Think of a DOL motor starter would you find it acceptable for say a saw to restart on the release of the e-stop button? No, I would not.Or would you expect to have to depress the start button first? Yes, absolutley.
Think of the failure modes for a moment, the OP’s specifier appears to have given them a cursory thought. He has asked for an “overall” e-stop. Presumably this would be in case there is a failure in the control system of the machine such that the stop system did not function, or the machine started unexpectedly, thus A.N. Other could de-energise the machines remotely without having to approach the local isolator, which by definition is local to the machine! I presume that the sterilisers do not have any control circuit, or e.m stop's, which is why the OP has been asked to provide them.
However, is a single e-stop adequate, this boils down to the old chestnut of risk assessment. As you said based on room size accessibility etc.
Agreed.
However, what is unacceptable under PUWER98 & BS EN 60204-1 is the re-energising of a control circuit via the release of a stop control.
The nearest analogy is the central switching systems specified by BS4163.
Here in the link is drawn to PUWER98 and the guidance there in which takes you to 60204, even though these systems are fixed wiring in buildings, 7671 does not cover these types of control, thus bows out to statutory legislation, i.e. EAWR89, & PUWER98 which takes you to 60204.
I have no knowledge of PUWER, I presume a lot of sparks haven't?
You should not allow a contactor to be re-energised by the release of a stop button under any circumstances, I have frightened a few people with this scenario!
Can you circumvate this reg with the use of lockoff stop buttons?
A bog standard em-stop/contactor circuit would be controlling machinery!
Why would you fit a contactor to control a ring main as a ring main is a standard arrangement of circuit from 7671? Have seen plenty of ring mains/radials controlled by contactors and e.m. stops, 'gasguards' and other such devices are regulary used in conjunction with stop buttons in schools, laboratory's etc.
This does not require an e-stop, if it does, then other legislation/guidance has come into play & you thus must therefore comply with that. Ergo my previous comments.
DP switching requirements should be checked, IIRC & it is now late & my copy of 4163 is not to hand, this requires all live conductors to be switched.
You must remember that in the event of an incident then the most appropriate guidance to the system will be selected and expert witnesses may well draw analogies to 4163 as it is the most similar to this situation.
Unsure of DP switching requirements.
Missed the comment wrt the neutral. No reason at all for the N to be taken anywhere except A2 on the contactor!
O/L protection should be looked at for the control circuit as the control devices will not be able to take the full 32A load of the power CPD. Also the controls are controlling supplies from 4 CPD’s.
Agreed, anyone wiring a control circuit without appropriate O/L protection shouldnt be wiring anything!
BTW I still think the original design is flawed and unable to function correctly, safely or even at all based on the info given, which is one of the limitations of such forums.
I presumed that there was at least one typo.
There is more to this circuit than 7671 which was the point of my advice to the OP.
Paul