France has more than 900 urban district heating networks supplying the equivalent of 2.5 million homes. With the Energy Transition Act and ADEME's Heat Fund, connections are multiplying. For the commissioning engineer, the substation is a key piece of equipment to master.
How it works
A district heating network carries hot water (or steam) from a central energy centre to the connected buildings. The substation is the interface between the primary network (owned by the operator) and the secondary network (owned by the customer). It contains a plate heat exchanger, control valves, energy meters and secondary pumps.
Commissioning the substation
- • Heat exchanger check: leak test, measurement of the heat output transferred (ΔT × flow rate × Cp).
- • Setting the primary control valve: it modulates the primary flow to maintain the secondary temperature setpoint.
- • Configuring the weather compensation curve: heating curve according to outdoor temperature.
- • Energy meter check: MID compliance, correct flow direction, consistency of readings.
- • Safety device tests: relief valve, pressure switch, safety thermostat, frost thermostat.
- • Balancing the secondary network: the building's radiators or AHUs must receive the correct flow rate.
Watch the primary network temperature regime! A district heating network often runs at 90-110°C flow / 60-70°C return. The operator monitors the return ΔT: a return that is too hot (poor heat transfer) leads to financial penalties.
Connecting to a district heating network keeps a commissioning engineer busy for several days: pressure tests, filling, balancing and control configuration. It is a growing market as urban networks expand.