Re: [EnergyPlus_Support] Re: the condenser fan energy for air-cooled chiller

Francesco,

I hope to learn every day. Today you are the reason I've learned something new :)

I think I know what is happening:

You have specified a non-zero Condenser Fan Power Ratio, so E+ is calculating the condenser fan power separately from the chiller. It's making the calculation exactly as described in the I/O Reference (shown below), based on the chiller capacity. That is not what I'd expect and is certainly not what occurs for a real chiller, but the output:variable confirms it when I run your IDF.Â
However......
When a chiller's COP is calculated by manufacturer testing, ALL power is included in the COP. That means compressor + condenser fan + controls energy are all included.Â (I'm 95% sure about this, but have not reviewed the test procedure recently)
As a result, a more realistic and correct energy calculation is made when you specify Condenser Fan Power Ratio = 0.

I hope that helps.

I/O Reference v8.9

1.22.7.1.20 Field: Condenser Fan Power Ratio

This field is used to model condenser fan power associated with air-cooled or evaporatively-cooled

condensers (for cooling towers, refer to Group - Condenser Equipment). Enter the ratio of the condenser

fan power to the reference chiller cooling capacity in W/W. If this input is greater than 0, the condenser

fan power is modeled separately from compressor power. In addition, if condenser fan power is modeled

using this input, the reference COP and â??Electric Input to Cooling Output Ratio Function ofâ?? performance

curves should not include condenser fan power.

On Tue, Apr 24, 2018 at 8:42 AM, fpasserini.tn@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

Â

Attached a simple file where you can check that (see the .eso file).

James V Dirkes II,Â CEO / President
The Building Performance Team Inc.
1631 Acacia Dr, Grand Rapids, MI 49504

(alphabet soup of efforts for greater understanding: PE, BEMP, BCxP, LEED AP)

Direct / Mobile: 616.450.8653
jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx

Website l Â LinkedIn

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