PAT testing - earth continuity

[alchemist]

I was taught that when testing a class 1 appliance, the resistance between the earth pin on the plug, and exposed metalwork should be less than 0.1 ohms + the resistance of the cord, which I can get from the in service inspection and testing book.

In practice, when testing even new equipment I never get readings that low.

Can anyone shed any light on what the acceptable values are?

Mike

 

[alchemist]

I was taught that when testing a class 1 appliance, the resistance between the earth pin on the plug, and exposed metalwork should be less than 0.1 ohms + the resistance of the cord, which I can get from the in service inspection and testing book.

In practice, when testing even new equipment I never get readings that low.

Can anyone shed any light on what the acceptable values are?

Mike

 

[ProDave]

From the niceic guide to PAT testing

"A value of 0.1 ohms should be met without difficulty for larger appliances. For low wattage appliances and luminaires, a value of 0.5 ohms applies"

My own tester has a pass fail threshold of 0.3 ohms.

Agreed it's difficult sometimes. Pat testing a Tumble dryer last week and could barely get down to 0.3 ohms, let alone 0.1

Sometimes you have to use your judgement. In the case of the tumble dryer, I took the back off, found the end of the cable, and tested right where the earth lead of the flex was bolted to the case of the dryer and tested there, and still only go 0.3 ohms, so I concluded that was really the resistance of the carp cable they had used and passed it.

Testing earlier in the year in an Office, I failed, and scrapped several IEC mains leads where I couldn't get below 0.7 ohm on a 1.5 metre lead.

 

[ProDave]

From the niceic guide to PAT testing

"A value of 0.1 ohms should be met without difficulty for larger appliances. For low wattage appliances and luminaires, a value of 0.5 ohms applies"

My own tester has a pass fail threshold of 0.3 ohms.

Agreed it's difficult sometimes. Pat testing a Tumble dryer last week and could barely get down to 0.3 ohms, let alone 0.1

Sometimes you have to use your judgement. In the case of the tumble dryer, I took the back off, found the end of the cable, and tested right where the earth lead of the flex was bolted to the case of the dryer and tested there, and still only go 0.3 ohms, so I concluded that was really the resistance of the carp cable they had used and passed it.

Testing earlier in the year in an Office, I failed, and scrapped several IEC mains leads where I couldn't get below 0.7 ohm on a 1.5 metre lead.

 

[Riggy]

Testing earlier in the year in an Office, I failed, and scrapped several IEC mains leads where I couldn't get below 0.7 ohm on a 1.5 metre lead.

Same here, IEC leads are a pain, particularly the ones with moulded plugs, I've found if you chop the moulded plug off and fit a new one you then get a decent earth bond.

Why should that be? - no idea but it's happened too often to be a coincidence!

 

[Riggy]

Testing earlier in the year in an Office, I failed, and scrapped several IEC mains leads where I couldn't get below 0.7 ohm on a 1.5 metre lead.

Same here, IEC leads are a pain, particularly the ones with moulded plugs, I've found if you chop the moulded plug off and fit a new one you then get a decent earth bond.

Why should that be? - no idea but it's happened too often to be a coincidence!

 

[matt.leung]

when was a tumble dryer classed as portable.

 

[matt.leung]

when was a tumble dryer classed as portable.

 

[ProDave]

when was a tumble dryer classed as portable.

For a rental property, all electrical appliances are usually checked, including washing machines and dryers.They may not be "portable" but can be just as lethal if something is wrong.

I pat test anything with a 13A plug on it. Actually I also test fixed machinery as well if asked to, in which case it's a grey area sometimes whether it's covered by a PIR or PAT test.

 

[ProDave]

when was a tumble dryer classed as portable.

For a rental property, all electrical appliances are usually checked, including washing machines and dryers.They may not be "portable" but can be just as lethal if something is wrong.

I pat test anything with a 13A plug on it. Actually I also test fixed machinery as well if asked to, in which case it's a grey area sometimes whether it's covered by a PIR or PAT test.

