Improved Controller:WaterCoil FindRoot error message with TemperatureAndHumidityRatio

[mjwitte]

Pull request overview

• User file (helpdesk ticket 16605) was tripping on the infamous FindRootSimpleController error, but the error message was missing one important detail, the ChW temp:

   ** Severe  ** FindRootSimpleController: Controller error for controller = "CENTRAL COOLING COIL CONTOLLER 1"
   **   ~~~   **  Environment=WEATHERFILEDAYS, at Simulation time=01/01 20:03 - 20:07
   **   ~~~   **   Controller function is inconsistent with user specified controller action = Reverse action
   **   ~~~   **   Actuator will be set to maximum action
   **   ~~~   ** Controller control type=Temperature and humidity ratio
   **   ~~~   ** Controller temperature setpoint = 6.31E-003 [C]
   **   ~~~   ** Controller sensed temperature = 7.62E-003 [C]
   **   ~~~   ** Controller humidity ratio setpoint = 6.31E-003 [kgWater/kgDryAir]
   **   ~~~   ** Controller sensed humidity ratio = 7.62E-003 [kgWater/kgDryAir]
   **   ~~~   ** Controller actuator mass flow rate set to 4.07 [kg/s]

This pull request modifies the error message to:

   ** Severe  ** FindRootSimpleController: Controller error for controller = "CENTRAL COOLING COIL CONTOLLER 1"
   **   ~~~   **  Environment=WEATHERFILEDAYS, at Simulation time=01/01 20:25 - 20:30
   **   ~~~   **   Controller function is inconsistent with user specified controller action = Reverse action
   **   ~~~   **   Actuator will be set to maximum action
   **   ~~~   ** Controller control type=Temperature and humidity ratio
   **   ~~~   ** Humidity control is active.
   **   ~~~   ** Controller humidity ratio setpoint = 6.73E-003 [kgWater/kgDryAir]
   **   ~~~   ** Controller sensed humidity ratio = 7.22E-003 [kgWater/kgDryAir]
   **   ~~~   ** Controller humidity ratio setpoint dew-point temperature = 7.94 [C]
   **   ~~~   ** Controller temperature setpoint = 17.00 [C]
   **   ~~~   ** Controller sensed temperature = 11.04 [C]
   **   ~~~   ** Controller actuator mass flow rate set to 3.94 [kg/s]
   **   ~~~   ** Controller actuator temperature = 8.00 [C]
   **   ~~~   ** The entering chilled water temperature (controller actuator temperature) should be below the humidity ratio setpoint dew-point temperature.

• Also implement a limit on setpoint temperature based one coil type (heating or cooling) and entering water temperature.
  • Initially use max/min(setpoint temperature, water temp), but this might need a small tolerance.
  • If this introduces diffs, then this part will be reverted and just the error message changes can go in for v24.1

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[rraustad]

I was thinking if we knew if CW or HW coil the message could be made even clearer.

[mjwitte]

@rraustad We do figure out the coil type earlier, but haven't been saving that. How's this?

   ** Severe  ** FindRootSimpleController: Controller error for controller = "CENTRAL COOLING COIL CONTOLLER 1"
   **   ~~~   **  Environment=WEATHERFILEDAYS, at Simulation time=01/01 20:25 - 20:30
   **   ~~~   **   Controller function is inconsistent with user specified controller action = Reverse action
   **   ~~~   **   Actuator will be set to maximum action
   **   ~~~   ** Controller control type=Temperature and humidity ratio
   **   ~~~   ** Controller temperature setpoint = 6.73E-003 [C]
New=>   **   ~~~   ** Temperature setpoint has been reduced for humidity control.
   **   ~~~   ** Controller sensed temperature = 7.22E-003 [C]
   **   ~~~   ** Controller humidity ratio setpoint = 6.73E-003 [kgWater/kgDryAir]
   **   ~~~   ** Controller sensed humidity ratio = 7.22E-003 [kgWater/kgDryAir]
   **   ~~~   ** Controller actuator mass flow rate set to 3.94 [kg/s]
   **   ~~~   ** Controller actuator temperature = 8.00 [C]
Modified=>   **   ~~~   ** Chilled water coils should be reverse action and the entering chilled
Modified=>   **   ~~~   ** water temperature (controller actuator temperature) should be below the setpoint temperature

Anything else you would like to add?

[rraustad]

This looks good, and I could live with it, but...

You already know the controller is set to reverse action:

**   ~~~   **   Controller function is inconsistent with user specified controller action = Reverse action

So these new lines don't need the "Chilled water coils should be reverse action and" in this case but do if controller is set to Normal action (I suspect this is warned elsewhere for CW coils?).

Modified=>   **   ~~~   ** Chilled water coils should be reverse action and the entering chilled
Modified=>   **   ~~~   ** water temperature (controller actuator temperature) should be below the setpoint temperature

And now I know what's causing the issue with the UnmetHours post (but not sure how to fix it):

New=>   **   ~~~   ** Temperature setpoint has been reduced for humidity control.

[mjwitte]

How's this?

