Modbus integration for Hoval systems made easy

When it comes to building automation, seamless communication between different systems and devices is key. Modbus has deservedly earned its title as a proven and widespread communication protocol as it allows different components to be integrated easily and efficiently to create an efficient overall system. 

To be able to integrate your Hoval heat pump or comfort ventilation unit using Modbus, you need a Hoval Modbus gateway. With this, you can establish your connection via Modbus TCP and Modbus RTU. The gateway takes on the role of slave here, with the on-site Modbus system acting as the master. Hoval products that are suitable for Modbus integration can be identified at a glance. The key is the TopTronic E system controller, which is easily recognised by the touchscreen built directly into the product. New heat generators have been equipped with the TopTronic E controller generation since 2015.

Please note that the data points described below refer to use for heat generators (heat pumps, gas boilers, pellet boilers, etc.) or to Hoval comfort ventilation, not to use for district heating transfer stations.

If you want to know more about integrating district heating transfer stations, take a look at the Loxone district heating template.

With Modbus, you get a communication protocol that allows you to control your Hoval system precisely and efficiently using a variety of available data points. Specific application scenarios and step-by-step instructions will help you to customise the Modbus integration to suit your needs.

Please note that for some functions, the Hoval service team will need to come and configure settings and perform software updates on site for you to be able to control the Hoval heat generator via Modbus. These functions are marked with an asterisk (*) in the use cases below.

You will also need to register the Modbus gateway in the HovalConnect app. By connecting to HovalConnect, you will benefit from automatic software updates for the gateway as well as from related features. Furthermore, registering in HovalConnect provides access to remote support – for example, regarding Modbus data points or more advanced integration topics.

The following use cases involve standard systems with only one heat generator. In more complex systems, such as those with multiple heat generators or more than three heating circuits, the system-specific controller modules and bus addresses must be taken into account. Detailed information on this can be found in the Modbus data point list in the Downloads area.

Use case 1: Setpoint specification for room temperature and domestic hot water via Modbus 

Use case 2: Setpoint specification for flow temperature and domestic hot water via Modbus

Use case 3: Specifying a set temperature value via Modbus directly at the heat generator

Use case 4: Specifying an output setpoint via Modbus directly at the heat generator

Use case 5: Controlling the HomeVent ventilation system via Modbus

Use case 6: Output limitation for Germany in line with Section 14a of the Energy Industry Act/grid-friendly control via Modbus

Use case 7: Reading out information values from the heat generator or ventilation via Modbus

Use case 8: Reliable control of heat pumps via offset values 

When it comes to controlling heat pumps, use case 8 should always take precedence over the use of other use cases, as it ensures greater operational reliability and, among other things, protects against short cycling as well as possible communication interruptions between the Hoval controller and the building management/energy management/home automation system.

Set room temperature specification
Proceed as follows:

• Via register address 1478 (Operation choice – Heat. circ. 1), write operating mode 4 (Constant normal mode).
• You can then specify the room setpoint via register address 1481 (Normal room temp. – Heat. circ. 1).

The set room temperature also affects the calculation of the set flow temperature. The heating characteristic set on the system refers to a set room temperature of 20°C. A higher set room temperature increases the set flow temperature; a lower set room temperature reduces it.

The same procedure applies to heating circuits 2 and 3 – only the data points change.
You can find all the details in example 1 in the Modbus guideline.

Setpoint specification for domestic hot water
Proceed as follows:

• Via register address 1496 (Hot water operation choice), write operating mode 4 (Constant normal mode).
• Then specify the set hot water temperature via register address 1497 (Normal hot water temp.).

The setpoint that you have written will remain active until a new value is sent. 
You can find all the details in example 1 in the Modbus guideline.

When it comes to controlling heat pumps, use case 8 should always take precedence over the use of other use cases, as it ensures greater operational reliability and, among other things, protects against short cycling as well as possible communication interruptions between the Hoval controller and the building management/energy management/home automation system.

Setpoint specification for the flow temperature – heating 
Proceed as follows:

• Write the required value under register address 1490 (Flow setpoint heating – Heat. circ. 1). 
• With a value of 0°C, the heating is switched off at the heating circuit. 
• Heating operation starts when you enter a value of more than 15°C. 

