Diesel Generator for Data Centres

The load the set really has to carry

A data centre is not powered by the servers alone. The generator feeds the whole facility: the IT load, the cooling plant, the lighting, the ventilation, the fire systems and the losses of the distribution itself. Add the starting current of the largest motor that can start while the set is carrying the rest of the plant, and that total is the number the set has to hold.

N+1 is the normal rule

Most data centres are built to N+1: one set more than the load requires, so a single set can be taken out for service while the remaining sets carry the plant. Our tables list the standby rating of every model, because N+1 is decided on the standby figures, not on the prime figures. Where the client runs a 2N design, we quote the sets in matched pairs so that the two halves are identical.

Ten seconds from the signal to the load

The generator has to be on the bus within ten seconds of the failure signal, and the voltage and frequency have to be inside the tolerance that the UPS expects. In practice that means a set that is warm, fuelled and in auto mode at all times, with the batteries on float charge and the coolant above 30 °C. We set the control panel for the start delay, the crank attempt time and the transfer parameters that match the site, and we write them into the quotation.

The voltage and the distribution

Most data centres run a 400/230 V, three phase distribution in the generator room and feed the racks through the UPS, with 6.6 kV or 11 kV only for the incoming side. Sets for 60 Hz markets are built to 400/230 V, 60 Hz with the same alternator and control approach, so the switching gear stays standard. If the plant sits on a medium voltage ring, the step-up transformer and the synchronising equipment are quoted with the sets.

The noise is part of the design

The generator room is often next to the office or the cooling plant, and a bare engine at full load is loud enough to be a problem long before it is a safety issue. The silent canopy set is the usual answer: a steel enclosure with acoustic lining, a radiused inlet and a discharge silencer, which brings the noise down to roughly 70 dB(A) at 7 m. Containerised sets outside the building, with the cable run back to the plant room, work well where the site is tight.

The fuel and the autonomy

Autonomy is quoted from the fuel tank level, as ISO 8528 requires, and 8 to 24 hours at full load is the normal band for a data centre. We can deliver the set with a day tank, a transfer pump, a base tank with a level alarm, and the pipework sized for the distance between the tank and the set.

The paralleling, the ATS and the monitoring

Two to six sets of the same model can be paralleled on a common bus with a parallel control panel, and one set then carries the load while the others are on standby. That is what makes N+1 real: a set can be serviced without touching the load. The automatic transfer switch, the remote monitoring over GSM or Wi-Fi and the fuel and temperature sensors are all quoted with the package, and the site acceptance test is done with a load bank so the load steps are proven before the client takes over.

What we deliver

Open frame or silent canopy, 50 Hz or 60 Hz, ATS or no ATS, single set or a parallel package, with the fuel system, the heaters, the battery charger and the monitoring written into the same quotation. Every set is run at full load in the factory before it is loaded, and the test record travels with the machine.