Pat Testing 'delicate' Equipment

[Apache]

Hello all.

I have done an online course, passed the exam and bought a book to do my own PAT testing at work.

Megger Mark hooked me up with a PAT tester:

http://isswww.co.uk/Pat-Testers/Seaward/Seaward-PrimeTest-100-PAT-tester-IEC-lead-tester-and-a-power-soc/

I have a question. When learning it was suggested that IT and delicate medical equipment the IR test should be done at 250V rather than 500V. This basic tester only offers 500V.

Am I likely to fry my computers/xray machine/ultrasound scanner at 500V?

I can do the IR with my MFT @ 250V but then not sure if I can test earth leakage in isolation.

Any thoughts guys?

 

[Apache]

Send it back to MM and get one that does a proper job ?

mmmmmmm - serious point?

 

[batty]

I have a really basic tester that has a low current test for IT and delicate stuff. Problem is Pache if you do knacker your stuff it could be really costly for you. I just would not risk testing at high current and voltage.

 

[Andy™]

just do what the 50p/item crew does. put a green sticker on and move onto the next item

 

[Apache]

just do what the 50p/item crew does. put a green sticker on and move onto the next item

The thought briefly crossed my mind, but if I am going to this trouble I'd rather do it properly.

Has anyone ever really fried anything @500V or is the risk theoretical?

 

[Evans Electric]

I never did a 500V insulation test on IT stuff , not willing to begger it all up and foot the bill TBH . I did the IDS leads or whatever they're called . Although I'd guess with a PC you'd only megger as far as the primary on the input transformer . I did a continuity test (Low volt) from the plug top plns to the metal casing of PCs .

And sensitive medical equipment ...no way TBH unless makers tell you in writing that you can wang 500V through it!!!

Told you to just hire a tester every 2 years did I not ?? Does anyone ever listen to me ? :C

We are told to disconnect stuff like emergency fittings and IIRC HF fluorescents shouldn't be meggered.

 

[M107]

Not fried anything myself, but we have had testers in who managed to cook some of our older sun pc's (used for old mobilising equipment) a few years ago...........

 

[Apache]

Told you to just hire a tester every 2 years did I not ?? Does anyone ever listen to me ? :C

You did and I looked at the option. I live nowhere near a place that hire these things. By the time I'd paid a Currier to deliver and collect and hire for a week there wasn't change out of £100. The tester only cost twice that to buy. And I can do the testing when I have a spare 20 minutes rather than having a load to do all at once.

 

[Andy™]

The thought briefly crossed my mind, but if I am going to this trouble I'd rather do it properly.

Has anyone ever really fried anything @500V or is the risk theoretical?

the risk is there of frying stuff, the main risk is 500v L-N. if your testing L-E, its not such an issue, however, some electronics have filters etc between L&E which could be damaged. also, because of the extra voltage, it could fail an IR test L-E even though at 230v there is no fault

 

[SPECIAL LOCATION]

The thought briefly crossed my mind, but if I am going to this trouble I'd rather do it properly.

Has anyone ever really fried anything @500V or is the risk theoretical?

The things you have got to consider is...

what electrical components are directly connected to the live and neutral of the equipment you are testing??

{ALSO: remember that 500v is DC!}


so...
if the equipment you are testing has an input transformer...
TBH you are unlikely to damage the transformer...

and as you are testing with DC...
the transformer will effectively stop the voltage going any further as the transformer relies upon AC to work!!!

You are unlikely to pop any resistors with your 500v DC..

and I don't think there is enough oooomph! to pop a capacitor or a diode with the test current @ 500vDC...

But....
if there is a device with a semiconductor package directly across the supply line then I wouldnt like to hazard a guess either way!!!!!


many years ago I think i may have Fried a central heating program controller...

But the customer never continued to pursue any claim against me & I never paid any thing extra....

 

[Steve3948]

I once tested a Glass Washing machine in a men's working club, that night it failed to work, so they called me wanting me to get the unit repaired and pay as I was the last one to touch it.

I called the manufacturer to clarify if it was remotely possible that carrying out the PAT would cause the machine not to function.

They said that doing the test would not cause damage to the machine but if a component was bordering on failure it may have helped it on its way.

I called the club and said the idea of the test is to make sure items are safe to use and not blow them up, also emailed letter from manufacturer saying my test was not responsible the failure.

Never got invited to re-test though.

The Seward I have now has various settings for IT equipment, Static Equipment, Portable Equipment, Leads of many sorts.

I'm not keen on PAT, so I don't do much, found that my machine would allow about 10 tests per hour, including unplugging sorting leads etc, so my £3.50 per appliance does not go down well, especially when local DNO do it at £1.50.

 

[Evans Electric]

You did and I looked at the option. I live nowhere near a place that hire these things. By the time I'd paid a Currier to deliver and collect and hire for a week there wasn't change out of £100. The tester only cost twice that to buy. And I can do the testing when I have a spare 20 minutes rather than having a load to do all at once.

That makes sense !

 

[Marvo]

I'd agree with Andy in post#10. You're likely to get false IR readings because of the surge arrestors in the power supply probably conducting to earth at that voltage  and it might cause damage to them. Many IT systems and medical appliances are class II in which case you could skip the insulation test entirely if your PAT tester gives you that option. On those that aren't you should short out the L+N when IR testing to reduce the possibility of damaging internal components.