Voltage Detector

[skind56]

Hi

I'm having a new front door installed soon and will require to re-fit the doorbell and burglar alarm door contacts.
I can isolate the current by use of one circuit breaker switch that does for both the bell and burglar alarm but I wish to ensure no current by use of a voltage detector - just to be sure.

Which voltage detector would be recommended for such a task?

Thanks in advance for any help.

Regards
Steve

 

[Lister1987]

The best way (and arguably only way) to ensure safe isolation is by the use of a GS38 approved 2-pole tester and proving unit.

The testers themselves can be found from a never of brands; from Di-Log to Kewtech to Megger and beyond, all operate on the same principle.

I use a Martindale VT12 myself and a Kewtech Kewprove 3 proving unit.

It is vital that you 'prove' (read:verify) the operation of your tester on a 'known source', the majority use proving units, however you can use the top of the main switch as your 'known source' and check for safe isolation at the bottom of the main switch. This must be done before and after the locking of device has been applied, to ensure the tester did not become faulty during the process.

Tools are nothing without proper training, the video below from GSH ELECTRICAL serves purely as a demonstration of technique and in no way takes the place of formal training.

As ever, the 'forum line' is to get a competent professional in if you are unsure what you are doing, neither the forum, myself or by extension GSH ELECTRICAL, take any responsibility for an actions from this. The very fact you're asking about the right kit, gives the impression you're likely to do it anyway so may as well give you an example of how to do it properly.

 

[telectrix]

you don't need to isolate the mains feed. if replacing the door frame remove the door contact being careful not to disturb the wiring. the magnet (on the door) is just a magnet. refit to new door in line with contact. As for the bell. diss. the wires from old bell push one at a time, and tape ends separate. refit in reverse order.

 

[pc1966]

I would get one that does not requiem a battery. They don't do anything else really beyond checking there is voltage or not, but that is what you want and you don't come back in a couple of years to find it destroyed by corrosion when you forgot to remove the battery...

As above it is vitally important that you know the tester is working so you should check it on something you know is live before accepting it telling you it is not. You can buy proving units for this job but in many cases you can get by without one E.g. test there is power then switch off and see there is no power (so you got the right switch/breaker). But proving unit or not, you must always verify it is working before (and ideally after) each test.

For example:
https://www.screwfix.com/p/lap-ms8922b-2-pole-voltage-tester-with-rcd/669hy

 

[James]

Check door bell works
Turn the breaker off, tape a note over it forbidding turning on.
Check door bell no longer works.
Go to alarm panel, it probably says mains failure on the screen.
Go to main alarm panel, might be same place, open cover and disconnect battery.
Alarm sounder will make noise, will stop within 20 minutes.
Check alarm control panel shows no lights or screen.

Change door
Do the reverse of above.

 

[skind56]

Thanks for all the replies. Very useful advice. I'll probably invest in the voltage tester suggested by pc1966.

telectrix, as you say the door frame (uPVC) will also be replaced, so both the doorbell and door contact will have to be removed allowing the fitters to feed the wires into place so I believe I require to turn off the breaker?

Thanks James re the alarm advice. So if I turn off breaker and disconnect battery then the door contact should be isolated? Will the alarm sounder not stop then too?

 

[James]

Alarm sounder have there own backup battery
When disconnected from the alarm, they will sound.
20min is the longest time they are allowed to sound for, so should turn off at that point or before if the batt runs flat first.

 

[inquisitive]

For example:
https://www.screwfix.com/p/lap-ms8922b-2-pole-voltage-tester-with-rcd/669hy

You also recommended this one to me, thanks. Screwfix are usually all right, and the price is really good.

But: any idea if this model meets the GS38 requirements? It doesn't say one way or another on the Screwfix description. Do you know if it says on the packaging?

Are we not better shelling out £50 on a model that explicitly says it meets GS38? Or are you trying to be realistic about what DIYers will spend, that they're better buying this 2 pole tester, if the alternative is them relying on a non-contact tester?

 

[telectrix]

You also recommended this one to me, thanks. Screwfix are usually all right, and the price is really good.

But: any idea if this model meets the GS38 requirements? It doesn't say one way or another on the Screwfix description. Do you know if it says on the packaging?

Are we not better shelling out £50 on a model that explicitly says it meets GS38? Or are you trying to be realistic about what DIYers will spend, that they're better buying this 2 pole tester, if the alternative is them relying on a non-contact tester?

GS38 testers have a specified bare tip length of 2mm. that cheap one does not comply, athough it's a better tool than a non-contact pen, a better option is the di-Log unit, also from screwfux.
https://www.screwfix.com/p/di-log-dl6790-combivolt2-2-pole-digital-voltage-continuity-tester/738jp

there's also the fluke a bit more expensive.

better spend a bit more as the one i linked to will last for years.

 

[pc1966]

The LAP one does not mention GS38 but it does claim CAT III rating to 400V which is an essential part.

I would still go for a non-battery one even if looking explicitly for a GS38 one. For example:
https://www.cef.co.uk/catalogue/products/4193118-voltage-tester-6-400v
(It shows exposed tips, but data sheet shows them with shrouds to me GS38 so presumably you get the choice)

Or this one is decent (probably you will get it cheaper than RS by searching):
https://uk.rs-online.com/web/p/voltage-indicators/7047753/

Or if you really want the daddy of them all:
https://uk.rs-online.com/web/p/voltage-indicators/7068573/

(If / when I replace my tester I am looking to get the Drummond type)

 

[pc1966]

Or this for £20 looks a bargin:
https://www.toolstation.com/tis-voltage-tester/p11032

The company says GS38 compliance (and RRP of £27):
https://www.testinstrumentsolutions.co.uk/view-product/tis-819-voltage-tester

 

[dodger421]

A previous workplace supplied that TIS819 with a proving unit to me and a new apprentice when I started. It was horrible, the PU only worked reliably if you pressed the probes in very hard and the probes on the tester bent at the slightest pressure.

It did come with shrouds though, and complied with GS38. I still preferred using my own Fluke though, I just trust it more.

 

[telectrix]

2 prong volt testers only use batteries for continuity tests. they will indicate voltage without batteries or if the batteries are dead.

 

[telectrix]

my current one is same as this but red with phase sequience indicator and half the price from china>
https://www.screwfix.com/p/di-log-dl6790-combivolt2-2-pole-digital-voltage-continuity-tester/738jp

 

[pc1966]

I got one of these proving units which it relatively inexpense:
https://www.cef.co.uk/catalogue/products/4457482-proving-unit
Needs only a light probe pressure to work, also has a button for checking non-contact detectors.

As an aside, the non-contact detectors have their use for seeing if something is live (e.g. tracing which cable is on without having to gain access to junction boxes, etc) but never for proving dead. Basically you only use them for some aspects of convenience but you can never rely on them to detect power or the lack of it. Generally I would advise not to get one as the temptation to use it inappropriately may be too high,