The gateway connects but active_power always reads zero. Why?

Register 110 reports the actual heater load only when at least one heating element is switched on. If no control input is active, the value is legitimately zero. Verify the heater step or feed-in setpoint is non-zero and that the safety thermostat has not tripped.

Values disappear from the portal after about a minute. What is happening?

The ASKOHEAT+ clears command registers including the feed-in setpoint after 60 seconds of Modbus TCP silence. Ensure the ModbusCloud Gateway maintains a continuous polling interval and that no firewall is dropping idle TCP connections between polls.

Writing to target_active_power_b has no effect. What should I check?

Address 202 expects a signed int16 written with function code 16. Negative values engage Power-to-Heat mode; positive values cause the device to switch off automatically. Confirm the value sent is negative and that firmware version 4.2.1 or higher is installed, as this register requires that minimum version.

Is it safe to write large negative values to the feed-in setpoint register?

Use caution when writing to target_active_power_b (address 202). Sending values beyond the rated heater capacity has no effect on power but abrupt or repeated writes can cause rapid relay cycling. The ASKOHEAT+ includes a switch-on inhibit to protect relay contacts, but always verify setpoints match your installation's rated power before automating writes.

Free Modbus template: Askoma Askoma

The Askoma ASKOHEAT+ is a multi-level immersion heating element for buffer tanks and boilers, designed to convert surplus PV or renewable electricity into stored heat. The ModbusCloud template communicates over Modbus TCP and reads active power consumption and measured tank temperature, reads back the configured temperature setpoint, and writes the feed-in power setpoint at address 202 to control Power-to-Heat operation. This gives installers and energy managers real-time visibility and remote control of thermal storage in a single cloud-connected template.

Name	Address	Function	Type	Unit	Access
active_power Current heater load, instantaneous active power in watts.	110	FC04	uint16	W	R
temperature_setpoint Configured target temperature setpoint for the heating element.	597	FC03	uint16	°C	R
temperature Measured water or storage temperature in degrees Celsius.	638	FC04	uint16	°C	R
target_active_power_a Feed-in power setpoint read back, signed watts, Power-to-Heat mode.	202	FC03	int16	W	R
target_active_power_b Feed-in power setpoint write: negative value activates thermal storage.	202	FC16	int16	W	W