Hi everyone.

Wonder if someone might be able to help. I have a Daikin LT system, with UFH, and also attached to solar.

So, firstly, the system constantly loses pressure. My HA send engineers, and they just turn a knob and the pressure comes back up to 2 bar on the manifold. However, I have noticed black stuff on the floor underneath the pipes where the boiler is. Engineer suggests it is Iron Oxide, which is the by product of a pipework leak somewhere. Am i right in thinking this could be the cause of the pressure drop?

Secondly ( re the UFH), the manifold is a 9 port one, and 1 of the circuits is 100m long (M1), and the other is 88m long (M2). When all the circuits are open (for the whole house), and calling for heat, M1 and M2 only have less than 1 litre per min going into them. Yet another circuit of only 14 m has 3litres per min going in! Another circuit of 30 m, has 2 litres per min going in! I think you might able to teell where this is going. Am i right in thnking that if there is inadequate flow to the circuits, it will take longer to reach temp (if at all?) And of course, be costing money all the time it is trying to reach temp?

From my investigations, the 100m circuit should have 2.5 litres per min, and the 88m circuit should have 2.2litres per min. (I'm taking the pipe length and dividing by 40 ) Am i correct with these calcs?

Moving on, the flow rate problem was explained to the engineer, who merely removed the actuators, and told me to "see how I got on" Well of course all this did, was remove my ability to control that circuit from the thermostat. So I put them back on. Maybe the engineer doesnt have an energy crisis in his town! Even with the actuators removed, the flow rate indicators, still showed less than 1l/p/min

The next engineer came, and said he needed to check the flow and return rate. Flow is 34, return is 25. How is the flow and return rate even relevant to this problem ?? This engineer suggested that the black iron oxide may have got into the UFH circuits, and be preventing the flow rate. I think this is entirely possible, but if someone could confirm?

Finally, I have the flow rates that the original installer set. All at 1.6litres per min. How can this be correct when the longest circuit is 100m, and the shortest is 14m.

I look forward to you comments to help me with my response to the HA. I am totally un convinced that their contractors have a scooby doo!

Thankyou in advance!