I have a hot water tank with two pressure vessels in the system, I have a filter and I have two grundfoss pumps which as has been pointed out have a few settings. 

There is a pump speed setting buried in the FTC somewhere, I’m nervous to dig around too much as it asks me if I want to switch off the system when I press certain buttons. 

The Mitsi certainly seems to put heat over economy in the room adaptation mode.   I’m keeping a close eye on it and I think I’m probably unfortunate in having the ‘learning’ days where we get to know the heat pump in the cold, as the tweaks cost more the longer it takes to get it right. 

I’m confident I can get the consumption down though. 

I can see boiler flow/ return and another set of temps flow/return- which should have the 5 deg plus loss? 

It's the other flows, not the boiler ones you should be looking at. I think 'boiler' = immersion in Mitsubishi. 

Don't worry about the system off warning if you want to have a look around. It's just a standby mode not a hard power down. You start it up again with the round button on the right. I haven't changed the pump settings on mine though. 

I have a hot water tank with two pressure vessels in the system, I have a filter and I have two grundfoss pumps which as has been pointed out have a few settings. 

There is a pump speed setting buried in the FTC somewhere, I’m nervous to dig around too much as it asks me if I want to switch off the system when I press certain buttons. 

The Mitsi certainly seems to put heat over economy in the room adaptation mode.   I’m keeping a close eye on it and I think I’m probably unfortunate in having the ‘learning’ days where we get to know the heat pump in the cold, as the tweaks cost more the longer it takes to get it right. 

I’m confident I can get the consumption down though. 

I can see boiler flow/ return and another set of temps flow/return- which should have the 5 deg plus loss? 

@derek-m 

One way around it is to use a PWM controlled pump on the secondary circuit too, piggybacked off the ASHP control boards PWM signal (provided it is available, mine is).... But if you're going to do that, you might as well ditch the buffer in the middle.

You have a Samsung ASHP, which does not have an internal water pump, hence the need for the PWM control signal, whether it is used or not, to control an external water pump. I'm not certain if other manufacturer's provide a speed control signal for external water pumps.

I’ve got a Cool Energy unit actually, I’ve just read a lot of the Samsung manuals over the last week.

If you have an external water pump within your system, I must assume that you also have some form of hydraulic separation between the heat pump circuit and the central heating circuit.

Not according to the paper schematic I have, but the circulation pump is wired into the ecodan control unit. Actually, it's not clear to me whether the pump control panel is overridden by the control unit. If so, I'm wondering about something that I cannot change anyway!

Would you care to post a photo of your schematic and details of your circulation pump?

One way around it is to use a PWM controlled pump on the secondary circuit too, piggybacked off the ASHP control boards PWM signal (provided it is available, mine is).... But if you're going to do that, you might as well ditch the buffer in the middle.

You have a Samsung ASHP, which does not have an internal water pump, hence the need for the PWM control signal, whether it is used or not, to control an external water pump. I'm not certain if other manufacturer's provide a speed control signal for external water pumps.

So- weather compensation only then?   I had thought I might do it.  

The installers are coming out again this week to fiddle about with it, so we’ll see what happens then.  Now I know that it uses at least 40kWh no matter what I tweak then I’ve a decent baseline to work from. 

I'm currently using weather compensation with a home automation system preventing overheating (acting as a smart thermostat) and making slight adjustments to reflect weather and activity in the house. In theory, it's an awful thing to do. In practice, it keeps us warm and not bankrupted. I make no claims that it's the right thing for anyone else to do, but you might like to test it.

Take pictures or notes of the settings screens after they've adjusted it and between each thing you try, so you can step back if needed. But you probably already knew that.

If you have an external water pump within your system, I must assume that you also have some form of hydraulic separation between the heat pump circuit and the central heating circuit.

Not according to the paper schematic I have, but the circulation pump is wired into the ecodan control unit. Actually, it's not clear to me whether the pump control panel is overridden by the control unit. If so, I'm wondering about something that I cannot change anyway!

One way around it is to use a PWM controlled pump on the secondary circuit too, piggybacked off the ASHP control boards PWM signal (provided it is available, mine is).... But if you're going to do that, you might as well ditch the buffer in the middle.

I’ve asked the installers about pump speed v Delta T, as I don’t feel confident to adjust the pumps myself.  

Does anyone know what mode a Grundfos pump in an Ecodan system should be set to anyway? The Ecodan has quite a wide range of acceptable flow rates (9-25 l/min for the 8.5kW I think) and the pump appears to offer a choice between Constant Pressure and Proportional Pressure modes, as well as 3 speeds of each.

As far as I am aware, the Ecodan has an internal water pump, the speed of which the controller varies to maintain the Delta T at the heat pump.

If you have an external water pump within your system, I must assume that you also have some form of hydraulic separation between the heat pump circuit and the central heating circuit.

For something like a buffer tank to operate most efficiently, the flow rate going in should be equal to the flow rate coming out, but I am not certain how you could achieve this if the pump 'pushing' the water in is being controlled automatically, whilst the pump 'pulling' the water out is set manually. It is like a stopped clock, it may only be correct two times each day.

I would be interested to hear what any installers have to say on the subject.