The EOH statement calculates the flow temperature (mixed water temperature) setpoint and the optimized values for starting and stopping the heating plant. The EOH function considers the residual heat in a building to avoid unnecessary heating operation and, thus, save energy. Required room conditions are met at all times.
EOH calculates the required flow temperature according to an integrated heating curve.
There are two optimization options:
Optimization without a room sensor uses the outdoor air temperature to determine the optimum start (preheat point).
Optimization with a room sensor uses the room control and needs a time constant and dead time to calculate the preheat point.
Any kind of start or stop optimization requires a time schedule for the room temperature setpoint.
EOH calculates the following values from the connected time schedule:
The EOH statement gets these values from the datapoint connected to the input “In RoomTempSp”.
The heating curve in EOH is automatically adapted if the internal and external adaptation (input ”In AdaptEnable”) conditions are fulfilled, see section "Heating Curve Adaptation".
With the parameter P20 occupied / un-occupied changeover, you can decide whether you want to run the heating circuit with night setback or with total cool-down. If the room temperature setpoint is higher or equal than P20, the flow temperature is controlled by the room temperature setpoint using the heating curve; otherwise it is set to 0.
“Out RoomTempSp” = Heating Curve Setpoint + P23*FADAPT*(“In RoomTempSp” +/- “In SetpointAdj” - “In RoomTemp”)
Heating Curve Setpoint = HC (“In RoomTempSp” +/- “In SetpointAdj”, “In FiltOATemp”, P15, P16)
“Out RoomTempSp” = 0, for total cool down
FADAPT = 1; if P19 = [4]
FADAPT = 0; if P19 = [0;1;2;3]
Total cool-down is possible only if one of the following conditions is true:
Fig. 172. Heating circuit control modes
Note: The heating pump must be controlled externally.
There are two ways of controlling the minimum room temperature during un-occupied periods
To enable minimum room temperature protection, set P24 to a higher value than the value of the room temperature setpoint during un-occupied periods.
To enable minimum room control P24 must be set to a value lower than the room temperature setpoint during the un-occupied periods.
The minimum room temperature protection ensures a minimum room temperature condition during un-occupied periods. If the room temperature drops below the value of the P24 setting, the mixed water temperature setpoint is set to the value of the Tprot. The minimum room temperature protection function ends if the room temperature rises above the value of P25 + P24. This leads to the reasonable heat up of the room. The next figure shows the minimum room temperature protection function.
Tprot = HC (P24 + P25 + 2K, “In FiltOATemp”, P15, P16)
Fig. 173. Minimum room temperature protection
The minimum room temperature control becomes active, when during un-occupied periods the room temperature drops below the value of the room temperature setpoint set in the time schedule. In this case, the heating circuit is re-started and calculates the mixed water temperature setpoint depending on the heating curve characteristics, outside air temperature and the actual room temperature setpoint. This function is an alternative for minimum room temperature protection whereby always maximum capacity is used. To enable minimum room temperature control, set P24 lower than the value of the room temperature setpoint during un-occupied periods.
Fig. 174. Minimum room temperature control
EOH calculates the flow temperature setpoint with or without optimization as a function of the room temperature setpoint “In RoomTempSp”, the outside air temperature “In FiltOATemp”, the heating curve parameters curvature and slope.
Heating Curve Setpoint = HC(“In RoomTempSp”, “In FiltOATemp”, P16, P17)
During total cool-down (see previous section), the flow temperature setpoint can be set to “0”.
Optimum Start can happen only if all the following conditions are true:
Optimum Stop can happen only if all the following conditions are true:
Fig. 175. Optimum start/ stop
The supply water temperature set “Out RoomTempSp” is calculated using te heating curve equation. The room temperature setpoint is equal to the required “In RoomTempSp” (next occupied switch point) + P3 (no room temperature compensation).
“Out RoomTempSp” = HC (“In RoomTempSp” + P3, “In FiltOATemp”, P16 (curvature), P17 (slope))
HC – meant heating curve equation
During preheat time, EOH generates the flow temperature setpoint according to the heating curve, where the effective room temperature setpoint is increased by P3.
