IR test bellow 1Meg

230V/1000Ω = 0.23A (=230mA) not 0.23mA


As for how much danger readings below 1MΩ suggest - it rather depends on the situation. Not only on how much current is likely to be escaping, but also where it's going and what other sort of damage a low reading might suggest.


1MΩ is pretty arbitrary - the actual figure and now much of the installation the figure applies to has changed hugely over the years - and in an even in BS 7671 only applies to new work (rather than EICRs). In many situations 1MΩ would be ridiculously low for a satisfactory installation (say a reasonably small modern PVC/PVC system with no connected appliances) - and figures many times that should really be treated with caution. For other systems (say old damp pyro) 1MΩ would be quite optimistic and much lower values might be considered satisfactory. Some appliances can have quite low IR values - some e.g. traditional cookers - may well have a lower values than the entire rest of the installation.


Leakage from within a pyro or SWA installation with metal clad equipment, all solidly earthed, is much less of a safety problem than the same leakage that's escaping to unearthed surfaces that people could touch.


As for this pump, 1kΩ though is VERY low. 230mA going the wrong way could be lethal (and no, conventional fuses or circuit breakers wouldn't stop that either - but  RCDs might, although you shouldn't really be relying on them). Presuming it's not a huge industrial pump, I presume water has got past the seals and the pump isn't going to last very long if left neglected any longer.


   - Andy.

Thanks again Andy. So 230Ma is a lot to be flowing to earth. So ideally this should be condemned really.

I suppose how dangerous would depend on the touch voltage?

Exactly so, and if the earth wiring is solid (say less than one ohm,), then even though this is nearly quarter of an amp running off the wrong way,  the case of the pump will not be significantly live, say 1/4 of a volt for those numbers ...


But now you only need one fault, rather than the usual two, to make things very dangerous - a single rusty bolt or a loose screw anywhere along that earth path might not normally be an issue,  but now suddenly in that case the motor (or worse some of the building metalwork connected to it) is not as safe to touch as you thought.


Also be aware that many insulation meters are not very accurate doing readings well away from the 1 meg pass-fail limits where they are calibrated. Unless you have verified that 1k ohm with another meter that has a resistance range that is more suitable I should just mark it up as very low, and not be too surprised if your missing quarter of an amp was actually twice or half that on another instrument. In the meantime, double check the reading really is due to the motor, and not the controller or a joint in the wiring, then ring round to get a quote for a new one, you'll be needing it soon.

Mike

That much leakage is very dangerous IF it passes through a human body.

For a pump that is presumably earthed, AND probably out of reach the risks seem small.


It is however a worrying sign WRT future reliability. If the pump is large and costly I suggest a full overhaul, if small and cheap, precautionary replacement might be prudent.


Apart from the potential dangers, energy is being paid for and wasted. About 50 to 60 watts is being wasted, depending on tarriff that could cost as much as a penny an hour. Or in the region of £80 a year.


Before condemming anthying, double check, preferably with a different instrument. Also double check that the observed result is not due to a pilot lamp, contactor coil, level switch or other ancillary item mis-connected between phase and earth, rather than between phase and neutral.

I

Where was the reading taken, which part of the circuit ?

and was the load disconnected ?

so the measurement was reading the fixed wiring?

or was it just the motor windings?

etc..........

230mA to earth while the motor is swiched on and powered up might be regarded as 'rather' leaky but not totally desparate as long as the cpc terminals connections throughout the circuit are in good order, if however the measurement was across the fixed wiring only then there may be a poor insulation problem. and as Mike says if the connections throughout the cpc are suspect then there will be volt drops and the likelihood of a shock potential with the potential to deliver a killing current..Circuits with >10mA leakage currents require extra eathing facilities (high integrity earthing arrangements)

Legh

The measurements were at the motor. What do you mean by two faults. Obviously it’s not good but the pump is out of reach but has metal work connected to it. My understanding was if it’s well earthed the voltage should be minimal due to the resistance of R1 plus the 1000kohm. But also confused as to if it was to become dangerous wouldn’t the fuses take care of that considering the ZS is correct. Thanks guys

But also confused as to if it was to become dangerous wouldn’t the fuses take care of that considering the ZS is correct.

ADS is only intended to work for faults of negligible impedance - say a live wire coming loose and touching a metal case of an appliance or insulation melting away to allow a live wire to touch something earthed (which covers the vast majority of dangerous faults). Traditional ADS doesn't work for faults of much higher impedance (say due water ingress or corrosion) or direct contact where a victim touches a live part and their body resistance limits the fault current.

   - Andy.

Double check - do you mean 1k ohm (thousand ohms) or 1000 k ohm = 1meg = 1 million ohms ?


A meg, or even a few hundred k, is an entirely believable leakage for equipment in a damp location.


less than a few tens of k isn't  and  10k passes  23mA  if L-E  on a 230V supply and in the wrong place that current is on the edge of fatal.


(In terms of shock currents, less than a mA you probably will scarcely feel it , 10mA is really painful, and by 100mA if the RCD does not take it off in a heartbeat or two, you are a goner.  Luckily the contact resistance of small regions of dry skin, shoes and clothing often conspire to keep otherwise dangerous shocks to the sub 10mA level where you can pull away and swear a bit,  but you should never rely on it - good contacts with damp hands on spanners or hand rails, can make even voltages lower than 50V quite  dangerous. There have been fatalities with 28v military vehicle electrics, where folk have been badly injured before electrocution, and the normally semi-insulating skin is damaged and wet with blood, though to be fair they may well not have made it anyway.)


As a rule of thumb for the basis of C1 vs C2  on inspections

C1 is immediately dangerous (there are already enough faults to give someone a fatal shock, live parts exposed)

C2 is could become dangerous (one more entirely credible event /fault  could make this dangerous)  - like it sounds like we have here - for example if the earthing relies on the mounting and the bolts are on paint instead of metal)