See all forum discussions about NC-2009 IEQc1
 Subscribe to new posts about NC-2009 IEQc1 Post a new question aboutNC-2009 IEQc1
See LEEDuser’s guidance on NC-2009 IEQc1»
FAQs about IEQc1 :

If my project is using air handlers that supply 100% outside air at a constant volume, do I still need to install an airflow monitoring device?

View answers »

Forum discussion

NC-2009 IEQc1:Outdoor Air Delivery Monitoring

DOAS units

I need some clarification on what definition of a "ventilation system" would be with respect to design that uses a DOAS unit that provides outdoor air to each space. If the OA from the DOAS is ducted to heat pumps distributed throughout the building would you need OA flow stations at each OA duct to each heat pump or just at the DOAS unit OA intake assuming the system is constant volume and balanced to the correct airflow for the space? Thanks!

0
Post a reply

You rely on LEEDuser. Can we rely on you?

LEEDuser is supported by our premium members, not by advertisers.

Go premium for $15.95  »

Profile picture for user jkmcfarland
John McFarland
Director of Operations
WorkingBuildings, LLC
LEEDuser Expert
39 thumbs up

Fri, 12/06/2013 - 20:38

Hi Mike, If the DOAS is constant volume, then the airflow measuring device just needs to be at the outdoor air intake for the DOAS equipment. This assumes fixed-position (i.e., non-modulating) balancing dampers at each heat pump. If the DOAS is variable volume where the OA flow to each heat pump could vary based on the OA requirements for each ventilation zone, then an airflow measuring device is needed at each heat pump since the flow could now vary from setpoint. Hope this helps clarify things. Good luck, John
Profile picture for user amber_2
Lauren Wallace
LEED Project Reviewer, LEED AP BD+C, Senior LEED Specialist
Certifications Department Manager, Epsten Group, Inc.
LEEDuser Basic Member
26 thumbs up

Fri, 12/06/2013 - 21:03

Hey, John! I'm not sure your comment about outdoor airflow measurement devices being located at each heat pump on a variable volume DOAS is accurate. The intent behind providing outdoor airflow measurement devices is to measure the outdoor air intake flow to ensure that the design minimum outdoor air rate prescribed by ASHRAE Standard 62.1 is being provided at the system level, not at the zone level. In a similar design where the DOAS was variable volume without heat pumps, the outdoor airflow measurement device would still be located at the DOAS. Is there something I'm missing here?

Fri, 12/06/2013 - 21:15

Lauren, this definition of system and zone were a bit of my issue to begin with... Seems like with a variable volume DOAS as you describe there would be no way to ensure the airflow to each zone is maintained. One zone may require less but the other zones would require the same. If this system is hard balanced and the DOAS modulates down all the zones would be receiving less OA. therefore it seems you would need the airflow station at each zone AND a modulating damper that would satisfy each zone OA requirement as the DOAS unit modulates airflow? John, thank you for the response. I hope that is indeed the case.

Fri, 12/06/2013 - 22:56

Mike, the answer to your question is dependant on your design intent. If you just want to comply with the credit requirements then all you would actually need is a CT at the DOAS motor to provide system status. You can look this up in the interpretations library. If you are looking at this from a practical design standpoint then John's answer is 100% correct.

Add new comment

To post a comment, you need to register for a LEEDuser Basic membership (free) or login to your existing profile.