The preheat start point is a function of the outdoor air temperature.
tVV = P5/”In RoomTempSp” * (“In RoomTempSp” – “In FiltOATemp”)
At an outdoor air temperature of 0 °C, the preheat time starts 2 hours (P5) before reaching the corresponding switch point in the Time Schedule.
If the outdoor air temperature (“In FiltOATemp”) is equal to the room temperature setpoint (“In RoomTempSp”), the preheat point is not advanced.
The value of tVV is limited to a maximum of P2 (default is 48 hours).
Fig. 176. Pre-start time without room temperature sensor
Example (at 10 °C):
Preheat time (P5) = 120 min
Minimum outdoor temperature for early setback (P4) = 0 °C
Setpoint (“In RoomTempSp”) = 20 °C
Outdoor air temperature (“In FiltOATemp”) = 10°C
tVV = (-120 min/ 20) * 10 + 120 min
tVV = 60 min
The following diagram illustrates this action:
Fig. 177. Optimum start without room temperature sensor
During this preheat phase, EOH transmits a 1 to the output “Out OptimStart”. You can use this output to determine to overwrite the supply temperature setpoint from the normal application program by the flow temperature setpoint (Y1) from EOH.
If the target time point of the switching program occurs in this time, EOH sets the output “Out OptimStart” to logical zero, meaning that the requirements of the normal applications program again apply. EOH calculates the supply temperature setpoint (Y1) in accordance with the heating curve. Parameter P16 provides the curvature. Parameter P17 provides the slope which is displaced in accordance with the room temperature setpoint including the increase (see "HCA Icon" section for further explanations of the heating curve).
EOH can calculate the residual heat in a building and the exact preheat points only if there is a room sensor “In RoomTemp”.
In order not to boost always with the maximum flow temperature P16, we will boost with the value defined in the heating curve using the next “In RoomTempSp” – see equation below:
T2boost = HC (next “In RoomTempSp” + P22 * (next “In RoomTempSp” - actual “In RoomTempSp”), “In FiltOATemp”, P16, P17)
Parameters P16 (curvature) and P17 (Slope) belong to the heating curve. Parameter P15 limits the supply temperature setpoint (“In RoomTempSp”) to the maximum permissible flow temperature.
During the setback period, the outdoor temperature, the current room temperature, and the T2boost are used to decide the start time of the preheating phase. First the heating curve equation is used to calculate the asymptotic room temperature limit T1lim (reverse heating curve).
T2boost = HC (T1lim, “In FiltOATemp”, P16, P17)
During the preheating period, “Out RoomTempSp” is repeatedly updated by the heating curve to allow variations of the outdoor temperature. The estimate of T1lim remains unchanged from the value calculated at the beginning of the pre-heat.
If the room temperature setpoint is reached earlier than the target point in time, room temperature control takes over.
After the target point in time is reached, room temperature control is enabled for another 30 minutes. The room temperature control is meant to compensate for cooling effects caused by walls and furniture after boost heating so that after switch over to weather responsive control, the room temperature remains nearly constant.
Output “Out OptimStart” has a value of 1.0 between the start of the preheat time and programmed time. For all other times, “Out OptimStart” = 0.
Variable Time Preheat
During the pre-heat period, the supply water temperature used will be T2boost (see equation above) except if less than the minimum preheat time (P1) would then be required. In this case the minimum time is used and the supply water temperature is re-calculated accordingly.
These two complementary ways of preheating are called time-variable and temperature-variable optimization respectively and the correct method will be selected.
During the setback period, the outdoor temperature, the current room temperature, and the T2boost are used to decide the start time of the preheating phase. First the heating curve equation is used to calculate the asymptotic room temperature limit T1lim (reverse heating curve).
T2boost = HC (T1lim, “In FiltOATemp”, P16, P17)
Then the building model is used to predict what the room temperature would be at the time of the next switch point if the heating would be switched on immediately.
When this predicted temperature is less than the next “In RoomTempSp” (room temperature setpoint), then it is time to begin the pre-heat period and switch on the heating.
