Lowering the supply temperature in underfloor heating more complex than expected?

A pleasant side effect with modern heating systems is that I can check during vacation if everything is working and turn it back up in time, now it is Viessmann

The architect, however, is also commissioned with the site management in the recommended standard and is supposed to ensure that all trades comply. The general contractor's site manager works in the interest of the general contractor and is often less useful to the client in his role than a site manager.

I have not yet met an architect whom I would have even remotely trusted with that! The sample size is still somewhat small, but I believe such an architect is more the exception than the rule.

Happy Monday ,,, there you are during the weekend .... folks folks.

I already tried to explain it last week. The sizing of the heat pump according to NAT with 35°C flow temperature has nothing, or almost nothing, to do with the actual values in everyday life. This is about a calculation parameter that determines the size of the heat pump, the design of the underfloor heating. And this happens in conjunction.

Yes, you can have all that changed and the heating installer can adjust his calculation accordingly. I'll put it on hold and wait for your HELP postings:
- HELP: I just can’t get my heat pump properly adjusted. The heating curve issue cannot be set so that the house is comfortable at every outdoor temperature, either it’s too cold in the house at -5°C outdoor temperature or too warm at +8°C outdoor temperature. I have to constantly readjust it
- HELP my heat pump is short cycling. It turns on every hour and then runs for 15 minutes. Is that normal?
- HELP I get an overpressure fault. I have to reset my heat pump several times a day
- My wife thinks the bathroom is too cold. Which electric bathroom radiator can you recommend?
- and finally: my heat pump broke after only 7 years, compressor defective. Never again Vaillant.

Is it really worth it? Again: we also calculated for 35°C flow, and in real life we never reach that. In the bathroom we have 5cm pipe spacing, in other rooms 10cm, in the bedrooms 15cm. This allows the flow temperature to be designed for the normal rooms, and in the bathroom it is automatically 2 degrees warmer.

Finally: your consumption essentially depends on your usage behavior. You cannot cheat physics; the heat you want in the form of warmth has to be consumed (the formula with Delta-T, the law of conservation of energy, etc.). Yes, you can lower the flow temperature and lay the underfloor heating pipes closer together. I claim, that won't bring you anything.

I would invest five-figure additional costs differently (for example in a nice photovoltaic system).

And last but not least: yes, you have the right to view the plans. But the general contractor has no obligation to build what the client wants. I assume the contract for work and services is already signed by both parties. Exactly what is stated in it MUST be done by the GC. Everything else is goodwill.

That's all well and good what you write. A brief digression about how it was for me. The planners have no idea and just type something into the program. - Supply temperature 40 degrees - Maximum heating circuit length 156 meters - Installation spacing 20cm, in the bathroom 10cm The argument was the same: It only applies with [NAT], otherwise the supply temperature is lower, the bathroom wouldn't get warm otherwise... I'm still glad I pushed back. It's nice that the design at 35 degrees works well for you. But I can't deduce from that that the OP shouldn't deal with it thoroughly so that the planning also turns out well.

Especially if, according to the design plan, 10 and 5 cm were still used at 35°C, then the practitioners simply did something different, or if it was also designed that way, he must have a pretty large heating load. Maybe his NAT is -18°C? In that case, however, he must not consider his construction to be universally valid.

As far as I'm concerned.. it's not my money. I have an annual heating demand of 8500 kWh at NAT of -11°C. I repeat myself, I wouldn't spend a cent just because a data sheet shows a lower flow temperature. I would invest the money in getting electricity cheaply.