Tamper light

[BR]

a wholesalers near me was broken into recently, which had a relatively modern alarm system. Apparently the system was disabled by meggering the main supply to the building with 5000V! Sound possible?

 

[securespark]

Surprised the siren didn't survive and self-actuate.

 

[breezer]

a wholesalers near me was broken into recently, which had a relatively modern alarm system. Apparently the system was disabled by meggering the main supply to the building with 5000V! Sound possible?

doubt it, that would mean physically isolating ingoing supply (how, cant cut cable it will melt what you cut it with) then connecting a meggar bit far fetched if you ask me.

i once heard of a w/house the police put an "alarm" in (they do on rare occasions) owner came in in morning, w/house empty except for little pile in middle which was police "alarm" and a note saying better luck next time.


Now how true it is i do not know, you decide,

but one thing is for sure the police DO put in their own "alarm" very rarely

 

[BR]

doubt it, that would mean physically isolating ingoing supply (how, cant cut cable it will melt what you cut it with) then connecting a meggar bit far fetched if you ask me.

I don't understand what you are saying, melt what? do you mean shorting out the supply cable when cutting it? But my question was:
i believe megger testing some fire sounders will "totally destroy" them, is the same true for security systems (i.e would this work)

 

[breezer]

sorry, yes i did mean melting what ever you cut the supply cable with.

megger testing most things incorectly will destroy them, when a fire alarm is meggard all sounders etc should be taken off, as its the cable you want to test not the sounders (the same is also true of any installation, all "appliances" inc lamps (but couldn't think of suitable word) should be removed if not .................

 

[altec]

generally speaking, will a 500v or 1000v megger test destroy/damage anything accidently left connected to the circuit? I assume it would destroy electronic equipment, what about fridges/freezers etc. What about the fuses in videos for example.


I know it's not to be recommended but in practice what applicences are in your openion 'fairly resilient' to accidental meggering


Are the 'neon indicators' in FCU's / Cooker control switches a cause for consern.


When applicance technicians megger test, washing machines for example, what has to be disconnected first? Or have i got this completly wrong.


Final Question! How to the fire brigade manage to operate a fire control panel, if they cannot get the key. Do they have master keys or something?

Thanks very much

 

[breezer]

a megger generaly destroys electronics

anything that isnt electronic

in what way?

see later

they dont, a fire alarm is to protect life if it is a genuine fire no one worries about the fire alarm once building empty, you may see a fireperson resseting a fire alarm, but that is usually "i wonder if this button stops the noise?"

they may know somethings about fire alarms, but in general it is leftto the owner to sitch them off, they will look at it on arival to see where the "fire " is but thats about it.

when meggering a washing m/c you check phase to earth and neutral to earth not phase to neutral, this is also true of most other things, when testing an installation you remove all lamps etc, unplug sockets, as its the wiring that is being tested,appliances are "PAT" tested, whicch is a bit of a contradicition in words, since pat is Portable Appliance Test

 

[altec]

a megger generaly destroys electronics

anything that isnt electronic

in what way?

see later

I'm lost i was just wondering wheather accidently meggering a fridge which was accidently left plugged in will completly destroy it or what?

What about neon indicators in FCU's etc?

 

[breezer]

as i said when testing everthing should be removed, but assuming a fridge did get left in it depends on fridge, if it has electronic display/ temp control, it does stand a chance of getting blown, neon indicators have no physical connection from L - N (apart from the gas) but either of these will show a "suspect "readinmg so investigation should take place, to find why the reading is low and rectify it

 

[Inspector]

The control box, sounder and each pir will have a tamper switch. I'd try shorting out each tamper switch individually at the control box for a test period.

 

[breezer]

The control box, sounder and each pir will have a tamper switch. I'd try shorting out each tamper switch individually at the control box for a test period.

why?

that just proves the panel is ok, a decent meter will show any faults.

If you are that "stuck" you should dissconect the tamper in the detector, that way if nothing happens you know the fault has to be the tamper switch not the cable, as the cable has still been working but the tamper switch has not.

 

[Inspector]

breezer
Short it out at the panel to identify the faulty sub-circuit then get your meter out.

 

[breezer]

breezer
Short it out at the panel to identify the faulty sub-circuit then get your meter out.

no point, you should find it with a meter, no need to short it it out, besides, shorting it out still leaves it connected, what if some joker has put a staple through the cable? if you short it out it is still connected, which means you can still get a voltage that you shouldn't coming back up through the cable into the panel

 

[Inspector]

breezer
I think we'll have to agree to disagree - you're method of fault finding is correct also. Hope you understand mine.

 

[Stod]

When you make a megger test you should tie L to N and test for resistance to earth.

Appliances shouldn't be affected because they should be able to stand 5kV to earth.

If electronics has a connection to an earthed ELV circuit, it can be made to withstand 5 kV (using an opto isolator).