Star-Delta motors on plugs and sockets

no PLC in this setup, its all relay logic, and very basic


just has the typical stop circuit linking the trips on the contactors, and a single stop button on the control panel.

Not Programmable Logic Controller (PLC), Performance Level c (PLc) as in the ISO 13849 performance level for the safety function that is the emergency stop.

If it has e-stops and it's machinery, which it would seem to be, then they should meet Performance Level c, as per ISO 13850.

that should be covered by the CE file we have on it, ill have a look at PLc now though - this sort of thing is something we outsource to a third party

Third parties like me ;)


That's pretty much most of what I do now machinery safety etc.


IF the machine is CE marked and you modify it, then just realise that you take on the responsibility, the OEM can walk away once they find a modification.

Now as the equipment is CE marked as an assembly, if you do pilot the plugs for e-stop, then you would need to re-check the 13849 validation, which is going to be very difficult whilst you may have the MTTFd & B10d of the devices, you will not know the exact number of operations they have preformed to know how far into that life cycle you are.

ISO 13850 requires PLc in the absence of a c-type standard requiring something different.

on the other hand, providing local isolation for the motor, without modifying the stop circuit would be different?


for some background, on this setup, the wiring, which is fairly extensive is existing, and the control panel was replaced and arrived on-site as a CE marked assembly, and was just connected to the existing wiring.

If the controls were upgraded to such an extent that the panel was replaced as an assembly then that wouldn't be a minor modification, so the remainder of the system would require review at that time with regard to CE marking as an assembly.

If this has not been done, then you can try and argue the point if it ever comes up with HSE.

You still need to comply with PUWER, and if it required local isolation this should have been implemented during the upgrade.

You need to review the hazards and risk to operatives who may un-plug the units whilst under full load, if there is enough of a risk then this must be engineered out.

PPE and procedures are the last resort, engineering solutions are available and are the specified means.

This may mean many things, including possibly bespoke units, or oversizing to allow for on load disconnection.

and this is what our health and safety department is supposed to be fior

You would think so, and maybe that is supposed to be their role but most, in fact almost all of the H&S people we meet when going into companies to do PUWER for them simply do not understand the engineering, unless that is their background, or they are specialist safety engineers, most H&S officers, advisers etc I find simply don't have the technical knowledge needed to understand the details of the engineering requirements.

hence the reason I used the word 'supposed'


they do our PUWER assessments. We do have a guy that issued CE certs for us when the need arises. 


I dare say we could have a few interesting conversations...