I don’t have UFH but… has the heating been running for just the one day? There is a lot of mass in that floor that initially will take a lot of energy to raise in temperature. Sounds as though the Delta T is very high but might this just be that the floor is sucking up all that energy so the return flow is very much cooler than the flow into the UFH pipes? Regards, Toodles.

Hi there @pie_eater, absolutely right to try it single zone 'open loop' first, and see if it's a success.

Buy or borrow an infrared thermometer or, better still, contact thermocouple, and measure some flow and return temperatures. Don't forget, anything below about 30degC feels cold to the touch, and for those new to low temperature heating, this takes a little getting used to. If your design flow is 32degC, then with a 5degC delta T, the return at 27degC will feel cold.

Enough flow in the UFH circuits? Water is a fluid and will take the path of least resistance. Assuming the total system flow is adequate, using only the integral circulator pump in the ASHP, water may be preferentially flowing through the radiators rather than the UFH manifold and circuits. Pushing more water through the UFH circuit may increase the hydraulic resistance and head the pump has to work against.

So question to your installers is 'what is the current total design flow and is it adequate?' For 8kW heat at 5degC delta T you need around 23litres/minute flow of water, and a little more if glycol antifreeze is used. It's OK for a slightly higher delta T of course, and a little lower flow, (provided you have the minimum flow the OEM requires). Up to 8deg delta T is OK with some heat pumps, but 5 is more typical.

@toodles thanks , sorry I should have added it's been running for 3-4 days now.

@allyfish thanks a lot. Good to know re not relying on my hand measurement totally! How can I figure out the "total design flow" please? when it was running it said 17l/min in the daikin information menu, but that does fluctuate. 

I first need to try and balance the radiators too I think - is it an idea to restrict the flow on those to the minimum possible to try and balance it between the UFH and radiators?

@pie_eater I think @allyfsh has replied and indicated the route to follow now. Toodles.

Some Daikin systems use PWM speed controlled pumps, I'm not that familiar with them, so the total system heating flow rate may vary according to heat load. Flow, approx., in l/s is a function of the total heating load divided by the delta T design divided by 4.2 (specific heat of water). Eg: 8kW / 5degC delta T / 4.2 = 0.381l/s or 23l/m.

Radiator balancing - can be very much trial and error. If they are all the correct size for the rooms they are in, you can measure the flow and return temperature across each emitter as a means to adjust the flow - you'll need to find out what delta T they've been selected at, but aim to get a consistent delta T across all. Ideally you want to avoid restricting anything too much, keeping valves open as much as possible. Start with the furthest radiator away in the circuit, if you know which it is, and work back. There's usually a few iterations and a lot of patience needed! You may need to further adjust individual radiators if room temperatures don't even out within your desired range.

Our UFH feels warm to the toes when running at 24C, but I have sensitive toes(!)

What floor covering do you have on the floor? Only ceramic tile will cope with all operating temperatures. Our vinyl tiles and fake wood laminate rooms need a maximum of 29C or the surface will spoil. When it’s below 0C you’ll be towards max flow temperature and Octo use 50C so that would be an expensive mistake on the glue for our tiles. The plumbers didn’t believe it at first and had to be told several times. In our case there is less than 2C between water flow temperature a floor surface.

No pump is only good if you have ceramic tiles.

@judith thanks for your reply. good point to consider.

we have solid engineered oak , I am unsure what the max temperature is but the previous mixer valve allowed up to 60c and was set to 45C in the past without issues (although recently I had it at 38C). 

At a flow temperature of 38 our floor reaches between 22-24c and then feels warm too. The temperature between input and floor temp is quite a drop off, so I'm not too concerned but you're right it's something I need to  monitor going into winter, or check somehow (not sure how!). I've dialled the octopus standard curve down to 47c which is not too far off the original 45C mixer setting but maybe that needs to go down a tiny bit more. 

Hi all

I’ve been rebalancing UFH versus the radiators, which help a lot. Too much flow went to the upstairs radiators relative to UFH. Also the UFH loops were not balanced so I’ve been adjusting the flow rates between them which helped.

however to get sufficient flow downstairs to UFH I need to almost constrain fully upstairs, created some more noise as the water . 

one additional issue is that the flow on the daikin drops automatically to 7l/m once it’s close to the chosen temperature (It seems achieves a delta T of 5 at that low flow ). However at that flow rate my downstairs doesn’t get warm enough as that is shared with the radiators so very low rate on the UFH. Any idea how to increase the min flow rate ? 

Octopus is coming tomorrow to have a look, but I’m just curious how this all ties together.thanks 

@pie_eater I’ve never needed to adjust the flow rate on the Daikin controller as I have a secondary pump connected to the output of the LLH. However, I’m not saying don’t adjust anything on the Daikin MMI as all these things are possible by setting the user profile as ‘Installer’ and this is achieved by using the code 5678 and then delving ‘til your heart is content = pum[ speed adjustments are there. However, if you don’t feel confident, I feel sure that a tentacle will sort it out for you tomorrow. Regards, Toodles.

Quick update for those interested. The octopus engineer confirmed part of the issue was balancing between radiators upstairs and UFH  and also the flows between UFH zones,  so that was tweaked a bit more (reduced flow to radiators to absolute minimum).
the other change was putting the main emitter type to “fan foil” . Unsure what that does, he wasn’t sure either but was told somewhere it should always be in that mode (?).

the biggest issue probably is that the thermostat is on the first floor where it heats up quickly relative to downstairs where it then stays too cool.

So they will now likely install a 3rd party wireless thermostat on the ground floor (getting wired unit downstairs was difficult hence it ended up on 1st floor).