Peak Demand

[mepengineer]

can someone tell me if am on the right track? am trying to calculate peak demand for a building i get all the demand and take the highest for 1 month (see attach )


then I apply this formula

kw/Pf (90%)= KVA

KVA/.36 *1.25%

 

[Ingenieur]

it looks like the kw is the peak for each month

I understand the pf 0.9 math
what is the 0.36 for (inverse 2.778) peaking factor?
the 1.25%? do you mean 125% or x 1.25? basically 25% 'cushion'

 

[mepengineer]

it looks like the kw is the peak for each month

I understand the pf 0.9 math
what is the 0.36 for (inverse 2.778) peaking factor?
the 1.25%? do you mean 125% or x 1.25? basically 25% 'cushion'

the 0.36 is (208*√3)

125% cushion

 

[Ingenieur]

the 0.36 is (208*√3)

125% cushion

that should work

144000/(208 sqrt3) x 1.25 = 500 A

 

[pv_n00b]

You are on the right track. Using a 0.9PF is conservative depending on the type of use, heavy motor use can get you down to 0.86 or less while commercial offices can get up to 0.93 or more. If the utility tracks PF you can get that for each month.

The 1.25 multiplier is in there because just based on the bill you can't tell how much of the load is rated as continuous (>3 hours) so you assume it all is to be conservative. Now if you want to add a little on top of this to allow for future load growth that is considered good planning.