I see new "BIAS connection" button in ApacheHVAC modul but it seems can not be used to create any link between controller.
Any one can tell me how to use this new function ?
Thank you.
BIAS connection
-
mshaynes1992
- VE Newbie
- Posts: 8
- Joined: Tue Dec 01, 2015 3:37 pm
Re: BIAS connection
It would be nice if someone from IES could respond to this. VE 2021 is 4 feature packs in and still no word on this and still no function for it.
Re: BIAS connection
TLDR: In a coil-then-fan (draw-through) AHU configuration, the BIAS controller is a dT sensor that measures the heat pickup from a Fan, then asks the coil to account for it; thus achieving the target leaving temperature.
https://imgur.com/a/n0YVGDF
Detailed notes below.
======================================================
BIAS controller connection
Title 24 ACM section 5.7.3.2. Standard model: Supply Fan configuration shall be Draw-Through.
Implementation:
• Ensure all T24 Standard (baseline) systems have the supply fan position as draw through. This places the fan, and thus fan heat gain, downstream of the cooling coil in a typical AHU.
• This must be accommodated by a new "BIAS" connection between controllers (see below) to adjust the controlled values for the Cooling Coil LAT and Heating Coil LAT both downward to compensate for the actual Fan Heat Gain at each time step, such that the SAT from the AHU will be as intended (e.g., just 55 F when controlled to that temp, and not 55 F + Fan heat gain).
• For T24 System Prototypes and most similar "draw-through fan" applications, there most often will need to be three BIAS connections emanating from the same dependent differential controller to:
o All Independent controllers that determine AHU Cooling Coil LAT.
o All Independent controllers that determine AHU Heating Coil LAT.
• The creation of a generic "bias" connection will prove useful in other applications, including but not limited to improvement upon the VE2019-FP2 OA Economizer Controls revision, which temporarily assumed 1-degree F heat gain across the fan component (in anticipation of this bias connection being developed).
• It will be acceptable if, by virtue of the controller simulation based upon node ordering, the Cooling Coil LAT compensation is based upon the fan heat gain from the prior simulation time step. The result will be SAT from the AHU roughly 1 F above the desired value for just the first time step that the Fan component is operating. Thereafter, the one-timestep delay will result in the SAT being off by only a fraction of 1-degree F (or C) in the case of a variable-speed fan, for which heat gain will vary somewhat from one sim time step to the next.
Details:
Provide a new kind "logical +/-" or "bias" connector for use with the existing Dependent Differential Controller. The new type of connector will add or subtract the differential value for the sensed variable, depending upon whether it is positive or negative, to/from the controlled value of any Independent controller to which it is connected.
• The differential between the sensor’s inputs of the dependent differential controller in this case is fed into an independent controller. This output (the differential value) can only influence another controller, and cannot directly set a controlled value on its own.
• This requires a new "BIAS" controller connection, similar to the logical AND & OR connections.
• The BIAS connection shall transmit only the differential value to directly influence the output (control signal) of the recipient controller whenever that controller is operational and the BIAS signal is present.
• Whereas the dependent differential controller generating the BIAS signal may have its own time switch profile or other determinant of its own on/off status, the BIAS connection shall not transmit any form of on/off signal that would influence the on/off state of the recipient controller.
• This connection is represented by the dashed red line in screen capture above, which should actually be a cyan or purple dashed line (whichever appears more distinct) in order to differentiate it from existing forest green (AND), navy blue (OR), and red (selected) connector lines.
• The new BIAS connection shall have its own toolbar button to initiate placement. The icon should be like that of the AND button, but with a red "+/-" symbol in replacing the red "+", as shown below and located in the noted Visio file:
• The BIAS connection must emanate from a Dependent Differential Controller and can be attached only to an Independent Controller as the recipient.
