AC Conditioning in optional load calculation

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binwork91

Senior Member
Location
new york
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electrical engineer
I have discussion with my coworker.
The story is: we need to do a apartment load calculation.
Each apartment has indoor fan coil (power come from each apartment's panel), and group of apartment share one outdoor condensing unit (power from building's panel). HVAC contractor/supplier will collect and provide data for tenant billing.

The problem is: we want to use optional method to calculate the meter bank. The argument is: is indoor fan coil an air conditioning?

in order to use optional method, we need to meet following code.
The code I citied is 2008 NEC code.
220.84 (A)(3)
Each dwelling unit is equipped with either electric
space heating or air conditioning, or both. Feeders and
service conductors whose calculated load is determined
by this optional calculation shall be permitted to have
the neutral load determined by 220.61.

Let me know your opinion. And why?
 
In my opinion the a/c unit is not on the panel you are trying to calculate so you cannot use the optional calculation. I suppose you can get the info on the unit and use that wattage in each apt calculation. It still may be less than the standard method.

I know it is allow for ranges so why not for hvac??
 
Dennis Alwon said:
In my opinion the a/c unit is not on the panel you are trying to calculate so you cannot use the optional calculation. I suppose you can get the info on the unit and use that wattage in each apt calculation. It still may be less than the standard method.

I know it is allow for ranges so why not for hvac??
Click to expand...
We don;t use standard method, because each meter bank will have 30 apartments, whole building has hundreds apartment. And each apartment has electrical range. So optional method will make total load small. because we can use the factor in Table 228.84.

The different opinion is, indoor fan coil is part of AC system. because it is blower. Also, when we buy a Ac system, it is common to have indoor unit.
We found the definition for the Air-Conditiong system in mechanical code.

AIR CONDITIONING. The treatment of air so as to control
simultaneously the temperature, humidity, cleanness and
distribution of the air to meet the requirements of a conditioned
space.

AIR-CONDITIONING SYSTEM. A system that consists
of heat exchangers, blowers, filters, supply, exhaust and
return ducts, and shall include any apparatus installed in connection
therewith.
 
What other loads are in the apartments? And what are their square footage? And are they 1ph or 3ph? The load for 30 units may not be that different between the standard and optional methods.
 
david luchini said:
What other loads are in the apartments? And what are their square footage? And are they 1ph or 3ph? The load for 30 units may not be that different between the standard and optional methods.
Click to expand...
each apartment is around 500-800 square foot. they are 208V 1PHASE, the meter bank is 208V 3 phase.
Each service switch feed 4 meterbanks. each meter bank has 30 apartment.
It may not have big different in each apartment, but the total load will have big different between standard and optional.
 
binwork91 said:
each apartment is around 500-800 square foot. they are 208V 1PHASE, the meter bank is 208V 3 phase.
Each service switch feed 4 meterbanks. each meter bank has 30 apartment.
It may not have big different in each apartment, but the total load will have big different between standard and optional.
Click to expand...
Microwave, electric range, dishwasher, washer and dryer, and indoor fan coil for the ac.
 
Looks like you answered your own question in post #3.

Yes, air conditioning is due to an "indoor fan coil".
 
Quick calculation using 750sf average apartment size: 11kW range, 1200w microwave, 800w dryer, 200w fan coil.

Standard calculation for 120 units: 691,950va.
Optional calculation for 120 units: 688,820va.

Pretty much the same.
 
david luchini said:
Quick calculation using 750sf average apartment size: 11kW range, 1200w microwave, 800w dryer, 200w fan coil.

Standard calculation for 120 units: 691,950va.
Optional calculation for 120 units: 688,820va.

Pretty much the same.
Click to expand...
Thank you. I found out a mistake in my calculation.
I guess i can use standard method.

But my op is regard to indoor fan coil. Do you have any opinion/idea?
 
binwork91 said:
Thank you. I found out a mistake in my calculation.
I guess i can use standard method.

But my op is regard to indoor fan coil. Do you have any opinion/idea?
Click to expand...
In my opinion, the fan coil wouldn't be air conditioning. I would consider air conditioning to be equipment covered by Art. 440.
 
Agree. And when you look at the components of an air conditioning system, the blower doesnt typically draw much power. It's all in the compressor and outside fan. Without that compressor unit, I dont think you meet the intent of electric AC or heat.
 
Agreed on the intent.

But to be pedantic, 220.84(A)(2) and (3) doesn't say that the feeder supplies the electric cooking equipment or the "electric space
heating or air conditioning". Just that the apartment is "equipped" with it.

So by the letter (not intent) of the requirement, 220.84(A)(3) is met.

Cheers, Wayne
 
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