How to use water heater diagrams:
Air Speed. Starting from 1450 m3/h on the air flow scale draw a vertical line 1 till the air speed axis which makes about 3.2 m/s.
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Supply air temperature. Prolong the line 1 up to the point where it crosses the outside air temperature (blue curve), e.g. -25°C; then draw a horizontal line 2 from this point to the left till crossing water in/out temperature curve (70/50 °C). From this point draw a vertical line 3 to the supply air temperature axis on top of the graphic (+28°С).
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Heating coil capacity. Prolong the line 1 up to the point where it crosses the outside air temperature indicated as red curve (e.g., -25°С) and draw a horizontal line 4 from this point to the right to the intersection of water in/out temperature curve (e.g., 70/50 °С). From this point draw a vertical line 5 up to the scale of heating coil capacity (31.0 kW).
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Water discharge. Prolong the line 5 down to water discharge axis at the bottom of the graphic 6 (0.38 l/s).
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Water pressure drop. Draw the line 7 from the point where line 6 crosses the black curve to the pressure drop axis (9.8 kPa).