The reheat time cannot be greater than 48h (P2, 2880 minutes) or shorter than the minimum preheat time (P1).
If the minimum preheat time is reached, the temperature variable preheating begins immediately.
The next two diagrams illustrate this operation for day and day/night operation.
Fig. 178. Time variable pre-heating
You can influence the type of optimization procedure that EOH uses by adjusting parameter P1, minimum preheat time. For very small values of P1, for example, zero minutes, EOH only uses the variable time preheat (rapid preheating) because it is never possible to reach the setpoint in zero minutes regardless of the boost temperature. Large values of P1, such as several hours, have the opposite effect. Large values lead to variable temperature preheats with moderate supply temperatures. During the preheat phase, EOH sends a logical 1 to output “Out OptimStart”.
If the room temperature “In RoomTemp” reaches the setpoint of the Time Schedule “In RoomTempSp” (X1) before the target time point, EOH switches over to room control automatically. The room control uses an internal PI controller whose integral action time (P14) and room control P-band (P13) can be set. After reaching the target point, EOH still works half an hour longer as a room controller. EOH then writes a logical 0 to the output “Out OptimStart” to allow the application program to take control. This extended control by EOH compensates the cool-down effect from the walls and furniture after a rapid preheating so that an almost constant room temperature is guaranteed with the transfer to temperature-dependent control after ending the preheat optimization.
Variable Temperature Preheat
If the time variable preheat has not started when the minimum preheat time is reached, then temperature variable preheating begins immediately.
Since for temperature-variable preheating, the preheat time is fixed, the required flow temperature can be calculated by first finding the required room temperature limit (asymptotic) T1lim using the building model defined by the parametersP8 to P11.
Then the required flow temperature setpoint can be calculated from the heating curve equation.
“Out RoomTempSp” = HC (T1lim, “In FiltOATemp”, P16, P17)
Fig. 179. Optimum start - temperature variable pre-heating
In cool-down optimization, EOH only looks at the outdoor air temperature to define the time point for early setback. The maximum advance of the switch-off point is 2 hours. EOH advances the switch-off point of the Time Schedule by this time interval when the momentary outdoor air temperature (”In FiltOATemp”) corresponds exactly to the room temperature setpoint of the Time Schedule (“In RoomTempSp”. If the outdoor air temperature is less than the limit defined by parameter P4, no early switch-off occurs. Between these two points, EOH uses the following linear interpolation to advance switch-off point tVV:
tVV = 120 min* (“In FiltOATemp” – P4) / (“In RoomTempSp” – P4)
Parameter P4 influences the switch off time as shown in the figure below.
The following diagram illustrates this action:
Fig. 180. Optimum stop without room temperature sensor
Example:
Outdoor air temperature “In FiltOATemp” = 6 °C
Minimum outdoor air temperature for early setback P4 = 0 °C
Momentary room temperature setpoint “In RoomTempSp” (Time Schedule value) = 20 °C
tVV = 120 min * (6 - 0) / (20 - 0)
tVV = 36 min
During this total setback phase, EOH transmits a 1 to output “Out OptimStop”. This value overwrites the supply temperature setpoint from the normal application program by flow temperature setpoint “Out FlowTempSp” from EOH.
Caution
During the total setback phase, EOH transmits a supply temperature demand of 0 °C to “Out FlowTempSp”. If the filtered outside air temperature is below the frost protection limit, EOH will calculate the flow temperature setpoint with the heating curve and the reduced room temperature setpoint.
After the cool-down phase, EOH resets output Stop (“Out OptimStop”) to zero so that the normal application program is again in control.
Caution
It is absolutely essential that the switch point for cool-down is the latest possible time point in the Time Schedule. This precaution prevents premature cool-down and problems with rooms being outside required conditions.
Cool-down optimization with a room sensor operates with the same principles as without a room sensor but it also considers the room temperature:
EOH calculates the early off time with room sensor (tVVR) with the following formula:
tVV = (120 min + tcorr)* (“In FiltOATemp” – P4) / (“In RoomTempSp” – P4)
Where tcorr equals (“In RoomTemp” – “In RoomTempSp”) * P6, which means: room temperature minus setpoint times optimum stop factor.