• At the time of placement of the BIAS connection, a check must be performed to ensure that the sensed variable in the differential controller on the source end of the BIAS connection (e.g., temperature) matches the controlled variable on the recipient end of the BIAS connection (e.g., also temperature --- same in any case at the source side). If a mismatch is detected, a pop-up warning should tell the user that they must correct this mismatch prior to placing the BIAS connection.
• The same check for consistency of the variables on both ends of the BIAS connection should also be performed as part of the overall network check function.
• The new connection will need to show up on a newly added list box within all independent controllers (the three controller types to which it could be attached on the recipient end).
o For all three the BIAS list box should appear below the list boxes for AND & OR connections.
o Within the Independent Time Switch controller, it appears that three modifications will be required to fit this in at the bottom:
Reduce the height of the frame for the Time Switch Profile selection;
Expand the height of the overall dialog;
If still needed after taking the first two steps, reduce the height of the list boxes for both AND & OR connections to show just one connection without a vertical scroll bar (whereas it presently appears, until populated, that the heading row is double height, this is owing to lack of a needed gray line separating the heading from the first listing row).
o Within the Independent Controller with Sensor and Independent Differential Controller dialog:
Re-label the "AND/OR Connections" frame as "AND/OR/BIAS Connections";
Add a field displaying the number of BIAS connections, labeled "BIAS:", to the right of "OR:".
Within the pop-up "Edit" window for these connections, the new "BIAS Connections" list box should be located below the list boxes for AND & OR connections. Mechanics for populating/deleting connection from this box should be the same as for AND/OR connections. If needed, the two existing list boxes can be reduced in height to display only three connections without vertical scrolling.
• The connection will need to be multiplexed in order to influence the controlled-value "vote" from a set of multiplexed zone-level controllers that, in turn, point to the system cooling coil.
Reasons for implementing this solution:
• This solution is reasonably consistent with current controller logic and concepts; however, it does introduce the somewhat new concept of modifying the output of the connected controller with the bias value, rather than simply influencing its on/off state.
• Leverages existing controllers with only very minor updates to reference the new type of connector, and thus allow for the connection to be removed when desired.
• This does not alter the "voting" logic for multiple controllers pointing to a single node. This might be helpful, given that we anticipate adding several other user-selectable arithmetic outcomes for that (e.g., winning vote is the high vote, low vote, average vote, etc.). Thus, upstream influence from the differential controller would be conceptually easier to understand and potentially easier to manage within the code.
https://imgur.com/a/n0YVGDF
Detailed notes below.
======================================================
BIAS controller connection
Title 24 ACM section 5.7.3.2. Standard model: Supply Fan configuration shall be Draw-Through.
Implementation:
• Ensure all T24 Standard (baseline) systems have the supply fan position as draw through. This places the fan, and thus fan heat gain, downstream of the cooling coil in a typical AHU.
• This must be accommodated by a new "BIAS" connection between controllers (see below) to adjust the controlled values for the Cooling Coil LAT and Heating Coil LAT both downward to compensate for the actual Fan Heat Gain at each time step, such that the SAT from the AHU will be as intended (e.g., just 55 F when controlled to that temp, and not 55 F + Fan heat gain).
• For T24 System Prototypes and most similar "draw-through fan" applications, there most often will need to be three BIAS connections emanating from the same dependent differential controller to:
o All Independent controllers that determine AHU Cooling Coil LAT.
o All Independent controllers that determine AHU Heating Coil LAT.
• The creation of a generic "bias" connection will prove useful in other applications, including but not limited to improvement upon the VE2019-FP2 OA Economizer Controls revision, which temporarily assumed 1-degree F heat gain across the fan component (in anticipation of this bias connection being developed).
• It will be acceptable if, by virtue of the controller simulation based upon node ordering, the Cooling Coil LAT compensation is based upon the fan heat gain from the prior simulation time step. The result will be SAT from the AHU roughly 1 F above the desired value for just the first time step that the Fan component is operating. Thereafter, the one-timestep delay will result in the SAT being off by only a fraction of 1-degree F (or C) in the case of a variable-speed fan, for which heat gain will vary somewhat from one sim time step to the next.
