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NC-v4 EQp1:Minimum indoor air quality performance

OA Flow Measurement on VAV Rooftop Units

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William Bates
Principal
GEMCO Constructors
LEEDuser Basic Member
0 thumbs up

Hello,

   We do a lot of projects where VAV RTU's are used.  It is very difficult to directly measure the OA flow on a RTU due to the lack of ductwork.  it is possible to calculate the OA flow using energy and mass flow balance equations.  The equation requires knowledge of the mixed air flow rate and outside return, and mixed air temperatures.  Does anyone know if this method is acceptable to the USGBC to satisfy this pre-requisite?

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Devendra Chaughule
Senior Manager - Sustainable Services
Surmount
LEEDuser Basic Member
29 thumbs up

Tue, 08/17/2021 - 08:37

Hello, For small systems such as RTU where outdoor air intake flow of not more than 1000 cfm (472 L/), there is no need to install outdoor intake flow monitors provided the systems are balanced per ASHRAE 62.1-2010, section 7.2.2 and the maintenance plan for EA prerequisite Fundamental commissioning and verification meets the requirements of ASHRAE 62.1-2010, sections 8.4.1.2 and 8.4.1.6 and includes preventative maintenance measures for the system. A current transducer is required to monitor the fan status of the RTU whether the fan is on or off. Refer LEED Interpretation ID# 10461 (https://www.usgbc.org/leedaddenda/10461).

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