Fixed industrial equipment and RCD

**mygoggie** · 27-Oct-22, 07:23 AM

I have become involved in the upgrade of very old industrial machines in a mini factory. Part of the upgrade plan is to move from the ancient analogue control system to PLC control with VFDs controlling stepper motors.

Electrical supply is three phase to each machine and then at measured 415VAC with a total current requirement of 16A-23A depending on which electrical motors are running.

Inspecting the current installation there are C-curve circuit breakers in the main DB protecting the too small sized cabtyre cable to each machine. No neutral is supplied to any machine.

Currently isolation and overload protection at each machine is provided by a rotary 3P isolation switch and three bottle fuses (one per phase). Nothing more.

Each machine is managed by an operator which is in constant contact with the metal parts of the machine due to the operation requirements. Add to this a leaking roof with noticed puddles of rainwater where the operator is standing ... and yes no bonding of the machine ...

Now the fun part starts ...

My common sense tells me that with the upgrade each machine needs to be supplied with a MCB and a RCCB or RCBO to protect the operator and the new PLC system. I know the SANS regulations requirements for RCD protection on fixed machines have been discussed numerous times and it boils down to no stipulated RCD requirement is found for fixed industrial machines in the SANS 10142-1 document.

As this installation has numerous squirrel cage motors per machine, all the breakers leading to the machine and in the control cabinet at the machine, in my opinion, needs to be D-curve and not C-curve. Secondly the RCCB finds VFDs downstream of it, so this needs to be Type B.

The cost of such 4P circuit breakers and RCCB is rather on the heavy side (if you can currently find such in SA) and the customer is not willing to spend such funds. You know the saying: "It has been working fine like this for the past 40 years". Now add in the comments of the MIA electrician.

I would love to hear your comments regarding the above. Especially pertaining to the RCCB or RCBO units.

Now we also need to add the requirements of the OSHA Electrical Machinery Regulations :-)

**Derlyn** · 27-Oct-22, 09:05 AM

And now you know why I only work on domestic installations 😄😄 Been keeping it simple my whole life.

I know this doesn't help you at all, but I've walked away from these situations in the past and saved myself many headaches and frustrations.

Good luck, my brother.

**Isetech** · 27-Oct-22, 02:01 PM

And this is why customers say, its been working for 50 years, now suddenly you come along and tell us it all has to be changed

**Dylboy** · 27-Oct-22, 02:19 PM

Quote high and if you get it have a lekker holiday after or a new bike and it not then carry on.

But to the subject. I don't know industrial too well.

The Type C for me or Tile D is fine but then the ZS needs to be good to allow disconnection still. If the Earth loop of the full system is high then not enough to trip a Type C or D. I'm sure you know all this but still just in case.

I am not to clued up but if there is no double isolation notice on the machine I would earth it/bond it. Anything extraneous shall be earthed... Something along those lines.

RCBO I don't even know if you can get in this country, SWAN I believe have an RCBO but not 100% sure if they even have stock anymore.

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**Dylboy** · 27-Oct-22, 02:26 PM

Do we even get Type B RCCB or even Type A ? I know UK they basically stopped Type AC for the DC components of electrical systems but are we adopting the same ?

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**mygoggie** · 27-Oct-22, 03:46 PM

ABB makes a Type B but is is expensive. I have asked their specialist for an alternative. Let's see what he has to say.

**Dylboy** · 27-Oct-22, 03:49 PM

Oh awesome ! And yes ABB so I imagine one breaker is the budget of the client haha.

Amazing how money trumps life until life is taken then "spare no expense" until the moment has passed then back to money trumps life...

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**mygoggie** · 27-Oct-22, 04:11 PM

So true what you said.

The client is willing to spend money effectively, but he has no understanding of the complexity of the current scenario and what it entails to resolve. So it is a rather steep road to climb with him.

**Isetech** · 27-Oct-22, 06:26 PM

I have been involved in a few large installation, and wired many engineering factories. My advise to you, get an electrical engineer involved, if the customer doesnt want to spend the money, keep walking.

**Dylboy** · 27-Oct-22, 07:38 PM

That's a good idea for an engineer also as they would do CoC as an engineer. ( As far as I know that is allowed but I may be very wrong).

Also sorry for the uphill task. Thing with things like this is you can't always charge for your time on thinking about it, asking questions, research, airtime to phone etc. It's hard.

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