To be able to integrate your Hoval indoor climate solution 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.

The setpoint specification is performed flexibly: depending on the requirements, you are able to specify the set room temperature or the set flow temperature. However, with domestic hot water, the set hot water temperature is always crucial. The set hot water value must always be implemented separately as heat generators prioritise a set hot water value and increase the output accordingly. 

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.

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 adjust the settings 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.

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 

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.

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.
 

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 up 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.
 

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.

The heat output, cooling capacity and hot water output can be limited for each individual heat pump via Modbus, but not the current consumption. Excepted from this are certain operating states such as the start routine, which is not subject to restrictions for safety reasons. 

Outside these operating states, the output can be limited on an individual basis. Please note that heat pumps require certain minimum output levels of 25 or 30% depending on the type. 

To limit the output, proceed as follows:

• Write the required values via register address 27550 (Max. output heating mode), register address 27551 (Max. output DHW operation) and register address 27552 (Max. output cooling mode).

With stage-operated heat generators, you can block the second stage by limiting the output to 49%.

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 6 in the Modbus guideline.

Numerous useful information values are available for the heat generator, as well as for HomeVent and the heating circuits. Each heat generator provides both operating and status messages, set and actual temperatures, modulation data and data about heating circuits and water heating.

Please note that if there is only one heating circuit, for example, the data for heating circuits 2 and 3 will remain empty. An unmixed heating circuit is always displayed as heating circuit 1.

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