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ASKOHEAT+   MODBUS

(c) 2020 Askoma AG Screw-in heaters and flange heaters for heating industrial ​and heating water with photovoltaic
​Einschraubheizkörper und Flanschheizkörper zur Erwärmung von ​Brauch- ​und Heizungswasser mit Photovoltaik ​

Functional Describtion and Modbus Register

Version 1.16 - 13.05.2024

Table of Contents

Overview of Functions

Status LEDs

Five Steps for Successful Implementation

• Settings for Modbus RTU

Modbus Registers

• 1. Short Data Block - Address 100...109 - read only
• 2a. Command Block - Address 200...202 - read/write
• 2b. Commands - Adress 210...212 - write only
• 3. Energymanager Block - Address 300...336 - read/write for selected registers
• 4. Parameter Block - Address 400...449 - read only
• 5. Configuration Block - Address 500...545 - read/write
• 6. Data Values Block - Address 600...646 - read only
• 7. Extended Values Block - Address 700...758 - read only

Overview of Functions

Actuator controls

ASKOHEAT+ is an actuator consisting of three switchable heating elements. By combination 7 steps are possible. In conjunction with the ASKOWALL, the pump is automatically switched on when the heating elements are activated.

The heating elements are controlled by the following input signals:

1. Manual thermostat, not via electronic evaluation, independently regulates (and limits) the set temperature.
2. Analog input: 0-10 volt signal (switches power corresponding to input signal)
   Up to eight threshold values can be assigned to heating level and temperature.
3. Digital input: Heat pump request (switches to full power)
4. ASKOHEAT+ Push button: toggles emergency mode on / off (on switches to full power)
5. (Modbus) Heater Step 0-7 (switches power in 7 steps)
6. (Modbus) Load Setpoint Value: poitive 0-max. watt (ASKOHEAT switches the power automatically)
7. (Modbus) Feedin Value: Regulation use case "Power to Heat": Grid feed-in of produced (e.g. solar) energy (represented by negative values as feed-in values to the EVU) is reduced by thermal storage with the ASKOHEAT+ through automatic selection of the optimum power level. If the value is positive, the ASKOHEAT+ switches off automatically.
8. (HTTP-JSON) Control the ASKOHEAT+ via the Modbus registers using the JSON format
9. Electronic thermostat with individual setting possibility for each control input
10. Heating during low tariff period
11. Supports SMA Sunny Home Manager 2.0 via SEMP: If enabled the ASKOHEAT+ will connected automatically with the Sunny Home Manager and will be listed with its three heaters.

Sensors

1. Temperature Sensor 0: PT1000 integrated in ASKOHEAT+
2. Temperature Sensor 1: optional external PT1000
3. Temperature Sensor 2: optional external PT1000
4. Temperature Sensor 3: optional external PT1000
5. Temperature Sensor 4: optional external PT1000
6. Simple Current Flow Sensor: Current flow is measured via an integrated sensor. If the temperature limiter or the thermostat has been deactivated, this can be detected via it. The sensor does not provide an exact measured value, therefore only a flag is output.
   

Saftey and Cost Prevention

1. Safety temperature limiter switches off independently when the protective temperature is exceeded.
2. Legionella protection: In intervals (daily, weekly, fortnightly, monthly) the boiler is heated to a temperature (50-65°C) to kill legionella. The heating time is limited to 240 minutes.
3. Monitoring of the temperature sensors. In case of a malfunction (e.g. cable break or accidental disconnection), errors are output (see register {502} MODBUS_VAL_TEMPERATURE_STATUS).
   Note: If the error is to be cleared, i.e. the ASKOHEAT+ should forget that the temperature sensor(s) was (were) connected, then this can be done with the command {213} MODBUS_VAL_TEMPERATURE_STATUS MODBUS_CMD_CLEAR_TEMP_SENSOR_ERROR or via the web browser with /CLEAR TEMP ERROR or by pressing the Emergency Mode button for at least 30 seconds until the LED error display stops).
4. Auto Heater Off: after 24 hours (this value can be adjust with {503} MODBUS_CON_AUTO_HEATER_OFF_MINUTES) of continuous operation, the ASKOHEAT+ switches off automatically until the control value is changed again.
5. Emergency mode will switches off after 24 hours (this value can be adjust with {503} MODBUS_CON_AUTO_HEATER_OFF_MINUTES)
6. Modbus Fail Save: Auto Heater Off also occurs if the master (e.g. Energy Manager) does not send any data to the ASKOHEAT+ for more than 60 seconds.
7. Monitoring of the relay switching cycles: Switch-on hysteresis of typ. 5 seconds, counting of the switching cycles.
8. Load Feedin Mode: Bias and activation delay prevent unnecessary load peaks or switching cycles that are too short.

