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# Fan Coil Unit - Convert cooling power capacity to maximum cold water flow

Hi all,

I have to size Fan coil units in my model with known cooling powers. But on EnergyPlus/DesignBuilder, we can only specify maximum cold water flow.

I've checked the Engineering reference of EnergyPlus (pasge 289 - Fan Coil Unit Sizing Formula (1257)) and they give the formula linking the two entities. However, it is unclear what are the other different parameters involved, didn't find any nomenclature explaining them (quite annoying actually), especially the DeltaTloop,des.

Can someone help me with it?

Best Regards,

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DeltaTloop,des should be the delta T specified in the Sizing:Plant object. I looked at the fan coil sizing equations and that section needs some serious help. I looked at page 553 in V8.5 Eng Ref named Fan Coil Sizing (pg 558 in V8.6). For example the cold water volume flow rate is notated as Vmax,hw. The variables are also not well defined. If this is not the section you looked at let me know. Added documentation issue on GitHub at 5896

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Thanks rraustad, It is still not clear and not easy to read. I base my assumptions for the delta t to be Tin=Design Temperature of the cooling coil Tout= Design temperature of the cooling comfort in the zone

Thanks for your input on GitHub.

( 2016-10-24 08:39:29 -0600 )edit

There are 2 equations in V8.5 Eng Ref on pg 553.

Qcoil,des = Mdot * Delta H
Vmax,cw = Qcoil,des / (Cp,cw * rho water * DeltaTloop,des)


Delat H is air side enthalpy difference as you described. DeltaTloop,des is water side loop delta T

( 2016-10-25 10:11:09 -0600 )edit

( 2016-11-08 04:49:52 -0600 )edit