Our expert responds #14

QUESTION
Can soft starters and/or inverters be used to control the main fire-fighting electric pumps?

ANSWER
According to UNI EN 12845 10.8.5, the pump control panel must be located in the same compartment as the electric motor and the pump, the electric panel of the electric pump must be able to:

• automatically start the engine when it receives a signal from the pressure switches
• start the engine in manual mode
• stop the motor only by manual operation (if the overpressure unit is exclusively used by a hydrant network, for activities not constantly monitored, the stop can take place automatically, after the pressure has been kept constantly above the pump start pressure for at least 20 consecutive minutes – UNI 10779

It should also be recalled that:

• UNI EN 12845:2020    10.7.5.2    "Once the pump is started it must continue to operate until it is stopped manually."
• UNI/TR 11438:2012     10.2        "Once started, whatever the cause, even on request to start the priming system, the pump can only be stopped manually by the operator."
• UNI EN 12845:2009    10.8.2.1    "Where permitted by the mains operator, the power supply for the pump control panel must be taken upstream of the main power switch to the buildings and where this is not permitted by the connection from the main switch. The fuses of the pump control panel must be high breaking capacity, in order to allow the start current to pass for a period of not less than 20 s."

From the above it is clear that:

• no automatic systems can be installed that, by controlling the various electrical parameters (absorbed current, current to ground, phase shifts, etc.…) can intervene to stop the operation of the pump, after the latter has been called into service by the intervention of the pressure switch. Consequently, even electronic systems such as soft starters or inverters cannot be installed on the pump supply line. In fact, they are equipped with protections that intervene automatically to safeguard the load and/or their internal circuits, in fact contravening the requirements of the standard. In addition, the presence of electronic components decreases the overall reliability of the system. In addition, the presence of electronic components decreases the overall reliability of the system.
• between the power interruption systems of the electric pump there is absolutely no other part than the STOP button located on the electric control panel of the electric pump itself, and which is located in the control unit, therefore no release coil with a dedicated button          
• to safeguard the line and the load, only fuses with high breaking capacity are allowed, even if a circular from the Ministry of the Interior no. 694/4144 of 23 April 1998 is still in force, which has better clarified the terms of the issue relating to the electrical protection of the power supply line, explicitly stating that "the safety objectives imposed by CEI 64-8 must be respected even if in disagreement with the specific requirement of UNI 9490", giving the official green light to the use of magnetic switches for the protection of the power supply lines of the fire protection pumps, still guaranteeing the overload parameters of the lines dictated by the same standard. By extension, being UNI 9490 replaced in its entirety by UNI EN 12845, it is assumed that the circular also applies to the latter standard.