220.84(A)(3)

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charlie b

charlie b

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We are designing an apartment building with over 400 units. Each unit will have cooking and laundry equipment. There will be no electric space heating in the units, and no unit will have its own air conditioner or heat pump. There will be a central chilling plant and a Variable Refrigerant Flow (VRF) system for distributing hot or cold water to the dwelling units. In each unit, there will be a Fan Coil Unit (FCU). This is essentially a small fan that will blow air over pipes that have either cold or hot water that they receive from the VRF unit on the roof.

Question: Can the FCU be considered “electric . . . air conditioning,” in the context of 220.84(A)(3)? Specifically, am I allowed to use this optional load calculation method?
 
charlie b said:
We are designing an apartment building with over 400 units. Each unit will have cooking and laundry equipment. There will be no electric space heating in the units, and no unit will have its own air conditioner or heat pump. There will be a central chilling plant and a Variable Refrigerant Flow (VRF) system for distributing hot or cold water to the dwelling units. In each unit, there will be a Fan Coil Unit (FCU). This is essentially a small fan that will blow air over pipes that have either cold or hot water that they receive from the VRF unit on the roof.

Question: Can the FCU be considered “electric . . . air conditioning,” in the context of 220.84(A)(3)? Specifically, am I allowed to use this optional load calculation method?
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I would say yes. The fan will not be the entire HVAC load for that unit, but the entire purpose of the fan is to deliver HVAC.
JMO, of course.
 
GoldDigger said:
I would say yes. The fan will not be the entire HVAC load for that unit, but the entire purpose of the fan is to deliver HVAC.
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My boss suggested that we assign each unit an HVAC load that is its portion of the chiller and VRF loads. It is similar to the exception that allows us to use this option method for units that do not have cooking equipment by assigning a fictitious amount of cooking load before applying the demand factors. I agree that this is similar, but the code does not have an exception that applies to cooling load.

 
jumper said:
Are all the FCUs in each apt fed from a circuit derived from that apt?
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Yes. I know that some VRF systems provide power to the FCUs from a central point associated with the VRF. This installation will power each FCU from the unit's panel.

 
charlie b said:
My boss suggested that we assign each unit an HVAC load that is its portion of the chiller and VRF loads. It is similar to the exception that allows us to use this option method for units that do not have cooking equipment by assigning a fictitious amount of cooking load before applying the demand factors. I agree that this is similar, but the code does not have an exception that applies to cooling load.
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Any diversity factor in the size and load of the common heater/chiller plant has already been taken into consideration when designing/specifying that system, so no additional diversity factor should apply to that single load.
By assigning part of that load to each housing unit and applying a diversity factor there you would double dipping.
 
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