# N°5 – Pressure or head loss charts training – A level

Now that we have understood how to use a head loss chart for piping we can understand how manufacturers can indicate water circulation head losses for their equipment.

#### Question

Referring to the boiler pressure loss chart below, what is the head loss in [mbar] and in [mmH2O] for a model of 500 [kW] with a flow rate of 10 [m³/h] (44 US gpm)?
2 [mbar]
20 [daPa]

Remember:
1 [bar] = 10 [mH2O] (32.8 ft H2O) = 10,000 [mmH2O] (394 inch H2O)
1 [bar] = 100,000 [Pa]
1 [mbar] = 100 [Pa]

#### Question

Referring to the boiler head loss chart above, what is the head loss in [mbar] and in [mmH2O] for a model of 300 [kW] and a debit of 20 [m³/h] (88 US gpm)?
20 [mbar]
200 [daPa]

#### Question

Referring to the boiler head loss chart below, what will be the head loss in [mbar] and in [mmH2O] for a model of 140 [kW] running at a temperature regime of 80/60 [°C] (176°F/140°F)?
4 [mbar]
40 [daPa]

Explanation:
140 [kW] at a temperature regime of 80/60 [°C] (176°F/140°F) corresponds to a flow rate of:
qv = P / (1.16 x ∆T)
= 140 / 1.16 x 20
= 6 [m³/h] (26.4 US gpm).
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