Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
These warnings are very hard to diagnose. The key is the change in temperature from one iteration to the next. Each of these "differences" between the demand and supply side nodes show a slight oscillation. Not huge, but exceeding the tolerance expected (tol = 0 would be perfect). From iteration to iteration the difference between the demand side outlet node and the supply side inlet node of this air loop is about 0.0005 C
* ~~~ * Demand-to-Supply interface mass flow rate check value iteration history trace: 4.427527E-002,4.367028E-002,4.334135E-002,4.394626E-002,4.427539E-002,4.367029E-002,4.334158E-002,4.394676E-002,4.427527E-002,4.367028E-002,
This is not a big problem. What is a problem is why this happens. Usually a warning like this means there is an OA system or HX in the air loop that slightly changes the mixed air temperature entering the air loop. This slight change in air loop inlet temperature means the air loop components will react just a little bit differently than the previous iteration and occasionally leads to max iteration warnings.
The only advise I have is to review the air loop control and try to provide a stable supply air temperature so that the "SA system air flow" remains constant from one iteration to the next.
| | 2 | No.2 Revision |
These warnings are very hard to diagnose. The key is the change in temperature from one iteration to the next. Each of these "differences" between the demand and supply side nodes show a slight oscillation. Not huge, but exceeding the tolerance expected (tol = 0 would be perfect). From iteration to iteration the difference between the demand side outlet node and the supply side inlet node of this air loop is about 0.0005 C
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** This is not a big problem. What is a problem is why this happens. Usually a warning like this means there is an OA system or HX in the air loop that slightly changes the mixed air temperature entering the air loop. This slight change in air loop inlet temperature means the air loop components will react just a little bit differently than the previous iteration and occasionally leads to max iteration warnings.
The only advise I have is to review the air loop control and try to provide a stable supply air temperature so that the "SA system air flow" remains constant from one iteration to the next.
