Measuring residual current. How do I know what RCD to fit?

[Inteificio]

Hi,

I have been tasked with rewiring most of the machines in a factory.
Due to the age of the equipment and usage I believe residual current protection is a good idea.

This presents an issue with how they want them wired.

Currently we have cables hanging from the ceiling at multiple points of the production line.
The want rid of this and want each machine in the production line to power the next.

My idea is to fit a dist board at one end and feed them off each other.

The only issue I have is what do I rate the RCD as?

The easy approach is to fit a 30mA RCD as the incomer and feed everything off individual mccbs.

However I do not know if these machines will cause nuisance tripping.


So the short version of this question is how can I measure the residual current on a 3 phase machine?

I've seen a PAT tester that could do single phase, but nothing for 3.

At the moment, the best idea I have (which sucks) is to get a settable RCD and keep reducing the current until it trips. This obviously does not take in to account any fluctuations in the device!

So do any of the sparks know how to do this properly or have any advice to offer?

Thanks,

 

[telectrix]

why on earth do you want to fit RCDs to factory floor machines?

 

[GLENNSPARK]

and i smell a cascading feeds epic here as well...

 

[Thefailsafe2012]

Hi,


I have been tasked with rewiring most of the machines in a factory.
Due to the age of the equipment and usage I believe residual current protection is a good idea.


This presents an issue with how they want them wired.


Currently we have cables hanging from the ceiling at multiple points of the production line.
The want rid of this and want each machine in the production line to power the next.


My idea is to fit a dist board at one end and feed them off each other.


The only issue I have is what do I rate the RCD as?


The easy approach is to fit a 30mA RCD as the incomer and feed everything off individual mccbs.


However I do not know if these machines will cause nuisance tripping.




So the short version of this question is how can I measure the residual current on a 3 phase machine?


I've seen a PAT tester that could do single phase, but nothing for 3.


At the moment, the best idea I have (which sucks) is to get a settable RCD and keep reducing the current until it trips. This obviously does not take in to account any fluctuations in the device!


So do any of the sparks know how to do this properly or have any advice to offer?


Thanks,

Ok so I haven't worked in an industrial setting before but this whole thing sounds a bit carp. As tel says, RCD's on a factory floor is asking for trouble, feeding machines off of each other? What happens when one machine packs up, it takes out another 3 or 4 or whatever?

Having a 30mA RCD upfront on a large DB is disastrous, this needs properly designing else your name will be mud if the whole trips every hour, or worse doesn't hold in at all!

 

[R G]

Wonder why he wants RCDs , is it possibly a wet environment or what ??

 

[Des 56]

What is the subject that opinion is sought
The post mentions machines powering the next,then talking residual current matters

Are you asking about sequencing the control of the production line ( mining conveyors and coal cutting machines being an example) or is it protection of the individual machines

Same as tel,why have you decided they need Rcd

 

[trev]

Imagine the scene, machine 1 needs maintenance and needs to be isolated. How are you planning to keep the rest of the factory running? Machine 3 develops a fault and takes out the RCD, how do you plan on keeping the rest of the factory running?
Remember, part of the job is advising clients that their ideas are pretty stupid and suggesting more suitable alternatives

 

[GMES]

Not enough information at all, we need to know factory environment, machine types, ratings etc etc etc.
About the only thing I could say is regarding the cables just hanging from above, install basket, or heavy duty traywork then bring a service post down to each machine with a lockable isolator for each machine. Regarding disboards you need to give ratings of machines, then you can determine wether you can use disboards 63 amp max or wether to install a panel board for mccb outputs, but like I said we need gallons more information or we back to the recent problem of having to be mind readers.

 

[mechelec]

To measure the earth leakage from each machine use a suitable earth leakage clamp meter. I think you really need to rethink the RCD idea.

 

[trev]

To measure the earth leakage from each machine use a suitable earth leakage clamp meter.

Not really brain surgery is it mate?

 

[Inteificio]

Wow lots of questions at once.

Reason for RCDs, many.
For a quick answer.
These will be fed off plugs and sockets, regs indicates RCD requirement.
Boss wants RCDs.
Operators are a f£$^%ing liability and are so reckless with equipment everything in this factory needs RCD protection.
No reason not to add additional safety, if something is designed correctly, it won't cause an issue, but stop an accident.

