Sunday, December 4, 2011

Low Voltage Wiring it can Catch on Fire

A long time customer of mine who loves making his yard look great with land scape lighting asked me to look at something the other day that puzzled him.
Seems he was smelling smoke the other day and came out to find his mulch on fire and smoking and that his land scape lighting had caused it.
He thought that low voltage wiring 50 volts and below could not cause a fire.
Well the answer is it depends what type of wiring is being used where it is being used and what wiring class and size of power supply being used.

Low voltage wiring is divided into 3 classes in the NEC National Electrical Code

Class I Class II and Class III

Class I -wiring- is wiring used in safety and essential circuits to make sure a piece of equipment operates properly like a furnace or boiler

Class II wiring is used primarily indoors and is designed to minimize fires and electrical shocks this includes door bells burglar ,fire alarms energy control etc.

Class III wiring is generally found outdoors includes outdoor lighting , and signalling
again it is designed to minimize fires and limit electrical shock
But no low voltage wiring is totally immune from it and it can cause fires, explosions and shocks under the right conditions when several things line up and goes wrong.

Such as power surges and lightning or when indoor rated system get soaked with water etc.
As you can see with the fire panel at left which was struck by lightning.

In my customers case he was tired of the wimpy out door power supply's which came with the lights so he bought a 900 watt commercial grade power supply that's well over 30 amps of power so yes you will get a significant spark if the wires short and in his case a loose connection filed with water caused a high resistance hot spot which eventually allowed the mulch to catch fire.
Well why did the fuse not blow? Well that's a good question because the short and arcing that occurred below the rating of the breaker on the unit the heat was allowed to build till it finally blew thru a process known as Pyrolysis.
here is a classic case of why Arc Fault breakers are such a good idea.
now luckily since the much is slow to burn there was never any danger to the home made of brick yet under the right circumstance of the home being wood etc. yes there could have been a disaster.

This is why it is important to install low voltage circuits to manufacturer and wiring codes so that the systems will self limit and prevent problems.

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