The Arc Fault Detection Device… again.

davezawadi (David Stone):

The eye is not bad at seeing significant trends Mike, isn't it? Assuming about 10% of installs have been replaced in the last 12 years we should see a trend, I don't. Yes when every installation has AFDDs it might go back to the already improving trend line, this is just the increasing safety of electrics of all kinds. The "noise" (randomness of this kind of data) is certainly bigger than any possible signal of improvement, the trend from "unknown" cause is much greater than the AFDD one.

Fires caused by faulty appliances in domestic dwelling houses tend to be from causes which an AFDD is not likely to prevent. For instance, fires in tumble driers from build-ups of fluff (see for instance this local news report from 2019: https://westbridgfordwire.com/fire-service-issues-warning-after-tumble-dryer-fires-in-nottingham/). 


Fires in electrical appliances are a significant but relatively small proportion of the total number of dwelling fires each year. I recently retired as the performance manager for Scottish Fire and Rescue, and was responsible for the publication of the Service's annual fire statistics (available if you are interested from https://www.firescotland.gov.uk/about-us/fire-and-rescue-statistics.aspx). Fire statistics in England, Wales and Scotland are based on data recorded on the National Incident Recording System by crews that attended the incidents, and represent what they found at the time. Accordingly, you won't necessarily be able to make deductions about arcing as a cause from the published statistics. Leaving aside obvious cases such as burnt out shower isolating switches, only detailed fire investigation work would be able to determine in many cases if arcing of some kind contributed to the fire. Fire investigation is a specialist activity undertaken after major fires or any in which there was loss of life, and an appliance fire limited to the room of origin in which no major injuries or fatalities arose would not normally need the services of a fire investigation team. 


All fire services look for trends in causal factors found by fire investigators to see if there is a common cause which needs action nationally. London Fire Brigade for instance spotted failures in LEC fridge-freezers (fires caused by spark-suppression capacitors failing if I remember correctly), and the Whirlpool tumble drier failures which have caused hundreds of fires nationally.


I doubt very much that AFDDs will make a significant improvement in fire safety. Over 60% of dwelling fires start in the kitchen and result from human factors - leaving pans unattended and so on. All fire services conduct home fire safety visits and try their best to advise homeowners on issues such as overloaded sockets, poor use of trailing power leads and so on. From what I've seen in the incident logs for fires where electrical supply or electrical appliances were involved, AFDDs would have been unlikely to have made much of a contribution. To give an example, AFDDs protecting an RFC would not do much to help stop the major fires that have occurred from criminal interference with meter tails to power the heating used for cannabis farms!


-Stewart

davezawadi (David Stone):

The eye is not bad at seeing significant trends Mike, isn't it? Assuming about 10% of installs have been replaced in the last 12 years we should see a trend, I don't. Yes when every installation has AFDDs it might go back to the already improving trend line, this is just the increasing safety of electrics of all kinds. The "noise" (randomness of this kind of data) is certainly bigger than any possible signal of improvement, the trend from "unknown" cause is much greater than the AFDD one.

Fires caused by faulty appliances in domestic dwelling houses tend to be from causes which an AFDD is not likely to prevent. For instance, fires in tumble driers from build-ups of fluff (see for instance this local news report from 2019: https://westbridgfordwire.com/fire-service-issues-warning-after-tumble-dryer-fires-in-nottingham/). 


Fires in electrical appliances are a significant but relatively small proportion of the total number of dwelling fires each year. I recently retired as the performance manager for Scottish Fire and Rescue, and was responsible for the publication of the Service's annual fire statistics (available if you are interested from https://www.firescotland.gov.uk/about-us/fire-and-rescue-statistics.aspx). Fire statistics in England, Wales and Scotland are based on data recorded on the National Incident Recording System by crews that attended the incidents, and represent what they found at the time. Accordingly, you won't necessarily be able to make deductions about arcing as a cause from the published statistics. Leaving aside obvious cases such as burnt out shower isolating switches, only detailed fire investigation work would be able to determine in many cases if arcing of some kind contributed to the fire. Fire investigation is a specialist activity undertaken after major fires or any in which there was loss of life, and an appliance fire limited to the room of origin in which no major injuries or fatalities arose would not normally need the services of a fire investigation team. 


All fire services look for trends in causal factors found by fire investigators to see if there is a common cause which needs action nationally. London Fire Brigade for instance spotted failures in LEC fridge-freezers (fires caused by spark-suppression capacitors failing if I remember correctly), and the Whirlpool tumble drier failures which have caused hundreds of fires nationally.


I doubt very much that AFDDs will make a significant improvement in fire safety. Over 60% of dwelling fires start in the kitchen and result from human factors - leaving pans unattended and so on. All fire services conduct home fire safety visits and try their best to advise homeowners on issues such as overloaded sockets, poor use of trailing power leads and so on. From what I've seen in the incident logs for fires where electrical supply or electrical appliances were involved, AFDDs would have been unlikely to have made much of a contribution. To give an example, AFDDs protecting an RFC would not do much to help stop the major fires that have occurred from criminal interference with meter tails to power the heating used for cannabis farms!


-Stewart