Generator Selection & Sizing

Emergency Generator Sizing in Mexico: How to Specify It

Technical guide to sizing and specifying a 60 Hz emergency generator for buildings, commercial properties, and offices in Mexico.

4 min read By SEER POWER
Open generator set in a generator room with an overhead exhaust pipe and electrical cabinet
On this page
  1. 1. What an Emergency Generator Must Cover in a Building
  2. 2. Separate Critical and Non-Critical Loads
  3. 3. Standby Rating and Power Output
  4. 4. Automatic Start and Transfer Time
  5. 5. Fuel Type and Runtime
  6. 6. Location, Exhaust System, and Service Life
  7. 7. What to Request from the Supplier

Guide snapshot

Direct answer

To size a generator set for a building in Mexico, separate critical loads from non-critical loads, sum the running power and motor starting demand at 60 Hz, define the transfer time, and select diesel or gas based on site conditions.

This guide covers

  • Separating critical and non-critical loads in buildings.
  • Standby power rating, declared power factor, and automatic start.
  • Fuel selection criteria, outdoor exhaust routing, and quoting data.

Best for

  • Property managers of buildings, condominiums, clinics, and shopping centers.
  • Electrical contractors, design engineers, and technical buyers.

What an Emergency Generator Must Cover in a Building

Installing an emergency generator in a building, retail facility, or office in Mexico protects essential services during utility outages. When the public power grid fails, the facility must maintain occupant safety and keep priority equipment running.

A generator set uses an engine to turn an alternator. The alternator makes power by electromagnetic induction. Its magnetic field induces a voltage, and the set delivers 60 Hz current to the site.

The goal is to keep essential circuits live during a grid outage. Continuous plant duty under a prime rating needs a separate guide. Commercial and residential buildings need standby backup. The right standby generator avoids both outages and oversizing.

Separate Critical and Non-Critical Loads

Sizing starts with a written load list that sorts circuits into critical and non-critical loads. In a building in Mexico, critical loads include elevators, water pumps and emergency lighting. IT equipment and essential refrigeration also count.

You can leave out comfort cooling or outdoor signs to make better use of the generator’s capacity. The electrical engineer does this survey by checking the existing panels. A separate emergency panel for priority circuits makes load control simpler when the standby generator starts. The set then runs with a predictable load.

Standby Rating and Power Output

Buildings on the public grid usually specify a standby rating. This rating fits a unit that waits on standby and supplies power during limited outages.

The real power formula is kW = kVA × PF. Use PF = 0.8 only where it is the declared equipment rating or an explicit calculation assumption. Use the load’s actual power factor and starting characteristics for the load study.

When summing critical loads, account for the higher starting current required by pump and elevator motors. The supplier must verify that initial inrush peak, while the electrical designer establishes the reserve margin.

SEER POWER product ranges cover from 30 to 1875+ kVA.

The 30 to 125 kVA industrial diesel series delivers between 24 and 100 kW prime. This line includes the SP-30WC, rated at 30 kW prime (37.5 kVA) and 33 kW standby (41.3 kVA). A Weichai WP2.3D40E200 engine drives a Leroy-Somer or SEER POWER alternator.

For higher capacities, see the 125 to 375 kVA series and the 375 to 750 kVA series.

Automatic Start and Transfer Time

A backup power system uses an automatic transfer switch (ATS) linked to the controller. When the controller detects an outage, it sends a start signal to the engine. Once voltage and frequency settle at 60 Hz, the switch connects the critical circuits.

The project engineer sets the maximum transfer time based on how sensitive the loads are. For servers that cannot accept any break, installers add UPS batteries to cover the first seconds. If the building requires two synchronized units, review our guide on generator synchronizing modules and paralleling.

Fuel Type and Runtime

Your fuel choice depends on space and local utility lines. Diesel sets keep fuel in a tank on site, so runtime depends on tank size and load. Gas units are practical where the site has a reliable natural gas line or LPG supply.

For natural gas or LPG power projects, contact SEER POWER. Share your load, voltage, operating duty and fuel-supply details to discuss the configuration. Both fuels give reliable backup power when you size the set to the real load.

Once you know the runtime hours you need, you can size the fuel tank or confirm the gas pipe capacity.

Location, Exhaust System, and Service Life

Engine exhaust contains carbon monoxide. Operators must not run portable generators indoors. You may install a fixed industrial generator in a dedicated generator room designed for the selected equipment. The room needs suitable ventilation, exhaust discharge and fire protection under applicable local requirements.

For open units in a plant room versus outdoor enclosures, see our guide to generator enclosures, airflow, and noise.

Service life depends on regular test runs and on avoiding common diesel generator issues. Clear space around the unit also lets technicians check filters and batteries safely.

What to Request from the Supplier

Before you ask for a quote, confirm with your designer whether the panel runs at 127/220 V or 220/440 V at 60 Hz. The SEER POWER 30 to 125 kVA series offers voltage options from 220 to 480 V for each site. Always ask for the datasheet with the standby rating and the alternator’s declared power factor.

You can also review enclosures and controllers in our backup power solutions.

Final checklist

  • Separate critical and non-critical loads in writing with your electrical designer.
  • Confirm local voltage (127/220 V or 220/440 V) at 60 Hz and motor starting requirements.
  • Define transfer time, room ventilation, and outdoor exhaust discharge routing.
  • Choose diesel or gas based on the building's fuel supply and request the technical datasheet.

Frequently Asked Questions

What size emergency generator does a building need?

The size depends on the total kW and kVA of critical loads that run together, plus motor starting. The building's engineer calculates the 60 Hz load with the real power factor and sets the margin. With that data, the supplier picks a model whose standby rating covers the load without overload.

How long does an emergency power generator take to come online?

A unit equipped with automatic start detects the utility outage immediately. It then starts the engine, stabilizes voltage and frequency within acceptable ranges at 60 Hz, and transfers the load within seconds. The exact transfer time depends on controller settings and the project engineer's specifications. For sensitive IT equipment, a UPS system bridges the brief initial interval.

Is a diesel or natural gas emergency generator better?

Both work well for buildings in Mexico, and the right choice depends on the site. A diesel set lets you store fuel on site as an independent reserve. A natural gas unit is practical where a gas line is available. Sites can also keep LPG in storage tanks.

Can an emergency generator power an entire building?

Yes, if the project sizes the unit for the whole connected load and motor starting currents. Many condos and office buildings back up only the critical load panel. Your designer can compare both options before you ask the manufacturer for a quote.

What electrical system data defines the right generator types?

A technical survey defines critical power needs during commercial grid outages. It analyzes kW, kVA, power factor, and starting currents to ensure a continuous power supply. This rigorous classification enables the proper operation of backed-up loads without oversizing the installation.

How do you compare diesel and natural gas options for generator operation?

Both technologies use reliable internal combustion engines, but they differ in their supply infrastructure. A diesel engine incorporates its own fuel system with an autonomous on-site tank. Meanwhile, natural gas units require a firm natural-gas connection. LPG can be stored in on-site tanks; both options require proper exterior exhaust systems.

Sources and technical references