"and i smell a cascading feeds epic here as well..." - Each piece of equipment will have it's own dedicated feed. Not sure what you meant though, so care to expand?

"What happens when one machine packs up, it takes out another 3 or 4 or whatever? " That's a good thing. If one item on the production line has an electrical fault the production line stops.


Des, I know little about mining, so your references are lost on me.
Basically a packing machine. Main boxer -> conveyor -> metal detector -> conveyor -> weigher -> LS.


RCDs are going in, no choice on that.
I need to know how to design to avoid nuisance trips.

 

[GLENNSPARK]

OK...

so we are up to 12 posts...and still dont know the thinking behind RCDs here...

 

[Marvo]

Due to the age of the equipment and usage I believe residual current protection is a good idea.

Bad idea.

........and want each machine in the production line to power the next.

Bad idea

The easy approach is to fit a 30mA RCD as the incomer and feed everything off individual mccbs.

Bad idea

So the short version of this question is how can I measure the residual current on a 3 phase machine?

I've seen a PAT tester that could do single phase, but nothing for 3.

If you're working on industrial equipment then you can leave your PAT tester at home. You can measure the earth leakage by using an earth leakage clamp meter and clamping all the phases (and neutral if there is one) simultaneously.

 

[GLENNSPARK]

Wow lots of questions at once.

Reason for RCDs, many.
For a quick answer.
These will be fed off plugs and sockets, regs indicates RCD requirement.
Boss wants RCDs.
Operators are a f£$^%ing liability and are so reckless with equipment everything in this factory needs RCD protection.
No reason not to add additional safety, if something is designed correctly, it won't cause an issue, but stop an accident.

"and i smell a cascading feeds epic here as well..." - Each piece of equipment will have it's own dedicated feed. Not sure what you meant though, so care to expand?

"What happens when one machine packs up, it takes out another 3 or 4 or whatever? " That's a good thing. If one item on the production line has an electrical fault the production line stops.


Des, I know little about mining, so your references are lost on me.
Basically a packing machine. Main boxer -> conveyor -> metal detector -> conveyor -> weigher -> LS.


RCDs are going in, no choice on that.
I need to know how to design to avoid nuisance trips.

OK...i thought it was something else....

 

[GLENNSPARK]

Wow lots of questions at once.

Reason for RCDs, many.
For a quick answer.
These will be fed off plugs and sockets, regs indicates RCD requirement.
Boss wants RCDs.
Operators are a f£$^%ing liability and are so reckless with equipment everything in this factory needs RCD protection.
No reason not to add additional safety, if something is designed correctly, it won't cause an issue, but stop an accident.

"and i smell a cascading feeds epic here as well..." - Each piece of equipment will have it's own dedicated feed. Not sure what you meant though, so care to expand?

"What happens when one machine packs up, it takes out another 3 or 4 or whatever? " That's a good thing. If one item on the production line has an electrical fault the production line stops.


Des, I know little about mining, so your references are lost on me.
Basically a packing machine. Main boxer -> conveyor -> metal detector -> conveyor -> weigher -> LS.


RCDs are going in, no choice on that.
I need to know how to design to avoid nuisance trips.

or proper training coupled with an effective preventive maintainence program....

what do you think?

 

[trev]

I need to know how to design to avoid nuisance trips.

And on that note, I'm out.

 

[MDJ]

My goodness

 

[Knobhead]

Ditch the RCD. As for daisy chaining machines, don’t! A ring feeding fused commando outlets makes a bit more sense. A single feed to each machine even better.

Yes the price is going up, but how much is lost when one M/C takes out the others?

 

[spark 68]

My goodness

Gasp! even lol

 

[Marvo]

These will be fed off plugs and sockets, regs indicates RCD requirement.

Why are they on plugs and sockets? Factory machinery is much safer if it's fixed and hard wired.

Boss wants RCDs.

The boss only wants them until the day the first one trips.

Operators are a f£$^%ing liability and are so reckless with equipment everything in this factory needs RCD protection.

It isn't the job of an electrical designer to prevent or protect against reckless or negligent behavior or willful damage by the machine operator.