

[Fishy]

On another front, how will you maintain the availability of the system during the installation if re-using the cable?

Very good point and one to quiz the contractor about!

[David Rooney]

On another front, how will you maintain the availability of the system during the installation if re-using the cable?

Very good point and one to quiz the contractor about!

We have done similar in the past .... effectively running two systems side by side and literally breaking each circuit so that you power it from both ends - one end in the existing CIE and one end in the new. As you trace the circuit from device to device and change to the new you leave the circuit broken (creating two radial circuits) until all devices are changed and you are running everything on the new and complete the loop.

Bit time consuming and needs thinking about but it is a good way of recording the existing as installed cable routes for any future fault finding .....

[SeaBass]

Its just a thought, but it may well be worth doing a cost benefit analysis on a wireless system, compared to the cost and inconvenience of testing and checking all of the existing cabling, upgrading the containment and having to endure the endless arguments with the service engineers about whether a particularly system  fault has arisen as a result of a problem with the cabling.     

[lyledunn]

I wonder what the CIBSE guide would say about the economic lifespan of humans. From the figures for cables it looks like we should be making our peace somewhere in our early thirties!
I am 58. I started contracting at 23. Many of my early fire alarm installations are still in operation, many of them still with the original JSB brick s***house panel. No issues with the cables, all well-installed MIMS.
Looks like the trade doesn't install like that any more. Difficulty finding guys who can install Pyro and the associated labour costs have meant that soft sheath cables are the order of the day. Apparently they do not need to be neatly fixed and dressed. Just chuck them in and connect them to a high tech panel that no one understands other than a pimply-faced kid with a laptop. Sounds like I am well beyond my economic life!