Demand Factors for AC-DC Power Supplies

[D_Bosco]

Hello All,

First time posting. Used to be a field electrician for 13 years and have transitioned to the engineering dark side lol. I am working on a project that has multiple DC power supplies (takes AC and converts to DC) that are not all being used at the same time (but not noncoincidental), and are not used at their full power ratings all the time. These are inverters but are not used for generation, they are used for testing DC loads at a research laboratory.

My question is this, is there a demand factor that anyone has used/is aware of for these types of loads? My gut feeling is no, and we will need to have a conversation with the AHJ. Right now they are all being considered 100% which is upwards of 500 kVA.

 

[tortuga]

if they wont be used all at the same time you could look at 220.60

 

[petersonra]

if they wont be used all at the same time you could look at 220.60

this gives you some leeway if loads are either on or off but not for partial loading.

if they are a total of 500 kVA then you need to consider that in your load calculations IMO. I don't see how a "conversation" with the AHJ is going to change that any, short of a wad of cash being passed as part of the conversation.

 

[synchro]

... I am working on a project that has multiple DC power supplies (takes AC and converts to DC) that are not all being used at the same time (but not noncoincidental), and are not used at their full power ratings all the time.

When you say the DC power supplies are not being used at the same time, does that mean that they will never be powered up together (with or without loads being present). The reason I ask is that inrush might also have to be considered in OCPD sizing which could impact other sizing in the system, unless the inrush of the supplies is relatively low due to their design.