Watts and voltamps

[mojoman]

Havent had to do many load cal in the passed 15 yrs. Im a resi guy. problem with Nstar. Are Voltamps and watts the same..... for a load calulation?

 

[charlie b]

No, in general they are not. But for many of the things we deal with, they are the same. For motor loads, the VA value will be higher than the W value. For a range, the two values will be the same. Are you looking at anything in particular?

Welcome to the forum.

 

[mojoman]

At the risk of sounding stupid, I have to do load cals for Nstar and everything in kva. It's just for 3 units. I have all the watt ratings.

 

[roger]

What is Nstar?

Roger

 

[templdl]

Now. questions to clarify the OP: What is meant by "units?' Are they individual devices such as ovens, ranges, or? Again, just a guess at this point, if what you have is watts it may be heating watts which it may very well be that it will be the same as VA.

 

[Jraef]

At the risk of sounding stupid, I just need to do load cals for Nstar. Everything is rated in watts and they require kva

Watts = VA x PF (Power Factor), so of all you know is watts, then VA = W/PF

If the load is resistive in nature, i.e. incansecent lamps (lol) or resistive heaters, then the PF is 1.0 so W = VA

If the load is inductive in nature, like motors, electronic power supplies etc., then you need to know the Power Factor to determine VA, no way around it. You can make a SWAG at it by ASSuming the PF is .80, but that's all it is, a SWAG. If you want an extra conservative VA value from only knowing watts, you can use .70 PF. It's very rare to see loads with lower than a .70 PF.

So for example lets say you have a 4kW load and you want to know the kVA. If you don't know the PF of the load and want to be conservative, you take 4kW/.7 = 5.71kVA. it will likely be less, but this may be the only way to be safe at guessing.

 

[mojoman]

Nstar is the power company. I gave them load calculations using NEC calculations but they want everything in KVA.

Lighting load
Appliances
Micro
Laundry
Heat
A/C
Misc load

They do not change the demand factor, they just want to know what is being supplied and its full load. Its a pain.

 

[templdl]

Nstar is the power company. I gave them load calculations using NEC calculations but they want everything in KVA.

Lighting load
Appliances
Micro
Laundry
Heat
A/C
Misc load

They do not change the demand factor, they just want to know what is being supplied and its full load. Its a pain.

This is a bit more than what you asked in your OP. Then Jraef has answered your question.

 

[Smart $]

Nstar is the power company. I gave them load calculations using NEC calculations but they want everything in KVA.
....

NEC calculations are in VA.

kVA = VA ? 1000