Further Features

1. Device status retrievable via a Modbus word register
2. The current switching step or heating load can be read out via the corresponding registers. If in Register {502} MODBUS_CON_INPUT_SETTING bit 1 (Heater Load value only if current flows) is setted, the value is zero if the safety temperature limiter or the thermostat switched off.
3. All important functions and parameters can be configured via Modbus.
4. For installation and local support a simple effective webbrowser interface is implemented.
5. Via HTTP-JSON all Modbus registers can be accessed and all settings can be made via HTTP-JSON.
6. Automatic functions for time-dependent temperature-controlled heating (minimum temperature and low tariff).
7. Use of an Askoma Smart Meter via Modbus RTU (the ASKOHEAT+ must then be operated in Master Mode). The heating element then uses the excess energy reported by the smart meter (= feed) to heat the boiler within the set temperature. (Use Case Power To Heat without Energy Manager). The simple use case does not support data logging and cannot take priorities into account.

Using Modbus TCP

1. Modbus TCP is served via the standard port 502.
2. The ASKOHEAT+ is the Modbus server whose registers are described here.
3. Currently up to 8 client connections can be served simultaneously.
4. Basically, there can be multiple socket connections per client ip.
5. Data is updated every second. Therefore we do not recommend faster polling cycles.
6. Note: The connection between ASKOHEAT+ and an external client is considered interrupted after 5000 milliseconds. After an interruption of 60 seconds, registers MODBUS_CMD_SET_HEATER_STEP and MODBUS_CMD_LOAD_SETPOINT_VALUE and MODBUS_CMD_LOAD_FEEDIN_VALUE are deleted for security reasons.

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Status LEDs

NOTE: With firmware 4.1.1 the LED status display changes. It is now reduced to the essential.

TOP LED: Heater Status

MIDDLE LED: Heater Connectivity

BOTTOM LED: Heater Mode

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Five Steps for Successful Implementation

STEP 1: Connection ASKOHEAT+ with local network router and find out its ip-address. In most cases askoheat-eth/ or askoheat.local/ will work.

STEP 2: Determine the IP address via the router. The ASKOHEAT+ is called "ASKOHEAT-ETH". To identify an ASKOHEAT LEDs flashes for 20 seconds via the Command askoheat-eth/identify or askoheat.local/identify

• NOTE: To prevent the IP address of ASKOHEAT+ from changing regularly, we recommend assigning a fixed IP address on the router. ASKOHEAT+ currently does not support a fixed IP address.

STEP 3: Enter in a browser of a device connected to the network askoheat-eth/ or askoheat.local/

• You will see the info screen. Check if you see any errors or wrong settings

• Use Quick Setup to make the most important typical settings askoheat-eth/quick or askoheat.local/quick

• To see all settings, you can view the advanced settings page askoheat-eth/expert or askoheat.local/expert

• To make all advanced settings use the setup page askoheat-eth/setup1 or askoheat.local/setup1

STEP 4: Connect your modbus client with the ASKOHEAT+

• Use the known IP address and port 502. The unit ID is not relevant.

STEP 5: Useful modbus registers:

• Using the browser commands:

  • The command askoheat-eth/fullstatus or askoheat.local/fullstatus shows the actual status, values and settings of the ASKOHEAT+.
  • With the command askoheat-eth/getall or askoheat.local/getall will you see the whole registermap with its actual values.

• For a simple implementation of monitoring the following registers are recommended: 1. Short Data Block - Address 100...109 - read only

  • {100} - Temperature Sensor 1
  • {102} - Temperature Sensor 2
  • {104} - Temperature Sensor 3
  • {106} - Temperature Sensor 4
  • {108} - Emergency Mode
  • {109} - Status of ASKOHEAT+ (Heater, input states, error flag)
  • {110} - actual heater load

• The heating element is switched via the following registers: 2a. Command Block - Address 200...202 - read/write

  • {200} - Set the heater to step 0 to 7
  • {201} - Load setpoint for automatic setting of the optimum power level.

Settings for Modbus RTU

• Settings are available starting with firmware 4.0.2.

• MODBUS_CON_RTU_BAUDRATE

• MODBUS_CON_RTU_SETTING

• MODBUS_CON_RTU_SLAVE_ID

• MODBUS_CON_RTU_ENERGY_METER_TYPE

• You can setup all this parameters using askoheat-eth/setup2 or askoheat.local/setup2

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Modbus Registers

• MODBUS TCP uses port 502
• MODBUS RTU is available with firmware 4.0.2
  

1. Short Data Block¹ - Address 100...109² - read only

For minimal implementations the essential values are summarized here. Historically, these have already been available in first generation devices and ensure backward compatibility.

