New 8 way 3 phase DB, what load to allow for?

[Carl Knowles]

Hi guys, we look after an industrial factory and they are wanting a new DB, they are expecting in the future around 5 machines all 3 phase so ive allowed an 8 way.
At the moment i know about 3 machines, a machine that pulls max 40amp per phase and 2 machines that pull around 13amps max per phase.
Im expecting the 4th machine to be around 40amps per phase too and the 5th machine around 20amps per phase.
The cable run for the DB is 50m back to the mains incomer.
Would you boys go about applying diversity to this?

 

[Adam W]

I'd probably allow more spare ways than that - another 3 for a 3 phase socket, lighting, small power, heating, air con in the office, water heater, and before you know where you are you're out of space.

You should be able to apply some sort of diversity to the machines, but that's going to depend on what kind of machines they are and how they're used - it could be that they won't all be run at the same time.

 

[Spoon]

As what @Adam W says. Hard to say if you can apply diversity until you know what the machines do.
Also what do they mean by "around 5 machines"...?? Is 7 'around 5'?? The you only have 1 spare way....

 

[LeeH]

With the information you have given, apply none.

 

[Pete999]

Hi guys, we look after an industrial factory and they are wanting a new DB, they are expecting in the future around 5 machines all 3 phase so ive allowed an 8 way.
At the moment i know about 3 machines, a machine that pulls max 40amp per phase and 2 machines that pull around 13amps max per phase.
Im expecting the 4th machine to be around 40amps per phase too and the 5th machine around 20amps per phase.
The cable run for the DB is 50m back to the mains incomer.
Would you boys go about applying diversity to this?

I think I remember seeingthi somewhere, where the max power P(max) = Pi x g whwere Pi is the total calculated load which can be a total of the MCB loads x g which is a factor which for factories IIRC is 0.8, could be wrong but no way of checking it was/is something that stuck in my mind for some strange reason.

 

[LeeH]

All those machines could pull their FLC 24/7 Pete so no magic number/factor can be used.

It has to be assessed by the designer with the spec from all the OEM’s with the production team at the factory.

 

[Pete999]

All those machines could pull their FLC 24/7 Pete so no magic number/factor can be used.

It has to be assessed by the designer with the spec from all the OEM’s with the production team at the factory.

I did say it was something that I thought Ihad remembered Mate, so the chances of being the correct information was/is slim, at least my thoughts have resulted in some debate on the subject, but to question your reply what are the chances of everything being switched on at FLC at the same time, not 100% in my opinion.
You could say the same when applying diversity on domestic installations, unlikely, but the possibility of everything being utilised to it's full extent is a possibility, the 80% factor is not that far from reality, but as I said "I think I remember" so I am possibly/probably wrong.

 

[Adam W]

I did say it was something that I thought Ihad remembered Mate, so the chances of being the correct information was/is slim, at least my thoughts have resulted in some debate on the subject, but to question your reply what are the chances of everything being switched on at FLC at the same time, not 100% in my opinion.
You could say the same when applying diversity on domestic installations, unlikely, but the possibility of everything being utilised to it's full extent is a possibility, the 80% factor is not that far from reality, but as I said "I think I remember" so I am possibly/probably wrong.

It is unlikely that everything will be running at full load but you can't just assume that - you should be able to apply some sort of diversity to the machines, but that's going to depend on what kind of machines they are and how they're used; they might include heaters with thermostats, intermittent pumps or motors, or it could be that more than one of the machines does a similar job and they will never use them all at the same time. At this point we don't know, but the way the machine works is more likely than its efficiency to affect diversity.

 

[LeeH]

What relevance has efficiency when calculating the load of 5 machines with a FLC from the manufacturer?

They are just as likely to fun flat out at 2 shifts a day then not IMO.

Production is king, machines sat idle are not making money.

 

[Nigel]

You need to have a conversation with the person ordering the works. You need to explain to him how diversity works and the risks.

For example if you apply a 75% diversity factor then they will need to understand that going over that could cause production to come to a halt. If you do not apply any diversity the costs for the installation will go up.

Once they have all the information it is really up to them to decide based on their financial circumstances and the risk they are willing to accept.