 

[Andy™]

when was a tumble dryer classed as portable.

portable appliance testing is short (and more common name) for 'in service inspection and testing of electrical equipment'

being portable has nothing to do with it.

generally, if it has a plug, test it

 

[Andy™]

when was a tumble dryer classed as portable.

portable appliance testing is short (and more common name) for 'in service inspection and testing of electrical equipment'

being portable has nothing to do with it.

generally, if it has a plug, test it

 

[alchemist]

Agreed, PAT is a misnomer. The guidance for 'in service inspection and testing', which is the reference for PAT testing from the IEE/IET covers appliances that are not handheld, portable, movable etc - and it defines each based on it's weight and whether it's designed to be moved or not.

I think the idea is to test every appliance, even if it's not got a plug. Lack of earth continuity is a danger whether there is a plug or an FCU or neither, because the fuse won't blow if the continuity is poor.

The reason for my question is that appliances I have tested typically have higher readings than recommended. I've found that (in the case of a metal kettle) it was actually because it had one of those bases it fits into and it depended on how it was rotated as to the quality of the connection. I don't think this is a fault, it's a design flaw. Should I pass or fail? Earth continuity varies between 0.25 ohms and 1.4 ohms depending on the orientation of the kettle on its base.

1.4 ohms is perfectly adequate to cause disconnection but not a pass based on the guidance notes because it's well above 0.5.

 

[alchemist]

Agreed, PAT is a misnomer. The guidance for 'in service inspection and testing', which is the reference for PAT testing from the IEE/IET covers appliances that are not handheld, portable, movable etc - and it defines each based on it's weight and whether it's designed to be moved or not.

I think the idea is to test every appliance, even if it's not got a plug. Lack of earth continuity is a danger whether there is a plug or an FCU or neither, because the fuse won't blow if the continuity is poor.

The reason for my question is that appliances I have tested typically have higher readings than recommended. I've found that (in the case of a metal kettle) it was actually because it had one of those bases it fits into and it depended on how it was rotated as to the quality of the connection. I don't think this is a fault, it's a design flaw. Should I pass or fail? Earth continuity varies between 0.25 ohms and 1.4 ohms depending on the orientation of the kettle on its base.

1.4 ohms is perfectly adequate to cause disconnection but not a pass based on the guidance notes because it's well above 0.5.

 

[Andy™]

The reason for my question is that appliances I have tested typically have higher readings than recommended. I've found that (in the case of a metal kettle) it was actually because it had one of those bases it fits into and it depended on how it was rotated as to the quality of the connection. I don't think this is a fault, it's a design flaw. Should I pass or fail? Earth continuity varies between 0.25 ohms and 1.4 ohms depending on the orientation of the kettle on its base.

1.4 ohms is perfectly adequate to cause disconnection but not a pass based on the guidance notes because it's well above 0.5.

i would go with fail - it may be 1.4 today, but what about next week? you already know its unstable

 

[Andy™]

The reason for my question is that appliances I have tested typically have higher readings than recommended. I've found that (in the case of a metal kettle) it was actually because it had one of those bases it fits into and it depended on how it was rotated as to the quality of the connection. I don't think this is a fault, it's a design flaw. Should I pass or fail? Earth continuity varies between 0.25 ohms and 1.4 ohms depending on the orientation of the kettle on its base.

1.4 ohms is perfectly adequate to cause disconnection but not a pass based on the guidance notes because it's well above 0.5.

i would go with fail - it may be 1.4 today, but what about next week? you already know its unstable

 

[Larnacaman]

Any appliance that is connected directly to a metallic water supply, ...ie, drinking fountain, kitchen sink water heater, will never pass a PAT test!! Not unless you disconnect the metallic pipe connection first....

 

[Larnacaman]

Any appliance that is connected directly to a metallic water supply, ...ie, drinking fountain, kitchen sink water heater, will never pass a PAT test!! Not unless you disconnect the metallic pipe connection first....

 

[Theorysparky]

[quote name='Andy

 

[Theorysparky]

[quote name='Andy