mousaconsultancy Contact
Case study / 03Feasibility & capacity

Critical power replacement

Lewisham, London · 2026 · Feasibility study

A data centre in Lewisham relies on ten 2.5 MVA diesel rotary UPS units (DRUPS). With their replacement under review and new loads planned on three levels, we developed the electrical feasibility study: the options for replacing them, and how the building can take the extra load.

Existing plant10 × 2.5 MVADiesel rotary UPS (DRUPS) units
Options2 routesReplace like for like, or static UPS with generators
New load3 levels400 kW loads added on Levels 1, 3 and 4
OutputReportTechnical comparison of the two routes
ILLUSTRATIVE SECTION · EXISTING BUILDING ADDITIONAL 400 kW LOADS NEW LOADNEW LOADNEW LOADLV SWBDS10 × 2.5 MVA DRUPS RISER LEVEL 4LEVEL 3LEVEL 2LEVEL 1GROUND SWITCHBOARD AND RISER CAPACITY CHECKED FOR THE NEW LOADS
Illustrative section, not the actual building layout. New loads on Levels 1, 3 and 4 are fed through the existing riser.

What we did

  • Assessed the existing critical power arrangement, built around ten 2.5 MVA DRUPS units.
  • Compared replacing them like for like with an alternative of static UPS and standby generators, including the resilience of each.
  • Checked how additional 400 kW loads on Levels 1, 3 and 4 could be supplied within the existing switchboard and riser constraints.
  • Engaged suppliers for technical input and compared the options side by side.
Why the choice matters

A DRUPS combines the UPS and the standby generator in one rotating machine. Moving to static UPS with separate generators changes the plant footprint, the switchboard arrangement and how the site rides through a mains failure. The decision has to be made on the whole system, not on the UPS alone.

Project experience of Mousa Consultancy’s director, delivered while working with another consultancy. Client name withheld.

Discuss a project All services