   ** Severe  ** FindRootSimpleController: Controller error for controller = "CENTRAL COOLING COIL CONTOLLER 1"
   **   ~~~   **  Environment=WEATHERFILEDAYS, at Simulation time=01/01 20:25 - 20:30
   **   ~~~   **   Controller function is inconsistent with user specified controller action = Reverse action
   **   ~~~   **   Actuator will be set to maximum action
   **   ~~~   ** Controller control type=Temperature and humidity ratio
   **   ~~~   ** Controller temperature setpoint = 6.73E-003 [C]
   **   ~~~   ** Temperature setpoint has been reduced for humidity control.
   **   ~~~   ** Controller sensed temperature = 7.22E-003 [C]
   **   ~~~   ** Controller humidity ratio setpoint = 6.73E-003 [kgWater/kgDryAir]
   **   ~~~   ** Controller sensed humidity ratio = 7.22E-003 [kgWater/kgDryAir]
   **   ~~~   ** Controller actuator mass flow rate set to 3.94 [kg/s]
   **   ~~~   ** Controller actuator temperature = 8.00 [C]
   **   ~~~   ** The entering chilled water temperature (controller actuator temperature) should be below the setpoint temperature.

[rraustad]

This warning is much clearer now and targets specific coil types (e.g., CW vs HW).

[rraustad]

This can merge once CI is clean. Now I want to know why the SPM or controller code was setting the CW SP temp below the CW temp (where CW SP temp = humrat SP???), and if that's a problem, and if that can be corrected.

[mjwitte]

Well, that's a good point, if the setpoint was limited to the ChW temp, then the findroot error shouldn't occur. The humidity control won't be achieved, but it's not achieved anyway in this case. I can try adding that here.

[mjwitte]

Should the setpoint always be adjusted to >= ChW temp (and similar to HW temp)? Even without humidity control?

[rraustad]

From what I recall of the controller code, I think the initial conditions need to be static, min/max flow, min/max SP, etc. There is a place where you updated the controller to switch between temp and humidity control where I think this is happening but not sure why it's showing up now. I think if on one iteration the CW SP is changed and then on a subsequent interation that CW SP is changed to something outside the initial limits then there is a problem. It's like a SolveRoot failure with -2.

case HVACControllers::CtrlVarType::TemperatureAndHumidityRatio: { // 'TemperatureAndHumidityRatio'
    if (thisController.HumRatCtrlOverride) {
        // Humidity ratio control
        thisController.SensedValue = state.dataLoopNodes->Node(SensedNode).HumRat;
    } else {
        // Temperature control
        thisController.SensedValue = state.dataLoopNodes->Node(SensedNode).Temp;
    }

[rraustad]

I think what's happening is the controller has switched to humrat control, set the controller vars based on humrat, and then reports that data as if it's temperature controlled. Here the SP is lower than the sensed value, which is fine, but the water temp is still the water temp at 8 C. Why haven't we seen this before?

**   ~~~   ** Controller temperature setpoint = 6.73E-003 [C]
**   ~~~   ** Temperature setpoint has been reduced for humidity control.
**   ~~~   ** Controller sensed temperature = 7.22E-003 [C]

 **   ~~~   ** Controller actuator temperature = 8.00 [C]

[mjwitte]

Correct, when humidity control is active, the sensed value is changed to humidity ratio, not temperature. Will re-work this section, yet again. I think I'll report the dewpoint temp of the humrat setpoint and say the chilled water temp needs to be below that.

Also, this file has other issues that are causing this problem in the first place - the chilled water coil is coming on at 8pm on January 1, probably because the OA dampers have closed and the fixed supply air temp in this VAV system wants cold air . . .

[rraustad]

Yes, but the controller converged on temperature control? before it switched over to humrat control. Is it just the warning that is incorrectly being reported? i.e., the humrat is below the water temp so the code threw this warning.

[Myoldmopar]

This feels like it might be ready...but the discussion earlier doesn't feel entirely wrapped. I'm not sure if I should dig in here or not. @rraustad approved the changes, so I'm leaning toward reviewing/merging. I'll pivot to other PRs for now but come back to this later.

[rraustad]

I have no other suggestions on the warning message. The issue of why this message is being reported can be addressed here or elsewhere. @mjwitte ?

[mjwitte]

Assuming CI is all green, this is finished.  -------- Original message --------From: Richard Raustad ***@***.***> Date: 3/15/24 8:10 AM (GMT-06:00) To: NREL/EnergyPlus ***@***.***> Cc: "Michael J. Witte" ***@***.***>, Mention ***@***.***> Subject: Re: [NREL/EnergyPlus] Improved Controller:WaterCoil FindRoot error message with TemperatureAndHumidityRatio plus Limit setpoints by water temp (PR #10435) I have no other suggestions on the warning message. The issue of why this message is being reported can be addressed here or elsewhere. @mjwitte ? —Reply to this email directly, view it on GitHub, or unsubscribe.You are receiving this because you were mentioned.Message ID: ***@***.***>

[Myoldmopar]

CI is green, just a few ERR diffs. Merging, thanks @mjwitte and @rraustad