Define "actual demand data" in the context of 220.87

[CelectricB]

Throughout the NEC, "total connected load" and "demand load" represent two allowed calculation methods for what is really our system's "real power". Apply the power factor(s) and you get the system's "apparent power".

NEC 220.87 uses the phrase "[actual] maximum demand data" for determining existing loads. Typically when applying this section, I see that utility maximum demand data is given in kW rather than VA. Is this a measure of the system's real power, and thus we have to apply power factor(s) to calculate apparent load?

 

[steve66]

I'd say you are correct - the max KW should be divided by the PF to get the max. KVA.

Or at the very least, an estimated PF should be applied, since you probably won't know what the actual PF is.

It's always amazing how low the utility measured max. demand is, compared to the actual connected load.

 

[brantmacga]

It's always amazing how low the utility measured max. demand is, compared to the actual connected load.

I have one of those Square D Wiser/Sense energy monitors on my house.

My house is under 2500 sq/ft, electric well pump, pool pumps, 5 ton heat pump, electric oven and cooktop, gas water heater. The peak recorded demand here is 23,696w. And that was one afternoon over the summer when the AC was running, my wife was doing laundry and baking, and the pool was running. Peak daily demand is usually around 16kw.


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[jaggedben]

220.87 just really doesn't say.

 

[steve66]

220.87 just really doesn't say.

Well one part says the peak demand is permitted to be measured by a recording ammeter. Multiplying the highest amps by the voltage would automatically give you apparent power. So in my opinion, that part is saying use the peak KVA, and not KW.

Everywhere else it uses the term "power", or it just says "maximum demand" without anything more specific. It doesn't say Kilowatts, and it doesn't say true power. IMO, power would be KVA, and not KW. "True Power" would be KW, but that term isn't used.

Even the word "maximum" implies we should use KVA instead of KW simply because it will be larger, or at least as large.