Full load versus demand factor result

[keynotez]

Hi Engineers, just want to clarify something. I have a computation of Total Full Load Current of 195 Amperes.
My client gives me a demand factor of 0.70, multiplied to my Full Load Current 195 Amperes results to 136.5 Amperes. My decision is to use a 200 Amperes Main Breaker, am I right with that decision? Please help and judge me with my decision. Thank you and more power to all of you! By the way, my client is an Industrial Type Building. Thanks to all!

 

[malcolmsanford]

Thanks Matt that is what exactly I meant. If your client as given you this factor then that is what you design the installation to, though in a commerical situation a rule of thumb is 0.8 for me.

As Matt as quite rightly said it is dependent on the installation use, an industrial processing plant would be a totally different design say to a manufacturing plant. You have to decide as the designer what diversity/factor you will use, and I'm afraid that is something that can not be taught.

Bottom line if the client wants 70% diversity that is what he gets.

 

[mattmoo1974]

Mattmoo, thanks... but where can I get my running current? From my full load current or from my full load current multiplied by the demand factor? Did I oversized my MCB which is 200 Amperes? Thanks! ^_^

Start up current and run current are 2 diff things. There stamped on the spec plate of the motors
All the information you need should be on the equipment (Fingers crossed)
Your MCB should be ok, Use a type c This will allow for "Inrush current"/Full load current.
Full load on a motor is the current it takes to get the thing spinning up, IE if if needs alot of torque to get something moving.
The current will drop back alot. If the guy giving you the spec is clued up you should nt have any problems.