RE: [EnergyPlus_Support] Re: Calculated load different from component sizing summery

"User specified" Did you have a sizing multiplier or value added to the IDF by you and not autosized?

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jcrossett@xxxxxxxxxxxxxxx
Date: Fri, 14 Sep 2012 09:41:41 -0700
Subject: [EnergyPlus_Support] Re: Calculated load different from component sizing summery

Update: I read much documentation and still can not understand why the HVAC sizing summery and the component sizing summery would be 54% different from one another. I did find the files ending in Zsz and this paragraph in the documentation that seems to indicate that the value from the "ZSZ.CSV" file would produce the actual sizing, but also I looked everywhere I could think of in the idf for anything that would change the size in component sizing and could not find anything. So my question remains- why would the component sizing be different from the HVAC sizing summery/"ZSZ.CSV"? and how could I make the results agree with each other? Any advise would be much appreciated as I need to understand how this works to explain it to others.

Here is a chart I piloted from the design cooling load "ZSZ.CSV" file- I would like to use this but can only do so if I can explain why this is correct and component sizing is not.

The only description I could find on these objects below did not provide any insight..

Jeremiah D. Crossett | Senior Analyst | Phase Change Energy Solutions

120 E. Pritchard St. | Asheboro, NC 27203 | Mobile 503-688-8951

www.phasechange.com

On Thu, Sep 13, 2012 at 7:19 PM, Jeremiah Crossett <jcrossett@xxxxxxxxxxxxxxx> wrote:

Dear E+ users, I provided results to an engineering firm today and they asked a question I am not sure how to search for the answer to in the documentation or archives, and I am hopeful that someone might get me up to speed so I can answer his question-

First the math;
Calculated Design Load= [Btu/h]3244.06

Maximum Total Cooling Capacity= [ton]0.416702 ( 0.416702*12,000=[Btu/h]5000.424

So what is the cooling system size recommended by this E+ run , as there is a difference of [Btu/h]1756.364/[ton]0.1463636
His questions on the attached HTML results are:

Design load is 3244btu/hr, system load is 5000 btu/hr (0.416 tons), why such a difference? It seems too much of a difference to be the ventilation load only

Can you check the space sensible and latent load, the 4000 Btu/h cooling loads I have the system designed to is the total load (sensible + latent), therefore this may further explain the difference, I suspect energyplus is quoting only the sensible load under the calculated design load, this taps into the above question and the system load is likely both, but now this looks too high?

From my understanding latent+sensible is total load, but if that is the case then why would the component sizing be different than the HVAC sizing summery?

Many thanks for any thoughts--

Calculated Design Load [Btu/h] User Design Load [Btu/h] Calculated Design Air Flow [ft3/min] User Design Air Flow [ft3/min] Design Day Name Date/Time Of Peak Temperature at Peak [F] Humidity Ratio at Peak [lbWater/lbAir]
BLOCK1:ZONE1 3244.06 4055.08 149.668 187.086 LOS ANGELES INTL ARPT ANN CLG 1% CONDNS DB=>MWB 8/21 16:35:00 79.27 0.00955

Maximum Heating Air Flow Rate [ft3/min] Maximum Cooling Air Flow Rate [ft3/min] Maximum Total Cooling Capacity [ton]
ZONE1AIR 32.12 187.09 0.416702

Jeremiah D. Crossett | Senior Analyst | Phase Change Energy Solutions
120 E. Pritchard St. | Asheboro, NC 27203 | Mobile 503-688-8951

www.phasechange.com

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