Multiple control stations for one three phase compressor. Best practice?

[Mark42]

I'm refurbishing my own workshops and fitting a new central three phase compressor and three phase dust extractor.

Both these appliances will be controlled by remote START/STOP switches, next to multiple compressed air and vacuum points, which may be in different buildings.

For future-proofing I want to have more than one control station for each appliance, for convenience when moving machines around the workshops.

Using what I believe is standard wiring for a three pole + aux n/o contactor (sketch below) it’s easy enough to use the existing three core and earth cabling for one station only, latching the contactor.

But to allow additional remote stations I can’t think of a way to do it without using four core + earth. An unlimited number of n/o START switches can be installed in parallel, but the STOP switches need to be in series as they are n/c.

Of course simple on/off switches powering the contactor would work, but that would be a terrible idea as you’d have always to switch off from the same position as you switched on.

Is there some clever way of making the wiring easier and clearer than having a long loop for the stop circuit? This would be particularly confusing if the geometry of the cabling is not simply point-to-point but partly a 'star' configuration.

I’ve not done this before and have no idea if there’s some standard method I’ve missed.



Thanks, Mark

 

[netblindpaul]

I know exactly what a “chip extractor” is.
You might consider it silly, but it’s the law.
Emergency stop functions are no longer considered a primary means if safeguarding.
They are primarily for the protection of the equipment and prevention of “collateral” damage.
The regulations prevent nothing.
They merely require that the modifications are done in a suitable manner.
This is absolutely no difference to what is required by Building Regulations, BS7671 & the competent person schemes.
It is merely the requirements differ because the hazards are different and the requirements of the legislation and standards differ.
The term “emergency stop” is a specific term which invokes the requirements of a safety function.
If the machinery doesn’t have any emergency stops then you will not have to implement them. However if it does then you need to continue that with the modifications.
A simple off switch cannot act as an emergency stop or means of emergency isolation unless it meets the requirements for such.
The standards are very clear on that.

This discussion would not be happening if the work was covered BS 7671, everyone would be supporting compliant work. Just because there is additional legislation and different standards, it is thought to be nonsense.

I believe that if the HSE enforcement archive is checked, then many more actions regarding PUWER and machinery legislation will be found than BS7671/EAWR/Building Regulations.
If you are unsure of the hazards posed then please look up the Essential Health and Safety Requirements in the SMSR, and then refer to the product standard for the chip extraction here:

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[netblindpaul]

One last point I missed.
Just because fob remote control units are available, perhaps from well known online marketplaces, does not mean that they are compliant.
Nothing is guaranteed to be compliant, hence why the law requires that the end users have to get the compliance checked before they use the equipment.
PUWER Reg 10.
Real Regulations, real law, the breach of which is a criminal offence.