Specifications & Amenities6 min read

Generator Power Backup: DG Set Sizing, Auto-Changeover, and Essential Load Coverage

A technical evaluation of acoustic diesel generator sizing (kVA), Auto Mains Failure (AMF) panels, and true flat-level essential load coverage.

S
SV Technical Editorial Team
Electrical & Infrastructure Engineering Desk•25 Mar 2026
Diesel generator set with open electrical control panel

Diesel generator set with open electrical control panel

Continuous Living in the Face of Coastal Outages

Tropical coastal storms and scheduled grid maintenance can occasionally interrupt city electricity supply. In modern apartment living, an uninterrupted power system is not a luxury—it ensures home offices remain connected, elevators never stall, and refrigerated medicines remain preserved.


1. Generator Sizing Calculations

A reputable builder sizes the central DG set using a disciplined mathematical formula:

$$\text{Total DG Capacity (kVA)} = \frac{\text{Common Area Loads} + (\text{No. of Flats} \times \text{Backup per Flat})}{\text{Power Factor (0.8)}} \times \text{Diversity Factor}$$

  • Common Areas: Lift motors (typically 7.5 to 11 kW with high startup inductive surge currents), borewell and booster water pumps, corridor lighting, and fire systems.
  • Individual Flats: Typically 1.0 kVA to 1.5 kVA dedicated to each flat via automated current limiters.
  • Benchmark Brands: Kirloskar, Cummins, Mahindra Powerol, or Ashok Leyland fitted with CPCB-compliant acoustic soundproof canopies (noise levels $< 75$ dBA at 1 meter).

2. Auto-Mains Failure (AMF) Automation

In poorly managed buildings with manual switches, a power cut at midnight requires searching for the watchman to start the generator. With an automated AMF panel:

  1. Grid electricity drops.
  2. The controller waits 5 seconds to verify it is not a momentary surge.
  3. The engine cranks automatically.
  4. Power is seamlessly restored to your home within 12 to 15 seconds.
Verified Authoritative Sources & Standards
  • •
    Central Pollution Control Board (CPCB IV+) Environmental Emission Norms for DG Sets — CPCB India
  • •
    IS 13364: Specification for AC Generators Driven by Reciprocating Internal Combustion Engines — BIS

Frequently Asked Questions

An AMF panel continuously monitors city grid voltage. Within 10 to 15 seconds of a power failure, it automatically cranks the diesel generator and transfers electrical loads without requiring manual watchman intervention.

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