fire alarm system supply

[murdock]

the cable from the DB to a fire alarm panel...is there a specific cable required?

just thinking about this...if there is a fire in the building and the cable is feed from the front of a building to the back feeding the fire alarm panel...the fire starts in the middle and melts and shorts out the cable...what are the requirements...

i noticed the fellas pulling in cables in the last project...the cables were all red with metal stifferning.

[daveob]

What are the chances that the majority of fires are started with electrical sources ? Wouldn't the ELB trip or the board blow, thereby disabling the fire alarm panel ?

I have my smoke and temperature sensors running off a battery ( same as the alarm system ) with the trigger tied into the alarm and instant sms alert panel.

2c

[AndyD]

I'm not sure what percentage of house fire are started as a result of electrical faults but it would be hit and miss at what stage an earth leakage unit would trip in the event of a fire. The alarm panel would only be disabled if it's in a standard socket outlet. If it's on a dedicated plug circuit (usually red sockets with flattened earth pin) then it wouldn't be supplied via earth leakage (unless the RCD was also the main breaker).

Most alarm systems have 12v lead acid batteries for back-up power in the event of supply failure as well so they should still run for an hour or more if the power fails.

[TECHNICIAN 810]

Absolutely correct, alarm and fire systems run off battery backup, the 220v supply charges the battery. The radio or telco link should send the fire, alarm, panic or medical signal long before the earth leakage detects any leakage to live or neutral. Besides the sprinkler system would kick in as well, preserving human life. Fire systems require that in the loss of Mains that a independent lighting system be activated by means of deep cycle batteries from the basement level, many options available.

[murdock]

something i learnt the other day...they no longer shut down the extraction system and close all the windows....due to the fact that more people die in fires from smoke inhalation than burning...instead everything opens and the smoke is extracted.

there is a special cable which can/must be used it has a fire rating.

[Sparks]

The fire retardent cable which I bought is red. They could be using the correct one.

[sparkydelux]

Good Guidline on Fire alarm systems. Worth a read

Hi. I have covered most fire alarms in the UK and here is some information I found uselful:

http://www.firesafe.co.uk/productGuides/firealarminstallGuide.asp

http://www.firesafe.org.uk/fire-alarms/

http://www.talk.electricianforum.co.uk/electrician-talk/11596-fire-alarm-supply.html

These fire alarm systems are regulated in a massive way. If you are not sure, take a few installation tips from these guys. The forum is also a good read re: cable and type.

Also I'd put a Panel on a MCB rather than ELCB as to avoid an unexpected nuiscence trip on a friday and only realising that the batteries have run out on Sunday and had no protection for Sunday Night - Monday. Insurance would be very sticky on this! It would be treated as a fixed appliance too.

Enjoy the read.

Its UK based but a good example and a very good guideline on how it should be done.