Details:
Provide a new kind "logical +/-" or "bias" connector for use with the existing Dependent Differential Controller. The new type of connector will add or subtract the differential value for the sensed variable, depending upon whether it is positive or negative, to/from the controlled value of any Independent controller to which it is connected.
• The differential between the sensor’s inputs of the dependent differential controller in this case is fed into an independent controller. This output (the differential value) can only influence another controller, and cannot directly set a controlled value on its own.
• This requires a new "BIAS" controller connection, similar to the logical AND & OR connections.
• The BIAS connection shall transmit only the differential value to directly influence the output (control signal) of the recipient controller whenever that controller is operational and the BIAS signal is present.
• Whereas the dependent differential controller generating the BIAS signal may have its own time switch profile or other determinant of its own on/off status, the BIAS connection shall not transmit any form of on/off signal that would influence the on/off state of the recipient controller.
• This connection is represented by the dashed red line in screen capture above, which should actually be a cyan or purple dashed line (whichever appears more distinct) in order to differentiate it from existing forest green (AND), navy blue (OR), and red (selected) connector lines.
• The new BIAS connection shall have its own toolbar button to initiate placement. The icon should be like that of the AND button, but with a red "+/-" symbol in replacing the red "+", as shown below and located in the noted Visio file:
• The BIAS connection must emanate from a Dependent Differential Controller and can be attached only to an Independent Controller as the recipient.
• At the time of placement of the BIAS connection, a check must be performed to ensure that the sensed variable in the differential controller on the source end of the BIAS connection (e.g., temperature) matches the controlled variable on the recipient end of the BIAS connection (e.g., also temperature --- same in any case at the source side). If a mismatch is detected, a pop-up warning should tell the user that they must correct this mismatch prior to placing the BIAS connection.
• The same check for consistency of the variables on both ends of the BIAS connection should also be performed as part of the overall network check function.
• The new connection will need to show up on a newly added list box within all independent controllers (the three controller types to which it could be attached on the recipient end).
o For all three the BIAS list box should appear below the list boxes for AND & OR connections.
o Within the Independent Time Switch controller, it appears that three modifications will be required to fit this in at the bottom:
Reduce the height of the frame for the Time Switch Profile selection;
Expand the height of the overall dialog;
If still needed after taking the first two steps, reduce the height of the list boxes for both AND & OR connections to show just one connection without a vertical scroll bar (whereas it presently appears, until populated, that the heading row is double height, this is owing to lack of a needed gray line separating the heading from the first listing row).
o Within the Independent Controller with Sensor and Independent Differential Controller dialog:
Re-label the "AND/OR Connections" frame as "AND/OR/BIAS Connections";
Add a field displaying the number of BIAS connections, labeled "BIAS:", to the right of "OR:".
Within the pop-up "Edit" window for these connections, the new "BIAS Connections" list box should be located below the list boxes for AND & OR connections. Mechanics for populating/deleting connection from this box should be the same as for AND/OR connections. If needed, the two existing list boxes can be reduced in height to display only three connections without vertical scrolling.
• The connection will need to be multiplexed in order to influence the controlled-value "vote" from a set of multiplexed zone-level controllers that, in turn, point to the system cooling coil.
Reasons for implementing this solution:
• This solution is reasonably consistent with current controller logic and concepts; however, it does introduce the somewhat new concept of modifying the output of the connected controller with the bias value, rather than simply influencing its on/off state.
• Leverages existing controllers with only very minor updates to reference the new type of connector, and thus allow for the connection to be removed when desired.
• This does not alter the "voting" logic for multiple controllers pointing to a single node. This might be helpful, given that we anticipate adding several other user-selectable arithmetic outcomes for that (e.g., winning vote is the high vote, low vote, average vote, etc.). Thus, upstream influence from the differential controller would be conceptually easier to understand and potentially easier to manage within the code.