• modbus function 4 read input register

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2a. Command Block - Address 200...202 - read/write

The commands are used to control the performance of ASKOHEAT+. Three options are available.

• modbus function 3 read holding register
• modbus function 6 write single register

MODBUS_CMD_SET_HEATER_STEP

low byte:

• bit2: switch heater 3 on (relay 3)
• bit1: switch heater 2 on (relay 2)
• bit0: switch heater 1 on (relay 1)

Important Notes

• Default value after any power on or reboot is zero.
• This register is only changed from an external energy manager.
• The pump is automatically active when one of the heater is switched on.
• To protect the relay contacts, a switch-on inhibit is activated after a relay is deactivated. (see MODBUS_CON_RELAY_SEC_COUNT
• If the emergency mode or heat pump request is active, all heaters 1-3 will be switched on until the emergency mode or heat pump request is reset and the setting in MODBUSIREGSTATUS are restored. (see MODBUS_CON_INPUT_SETTING)
• If activated, results of analog input 0-10V measuring will override the MODBUSIREGSTATUS. (see MODBUS_VAL_ANALOG_INPUT_STEP)

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2b. Commands - Adress 210...213 - write only

These commands are helpful for service and support or during setup.

• modbus function 6 write single register

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3. Energymanager Block - Address 300...336 - read/write for selected registers

This register set is useful for use by energy managers. All important values are contained in one block. This reduces the implementation effort, as only one data set has to be loaded. Three registers can be read and written. These are implemented as Holding Registers as well as Input Registers.

• modbus function 4 read input register
• modbus function 6 write register for selected registers

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4. Parameter Block¹⁰ - Address 400...455 - read only

Parameters are information about the device configuration, serial number and versions that is permanently stored in the device.

• modbus function 4 read input register

MODBUS_PAR_TYPE

• bit7: OEM version
• bit5: wired as delta connection (L1-L2, L2-L3, L3-L1)
• bit4: wired as star connection (L1-N, L2-N, L3-N)
• bit3: heater type screw in
• bit2: heater type flange
• bit1: 7 stage version
• bit0: 3 stage version

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5. Configuration Block¹² - Address 500...545 - read/write

This is the configuration area. Here the behavior of ASKOHEAT+ is adjusted to the individual requirements. Typically, only settings for legionella protection are necessary. In some cases, adjustments to the inputs can be useful. When used in a ASKOWALL, the pump run-on time can be adapted to the local conditions. With the "info string" an individual device tag can be assigned.

• modbus function 3 read holding register
• modbus function 6 write single register

MODBUS_CON_INPUT_SETTING

high byte:

• bit3: software control input SENEC.Home is enabled (Note: This feature requires firmware 4.4.1 or higher.)
• bit2: software congrol SMA.SEMP is enabled (Note: This feature requires firmware 4.2.1 or higher.)
• bit1: hold minimal temperature option is enabled
• bit0: low tariff option is enabled

low byte:

• bit7: emergency mode switch is enabled
• bit6: heat pump request input is enabled
• bit5: analog input 0-10V signal is enabled
• bit4: set heater step is enabled
• bit3: load setpoint value is enabled
• bit2: load feedin value (use case power to heat) is enabled
• bit1: heater load value only if current flows (see MODBUS_VAL_HEATER_LOAD and MODBUS_IREG_HEATER_LOAD)
• bit0: missing current flow triggers error (see MODBUS_VAL_ERROR_STATUS)

MODBUS_CON_AUTO_HEATER_OFF_SETTING

• bit7: auto off function is enabled for emergency mode switch (see MODBUS_CON_AUTO_HEATER_OFF_MINUTES and MODBUS_VAL_AUTO_HEATER_OFF_COUNTDOWN)
• bit6: auto off function is enabled for heat pump request input (see MODBUS_CON_AUTO_HEATER_OFF_MINUTES and MODBUS_VAL_AUTO_HEATER_OFF_COUNTDOWN)
• bit5: auto off function is enabled for analog input 0-10V (see MODBUS_CON_AUTO_HEATER_OFF_MINUTES and MODBUS_VAL_AUTO_HEATER_OFF_COUNTDOWN)
• bit4: auto off function is enabled for modbus control
• bit1: auto restart if energymanager connection lost (modbus tcp or rtu) -> after 300 seconds (bit0 must be activated)
• bit0: auto off function is enabled for timeout of modbus tcp communication -> after 60 seconds