If Parameter P6 is zero, the cool-down optimization procedure with room sensor is the same as without a room sensor.
Fig. 181. Optimum stop without room temperature sensor
Example:
Outdoor air temperature “In FiltOATemp” = 5.6 °C
Minimum outdoor air temperature P4 = 0 °C
Factor for early switch-off P6 = 10 min/ K
Room temperature “In RoomTemp” = 21.1 °C
Target room temperature setpoint “In RoomTempSp” = 20 °C
Advance preheat time with room sensor:
tVVR = 39 min (without a room sensor tVV = 36 min)
During this cool-down phase, EOH transmits a 1 to output “Out OptimStop”. This 1 overwrites the supply temperature setpoint from the application program by the flow temperature setpoint “Out FlowTempSp” from EOH.
At the end of the cool-down phase, EOH sets the output “Out OptimStop” to 0.
To allow an optimum stop to save a significant amount of energy without losing comfort, the room temperature can drop by P7 below the actual room temperature setpoint “In RoomTempSp” – P7. In this moment the EOH switches to room control mode with the room temperature setpoint equal to actual “In RoomTempSp” – P7 and keeps this setpoint until the start time of the next lower “In RoomTempSp”. The room temperature control uses an internal controller of which integral action time (P17) and room controller P-band (P14) can be set.
Fig. 182. Pre-start with room temperature sensor
After reaching the target time, EOH still works with the supply temperature setpoint from the heating curve. EOH sets the output Stop (YD2) to logical 0.
When preparing the Time Schedule, ensure that the switch point for cool-down is always the latest possible time in the Time Schedule to avoid premature cool-down and room temperatures outside the comfort zone.
EOH calculates the times for the beginning of preheat and cool-down optimization in advance. Because the time for optimized preheat varies from system to system even with the same temperature conditions because of the behavior of the heating system and the building, EOH maintains a “model” of the building. The dead time and time constants for the building determine the dynamic behaviour of the model. EOH maintains two models for preheat because it is necessary to distinguish between building characteristics after a short cool-down and after a lengthy cool-down.
Dead time short (parameter P8) and Time constant short (parameter P9) define the first model. This building model applies for a pre-heat that follows a short cool-down (less than 24 hours).
Dead time long (parameter P10) and Time constant long (parameter P11) define the second model. This building model applies for a pre-heat that follows a lengthy cool-down (greater than 24 hours).
After a lengthy cool-down phase, the building walls are also cooled down and must be heated if the room is to be heated.
When operating EOH without a room sensor, you must determine dead times and time constants manually.
The following diagram shows how you can determine dead time (Tu) and time constant (Tg) from the building characteristic curve.
Fig. 183. Building model
The diagram plots the development of the room temperature at the point of the heating switch-on time until it reaches the room temperature setpoint. You can draw this type of characteristic curve by recording the room temperature (analog input at the controller) and outputting this value to a plotter via an analog output with the characteristic curve 0 through 50 °C = 0 through 10V. You need to record separate characteristic curves for preheat after a short cool-down and after a lengthy cool-down.
When operating EOH with a room sensor, you can define dead times and time constants with the corresponding parameters. If you select ´Disabled` for adaptation in the internal parameters dialog box (parameter P12 = 0), these parameters remain valid.
If you select ´Enabled´ (parameter P12 = 1) or ´Restart` for adaptation (parameter P12 = 2), EOH determines dead time and time constants automatically from the actual temperature development during the preheat phase. EOH weights the new values and uses them to correct the old parameter values.
If the mode is ´Restart´ then the EOH automatically switches the mode of operation to ´Enabled` (P12 = 1). While enabled, the room model time constants are continuously improved at the end of every optimize start phase.
The heating curve slope adaptation has the following settings:
If any type of adaptation is set, no direct room temperature compensation of the flow temperature setpoint is possible.
