[Equest-users] DOAS Warning/Caution Messages

[Robert Stephenson]

I am following up on the comments from a LEED for Homes Midrise review for a recent model. This is the first time I have provided a full .SIM file to go with my model to a reviewer (LEED for Homes requests so many reports from the output that I thought this would be easier), and now I am being asked to explain every single caution and warning associated with the simulation. All of the following are associated with my DOAS units, which are giving me a real headache.


**CAUTION**********************************************************************

             ERU 1                            defined as an OA-FROM-SYSTEM

             has   9 CONDITIONED ZONEs - only one was expected.


Each of my DOAS units serves multiple corridor zones and directly provides outside air to the building's residential apartments.  I am using system type, packaged multizone. Is this caution something I should be worried about?



**WARNING**********************************************************************

In ERU 1                           , the return humidity for a coil exit T of 52.0 is 0.0095

Your setpoint is 0.0089, which may not be held.

This is for a DOAS that includes energy recovery, DX cooling, Furnace heating, and humidity control via hot gas reheat. I have maximum humidity set to 49% per the design documents. Creating an hourly report for supply air humidity, I found that the humidity setpoint (lb H20/lb dry air) does not exceed 0.0089. Even with lowering the coil exit temp, I could not manage to get it to go away.


**WARNING**********************************************************************

             ERU 2                            defined as an OA-FROM-SYSTEM

             has OA flow requirement of     2839. CFM but its calculated/specified

             OA flow is only      2600. CFM.

             Its MIN-OUTSIDE-AIR has been reset to meet the requirement, however

             it is strongly recommended you re-run with this MIN-OUTSIDE-AIR specified.

I'm getting this on all my DOAS units, and I've tried multiple approaches to overcoming this warning without success. Even setting the outside air ratio to 1.0, eQUEST continues to set the system outside air to this same number, 2839 cfm. The actual system flow is set to 4,515 CFM per the design documents.


**WARNING**********************************************************************

             Energy-recovery ventilator: ERU 1                            is

             enabled to run, but cannot run because there is no central

             exhaust flow.  First occurrence:  1/ 1/ 1


I have an exhaust air flow specified on the Heat Recovery 1 tab under outdoor air. I also have the exhaust schedule set to 1.0 for the entirety of the year. Am I not enabling something correctly?

As always many thanks in advance.

Robert Stephenson
Technical Energy Analyst
Evaluation, Measurement & Verification Services
Vermont Energy Investment Corporation
rstephenson at veic.org
(802) 540-7886

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