..A video showing the dramatic moment a house exploded has been released by West Yorkshire's fire service.

Officers were called to reports of a small kitchen fire in Castleford but when they arrived they found a series of fires in six terraced houses.

Firefighters had only just evacuated the 30 residents from their properties when the huge blast happened and one of the houses was engulfed in flames.

The footage has been released as a warning about the dangers of stealing copper wire and tampering with electricity and gas supplies.

A spokesman said a piece of cable had been cut from an overhead line which affected the earthing of the electrical network in the area and resulted in unusual electrical activity which, in turn, affected some of the gas pipes within the properties.

He said this resulted in the fires and explosion which left two firefighters with minor injuries.

Two homes were partly demolished and the four other houses suffered extensive fire and blast damage.

The video was captured by one of West Yorkshire Fire and Rescue Service 's "silent witness" cameras which are attached to appliances.

A 27-year-old man from the Castleford area arrested on suspicion of the theft of cable has been released on bail pending further inquiries.

http://uk.news.yahoo.com/firef...plodes-163438959.html
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I suppose if RCDs had been fitted to the properties, then the out of balance currents might have avoided a lot of the damage by disconnecting supplies.
Do you think a 'standard' 4ft rod with 10mm would have helped?

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Norman

"I suppose if RCDs had been fitted to the properties, then the out of balance currents might have avoided a lot of the damage by disconnecting supplies." normcall

Diverted neutral current will still flow through the bonding when the main switch is off.......

Regards

BOD

Not sure RCD's would help here Norm.

I'm assuming that these diverted neutral currents are coming from the Neutral/Earth connections made at the service head by the DNO. Hence the neutral is flowing along the metalic water & gas mains via the bonding connections.

The RCD would only 'see' this as a problem if the current came from a neutral/earth fault AFTER the RCD.

Obviously, this event has happened & we can only speculate.... but Im interested in what actually happened here to cause the explosion. There must have been something else at play other than just diverted neutral currents. Poor bonding connections getting hot when carrying a large current perhaps? But would that itself cause an explosion? Looking at the video it seems like the entire house was filled with gas before it exploded - something not quite right here.

Adrian

Not had time to watch it yet, but perhaps my call to UKPN this morning regarding missing pme earths off the LV overheads in my village might have been well placed

Stu

Reading between the lines, it seems the gas mains were damaged by 'hot spots' (951 clips on old lead) as Adrian suggests and it would only need a small spark to set the whole thing off.
I hope there is enough evidence left to pinpoint the cause so that both the DNO's and ourselves can find a way to minimise the risk as I don't think the price of copper etc. is going down in the foreseeable future. I don't want the usual 'it was an electrical fault' excuse coming out and suddenly finding we are blamed once again.

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Norman

RCDs will not help. Large CSA bonds to gas and water might stop the 0.75mm CPC in the flex to your gas boiler or immersion heater becomming a fuse if you have diverted large neutral currents. Also as recommended by the IET an auxilary earth rod on a PME supply to reduce touch voltage would be useful. I have a house with an overhead TNCS supply and I have fitted an earth rod, I might try and get all my neighbours to do the same.

In the videa there looks to be at least 2 explosions? One from the ground floor and a later one from an upper floor. Splash and dash seem to be rolling up their hoses getting ready to go home. I assume these were gas explosions?

I wonder how many "Ms" there were in the PME supply?

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John Peckham

http://www.astutetechnicalservices.co.uk/

How about just making your home a TT system.

With the increase in the theft of copper that is likely to continue would this be a good idea?

Give PME the boot.

Just had time to watch the video.

What happened to isolating supplies to properties ??? You would have thought they would have turned the gas off given the nature of the incident (unless of course they did not realise what was happening until later)

The video from I assume a second appliance showing a different view suggests the explosions came from two properties.

