Negative Air Flow at node error

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toemoss
VE Beginner
VE Beginner
Posts: 10
Joined: Mon Aug 11, 2014 3:23 pm

Negative Air Flow at node error

Post by toemoss »

I have a situation where I'm exhausting more air from a zone (170 cfm) than supplying (135), in order to keep the space negative with respect to nearby areas.
When I run a system plant sizing report I get the negative airflow at node 12 error (this node is at entrance to adiabatic space).
I've tried the following approaches to fix the error with no success:
* Set system fan to "automatic Sizing"
* Tried setting OA and exhaust to same value, and transfer air to 0 (completely baffled as to why this would not work)
* Let OA be 135 cfm, exhauast air 170 cfm, transfer air 35 cfm

This is my first Energy Model with VE pro, so I'm fairly sure its just a basic error, but I can't figure it out.
Please help if you what I should be changing or checking.

Attempting to include image of my system below:
Image
Megan
VE Graduate
VE Graduate
Posts: 52
Joined: Thu Dec 12, 2013 3:03 pm
Location: Atlanta, GA

Re: Negative Air Flow at node error

Post by Megan »

When there is enough supply or transfer air to make up for the exhaust flow rate and this error still occurs, it is generally a result of scheduling discrepancies. Make sure each flow controller is operating on the same schedule - or at least that there is always supply when exhaust is called for.

Often, exhaust controllers are set to "on continuously" where supply controllers only operate during operating hours.
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