Load Calcs vs Energy Model for LEED - FieldNote:00028:ieOVB

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Great, This really worked! Thanks Scott. Catalina Caballero. AIA. Assoc., LEED GA. Sustainability Coordinator Johnson, Avedano, Lopez, Rodriguez & Walewski Engineering Group, Inc. Engineering for High Performance Buildings. MEPF - BIM - LEED - Cx 2510 NW 97 Ave, Ste 220, Miami, FL 33172. P: 305.594.0660 Ext: 217 ? F: 305.594.0907 www.jalrw.com | ccaballero at jalrw.com [cid:image003.png at 01CFE261.F5E5FFF0] [cid:image004.png at 01CFE261.F5E5FFF0] [cid:image005.png at 01CFE261.F5E5FFF0] [cid:image006.png at 01CFE261.F5E5FFF0] This email and any files transmitted with it are confidential and intended solely for the addressee. If you are not the named addressee you should not disseminate, distribute, copy, or alter this email. Please consider the environment before printing this email.
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All, On the issue of fan sizing, here is what I have observed: There are two ways to oversize (or undersize) the air handler to match the installed capacity. 1. Input airflow under block cooling airflow: Create Systems --> Advanced 2. Input coil capacity percentage with Capacity Units of ?% of design capacity by adjusting airflow? Both of these do indeed make the unit larger, and they do this by increasing the airflow for each room by a proportional amount. This gets the fan the right size, but adds extra capacity on a room basis that does not exist. Then Trace uses this extra capacity in the hourly analysis. Actual numbers from one air handler on a current project: No oversizing: ? Block CFM = 11,453 CFM (from Load-Airflow Summary report) ? Sum of Peaks = 11,469 CFM (from Load-Airflow Summary report) ? Fan size = 11,453 CFM (Equipment Energy Consumption Report) ? Peak hourly airflow = 10,570 CFM (from Visualizer) Manually input block airflow to match scheduled capacity: ? Block CFM = 15,000 CFM (from Load-Airflow Summary report) ? manually input ? Sum of Peaks = 15,000 CFM (from Load-Airflow Summary report) ? Fan size = 15,000 CFM (Equipment Energy Consumption Report) ? Peak hourly airflow = 11,469 CFM (from Visualizer) When I manually input the block airflow it did increase the fan size, but when looking at the hourly results the actual hourly airflows increased as well since each room was given a proportional increase in CFM capacity to get to the right unit capacity. This extra capacity would be used for periods when the load exceeds the actual capacity for a short duration: cool down or when OA conditions are more extreme than used for the load calculation (design weather <> hourly weather data). Thus you cannot set the unit capacity separate from the room capacity in Trace (as far as I can tell). This partly solves the problem of getting the fan the right size, but the added capacity can have an unintended impact of cooling energy use or on fan power by allowing the room by room airflow to be higher than the actual system. The overall impact of the consequences of oversizing each room may not be significant, but you can run the model with and without a manual input for fan block airflow and see the impact on cooling, heating and fan power. This does allow you to exactly match the unit CFM in Trace model which should keep the LEED reviewer happy. See below for screen shots of inputs (for oversized system) and Equipment Energy Consumption Report excerpt for oversized and non-oversized air handler in Trace. It does show the expected fan power savings for the oversized fan. [cid:image007.png at 01CFE245.23954680] [cid:image008.png at 01CFE246.EA467D70] [cid:image009.png at 01CFE248.2A9F7650] Scott Parker PE LEED AP BD+C Mechanical AEI | AFFILIATED ENGINEERS, INC. 1414 Raleigh Road, Suite 305 | Chapel Hill, NC 27517 P: 919.419.9802 | F: 919.419.9803 sparker at aeieng.com | www.aeieng.com
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Alright, So I have a question. When I input the airflow as explained but the capacity of the equipment comes up to be around 17% above of the original scheduled capacity. Would it raise a flag to the reviewer even though I?m getting 27% of energy savings even though this unit is oversized by 17% and the software is accounting for it? Thanks. Catalina Caballero. AIA. Assoc., LEED GA. Sustainability Coordinator Johnson, Avedano, Lopez, Rodriguez & Walewski Engineering Group, Inc. Engineering for High Performance Buildings. MEPF - BIM - LEED - Cx 2510 NW 97 Ave, Ste 220, Miami, FL 33172. P: 305.594.0660 Ext: 217 ? F: 305.594.0907 www.jalrw.com | ccaballero at jalrw.com [cid:image001.png at 01CFE848.C6420AE0] [cid:image002.png at 01CFE848.C6420AE0] [cid:image003.png at 01CFE848.C6420AE0] [cid:image004.png at 01CFE848.C6420AE0] This email and any files transmitted with it are confidential and intended solely for the addressee. If you are not the named addressee you should not disseminate, distribute, copy, or alter this email. Please consider the environment before printing this email.
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Catalina, Not sure I fully understand your question. Trace should show the fan sizing equal to the airflow scheduled on the construction document plans. You can see this airflow (CFM) on the Equipment Energy Consumption Report. Using my previous example that was 31% oversized on airflow versus the block load 15,000 CFM - Air handler schedule 15,000 CFM ? Trace Equipment Energy Consumption Report 11,453 CFM ? Block load calculated by Trace before fan block airflow was oversized This oversizing will show savings and will be acceptable to the LEED reviewer. In this particular case the supply fan energy use was reduced from: 29,498 kWh/yr to 27,396 kWh/yr (~7% savings on fan power). This is based on using the same kW/CFM for fan power input in each case. [cid:image007.png at 01CFE859.87166940] Scott Parker PE LEED AP BD+C Mechanical AEI | AFFILIATED ENGINEERS, INC. 1414 Raleigh Road, Suite 305 | Chapel Hill, NC 27517 P: 919.419.9802 | F: 919.419.9803 sparker at aeieng.com | www.aeieng.com
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Alright, So I have a question. When I input the airflow as explained, Would it raise a flag to the reviewer even though I?m getting 27% of energy savings that this unit is oversized by 17% of the original scheduled capacity and the software is accounting for it? Thanks. Catalina Caballero. AIA. Assoc., LEED GA. Sustainability Coordinator Johnson, Avedano, Lopez, Rodriguez & Walewski Engineering Group, Inc. Engineering for High Performance Buildings. MEPF - BIM - LEED - Cx 2510 NW 97 Ave, Ste 220, Miami, FL 33172. P: 305.594.0660 Ext: 217 ? F: 305.594.0907 www.jalrw.com | ccaballero at jalrw.com [cid:image001.png at 01CFE86A.09887930] [cid:image002.png at 01CFE86A.09887930] [cid:image003.png at 01CFE86A.09887930] [cid:image004.png at 01CFE86A.09887930] This email and any files transmitted with it are confidential and intended solely for the addressee. If you are not the named addressee you should not disseminate, distribute, copy, or alter this email. Please consider the environment before printing this email.
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Classification: UNCLASSIFIED Caveats: NONE I'm using the user's manual version 6.2, I am using Trace version 6.3.0 I am following the instructions in 3-76 for the central geothermal chillers. When I run the model I get a large gas load. The building has a large unbalanced load. I plan on oversized well field and to not have any boiler or electric resistance backup. I put the gas boiler in the model just to see how much 'not geothermal' energy is being used. How do I get the model to only use the well field? Classification: UNCLASSIFIED Caveats: NONE
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