The setpoint that you have written will remain active until a new value is sent. If there is an interruption, the setpoint remains active until a new value is received via Modbus.

The same procedure applies to heating circuits 2 and 3 – only the data points change. 

You can find all the details in example 2 in the Modbus guideline.

Please note that buffers installed in the system, such as those installed for heat pumps, cannot be influenced directly. For this, you specify the setpoint via the set flow temperature. For example, if the flow requires a value of 35°C, this is sent to the buffer and the buffer retains this temperature while maintaining a defined increase.

Setpoint specification for the flow temperature – cooling (*)

When cooling via the respective heating circuit, it is not possible to using the set flow temperature for the heating case. Instead, a separate setpoint using defined data points is required for cooling. For this, the Hoval service team need to come and adjust the required basic settings on the system on site. Only then will you be able to use the data points marked with (*) in the Modbus guideline.

After the Hoval service team have adjusted the basic settings, proceed as follows:

• Write the required value under register address 23754 (Flow setpoint cooling – Heat. circ. 1). 

The setpoint that you have written will remain active until a new value is sent. If there is an interruption, the setpoint remains active until a new value is received via Modbus.

For cooling via heating circuits 2 and 3, the same procedure applies – only the data points change. If there are several heating and cooling circuits on site, it depends on the hydraulic system installed on site and the heating system as to whether different requirements – such as heating and cooling at the same time – are possible on the heating circuits. 

Setpoint specification for the flow temperature – combined heating circuit/cooling circuit

With a combined heating circuit/cooling circuit, you can only write one value – either the one for the heating set flow temperature or the one for the cooling set flow temperature. When you send the value 0 to the respective data point, the heating or cooling is switched off. 

Example: Cooling is to be performed via circuit 1.

• Write the value 0 to the register address (Flow setpoint heating – Heat. circ. 1). 
• At the same time, write the required setpoint via register address 23754 (Flow setpoint cooling – Heat. circ. 1).

If a setpoint specification is also required for domestic hot water, you must also do the following:

• Via register address 1496 (Hot water operation choice), write operating mode 4 (Constant normal mode).
• You will then be able to specify the set hot water temperature with register address 1497 (Normal hot water temp.).

The setpoint that you have written will remain active until a new value is sent. If there is an interruption, the setpoint remains active until a new value is received via Modbus.

You can find all the details in example 2 in the Modbus guideline.
 

When it comes to controlling heat pumps, use case 8 should always take precedence over the use of other use cases, as it ensures greater operational reliability and, among other things, protects against short cycling as well as possible communication interruptions between the Hoval controller and the building management/energy management/home automation system.

If the building management system is responsible for the higher-level control of the heat distribution, you can also specify a set temperature value in manual mode directly at the heat generator. 

Proceed as follows:

• Set the operation choice for the heat generator to manual mode (write register address 1561 – Heat generator operation choice – to the corresponding value: 0 for OFF, 4 for heating, 5 for cooling).
•  If necessary, specify the maximum output via register address 19484 (Manual mode output setpoint) (for stage-operated heat generators, up to 49% is the first stage and 50% to 100% is the second stage).
• Write the required setpoint temperature directly via register address 1562 (Manual mode set temperature).

The setpoint that you have written will remain active until a new value is sent. If there is an interruption, the setpoint remains active until a new value is received via Modbus.

You can find all the details in example 3 in the Modbus guideline.
 

When it comes to controlling heat pumps, use case 8 should always take precedence over the use of other use cases, as it ensures greater operational reliability and, among other things, protects against short cycling as well as possible communication interruptions between the Hoval controller and the building management/energy management/home automation system.

If the building management system is responsible for the higher-level control of the heat distribution, you can also specify an output setpoint in manual mode directly at the heat generator. 

Proceed as follows:

• Set the operation choice for the heat generator to manual mode (set register address 1561 – Heat generator operation choice – to the corresponding value: 0 for OFF, 4 for heating, 5 for cooling).
• When specifying the output, you need to write a lower (e.g. 5°C) set temperature value for cooling and a higher one (e.g. 80°C) for heating via register address 1562 (Manual mode set temperature). This overrides the internal output control of the heat generator so that it only responds to the external output specification. 
• Specify the required set output value directly via register address 19484 (Manual mode output setpoint).

