When you say "mixing tank" do you mean a buffer tank or a large thermal store? Are you able to post so photos and/or a diagram of your system?

"mixing tank" is a terminology from Mitsubishi manuals, especially from Ecodan installation guide. In other words, it is a barrel of water with a capacity of 500 liters, which is used to store water used to heat living quarters with radiators and underfloor heating. Hot water from the heat pump first enters this barrel, and then it is pumped out of it by two water circulation pumps to the radiators and the underfloor heating circuit.

DHW tank is also a barrel of water with a capacity of 300 liters, which is used for domestic needs (shower, bath, washing hands and so on)

The 3-way valve controlled by Ecodan controls which of the two tanks will receive hot water from the heat pump.

Schematic of my system below.

500l?????

That's enormous for a buffer tank and even pretty big for a thermal store.

You're storing a huge amount of heat in that cylinder so I would expect your heat pump to be monitoring the temperature of the cylinder and running when the cylinder cools. I would expect the heating circuits to operate independently of the heat pump. The circulation pumps should switch on when the house needs heat.

A have near 1500 meters of pipes for water warm floor, its water volume is ~200 liters. All radiators volume is ~50 liters. Total is ~250 liters. Heated area of the house is ~200 square meters. So, 500 liters for buffer tank ("mixing tank") is a normal size. Maybe, 600-700 will be better. Heat pump can easy produce 15 kilowatts of heat so huge volume of water is required for such power. I also have an electric heater with a capacity of 15 kilowatts installed as a backup source of heat. Such boilers need large buffer tanks.

"I would expect the heating circuits to operate independently of the heat pump" - I thought so too. But water circulation pumps are dependent from Ecodan controller, and I want to know, is this setup is ok, or it will be better to move pumps control from Ecodan to some other logic. Maybe, just put pumps to power sockets and let them work 24\7, and ecodan only controls the heating of the water in the mixing tank. 

Initially, my question was more about how to set up the water pumps schedule without changing the heating scheme, through the Ecodan settings, if any. And your solution has disadvantages: every time at the beginning of the heating season, you must manually turn on the pumps, and every time after it is turned off from the power socket. Now the pumps are always connected to the power supply from Ecodan PCB, and I can remotely control the turning on of the heating: turn on the heating of the water in the tank, and, as a result, the circulation pumps will turn on themselves using ecodan. Now there is a single "control point" of my heating system - Ecodan control panel on the wall (and app on my phone).
 

Hey @fox,

Did you ever get a suitable solution to this query?

@Emmanuelle_OVO hi. TL;DR: no.

In my case, part of the heating control logic is controlled by Danfoss equipment: control of valves on the water manifold and some other little things.

The Danfoss control unit has the ability to control the pumps directly, so in theory it is possible to switch the pumps to it using temperature sensors and room thermostats from the Danfoss control unit instead of Ecodan. Also, in their list of equipment there are collectors with already built-in pumps.

So maybe I'll follow this path to keep some amount of automation in my heating system.

Well, the "dumb" way to simply plug the pumps directly into the power sockets for winter period can still be considered working.