Service Calc with FCUs and Humidifiers

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Allied

Member
Working on a 7500sft house with an existing 200A 208V 3phase service. The Majority of the house is going to be gutted, so everything will be new.

The heating and cooling loads consist of the following:

A/C: 13KW chiller with 12 fan coil units
Heating: Gas Boiler with (6) 3.3KW (19.8kw total) humidifiers and the same 12fan coil units as the A/C.

Would the humidiers and fan coil units be considered an appliance? If so then clearly the A/C would be the larger of the loads and would be calculated at 100% where the humidiers and fan coil units can be diverisified with the appliances. But, if the humidiers and fan coil units are considered part of the heating load, then they would be more than the A/C at 19.8KW vs the 13KW.

The way I read the code, the fan coils units are considered an appliance (fastened in place) and do not produce the heat, like electrical baseboard would, but simply distribute the heat even though they are associated with the heating system. Same with the humidifiers except that they do not produce heat but are associated with the heating system. I was curious what everyones take was on this.

If the humidifiers and fan coil units are considered appliances then the 200A service can remain, but if not, the service would need to be upgraded. Thanks for everyones help.
 
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BJ Conner

Senior Member
Location
97006
Fan coils are part of the HVAC system.
On a very hot day the dishwasher may or may not run, the fridge may or may not run, microwave same. All appliances.
Can you say the same about the fan coils?
 
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Allied

Member
Thanks for you reply.

I understand your point. But, can you provide an article and section?

How about the humidifiers? Would you calculate that at 100% as well?
 
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Allied

Member
Can anyone else chime in on this? What part of the calc would you put the humidifiers and fan coil units?
 
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broadgage

Senior Member
Location
London, England
Presuming that these are 4 pipe fan coil units, used for both heating and cooling, then I believe that the fan coil load must be added to both the heating AND the cooling load, since the fans will run when heating or cooling is required.
If you have a 13KW chiller, and 12 FCUs each of 100 watts, then I make that a cooling load of 14.2KW.
On a hot day it is probable that the chiller and the fan coils will all run continualy.

As regards the humidifiers, then it depends on how they are controlled.
If they can only run when heating is called for, then consider the humidifier load, plus the fan coils, as the heating load.
On a cold dry day it is probable that the humidifiers and fan coils will run continually.
In this case the heating/humidifier load is the greater, and therefore used for sizing the service.

In the unlikely event that the humidifiers can run at the same time as the chiller, then I believe that the chiller/fan coil/humidifier total should be used.
 
Smart $

Smart $

Esteemed Member
Location
Ohio
Allied said:
Can anyone else chime in on this? What part of the calc would you put the humidifiers and fan coil units?
Click to expand...
Chiller + FCU's = Cooling Load
Humidifiers + FCU's = Heating Load

If there is a possibility of the humidifiers running during a cooling cycle, then:
Chiller + Humidifiers + FCU's = Cooling Load
 
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