The setpoint that you have written will remain active until a new value is sent. If there is an interruption, the setpoint remains active until a new value is received via Modbus.

You can find all the details in example 4 in the Modbus guideline.
 

If you wish to control the HomeVent comfort ventilation unit via Modbus, proceed as follows: 

• Set the operation choice for the unit to “Constant” via register address 23622 (Op. choice ventilation).
• After activating via register address 23623 (Normal ventilation modulation), specify the set air quantity. 
• To prevent excess humidity from being created, the air humidity overrides the air quantity. You can specify set air humidity via register address 23626 (Humidity set value). If the “Humidity extract air” (register address 23627) deviates from the set air humidity, the system automatically regulates the specified air quantity accordingly. You may also find that the system overrides the written air quantity to prevent excess humidity from being created.

The setpoint that you have written will remain active until a new value is sent. If there is an interruption, the setpoint remains active until a new value is received via Modbus.

You can find all the details about this and the possible HomeVent status messages in example 5 in the Modbus guideline.

To implement output limitation in line with Section 14a of the Energy Industry Act and/or the required grid-friendly control via Modbus, data point 27536 “available electrical output restricted” must be written to, and the Smart Grid function must be activated beforehand.

• The value written to data point 27536 specifies the maximum power consumption of the heat pump in kW. Select a suitably high power consumption in order to ensure the minimum capacity of the Hoval heat pump at the current source temperature (e.g. 0°C outdoor temperature).
• Setting a value of 2 for “System bus” on data point 27546 activates data point 27545.
• If a value of 1 is now set for “Priority mode” on data point 27545, Smart Grid becomes active and data point 27536 takes effect. If the value switches back to 0 for “Normal mode”, the Smart Grid is deactivated and data point 27536 becomes inoperative.

The Hoval service team need to configure the necessary basic settings and perform software updates on the system beforehand. 

Only after these basic settings have been made does the Modbus data point take effect.

Anyone who, in addition to output limitation, wants to utilise PV surplus or cheap energy from dynamic electricity tariffs should contact Hoval Integrate Support for optimal control.

Numerous useful information values are available for the heat generator/heat pump and for HomeVent. Each heat generator/heat pump provides status messages, temperatures and energy quantities that can be read.

As the number of requests increases, the intervals should be set sufficiently long to prevent the HovalConnect Modbus Gateway from locking up.

You can find all the details on information values and status messages in example 7 in the Modbus guideline.

Use case 8 is ideal for ensuring operational reliability when controlling heat pumps.

Operational reliability means being as free from short cycling as possible in order to increase the heat pump’s service life.

Operational reliability is also ensured in the event of a communication interruption between the building management/energy management or home automation system and the Hoval controller.

This involves triggering boosted operation, which is ideal for coupling when activated by dynamic electricity tariffs or connections to photovoltaic systems.

• Setting a value of 2 for “System bus” on data point 27546 activates data point 27545.
• If a value of 1 is now set for “Priority mode” on data point 27545, Smart Grid becomes active and the offset values for the system parts (domestic hot water, heating circuits, buffer storage tanks) become active. If the value switches back to 0 for “Normal mode”, the Smart Grid is deactivated and the offset values become inactive. To allow the offset values to take effect, it is recommended to reduce the setpoints for domestic hot water (e.g. 42°C) or in the heating circuits (e.g. 20°C room temperature).
• By setting a domestic hot water offset value of, for example, 30 kelvin in the “Domestic hot water” system part (data point 27509), the heat pump will heat up to its maximum hot water temperature (usually 60°C) when the setpoint is undershot.
• By setting a room temperature offset value of, for example, 2 kelvin in the “Heating circuit 1” system part (data point 27528), the flow temperature of the heating circuit is increased indirectly. Thanks to the automatic control chain, this value is subsequently also transferred to an upstream buffer storage tank without writing an additional setpoint.
• If only the heating of a large heating or cooling buffer storage tank is required, offset values are available for increasing (data point 28839) or reducing (data point 28840) the setpoint accordingly. In this case as well, the minimum and maximum temperatures are restricted.