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Access 4.x |
Water heater configuration example |
Water - the most common medium for heating. Sequence regulator for such heater is enhanced with freeze protection and pump control functionalities.
For freeze protection - temperature of the return water in the heating coil is monitored. If the temperature decreases to a low level, the freeze protection regulator takes control of the sequence output. Normally the output is forced up to avoid freezing. Once the risk is eliminated - the control is handed back to the supply temperature controller.
As an alternative or in addition to the freeze protection, the freeze guard (e.g. thermostat) can be used for emergency stop at freeze-risk temperatures.
The pump control includes periodic pump exercises and forced water circulation during low outdoor temperature to prevent freezing. Access also monitors if the pump is functional (run indication) then it is expected to run or if the pump has active alarms.
The table below shows a configuration example of the water heater including freeze protection, freeze guard and pump control with alarm monitoring.
Variable |
Available options & Selection |
Note |
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Sequence selection |
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Configuration > Functions > Function activation > Heating/Cooling sequence setup |
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Sequence for heating |
| SEQ-A Heating |...| |
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Sequence settings |
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Configuration > Functions > Function activation > Heating/Cooling sequence setup > Heating |
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Type of sequence |
|Cooling | Exchanger | Heating | Damper | Fan setpoint compensation | |
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Type of heater |
| Water | Electric | DX | Combi coil | |
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Type of freeze protection |
| None | Temperature sensor | Freeze guard | Sensor + Guard | |
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Freeze protection sensor |
| Freeze protection temperature 1 | ..2 | ..3 | |
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Pump control |
| No | Yes | |
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Pump running mode |
| Always running | Auto | |
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Type of feedback |
| None | Alarm | Run indication | |
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Digital start output |
| No | Yes | |
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Sequence output when recirculation / support |
| 0% | 100% | Auto | |
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Sequence output min limit |
0% |
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Sequence output max limit |
100% |
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Sequence output when the unit is stopped |
0% |
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PID Settings |
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Configuration > PID controllers > Heating |
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P-band |
10 oC |
PID settings for the sequence |
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I-time |
100 s |
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D-time |
0 s |
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Hardwired interface to the heater, pump and valve |
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Configuration > I/O allocation settings > |
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Analog inputs > Freeze protection temperature 1 |
Any available I/O |
Heating medium temperature |
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Digital inputs > Freeze protection guard |
Thermostat |
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Digital inputs > Feedback heating (SEQ-A) |
Pump control and feedback signals |
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Digital outputs > Heating pump (SEQ-A) |
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Analog outputs > Heating (SEQ-A) |
Heating sequence output (input for valve) |
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Pump control settings |
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Data & Settings > Temperature control > Heating |
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Pump stop delay |
5 min |
Delay for switching off DO: Heating pump (SEQ-A) |
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Pump-kick hour |
15 h |
Daily exercise run of the pump starts at 15h |
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Pump running when outdoor temperature < |
10 oC |
Water circulation for freezing prevention |
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Hysteresis to allow pump stop |
1 oC |
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Freeze protection settings |
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Data & Settings > Temperature control > Heating > Freeze protection 1 |
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Freeze protection |
- |
Actual temperature of freeze protection sensor |
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Alarm limit running mode |
7.0 oC |
AL-96 Freeze protection alarm 1 if temperature < 7 oC |
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P-band running mode |
5.0 oC |
AL-64 Warning freeze protection if temperature < 12 oC (7 oC + 5 oC : "Alarm limit" + "P-band") |
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Setpoint standby mode |
25.0 oC |
If frost protection is activated - freeze protection controller will control the heating output to maintain a constant temperature at the frost protection sensor |
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Graphical representation |
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Flowchart |
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32.0 oC - indication of freeze protection temperature 87% - indication of sequence output On - indication of pump status |
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