[Equest-users] Relief Fan Flow Rate

[Mike Karpman]

Hello All,



I’ve come across an unexpected result and thought I’d share… maybe someone
here can shed some light. I am modeling a VAV air handler with supply and *
relief* fans.



When I try to enter the design flow of the relief fan (RETURN-FLOW
keyword), which is about 90% of the design supply flow, the model forces
outside air to be at least 10% (the leftover from 90%) * [supply flow] for
all hours that the fans are running, including night cycle hours when I
force outside air to 0 using the MIN-AIR-SCH keyword. I believe this
behavior is intended for return fans, and I’ve indicated that I want to
model a relief fan using the RETURN-FAN-LOC keyword. The increased outside
air, affecting all of the night cycle hours and sometimes interfering with
DCV control, has a significant effect on simulation results.



For the project I’m working on, I’ve restored the RETURN-FLOW keyword to
default, since I don’t think the effect on the results will be significant.
But I’m curious whether anyone else has noticed this, or has any thoughts
on the issue?



Regards,

Mike



Mike Karpman

*Karpman Consulting*

(860) 430-9110

41C New London Turnpike

Glastonbury, CT 06033
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