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Is the MCB tripping? Any signs of thermal damage? Have you clamped the cable to get an idea of actual current flow?

Sounds like a kitchen, in which case diversity may apply to a lot of the 25kW. The two dishwashers won't be pulling 5kW each all the time they are on, much of that is likely to be the wash water heating which will cycle reducing the overall load, depending on size, it could well be just a few hundred watts for control and pump power.

A full list of appliances and their loads may help provide a better answer, but if it's not tripping, there's no evidence of thermal damage to the cable or breaker, I'd be inclined to leave well alone pending a better assessment of the actual current that is likely to be flowing.

Not on the sub panel circuitry. But on the main CU circuitry. Melted socket internally but no tripping of MCB which is odd. I suspect the MCB may be faulty so you can't take it for granted that there is no tripping. It's a busy cafe. But even without the dishwashers the MCB is at full capacity. I don't know about the cable. Other have sugested data logging exercise so that would appear to be the next logical step.
 
MCB's detect current overload and short circuit, a loose connection overheating will not be seen by the mcb (unless it damages the cable or socket enough it shorts out), I really think this install needs a detailed test and inspection as it sounds like you have a list of issues and concerns here.
With a full electrical report you can then approach the original contractor and present your concerns and a good case if the report reveals anything.
 
MCB's detect current overload and short circuit, a loose connection overheating will not be seen by the mcb (unless it damages the cable or socket enough it shorts out), I really think this install needs a detailed test and inspection as it sounds like you have a list of issues and concerns here.
With a full electrical report you can then approach the original contractor and present your concerns and a good case if the report reveals anything.
Absolutely.
 
MCB's detect current overload and short circuit, a loose connection overheating will not be seen by the mcb (unless it damages the cable or socket enough it shorts out), I really think this install needs a detailed test and inspection as it sounds like you have a list of issues and concerns here.
With a full electrical report you can then approach the original contractor and present your concerns and a good case if the report reveals anything.
That's reasonable. I believe I have enough ammo to make that recommendation but I think the conclusions will be much the same as mine ie: it needs changing. Sooner rather than later. It's just a matter of defining the scope.
 
I am a bit lost with this. You have been asked to look at a situation in an advisory capacity but you come on an internet forum asking advice which says to me you don't have the necessary knowledge or experience to give advice?
 
It is very difficult not to overload the socket curcuits off the main CU. There are 16 x 13 amp outlets and only 3 x 32 amp MCBs. Total potential load is 208 amps. Like I said. Bewildering.

Are these general use sockets or are they intended for specific appliances?

16x 13A outlets spread across 3x 32A ring circuits seems well provisioned for general use outlets
 
I am a bit lost with this. You have been asked to look at a situation in an advisory capacity but you come on an internet forum asking advice which says to me you don't have the necessary knowledge or experience to give advice?
I have plenty of knowledge and experience. It's called "seeking a second opinion". The reason I have come here is because I am bewildered at what I am seeing given that it was designed and installed by someone who you would probably be happy to describe as having the "necessary knowledge and experience". Everything I see is way beyond the boundaries of what I would expect from someone with the "necessary knowledge and experience" required to install safe systems. So, I have come here to see if there are others on here who find this as alarming as I do. That would appear to be the case and I am grateful for their indulgence.
 
Are these general use sockets or are they intended for specific appliances?

16x 13A outlets spread across 3x 32A ring circuits seems well provisioned for general use outlets

They are all general sockets. 8 x 2 port 13 amp. But it's more to do with the layout. The list of equipment detailed 4 main items along with a few other peripheral devices. A grill and three hotplates. A total of 50 amps for those items alone. I would have liked to see dedicated outlets for these 4 devices with their own single 64 amp MCB and circuit. At this point in time there is nothing to stop someone plugging 8 x 13 amp devices into one of these segments while it only has a 32 amp MCB. You can't expect the end user to know the dangers of doing so. The layout should be designed to prevent it in my opinion. As far as is reasonably possible at least. If you tskr this to its extreme it is possible to demand 208 amps from the CU through three segments each with a 32 amp MCB.
 
