P.A.T

snip

How does keeping records of a pass/fail result help determine whether the insulation resistance of a device is lower than should be expected, while still better than the legal minimum?

-- Regards Malcolm. Remove sharp objects to get a valid e-mail address

You keep a record of the insulation resistance and compare with previous readings. A sudden drop, even if the appliance is still above the minimum value, would be cause for concern. Depending on the circumstances, you might fail the appliance or schedule a retest sooner than would otherwise be the case.

A PAT tester which only gives you a pass/fail indication isn't suitable for meeting the record keeping requirements of a routine PAT testing schedule.

You need a tester which tests insulation resistance by earth leakage. The one you identified does appear to have this capability, although I'm not personally familiar with it. The earth continuity test current is rather low and this means you will take longer to perform that part of the test as you will have to work your way along the entire mains cord flexing each part of it. A unit with a higher earth continuity test current would enable you to perform this test as a one-shot test. If you have only a small number of class I appliances to test, this won't matter much, but if you had hundreds, then it might -- depends what your time is worth.

Most of the equipment you listed counts as IT equipment, although one important bit of information you didn't give is the environment in which it is used. If we're talking about an office which isn't in use by the general public, then the recommended full testing period for such equipment is, IIRC, 4 years. That's often longer than such equipment is kept, as it becomes technologicaly obsolete before then. In such a case, you might decide to ensure the equipment is disposed of within 4 years, rather than spending money PAT testing worthless equipment. You should schedule formal visual inspections though, say on delivery and at 2 years old.

In other situations, e.g. a school, or equipment used by the general public, or if the equipment is frequently moved around or roughly handled, then a more frequent inspection regime would be appropriate.

Also, if your inspections are picking up significant failures, then you should schedule them more frequently, and question if the equipment is suitable for the environment in which it is being used. Conversely, if you are never picking up failures (and you keep records to show this is the case), then you could reduce the testing frequency.

Ah. My original comments clearly related to PAT's with pass/fail indication because that was the type that the OP was considering buying.

But they are suitable for satisfying the standards and legal requirements, which was JW's comment.

-- Regards Malcolm Remove sharp objects to get a valid e-mail address

A demented Sloth could do PAT testing anything is better than nothing

Chris

500H is good for IT gear & actually gives meaningful readings which can be recorded - Ive had mine for 6 years ..operates like a Wheatsone bridge so you can extend the earth test lead to cope with physically large equipment. I've mentioned before that it's a good idea to get a loop tester as your PAT gear only confirms earth to the socket this is cheap also does phase reversal etc this one as it doesn't trip all the RCD sockets we have to use.

also use this

insulation testing & bonding resistance

I don't - bonding beyond SELV has gone - I'm trying to avoid danger as much as I can.

We have a system of paperwork for reporting back to manufacturers which works quite well - I recently complained to a Spanish manufacturer about using Blue as Live & Brown as neutral - this apparently is common in Spain but they have agreed to modify future equipment.

Happens occasionally when an IEC connector looses earth & the equipment chassis goes half mains potential through the filter caps or MOVs - another reason for not bonding everything in sight.

Well that's just me - done death at work & don't want to do it again doing CPR & mouth to mouth on a ten year old that's dead & losing stomach contents just in case a defibrillator arrives is no fun - we thought he'd been electrocuted by us.

Yep - I know what you are saying - I don't just PAT test ...in conjuction with my local HSE & our self regulating body I try to ensure the safety of our customers & employees

I read in sci.engr.electrical.compliance that Chris Oates wrote (in ) about 'P.A.T', on Mon, 1 Mar 2004:

I don't understand what you mean by that. What has bonding to do with SELV?

Well, perhaps we need to make clear which country's legal requirements. I was talking about the UK. We have no legal requirement to perform PAT testing at all, but we do have several legal obligations placed on employers. The IEE and HSE have come up with a PAT testing procedure which is recognised as meeting the relevant parts of those legal obligations, but it is not only way to do so. Employers are free to define their own procedures, although they may have to defend them in court.

Just attaching equipment to a pass/fail PAT tester is most unlikely to meet anyone's legal requirements for PAT testing. As I said earlier, that will pass over 90% of the appliances which should fail.

Aha - sorry My problem is an environment which caters for 1 - 99 years inquisitive babies, drunken yobs, mindless thugs, total lunatics and sometimes normal people.

All exposed metalwork had to be bonded & this led to silly situations where acres of earthed metal were on hand for people to potentially pass current through their bodies from a fault.

Things like door locks got earthed despite there being no 'unsafe' voltage within feet of them.

Our customers are quite likely to attack an appliance's lead with lighters, knives or attempt strangulation with it or just try to destroy the machine leaving it in a dangerous state.....baby comes crawling along and picks up burnt lead & touches door lock (for instance)

Rules changed so bonding wasn't required after an SELV so we could get rid of the earthed metal that could never have become live anyway

B4 anyone mentions RCDs - we do make extensive use of them (on sub mains that will bear them) & on critical equipment but with 300 odd sockets running mostly SMPS it's very expensive and troublesome.

I read in sci.engr.electrical.compliance that Chris Oates wrote (in ) about 'P.A.T', on Tue, 2 Mar 2004:

You mean, like a newsgroup? (;-)

Yes. I hope you have earthed the castors of your pool tables. (;-)

I still don't understand that. What do you mean by 'after an SELV'?

Bonding ('equipotential bonding') isn't actually intended to prevent accessible metal becoming live. It's intended to keep such metal at the

**same potential as accessible metal connected to the protective earth conductor (PEC) under high-current fault conditions**, which is higher than 'true earth' potential by the voltage drop across the PEC caused by the fault current.

But you are quite right about the ludicrous interpretations of the bonding rules. Accessible metal that is electrically isolated by high- quality insulation does not present a hazard under high-current fault conditions.

You have sub-mains that leak too much to use RCDs?

Can I suggest that the relevant Regs would mainly be PUWER (Provision and Use of Work Equipment Regulations). Which states that equipment must be maintained safely and one way to demonstrate this is by PAT Testing. Not forgetting to do a risk analysis to determine the time interval between tests depending on the conditions of use.

Blue Skies Pat Carpenter