At the bottom of page 6 it states the water flow rate range is 10.0 to 24.8 l/m. Similar to mine, though I have also seen the tank installation manual be a bit more specific that the flow rate should be 24l/m. Not sure what to make of that difference. There is discussion in other threads about altering the flow rate to manage the difference between flow and return temperatures to 5°C, but if the manifold temps of 28 and 21 are typical then you have a slightly too large difference, which is to be expected if the flow rate is lower than it is meant to be.

Hi @Harriup

i thought I ought to add some comments on this for Sarah to consider.

Theres a good reason why there is a flow rate range quoted, and probably other reasons too. 
It was generally believed in an earlier thread (Keystone COP) that Ecodan does not have an internal pump to regulate deltaT so there are 2 things that can control it. 1. Adjusting the flow rate via the circulation pump of the primary flow and primary return and 2. The internal modulating electronics which cannot regulate the circulating pump. In other words the ecodan operates at a constant flow rate depending on the chosen set pump speed.

A flow rate must therefore be measured on the return primary pipe since that is precisely en-route back to the heat pump and will give a near accurate measurement of flow through the heat exchanger. (I would say it’s essential to check this before any adjustment of flow rate)

another thing to point out is that a 28 to 21 differential is only 7c which is quite common when the hp is still settling down. I’ve noticed it fluctuates all the time between 3c and 8c and when it starts up it can be more. 

So a flow rate of 13LPM is within the acceptable band of the ecodan 8.5 provided it is being measured in the correct place in the circuit. But if the temperature difference never settles close to 5c then a slightly faster pump speed will lower the temperature difference. However there are other issues such as balancing flow rates between the primary loop and other heating circuits so this kind of adjustment really needs to be done by a professional. 
Hope this helps

What are the readings on the temperature gauges at the UFH manifolds?

If you are changing the pump speed on the FTC controller, it will only vary the flow rate if it is wired to the main water pump and is actually varying the pump speed. Do any of the pumps have two cable connected?

If, as I suspect, the main water pump is not being controlled by the FTC controller, the only way to vary the flow rate would be by using the button on the actual pump. I suggest that you download the manual for the pump.

Temp - 60 (it was 65)

Frequency 15

Start 10:00 (was 03:00)

Max Op time 1 hour (was 3 hours)

Duration of max temp 1 minute (was 30 mins)

At least you know that the filter is clean. I don't suppose that it has made any difference to the flow rate.

The next task will be to confirm that all the manual valves in the pipework are fully open. Then make a note of the setting of all the flow regulation valves at the UFH manifolds.

What are the manifold temperature gauges reading?