Strand

At nights I have set up a zone1 room temp drop from 22 deg C to 19 deg C. When that happens the pump starts to short cycle. I think it's because both returns come from the tank. And as zone 1 water return temperature was higher than zone 2 it will still get the higher return temp. Shouldn't at least the pipes on buffer be different? Return from the zone's should be at the bottom and from the buffer to the 2-zone box be at the top? 2-zone box has it's own two pumps and a 3-way valve for zone 2. It's built like a pass through even if both zone pumps should be off there is still flow in the main lines between the pump and 2-zone box. No coil in the buffer. Cold water straight to the ecodan 200L DHW tank.

But this buffer location will not help against short cycling. That was the reason I wanted them to install it.

Hi, I'm looking some advice on our ASHP installation. I think that the buffer is in wrong location to work in my setup. Have a look at the plan and tell me waht you think. Its Mitsubishi Ecodan Zubadan 12 kW EHST20D-YM9D/PUD-SHWM120YAA with 2 zone box PAC-TZQ1-E. Underfloor heating is about 35m² and radiators 73m² (second floor will be added this summer and is 50m²). Zone 1 has wireless temperature controller/remote from Ecodan. Buffer tank is 120L.