Mitsu Zubadan Flow Temperature Issue

Had a good visit to site today and met up with an installer there. He usefully had temperature pipe clips and was quickly able to ascertain that the rads were getting about 32C water to them and 31C back. I stupidly hadnt picked up on the fact that all the rads pipework is in the concrete floor slab which might not even have insulation under it. The floor certainly doesnt feel warm.

He also measured the temps to and from the heat pump at 45C/40C although this might not be that accurate as the flow temps were oscillating again.

I positioned the temperature probes I bought around the LLH. Here is whats happening. The pictures are taken minutes apart and you can see the oscillation in flow temps

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Best to wait until they steady down, can you confirm that (from the top) the first probe is the primary flow, the second is the primary return, the third is the secondary return and the fourth is the secondary flow?

I had assumed a different order of sensors, so I’ll wait for Mark to confirm.

Are these sensors strapped tightly to the pipework, or just stuffed under insulation?

A question that’s not been asked yet: where and how is the room temperature being measured?
Is this with Mitsubishi’s own “remote room controller”, or something else?
Is there a 3rd-party thermostat somewhere that is also connected?

Also, is the property managing to maintain the desired temperature, or is it struggling?

OK, so the order of sensors is the same as the pipes coming off the vertical LLH. Top sensor - Top pipe, bottom sensor bottom pipe. With all the insulation it was hard to see. I was just looking for a schematic but no joy yet.

They are all stuffed under the insulation.

The room temperature is measured in the hallway by the remote mitsubishi sensor/controller, no third party thermostat.

The property cant reach the the set 23C but seems to be able to hold 20.5C more or less.

Its probably safe to assume that the top probe is the primary flow, what’s a bit surprising is that neither of the secondary probes is reading some where close to 40C, except that there is a huge imbalance with the secondary flow far in excess of the primary.

Also worth checking that the two circ pumps are installed on the correct pipes and orientated correctly.

So, how is the secondary return (bottom pipe) hotter than the secondary flow (top pipe), have a look at the pump installation.

These are my best pics pre insulation

Does this help?

If its not making sense, then I will go back and check. take off the insulation and zip tie the probes to the pipes.