IEC 60601 Ground Bond Test Requirements for a Plastic Enclosure

[ale_pb]

Hello

My question is:

Let's say that I have a CLASS I EQUIPMENT, with a plastic enclosure and no accessible metal parts.
Reading the 60601-1 it seems to me that, if I don't have any accessible metal parts, the ground bond test is not necessary. Am I correct?

Best Regards

 

[Pads38]

Re: Ground bond test - Plastic enclosure

The ground bond test verifies the impedance of the protective earth. If you have a protective earth (defined term in 60601-1) then you need the test.

For a type approval test this could be done 'with the lid off' but it is also one of the tests that a hospital service department would expect to do and you run the risk of problems if you don't make it easy for them. (Things like trying to use 25A test current on a point that goes via a small circuit board trace).

I have found that adding an equipotential point on the rear panel gives a nice easy place to test without being difficult or expensive to fit.

 

[ale_pb]

Thanks Pads.

 

[Marcelo]

Let's say that I have a CLASS I EQUIPMENT, with a plastic enclosure and no accessible metal parts.
Reading the 60601-1 it seems to me that, if I don't have any accessible metal parts, the ground bond test is not necessary. Am I correct?

For your equipment to be class I, it has to have accesible or internal parts that are protectively earthed. As yours do not have accessible protectively earthed parts, i'm assuming your equipment has internal parts which are protectively earthed.

The ground bound test verify that protectively earthed parts, accessible or internal, have the right impedance. So, assuming that your have those internal parts, the test has to be done in those parts.

If your equipment do not have protectively earthed parts, it cannot be class I.

 

[Peter Selvey]

Under IEC 60601-1:1988/A2:1995 this is poorly written part of the standard so easy to overlook.

Clause 18g covers only accessible protectively earthed metal parts, with the typical 25A / 0.1ohm test.

Clause 18f covers "other" protectively earthed metal parts and then goes on to describe an alternate test. The way it is written means it is often mistakenly considered not applicable if the alternate test is not applied, and the IECEE CB scheme protocol has promoted this mistake (many test engineers read only the protocol, not the standard). As such, the test of internal protectively earthed parts is frequently overlooked.

But the correct interpretation is that for internal parts, either the test of 18g (i.e. 0.1ohm / 25A) or the alternate test applies. Either way, internal protectively earthed parts must be tested with the result recorded under Clause 18f.

The 3rd edition, IEC 60601-1:2005 has removed the word "accessible" from the applicable clause, so the problem no longer exists.