The heating curve slope adaptation is enabled if all the following conditions are true for 6 hours or longer:
Note:
The external calculated conditions described below have to be considered and connected to the input adaptation enable (“In AdaptEnable”).
External conditions can be, for e.g.
If the parameter P19 set to 2 = ´Restart`, the heating curve slope adaptation will be restarted. This new start has to be selected before the first download of the controller or when the building load has been changed after a renovation. After 24 hours of operation, the heating curve slope adaptation will automatically be reset to the 1 = ´adaptive`.
If the parameter Adaptation is set to 3 = ´refreshed new start`, the heating curve slope adaptation will be execute a ´Restart` function based on the outside air temperature values of +10, +5, 0, -5, -10 and -15 °C, etc. This means, when the average outside air temperature during 48 hours crosses the former mentioned temperature levels upwards or downwards, the ´Restart` function is activated once again, as shown in next figure.
Note:
Fig. 184. Heating curve slope adaptation
For direct room temperature compensation, the flow temperature setpoint is calculated according to the formula:
“Out RoomTempSp” = Heating Curve Setpoint + P23*FADAPT*(“In RoomTempSp” +/- “In SetpointAdj” - “In RoomTemp”)
Heating Curve Setpoint = HC(“In RoomTempSp”, “In FiltOATemp”, P16, P17)
“Out RoomTempSp” = 0, for total cool down
FADAPT = 1; if P19 = [0;4]
FADAPT = 0; if P19 = [1;2;3]
EOH Operation Example 1
The following schematic diagram illustrates the usage of the EOH statement.
A switching logic implements an outdoor air temperature-dependent frost protection function outside of EOH1. When the outdoor air temperature is less than or equal to 2 °C, the logic sets a constant room temperature setpoint (for example 10 °C)
Frost protection applies only during the cool-down phase because EOH demands a 0 °C flow temperature during this time and the flow temperature setpoint of the application program that is equipped with frost protection is overwritten.
The following flowchart illustrates the logic decisions of this example.
Fig. 185. EOH Operation Example 1
EOH Operation Example 2
The following diagram shows another example of EOH use
Fig. 186. EOH Operation Example 3
At optimum start, “Out OptimStart” goes to logic 1 and returns to logic 0 at occupancy start time.
At optimum stop, “Out OptStop” goes to logic 1 and remains at this value until optimum start occurs (next day or later).
Switch ON time depends on the load on the system:
Light load — switch ON time is occupancy start (P1 minimum preheat time) with a corresponding low flow temperature setpoint.
Medium load—switch ON time is occupancy start minus a value between P1 and P5:
Fig. 187. EOH Optimum Start with a Room Sensor
Both the “In FiltOATemp” (outside air temperature) and “In RoomTemp” (room temperature) have an effect on the switch-on time. The statement calculates the flow temperature setpoint from the heating curve (default slope 1.6) and further modifies it with room temperature and room temperature setpoint of the time schedule.
Heavy load — if the load on the system was so high that even an occupancy start time minus P5 and a maximum flow temperature setpoint P15 would be insufficient, then software calculates an even earlier start time.
During the pre-heat period, the “In FiltOATemp” causes the flow temperature setpoint to vary. If room temperature rises above the time program setpoint, the statement resets the flow temperature setpoint accordingly. At occupancy start, EOH calculates the flow temperature setpoint using the heating curve.
If the room temperature is below the setpoint at occupancy start time, the statement increases the flow temperature setpoint. This effect on the flow temperature setpoint continues for a period of 30 minutes after occupancy start. After this time, EOH calculates the flow temperature setpoint using the heating curve.
EOH software includes HCA functions. For automatic adaptation of the heating curve (flow temperature vs. outside air temperature):
At the calculated stop time, the statement resets the flow temperature setpoint to zero and changes the digital output “Out OptimStart” to logic 1. “Out OptimStart” remains at logic 1 until optimum start (next day or later).
