Kospel PPE2 Electronic LCD 18/21/24kW: Connecting BLOCK & NA Terminals for Water Heater Integration

Hello
I have installed two water heaters Kospel PPE2 18/21 / 24kW - in the instructions is note that, can work with other devices I quote
"The heater is equipped with BLOCK and NA terminals.
BLOCK - relay output that switches off the slave, when the heating is switched on, opening the circuit connected to the BLOCK terminals (max. 0.1A 250V ~)
NA - the input blocking the heater on, opening the NA contacts causes
heating block - cooperation with the master device
Connections under BLOCK and NA terminals should be made with a 2 x 0.5mm2 conductor, leading
it on the right side of the interior of the heater " end of the quote
My question, how (where) to connect the wires 2x05mm2? that one be blocked when the second or other device with more power is turned on.
NA - is now bridged

MASTER BLOCK connect to slave ON (blocked).

ireneusz.strama wrote:

BLOCK - relay output that switches off the slave, when the heating is switched on, opening the circuit connected to the BLOCK terminals (max. 0.1A 250V ~)

you have the answer in the quoted passage. It follows that the BLOK connector is the output in the master device and is used to block the slave device.
When the master device is switched on, the BLOCK circuit is opened.

ireneusz.strama wrote:

NA - the input blocking the heater on, opening the NA contacts causes
heating block - cooperation with the master device

The NA connector is an input on the slave device and circuit opening that locks this slave device.
From here it is already known why on the NA connector in a single heater you have a jumper, otherwise it would be in a permanent blocking mode.
You can remove the jumper for the test on the NA connector and then the heater should enter the blocking mode.