Meaning of supply water temperature and return water temperature

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I have NAVIEN NCB 240E combi in my house.

Paragraph 3.2 says:

The default space heating supply water temperature range is 104°F (40°C, Absolute MIN) to 180°F (82°C, Absolute MAX).

● The default space heating return water temperature range is 86°F (30°C, Absolute MIN) to 149°F (65°C, Absolute MAX).

You can adjust the temperature range in the parameter settings menu.
I can change Space Heating Temperature in the menu. So, I have few questions:
1. How this temperature correlates with supply water temp and return water temp settings.
2. Why there is also a DIP switches with mechanical controls to set the same temps. Why and what the difference from setting them through the menu?
3. I could understand return water temp, let's say the Boiler try to keep this temp in pipes, or I am wrong?
4. I DO NOT understand the options to change supply water temperature. This is what entering into my house, right? How can I change this temp?

I am confused with manual. Thank you!


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Supply water is the temperature of the water at the boiler's output.

Return water is the entering water temperature at the heating system input part of the combi boiler, (and NOT the temperature of the potable water "...entering into my house... ".)

Navien's internal algorithms allow you to set up the modulation controls to adjust based on either the supply temperature OR the return water temperature.

You may have to read the whole setup portion of the manual several times to figure it all out, but it's in there.
Hey, wait a minute.

This is awkward, but...

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