PAT Testing IWBs

[mk_193]

Hi,

 

I'm doing some PAT testing at my school, and am not sure if I need to PAT test our IWBs? They are hung on to our motorised bars but are essentially an individual unit.

If so, how would I go about doing this? I have only ever tested fixtures before so may not be something I could do myself

 

Thanks

[Andrew C]

If connected to the dimmers by plug & socket (any type) -

 

Test as an IEC lead with appropriate jumpers. This will check polarity as well as earth bond. You will need to decide an appropriate pass level for bond resistance, dependant on conductor csa and length.

 

Then test that the structure of the bar is bonded to earth on all circuits, unless it is on a single multipole connector.

If hardwired - over to your electricians for testing as part of the installation.

 

[Simon Lewis]

If hardwired - over to your electricians for testing as part of the installation.

 

...but do impress on any electricians that standard circuit insulation resistance tests may well cause damage to a dimmer hardwired to the IWB. They ought to know this, but.... ;-)

[sunray]

If hardwired - over to your electricians for testing as part of the installation.

 

...but do impress on any electricians that standard circuit insulation resistance tests may well cause damage to a dimmer hardwired to the IWB. They ought to know this, but.... ;-)

but.... ;-)

T-shirts in the drawer.

 

 

The first time I came across the problem, the testers had failed 72 channels of dimmer circuits as low insulation resistance and functional test.

 

Requiring the replacement of 72 triacs and capacitors. Fortunately the 3 main switches were off which potentially saved the power supplies.

 

Edited April 15, 2021 by sunray

[mk_193]

Thanks all for your help.

 

To be on the safe side I'm going to hand it over to a more experienced electrician!

[Robertdazzler]

I'm with Sunray on this one. My local authority employed testers to check hard wired bars etc for insurance purposes. If I had not stopped them they would have happily megger tested all sockets on the bars and destroyed many triacs. Theatre electrics are not so run of the mill and electricians need to be trained accordingly- not all are! The solution in our case was to disconnect the pairs of tails in the dimmer panels before testing and then everyone was happy although it took a long time.

[sandall]

When my local authority outsourced their technical services the new "electricians" wrecked 2 racks of LD90 by meggering all the sockets they could find. The company then effectively vetoed getting them repaired, which meant having a new set of racks installed, all at the ratepayers'' expense !!

[J Pearce]

I've always used theatre/events specific electricians for this exact reason. Though at a previous job it did take the contract PAT testers wiping out nearly a whole recording studio (best to unplug peripherals before earth bond testing at 25A...) to persuade those in charge that the extra expense was worth it.

[kgallen]

I'm confused - and concerned for my own venue which has just gone through IWB "PAT".

 

How can you "PAT" this connection for earth bond and insulation unless you have access to both ends of the cable? In my case we have Betapacks with 15A sockets, so the earth bond and insulation test would require the 15A plug to be withdrawn from the Betapack in order to be connected to the tester, then a flying lead to connect to the IWB socket. I don't understand how this test could be performed purely at the socket end of the IWB and thus damaging the triacs inside (presumably hard-wired dimmer-per-outlet) dimmers.

 

Please elaborate!

 

 

Thanks,

Kevin

[Andrew C]

The OP asked about PAT. You can sort of PAT if, as you say, you can get to both ends. IWBs that are hardwired still need testing; you just can't PAT them. Hence the need for a competent sparky to do insulation tests.

[DrV]

I'm confused - and concerned for my own venue which has just gone through IWB "PAT".

 

How can you "PAT" this connection for earth bond and insulation unless you have access to both ends of the cable? In my case we have Betapacks with 15A sockets, so the earth bond and insulation test would require the 15A plug to be withdrawn from the Betapack in order to be connected to the tester, then a flying lead to connect to the IWB socket. I don't understand how this test could be performed purely at the socket end of the IWB and thus damaging the triacs inside (presumably hard-wired dimmer-per-outlet) dimmers.

 

Please elaborate!

 

 

Thanks,

Kevin

 

It's easy to do an insulation resistance test from the socket end. Checking the earth bond, however, required a flying lead from the earthing connection at the supply end up to the socket, or shorting the live and neutral to earth at one end and effectively using the L and N as your flying lead. Obviously part of the insulation resistance test will apply your test voltage to the dimmers.

 

Edit: None of these tests is a basic "PAT" test though, so needs to be done by someone who understands what they're doing rather than someone who has done an internet "qualification"!

Edited April 20, 2021 by DrV

[kgallen]

Thanks all.

It's easy to do an insulation resistance test from the socket end.

 

Understood, but doesn't this require a widow-maker plug-plug lead into the tester and IWB socket - with the 500V insulation test voltage on it? This all sounds very dodgy. Hopefully the "PAT Tester" used by our hall doesn't carry a 13A-15A plug-plug lead for such an exercise (I'm surprised they could even handle the 15A plug/sockets at all - at least no "failing" plugs were cut off...)

 

However it seems it would be prudent to do some dimmer checks at my venue...

 

 

 

[DrV]

Thanks all.

It's easy to do an insulation resistance test from the socket end.

 

Understood, but doesn't this require a widow-maker plug-plug lead into the tester and IWB socket - with the 500V insulation test voltage on it? This all sounds very dodgy.

No more dodgy than a pair of test leads with croc clips on the end. In fact my installation tester came with a ready made lead with 3 4mm plugs on one end and a 13A plug on the other. But this sort of testing needs to be done by someone who understands that they can get a shock off their own test equipment. The current it supplies is non-lethal but the surprise it can give you could be enough to make you fall off the ladder (that you're not using for safety reasons ?)

[kgallen]

In fact my installation tester came with a ready made lead with 3 4mm plugs on one end and a 13A plug on the other.

 

Aha - key point: electrical installation tester (hence the banana plugs and 13A plug ready for house socket-based testing) versus a PAT machine with a 13A socket on the front!

Edited April 20, 2021 by kgallen

[Andrew C]

Understood, but doesn't this require a widow-maker plug-plug lead into the tester and IWB socket

Nope.

13>15 from the tester, 15>iec from the bar to the tester. All fairly standard stuff it you are doing theatres.