Rinnai in floor will not reach high temp on thermostat

benski

Anyone can help me out please. In floor heat will not reach higher temps on thermostat. Floor warms up but not much more. Place is very cold and we have cold weather on the way.
Its a tankless system. The water taps have hot water but not floor. The return line (red) third from the left when looking at pumps is kind of cool? Any suggestions. Is one of my pumps shot? How to find out which pump?
System has an error code "LC". System needs descaling. I think that was there before the system stopped working. And we had is descaled 2 years ago.

hot_rod

Has it worked properly in the past.
Make sure both circulators are running. Any strainers in that heater, most tankless water heaters have strainers or filters on the inlet connection.

The grey knob mixing valve, is it turned all the way clockwise? It could be scaled up also.

It’s not the best heater to be used for combined DHW and radiant. The two systems should be separate water. A combi boiler, when that one fails would be a better, safer system.