Pipework design/ pressure distribution

[gsplum]

I would appreciate some help in evaluating a pipework design for a CH system which needs to distribute a max load of 22kW (when the outside temp falls to -5).

We plan to use Uponor MLCP and run the main distribution in a ceiling so there is a 1,5m rise at boiler and a 3m drop to each local circuit.

The basic idea is to use 25mm for distribution, 16mm for the drops and 12mm for the radiator circuits. However, the reviewing the friction pressure data with delta = 11 K (82°C/71°C), there are sections with poor pressure distribution.

In the attached diagram you can see the circuit to far, figures for the distribution sections start with A and drops start with B. Each radiator has its local loop figures.

Should we ask for smaller piping in the distribution (16mm) and larger in the local loops with >800 Pa/m?

Also, there are no drain taps in each drop circuit, should we install them?

Do modern boilers not need expansion chambers?

Thanks in advance for comments

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[gsplum]

Looking again, the areas of high pressure are at the end of the friction tables but there are figures so I guess the MLCP is certified to these levels. Perhaps the only issue will be noise? (water moving at a higher velocity)

I'm assuming that the worst case is 11 K (82°C/71°C), the aim would be to run at 70/50 or lower if possible.