To further JP's thoughts, I'm TNCS but it's also got a rod for several reasons, but I might disconnect my TNCS earth completely in light of this sort of incident. After all living in mid Essex I'm a bit too close to the copper thieves main headquarters


Stu

You are never going to please the paranoid or the EMC brigade who believe ring mains are frying their brain that PME is a safe system and adding more and more green and yellow to a neutrally bonded system can in itself be hazardous, many papers and information from the once DTI have commented on the 'DIYing of PME by adding an earth rod', they call it DIYing because the people who do it are not generally skilled at earthing systems, the danger with fitting an earth spike in an urban, town, city or industrial site that are globally earthed is that as many as 100 houses could see your rod as the only passage to earth in the event of faults, or even network faults such as neutral problems and could raise the potential of your installation causing fire, injury and damage to equipment within the household.

Just waiting for the next attack!

PITA - RIP
Paradigm - RIP pending, collateral damage.

Not being a mod button presser because I dont care I would like to thank the person who obviously did.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------

Nice explosion, just goes to show what can happen when things are removed.


Still here at the moment but what will be, will be, after all, they are my words, my responsibility, unlike some.




regards

-------------------------
"be careful of what you write"

RnR,

When I put a rod on my PME system quite a few years ago (because of possible risk to radio equipment) I had a long and detailed technical conversation with an engineer from the then electricity board. We both came to the conclusion that a serious neutral fault upstream of my property could result in something rather unpleasant happening to my bonding as many properties looked at it as a return path. We decided that as there would be multiple earths on the network which would act to reduce the current flow through my electrode that the safest option would be to go for it.

He did add as a closing comment that "if anything strange started to happen" it would be best to call them promptly......

Stu

RnR

You are wrong about adding an earth electrode to a PME supply. It matters not whether 10,100 or a 1000 houses might use your electrode as a neutral return path as the current flowing to earth in the conductor and rod is limited by the earth electrode resistance, basic ohms law!

You will already have hopefully lower resistance paths to earth via the main protective bonding conductors so a higher current will flow in these conductors than to an earth electrode. If you do not have main bonding then diverted neutral current may flow in CPCs of a small CSA to earth via boiler and immersion heater flexes.

GN5 and an excellent paper written by Paul Cook to be found somewhere on this site recommend fitting an earth electrode to PME supplies to hold down the touch voltage depending on the connected loads in the event of losing the supply neutral.

Stu

Going over to TT will not protect you from over voltage caused by the loss of the supply neutral. It could be the fires in these properties are due to over voltage causing damage to appliances setting them on fire.

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/

Edited: 17 July 2011 at 04:44 PM by John Peckham

Thats Mr Cooks opinion not everyone shares the same view, most of it is theory and in the event of an incident no-one can predict the outcome as current takes on a life of it own and becomes unpredictable, its a Paradox, at the end of day its your house and you must make a judgement one way or the other.



Your already panicking about it by trying to convince your neighbours to do the same in case your installation becomes the hotspot for your area if there is a neutral problem.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------

Edited: 17 July 2011 at 04:52 PM by rocknroll

Its not just the number of houses.
It depends where the DNO earth electrodes are along the supply line and if they have been stolen or not, or
damaged by countryside hedge cutting etc.

Other domestic loads varying with time of day or night obviously.

We are becoming like South Africa with our stolen neutrals, but without their tailored protective devices for stolen neutrals.

Had a similar experience with a pole mounted tx feeding a farm house.
the neutral connection on the tx had failed & the entire neutral current was returning via a flexible rubber covered(smoking) gas pipe and next doors bonding & neutral connection.
hz

I don't understand this, how can the loss of a neutral create over voltages above 230V in a domestic location?

Postman

Your single phase installation is part of a bigger 3 phase installation.

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/

I believe even if supplys from a transformer being TNS would not removed the change causing 400 volts flying through a house hold on the effected phase ?

As for the video, possibly those houses were on the phase suffering overvoltage, with the possbility of them being TNCS and the pipe work become the reference to earth with high resistance and the pipe work to heat up and ignited ? So many factors play a part.

Will be of interest to see the report.

Many moons ago I was attached to a company in the West Midlands who had the DTI contract for upgrading the earthing and manufacturing and installation of N and E monitoring devices, most of the network has monitoring of some kind, one of their biggest customers was S Africa.

The copper thefts in the 80's was ten times more than it is now.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------