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8
Air temperature downstream of the heater [°C]
O
utside air t
emper
atur
e [°C
]
Heating coil capacity [kW]
W
at
er pr
essur
e dr
op [kP
a]
Water flow through the water heating coils [l/s]
Air flow through the heating coil [m
3
/h]
Air speed inside the heater [m/s]
Air temperature downstream of the heater [°C]
O
utside air t
emper
atur
e [°C
]
Heating coil capacity [kW]
W
at
er pr
essur
e dr
op [kP
a]
Water flow through the water heating coils [l/s]
Air flow through the heating coil [m
3
/h]
Air speed inside the heater [m/s]
Calculation of water heater parameters for VUT R 400/700/900 WH EC
Calculation of water heater parameters for VUT R 1200 WH EC
Water heater parameters calculation example:
Air Speed. Starting from 650 m
3
/h on the air flow scale draw a vertical line (1) till the air speed axis which makes 2.35 m/s.
Supply air temperature: prolong the line [1] up to the point where it crosses the outside air temperature (blue curve, e.g. +5 °C); then draw a horizontal line [2] from this point to the left until it crosses the water
in/out temperature curve (e.g. 70/50). From this point draw a vertical line [3] to the supply air temperature axis on top of the graphic (+26 °C).
Heating coil capacity: prolong the line [1] up to the point where it crosses the outside air temperature (e.g. +5 °C, red curve) and draw a horizontal line [4] from this point to the right until it crosses the water in/
out temperature curve (e.g. 70/50). From here draw a vertical line [5] up to the scale representing the heating coil capacity (5.8 kW).
Water flow: Prolong the line [5] down to the water flow axis [6] at the bottom of the graphic (0.04 l/s).
Water pressure drop. Draw the line (7) from the point where line (6) crosses the black curve to the pressure drop axis (0.5 kPa).
Water heater parameters calculation example:
Air Speed. Starting from 1000 m
3
/h on the air flow scale draw a vertical line (1) till the air speed axis which makes 2.22 m/s.
Supply air temperature: prolong the line [1] up to the point where it crosses the outside air temperature (blue curve, e.g. +5 °C); then draw a horizontal line [2] from this point to the left until it crosses the water
in/out temperature curve (e.g. 70/50). From this point draw a vertical line [3] to the supply air temperature axis on top of the graphic (+28 °C).
Heating coil capacity: prolong the line [1] up to the point where it crosses the outside air temperature (e.g. +5 °C, red curve) and draw a horizontal line [4] from this point to the right until it crosses the water in/
out temperature curve (e.g. 70/50). From here draw a vertical line [5] up to the scale representing the heating coil capacity (9.0 kW).
Water flow: prolong the line [5] down to the water flow axis [6] at the bottom of the graphic (0.11 l/s).
Water pressure drop. Draw the line (7) from the point where line (6) crosses the black curve to the pressure drop axis (0.8 kPa).
