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Young & Keen

Hi All,

Can anybody advise me as to what is the best set up for the installation of a power supply to machinery. On site we currently have various commando sockets fed directly from the MCB's. These are all operating perfectly and have been for some time. The problem is, an ex-electrical engineer on site is suggesting that it shouldn't be left to the MCB to be the sole protection for the machines and soft-start isolator-starters (incorporating overloads) should be used. Just to add, these machines are only relatively small single or three-phase, typically drawing less than 20A. Aside from the cost issues, are there any safety implications which determine whether or not machines should be protected via overloads or will switched commando sockets or isolators suffice?
 
Well any machine with a motor in it needs overload protection IMO, however I would wait for Tony or E54 or even some of the other guys here to confirm my thoughts, I may be wrong, however in saying that I always install starters for motors, but have your machines got motors?
 
I would have thought that motors of the type and size you mention should have some sort of O/L protection, this surely would be incorporated in the starter. Just plugging a motor in directly is a bit dangerous, not sure of any regs but if the socket isn't local, where is the local isolation?
 
Are you sure the machine itself hasn't got any OL protection? You mention soft starts, some have built in protection. If it's been CE marked it will/should comply. It will have a isolator on it and all the appropriate control and motor protection.

If you are saying does the circuit supplying the machine need OL protection? Then it's most certainly a no. If somebody isn't happy a 32A CB supplying a 20A machine of a 32A socket you can do 1 of 2 things. Either remind them the CB is there to protect the cable in the installation, and/or reduce it down to a smaller size if it appeases them.

If the socket is supplying a motor in a machine and is the sole method of protection the yes, it's a bit naughty. But I've never seen that and I doubt it's the case here.

The BGB does not cover machinery but I think it states any motor over 0.37KW requires OL protection.


Just my 10p....
 
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Much of this probably falls under EN 60204-1. There are many factors to consider when deciding on the appropriate protection and safety devices for the electrical equipment of machinery, so I don't think we will be able to help you much over the forum. However if you have motors connected directly to 16A plugs, your man is right to be concerned and you should get a competent engineer to look at the specific requirements of your setups, and/or seek clarification from the manufacturers of the machines that they are compliant with the applicable regs both electrically and for machinery safety.
 
Much of this probably falls under EN 60204-1. There are many factors to consider when deciding on the appropriate protection and safety devices for the electrical equipment of machinery, so I don't think we will be able to help you much over the forum. However if you have motors connected directly to 16A plugs, your man is right to be concerned and you should get a competent engineer to look at the specific requirements of your setups, and/or seek clarification from the manufacturers of the machines that they are compliant with the applicable regs both electrically and for machinery safety.

The CB in question does not though and I think that is the device in question....if I'm reading it right?

I think the simple answer is the CB is fine. Everything after the socket fall under 69204. So, if the machine is up to spec, it's all good as is.
 
Well any machine with a motor in it needs overload protection IMO, however I would wait for Tony or E54 or even some of the other guys here to confirm my thoughts, I may be wrong, however in saying that I always install starters for motors, but have your machines got motors?

Darkwood also pretty clued up in this area
 
Reading it again maybe you're right Lee, perhaps the OP could explain in more detail what the machines are and whether they have electrical control-gear built in already.
 
Are you sure the machine itself hasn't got any OL protection? You mention soft starts, some have built in protection. If it's been CE marked it will/should comply. It will have a isolator on it and all the appropriate control and motor protection.

If you are saying does the circuit supplying the machine need OL protection? Then it's most certainly a no. If somebody isn't happy a 32A CB supplying a 20A machine of a 32A socket you can do 1 of 2 things. Either remind them the CB is there to protect the cable in the installation, and/or reduce it down to a smaller size if it appeases them.

If the socket is supplying a motor in a machine and is the sole method of protection the yes, it's a bit naughty. But I've never seen that and I doubt it's the case here.

The BGB does not cover machinery but I think it states any motor over 0.37KW requires OL protection.


Just my 10p....

Hi mate, I'll reply to your message but it's aimed at everyone. All of our machines incorporate motors but they all have built in protection. They are mostly packaging or food processing machines which all have panels with protection built in. All of the machines are supplied with commando plugs on the incoming supply but the guy I mentioned says when he used to work in the trade he always protected the supply cable from the dist boards with an MCB (which of course is normal) then protected the machine with a soft start overload. He's mentioned this a few times so I wanted to find out whether it is particularly necessary or will the MCB do the job on its own?
 
Its horse ----.

As simply as I can put it....

The CB protects the cable on that circuit with the socket on.

The panel on the machine deals with everything on the machine.

Also, there is no such thing as a soft start over load. Soft start with built in overload, yes but you don't soft start a full machine.

Maybe his trade was a plumber or instrument tech?
 
Its horse ----.

As simply as I can put it....

The CB protects the cable on that circuit with the socket on.

The panel on the machine deals with everything on the machine.

That's as I thought, thanks mate!
 
Having read all the posts and agreeing with many, as far as i can see these production machines all have control panels which incorporate motor protection (i'd be extremely surprised if they didn't) so i can't really see how this new guy is actually saying the motors need protection.

Maybe he's talking about updating these production machines to incorporate new cost saving technology?? That's all i can think of...
 
Having read all the posts and agreeing with many, as far as i can see these production machines all have control panels which incorporate motor protection (i'd be extremely surprised if they didn't) so i can't really see how this new guy is actually saying the motors need protection.

Maybe he's talking about updating these production machines to incorporate new cost saving technology?? That's all i can think of...

I'm afraid not. He's an ex-Electrical engineer who just works in our warehouse. He reckons that in his old company they used to protect all of their machines with overloads - obviously just being over-cautious and costing the company a fortune at the same time!!
 
I'm afraid not. He's an ex-Electrical engineer who just works in our warehouse. He reckons that in his old company they used to protect all of their machines with overloads - obviously just being over-cautious and costing the company a fortune at the same time!!

All of your machines DO have close protection overloads where required from what you tell us. The supply MCB's will also provide a coarser overload protection, via the bimetallic element. Are you sure he's an Engineer and not a maintenance electrician that's gotten too familiar with a company, doing things one way?? lol!!
 
I'm afraid not. He's an ex-Electrical engineer who just works in our warehouse. He reckons that in his old company they used to protect all of their machines with overloads - obviously just being over-cautious and costing the company a fortune at the same time!!

Either this bloke has misguided understanding of the requirements of both BS7671 and BS60204 or your interpretation of what he's saying is wrong.

The machines and control panel fall under BS60204 the socket outlet that you are connecting to via a lug to falls under the BS7671, the section regarding overload protection chapter 43 - 430.1 Note 4 means that the machine and control panel will be subject to BS60204 and further OL protection should not be required upstream of the control system to protect the motor as this should already be fitted if required.

If the machine is hard-wired to the supply (not on a plug) then in most cases the above applies still but if you are providing the means to start/stop the motor yourself then you will be required to ensure correct O/L protection is incorporated - again if required but this is also subject to BS60204 and very lightly skipped over in BS7671.

See 537.5.4.
 

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