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Severe errors in air loop....!

asked 2019-03-27 01:53:14 -0500

Fustrated gravatar image

updated 2019-03-27 13:25:22 -0500

Hi all, Apologies because this question has been asked before........ but I just don't exactly know what is the problem with the following severe error: (please note that I have a VAV with two setpoint single zone cooling and another one single zone heating) The simulation can still run.

* Severe * FindRootSimpleController: Controller error for controller = "AIR LOOP 8 AHU COOLING COIL CONTROLLER" * ~~~ * Environment=HEAVYWEIGHTNCC2016 (01-01:31-12), at Simulation time=03/30 06:06 - 06:09 * ~~~ * Controller function is inconsistent with user specified controller action = Reverse action * ~~~ * Actuator will be set to maximum action * ~~~ * Controller control type=Temperature * ~~~ * Controller temperature setpoint = 8.57 [C] * ~~~ * Controller sensed temperature = 9.30 [C] * ~~~ * Controller actuator mass flow rate set to 66.53 [kg/s] * ~~~ * Controller actuator temperature = 9.36 [C] * ~~~ * Note: Chilled water coils should be reverse action and the entering chilled * ~~~ * water temperature (controller actuator temperature) should be below the setpoint temperature * ~~~ * Note: Hot water coils should be normal action and the entering hot * ~~~ * water temperature (controller actuator temperature) should be above the setpoint temperature * Severe * FindRootSimpleController: Controller error for controller = "AIR LOOP AHU COOLING COIL CONTROLLER"

Thanks a lot for your help,

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3 Answers

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answered 2019-03-27 11:42:33 -0500

The Action field in your Controller:WaterCoil objects is set incorrectly.

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answered 2019-03-27 18:28:11 -0500

updated 2019-03-27 18:29:53 -0500

Water cooling coils are reverse action ... more flow = lower outlet temp. The warning shows the sensed (air) temp = 9.3 C. The actuator (water) temp = 9.36 C. The set point temp = 8.57 C. With a water temp higher than the air temp, and also higher than the set point temp, there is no way to get to the set point temp of 8.57 C, and thus the warning. So to resolve this, look to see why the plant cannot supply, or maintain, a colder supply temperature. Also, a coil entering air temp of 9C is pretty low so then why would you need cooling? It's certainly possible, but then also is using an economizer in some situations. Make sure you actually need the cooling coil to turn on at this point in the simulation.

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answered 2019-03-27 17:29:47 -0500

Fustrated gravatar image

Thank you very much for your response. Unfortunatly that was not the issue... As when I change the action field of the controller:Water coils it reverts to Reverse, i.e.The action field is overwritten to be Reverse again, and I get the same errors.

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So why are you trying to control a water cooling coil as normal action (i.e., more water flow = higher outlet air temp)?

rraustad gravatar image rraustad  ( 2019-03-27 17:45:03 -0500 )edit

Thanks for your comment. Initially the control was set to Reverse. As I do not understand what is the issue with the error above, I tried to change it to normal to see the effect, but it revert to Reverse.

Fustrated gravatar image Fustrated  ( 2019-03-27 18:19:48 -0500 )edit

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Asked: 2019-03-27 01:53:14 -0500

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Last updated: Mar 27 '19