Dealing with Device/Design changes by a "Letter to File" vs. 60601 Retesting

[robert.beck]

a related question ..

how does one go about determining what critical components are (in terms of testing - the test house requires a list of critical components)?

[raymond02302]

A critical components are all the components that can impair the safety of the appliance if replaced by components that are similar but not the same as far as the electrical and mechanical features are concerned. such as components assuring insulation between pri circuit and sec circuit (transformer, optical isolatior, X, Y capacitor), patient circuit and live part/enclosure (optical isolator, non-optical isolator) etc.
Of cource, if one component's specificaton can affect compliance with standard, this component should be treated as critical components. for eg. components affecting residual voltage (bleeding resistor), defibrillation protection (GDT), temperature test (sink design, opening) and so on.

[Peter Selvey]

For the first question, it appeared to be related when to notify the FDA of changes associated with 60601 compliance. For this I would not recommend consulting a test lab as they have a different point of view. The test lab thinks in terms of "certified product", in which case any change affecting compliance should be reported. For example, if you change the PCB tracks around a the isolation barrier, you need to report this change, even if you still keep the required spacing.

The FDA does not approve or certify the device per se, and they don't have the resources to be checking minor details like changing the layouts of a PCB track. They expect you to handle those things internally (or with your test lab). The FDA is more likely to be interested in bigger things like a change the intended purpose of a device.

With respect to component lists: in principle these are intended to keep track of all parts which affect compliance. But in practice this is really hard to do because there are so many parts. As a result, there is kind of unwritten agreement on particular components should be in the list, with a small variation depending the agency or office you are dealing with.

These lists are intended for use by the factory inspectors to check there are no changes for certified products (e.g. NRTL marks).

Regardless of what is on the list, manufacturers are still required to report changes that affect compliance for certified products (it is part of the general contract for product certification). It is a common mistake that manufacturers limit reporting of changes only for parts on the list.