Fig. 188. Wire-sheet Icon
Fig. 189. Property Sheet
Fig. 190. Slot Sheet
Table 117. Inputs
Inputs |
Type |
Functional description |
In RoomTempSp |
numeric |
Room temperature setpoint Must Do ⇒ The datapoint connected to the input “In RoomTempSp” datapoint must be assigned to a time schedule so that EOH can access occupancy start/ stop times. You must enable the "EOH / EOV Optimization" option (Analog Value properties); the defaults is ´disabled`. |
In RoomTemp |
numeric |
Room temperature, active if “In RoomTempSpOvr” = 999 |
RoomTempSpOvr |
numeric |
Room temperature setpoint from overrides like wall module, extended operation button, summer or holiday switch. The input “In RoomTemp” will be used only if “In RoomTempSpOvr” = 999, otherwise the input “In RoomTempSpOvr” will be the room temperature setpoint (<> 999 if override, = 999 if no override). There will be no optimum start/ stop optimization during room temperature setpoint override. |
In FiltOATemp |
numeric |
filtered outside air temperature |
In OptimMode |
numeric |
Optimization mode •0;1 = no optimization •2 = optimum start •3 = optimum stop •4 = optimum start and stop |
In AdaptEnable |
boolean |
Heating curve adaptation 0 = disable 1 = enable |
In SetpointAdj |
Numeric |
Control point adjustment – from the setpoint wheel of a wall module [-7, 7]. |
In Enabled |
boolean |
If the input “In Enabled” is set to false disabled in the slot sheet, the output “Out” will be disabled and is set to the value “0”. |
Table 118. Outputs
Outputs |
Type |
Functional description |
||||||||||||||||||
Out FlowTempSp |
numeric |
Flow temperature setpoint |
||||||||||||||||||
Out OptimStart |
boolean |
Optimum start goes to logic 1 during the preheating time |
||||||||||||||||||
Out OptimStop |
boolean |
Optimum stop goes to logic 1during the early setback time |
||||||||||||||||||
Out OperatingMode |
numeric |
The following operating modes are possible:
|
||||||||||||||||||
Out RoomCtrlMode |
numeric |
Indicates room control mode:
|
Table 119. Parameter List
Description |
Value Range |
Default Value |
Unit |
P1 Minimum pre-heat time |
0…1440 |
60 |
min |
P2 Maximum pre-heat time |
0…2880 |
2880 |
min |
P3 No room sensor compensation |
0…40 |
10 |
°C |
P4 Minimum outdoor temperature for early setback |
-30…15 |
0 |
°C |
P5 Pre-heat time at 0 °C outdoor air temperature (without room sensor) |
0…2880 |
120 |
min |
P6 Optimum stop factor (with room sensor) |
0…55 |
10 |
min/ K |
P7 Room comfort zone optimum stop |
0…10 K |
2 K |
K |
P8 Dead time short |
0..60 |
5 |
min |
P9 Time constant short |
0…2880 |
15n |
min |
P10 Dead time long |
0..60 |
5 |
min |
P11 Time constant long |
0…2880 |
150 |
min |
P12 Building model adaption: |
0 = disabled 1 = enabled 2 = restart |
1 = enabled |
- |
P13 Room control P-band |
0...∞ |
10 |
K |
P14 Integral action time |
0...∞ |
300 |
s |
P15 Maximum flow temperature |
0…150 |
80 |
°C |
P16 Heating curve curvature |
0…2 |
1,33 |
- |
P17 Heating curve slope |
0…10 |
1,6 |
- |
P18 Max. heating curve slope for adaptation (with room sensor) |
0,4…4,5 |
4,5 |
- |
P19 Heating curve adaptation mode |
0 = disabled 1 = enable 2 = restart 3 = adaptation refreshed new start 4 = direct RMT compensation |
1 |
- |
P20 Occupied/ unoccupied changeover |
0…30 |
16 |
°C |
P21 Frost protection limit |
0…1 |
2 |
°C |
P22 Boost factor |
0…50 |
1 |
- |
P23 Room temperature compensation |
0…50 |
4 |
- |
P24 Minimum room temperature |
0…30 |
13 |
°C |
P25 Differential minimum room temperature |
0…10 |
2 |
K |