MODBUS_CON_HEATBUFFER_TYPE

• bit7: other
• bit7: heat pump
• bit6: oil burner
• bit5: gas burner
• bit4: pellet firing
• bit3: combind heat and power unit (CHP)
• bit1: heating water
• bit0: tap water (Brauchwasser)

MODBUS_CON_HEATER_POSITION

• bit7: ASKOWALL (c)
• bit1: at middle of boiler
• bit0: at bottom of boiler

MODBUS_CON_LEGIO_SETTING

high byte:

• bit7: legionella protection is enabled
• bit6: preferably use feedin energy, otherwise it will waiting until pv energy is available in the following days
• bit3: interval monthly (30 days)
• bit2: interval fortnightly (14 days)
• bit1: interval weekly (7 days)
• bit0: interval daily

low byte:

• bit4: use temperature sensor 4 (optional external PT1000) for heat up
• bit3: use temperature sensor 3 (optional external PT1000) for heat up
• bit2: use temperature sensor 2 (optional external PT1000) for heat up
• bit1: use temperature sensor 1 (optional external PT1000) for heat up
• bit0: use temperature sensor 0 (ASKOHEAT+ internal PT1000) for heat up

MODBUS_CON_HOUSETYPE

• bit7: commercial building
• bit2: appartment building
• bit1: private two-family house
• bit0: private single-familiy house

MODBUS_CON_ADVANCED_SETTING

• reserved for advanced functions

MODBUS_CON_RTU_BAUDRATE

valid values

• 1200
• 2400
• 4800
• 9600
• 14400
• 19200 (default)
• 28800
• 38400
• 57600
• 76800
• 115200
• 230400

MODBUS_CON_RTU_SETTING

high byte:

• bit7: master mode active -> useable to connect an external energy meter via RS485 to ASKOHEAT+ (compatible devices)

low byte:

• bit7: slave mode active -> ASKOHEAT+ can be controlled by any Modbus master connected at RS485
• bit2: (1) send parity bit odd
• bit1: (1) send parity bit even
• bit0: (1) send two stop bits / (0) send one stop bit

MODBUS_CON_RTU_ENERGY_METER_TYPE

Supported energy meter:

• 001 AUTOMATION ONE TYPE A1EM.BIMOD.3.100
• 002 AUTOMATION ONE TYPE A1EM.MOD
• 010 CARLO GAVAZZI EM300 / ET300 SERIES (e.g. EM340)

** MODBUS_CON_TEMPERATURE_SETTING**

low byte:

• bit4: use temperature sensor 4 (optional external PT1000) for heat up
• bit3: use temperature sensor 3 (optional external PT1000) for heat up
• bit2: use temperature sensor 2 (optional external PT1000) for heat up
• bit1: use temperature sensor 1 (optional external PT1000) for heat up
• bit0: use temperature sensor 0 (ASKOHEAT+ internal PT1000) for heat up

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6. Data Values Block - Address 600...698 - read only

All relevant information about operating times, current measured values, status flags and internal counter are listed here. Many of the registers are output for information only.

• modbus function 4 read input register

| Summary | | block: [99] words / [198] bytes | | |

MODBUS_VAL_STATUS and MODBUS_IREG_STATUS

high byte:

• bit7: any error occurred (see MODBUS_VAL_ERROR_STATUS)
• bit6: temperature limit reached, heaters are switched off (see MODBUS_CON_TEMPERATURE_SETTING)
• bit5: pump ralay follow-up time is active (see MODBUS_VAL_PUMP_COUNTDOWN)
• bit4: auto heater off is active (see MODBUS_CON_AUTO_HEATER_OFF_MINUTES and MODBUS_VAL_AUTO_HEATER_OFF_COUNTDOWN) and MODBUS_VAL_EMERGENCY_OFF_COUNTDOWN)
• bit3: load feedin value is active when register MODBUS_CMD_LOAD_FEEDIN_VALUE indicates a negative value and ASKOHEAT+ will reduce the grid feed-in
• bit2: load setpoint is active when register MODBUS_CMD_LOAD_SETPOINT_VALUE has valid positive values
• bit1: analog input 0-10V is active (see MODBUS_CON_INPUT_SETTING and MODBUS_VAL_ANALOG_INPUT_STEP and MODBUS_EXT_ANALOG_INPUT_FLOAT)
• bit0: legionella protection is active (see MODBUS_VAL_STATUS and MODBUS_VAL_LEGIO_COUNTDOWN and MODBUS_CON_LEGIO_SETTING)

low byte:

• bit7: emergency mode is active (see MODBUS_CON_INPUT_SETTING)
• bit6: heat pump request is active (see MODBUS_CON_INPUT_SETTING)
• bit5: heater 1-3 current flow (ASKOHEAT+ internal saftey switch or thermostat switch have not triggered)
• bit4: ASKOHEAT+ 2.0 -> relayboard is connected
• bit3: relay 4 - pump is active
• bit2: relay 3 - heater 3 is active
• bit1: relay 2 - heater 2 is active
• bit0: relay 1 - heater 1 is active

MODBUS_VAL_STATUS_EXTENDED (ASKOHEAT+ 2.0)

high byte:

• bit7: any error occurred (see MODBUS_VAL_ERROR_STATUS)
• bit6: lock heater input is active
• bit5: ew-sperre is active
• bit4: feed in time locked
• bit1: current flow 2 flag (right side of relayboard6 heater 5, 6 and 7)
• bit0: current flow 1 flag (left side of relayboard6 heater 1, 2 and 3)

low byte:

• bit7: relay 8 - heater 6 is active
• bit6: relay 7 - heater 5 is active
• bit5: relay 6 - heater 4 is active
• bit2: relay 3 - heater 3 is active
• bit1: relay 2 - heater 2 is active
• bit0: relay 1 - heater 1 is active

MODBUS_VAL_ACTUAL_CONTROL_INPUT

high byte:

• bit3: software control input SENEC.Home is enabled
• bit2: software congrol SMA.SEMP is enabled
• bit1: heater actual controlled by auto heater off
• bit0: heater actual controlled by legionella protection

low byte:

• bit7: heater actual controlled by load setpoint
• bit6: heater actual controlled by load feedin
• bit5: heater actual controlled by emergency mode
• bit4: heater actual controlled by heat pump request
• bit3: heater actual controlled by analog input
• bit2: heater actual controlled by set heater step
• bit1: heater actual controlled by low tariff mode
• bit0: heater actual controlled by minimal temperature mode

MODBUS_VAL_LEGIO_STATUS

low byte:

• bit 7: error: settings or not correct
• bit 6: error: temperature cannot be reached after 240 minutes (the temperature value set on the thermostat may be too low)
• bit 5: error: no valid temperature sensor is connected
• bit 4: error: Unexpected drop in temperature while pleateu timer is active
• bit 2: temperature outside legionella protection interval reached
  
• bit 1: temperature is reached, plateau time is active
• bit 0: heating up phase (see MODBUS_VAL_LEGIO_COUNTDOWN)

MODBUS_VAL_ERROR_STATUS

high byte:

• bit7: WLAN connection error (wifi)
• bit6: LAN connection error (ethernet)
• bit4: MODBUS RTU connection error (rs485)
• bit3: Error Settings: minimum one setting causes malfunction
• bit2: legionella proctection error (see MODBUS_VAL_LEGIO_STATUS)
• bit0: current flow error (If at least one radiator is activated and no current flows, then the thermostat has been deactivated or the temperature limiter has tripped. This function can be activated with the setting bit0 at MODBUS_CON_INPUT_SETTING can be activated.)

low byte:

• bit7: error in the internal real time clock (actual no connection to the ntp server possible)
• bit6: error in the temperature settings (no sensor used or used sensor is not available)
• bit4: temperatur sensor 4 without function (wire break, disconnected or fault of PT1000)
• bit3: temperatur sensor 3 without function (wire break, disconnected or fault of PT1000)
• bit2: temperatur sensor 2 without function (wire break, disconnected or fault of PT1000)
• bit1: temperatur sensor 1 without function (wire break, disconnected or fault of PT1000)
• bit0: temperatur sensor 0 without function (wire break, disconnected or fault of PT1000)

MODBUS_VAL_TEMPERATURE_STATUS

high byte:

• bit6: temperature limit set by control input set heater step
• bit5: temperature limit set by control input load setpoint or feedin
• bit4: temperature limit set by control analog input
• bit3: temperature limit set by control input heat pump request or emergency mode
• bit2: temperature limit set by control input legionella protection
• bit1: temperature limit set by control input low tariff mode
• bit0: temperature limit set by control input hold minimal temperature

low byte:

• bit6: temperature limit reached, heaters are switched off
• bit4: temperatur sensor 4 is available, optional external PT1000
• bit3: temperatur sensor 3 is available, optional external PT1000
• bit2: temperatur sensor 2 is available, optional external PT1000
• bit1: temperatur sensor 1 is available, optional external PT1000
• bit0: temperatur sensor 0 is available, ASKOHEAT+ internal PT1000

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7. Extended Values Block - Address 700...758 - read only

Additional values are listed in this block, e.g. temperature values as floating point. In normal applications these registers are not needed.

• modbus function 4 read input register

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