It is not possible to demand 208 amps from the CU... if this is the sub-board, it's protected by a 63A MCB which will allow a small overload for some time, but not a significant one, and if it's all on one phase (the fact the MCB is a single phase unit - unless the model number is wrong), unless it's a 200A supply, I would expect the suppliers fuse to rupture.

So why is this being investigated now? What reason has the business had to get so concerned?
 
It is not possible to demand 208 amps from the CU... if this is the sub-board, it's protected by a 63A MCB which will allow a small overload for some time, but not a significant one, and if it's all on one phase (the fact the MCB is a single phase unit - unless the model number is wrong), unless it's a 200A supply, I would expect the suppliers fuse to rupture.

So why is this being investigated now? What reason has the business had to get so concerned?
Trippings and internally melted sockets. All equipment recently PAT tested and deemed fit for purpose.
 
Is it the 63A MCB supplying the sub-board? If so, how long has it been going on? I ask how long because if it's significantly less than 4 years one might assume that something has changed. If it's not that MCB, what is supplied by the MCB(s) that trip?

As for the melted sockets, that's not an indicator the design is bad... could be a loose connection in the plug, loose fuseholder, cheap socket outlet, substandard fitted plug (on a piece of cheap equipment maybe). There are plenty of reasons a plug can melt that are nothing to do with the design.
 
We used to do a lot in fast food restaurant kitchens and there was a practice of multiple radial circuits to single point sockets. The layout was often mirrored especially the drive-through outlets and a socket served a particular piece of equipment and it had nothing to do with the current load of the equipment. The chain of thought was losing a multiple outlet radial or ring final through whatever reason meant the loss of several items of equipment and possible closure of the outlet. Lose a single point radial was not likely to prevent trading.
 
It is not possible to demand 208 amps from the CU... if this is the sub-board, it's protected by a 63A MCB which will allow a small overload for some time, but not a significant one, and if it's all on one phase (the fact the MCB is a single phase unit - unless the model number is wrong), unless it's a 200A supply, I would expect the suppliers fuse to rupture.

So why is this being investigated now? What reason has the business had to get so concerned?

I'm not sure what you mean by "not possible to demand 208 amps". If I walk in there now and plug a 3Kw kettle into each of the 16 outlets and switch them on what do you suggest would happen?
 
We used to do a lot in fast food restaurant kitchens and there was a practice of multiple radial circuits to single point sockets. The layout was often mirrored especially the drive-through outlets and a socket served a particular piece of equipment and it had nothing to do with the current load of the equipment. The chain of thought was losing a multiple outlet radial or ring final through whatever reason meant the loss of several items of equipment and possible closure of the outlet. Lose a single point radial was not likely to prevent trading.
I would have thought that this would have been a more suitable design.
 
I'm not sure what you mean by "not possible to demand 208 amps". If I walk in there now and plug a 3Kw kettle into each of the 16 outlets and switch them on what do you suggest would happen?
But that would not happen in the real world. Have you got a list of equipment that they are using?
 
I'm not sure what you mean by "not possible to demand 208 amps". If I walk in there now and plug a 3Kw kettle into each of the 16 outlets and switch them on what do you suggest would happen?

I would expect the OCPDs protecting the circuit or if this on the sub-board (protected by a 63A MCB) to trip at the very least, and unless the suppliers OCPD is over 100A, I'd expect that to rupture.
 
But that would not happen in the real world. Have you got a list of equipment that they are using?
I doubt you would get away with that excuse if you found yourself on the end of a corporate manslaughter charge through negligence. The way I see it is this. You can't do a great deal with existing layouts other than enhance and improve. But when you start off with a blank sheet it should never be possible at sign off for the end user to demand more from the system than it is capable of supplying. That's the whole purpose of the legislation. You start off with a list of the demands that need to be catered for safely at the outset. Then you can discuss issues of scalability with the client. For example you might only need 3 hotplates today. Tomorrow you might need 6 if business goes well. So you design for expansion if that arises. Whatever the total demand is then that's what the supply should be capable of delivering. Ideally at 80% capacity. Certainly not 50% less.
 

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