Looking at the DIP switch settings, is it just a case that SW1-3 should be set as ON on the slave controller for ASHP1, and OFF on the slave controller for ASHP2?

None of the manuals seem to specifically mention how to set the dip switches for my scenario.

I'm trying to visualise this, your plumbing would require a return tee'd between ASHP 1 and 2 for ASHP 2 to service UFH while ASHP 1 is doing DHW?

This is a difficult scenario, i wouldn't generally split the two units from working together as suggested unless you modify the pipework to service different area's

How (if any) is zoning between UFH / Rads / Pool done?

@f1p From the Ecodan databook / installation guides, it is this scenario:

So when the top unit starts doing DHW, the bottom one starts outputting 50 degree flow for a short while, then the logic seems to decide it is not needed, so stops sending any heat into the UFH, until DHW heating stops. Hence I am wondering if sw 1-3 is OFF for the bottom unit and ON for the top one, will the bottom one then not think it is supposed to join in with DHW heating? (or something else...?)

It is a single zone for all the UFH / rads / pool as far as Ecodan is concerned, with Heatmiser thermostats and actuators controlling the various UFH loops.

Thanks,

Yes i think your logic is correct that for some reason the 2nd pump will sit idle until DHW completes and i don't know the reasoning Mitsi did this.

However, i would note that it sounds a little off that it takes a 14kW unit nearly 2hrs to complete a 300li tank
To compare, my 8.5kW unit can heat 250li from 8 > to 47 in 1.5hr @ OAT 6C and an 11.2kW unit can heat 300li 15 > 49 in 1hr

It's a bigger ask to 55 though, hotter than most heat pump users would store DHW

@f1p I am fighting one battle at a time here... hoping to get someone to say for definite if the SW 1-3 on the second pump is off, it should not then get involved with DHW, but continue with its job to heat the UFH / pool.

WRT tank heating, I see some interesting variations: A normal heat up at 22:00-00:00 always reaches 55 degrees, and the tank warms faster than when the same thing happens at 04:00 - 06:00 (45 to 51 degrees) - the tank temp graph is much steeper at 10pm than at 4am. I am then doing a boost at 13:00-15:00 as I loose a lot of heat (circulation pump running from 03:30 - 10:00). If I just use the prohibit settings, the heat up time at 13:00 is longer than if I boost - a boost for 2hrs takes the tank from 36 degrees up to 47, whereas on Friday night at 22:00 the tank was 12 degrees, and lifted to 55 by midnight! This is a property with only 1 person living in it, and the whole DHW function / cost seems ridiculous!

@fosterl2

I will ask around about the dip switch for ASHP 2

WRT tank, how does the frequency compare? 
Looks like your graph is just from one of the temperature sensors (some have upper & lower fitted) - i would question with that consumption and tank size if 55C and 3x heats per day are required.
We do 1x heat to 47 of the full 250li per day and it covers washing up, 2 showers + kids bath per day

@fosterl2 I will send this thread to the tech guys at Mitsubishi tomorrow to see if they can provide technical insights.

@ashp-bobba I don't suppose you have any insights on this?

@editor I would have to check but as I understand it, the dip switching would only tell the master controller which ASHP is not the DHW plumbing circuit. So, if you cascade the system you do not have 2No 14kW ASHP's you have 1No 28kW system and in hot water mode it will work as a 28kW system but only run the 14kW unit (so 1 system) when in hot water mode and the other ASHP would rest. All ASHP work the way you are describing, when in priority HW they no longer heat the rooms. 

Think of it like there is only one controller not 3, the slave 1 and slave 2 FTC7's only programme the units, the master FTC7 is really your only interface controller which tells everything what to do. If you want to run it the way you are thinking and it is piped 4 pipes in and 2 out on a low loss header type buffer then you could (providing you set all controls and timers up the same in heating mode not to strain a single unit for to long) run them as 2 x 14kW systems, programme system 2 as heating only and system 1 as heating and hot water, they would then ignore each other and you could keep 14kW of heat running through the emitters. 

a 14kW unit will likely heat 300ltrs from 10 DegC in 80 mins so something is wrong with your set up if it is not reaching temp, you should check the cylinder is high gain for a heat pump, is it a Mitsi cylinder? you should check you get 60 deg flow at a flow rate of around 8kW which is about right for a 3m coil for a 300ltr cylinder (24l/pm) a little more or less is fine but somewhere near this. 

@f1p The graphs do show there is about a 3 degree an hour loss of heat, and that is with very little hot water being drawn off - a morning wash, and a couple of plates after breakfast. BTW - at present the pool is not connected, all I am running is DHW and UFH, plus a few rads.