Backup Power for Hospitals

A hospital’s backup power system has one job: keep patients alive when the grid fails. In an operating theatre or ICU, the allowed interruption is measured in fractions of a second, not minutes.

Malaysia’s grid is reliable, but it is not immune. On 27 July 2022, a fault at the Yong Peng North main intake substation cut 2.2 GW of supply, around 10% of Peninsular demand, hitting areas from Petaling Jaya and Cheras to Bayan Lepas and Seberang Jaya. In September 2021, Hospital Sultan Ismail in Johor Bahru lost mains power overnight and ran its essential supply on generators until normal power returned the next morning.

This guide explains what Malaysian hospitals and medical facilities need from a backup power system, which standards apply, and how to select the right diesel generator set. It is written for hospital facility managers, M&E consultants and engineers planning new builds, extensions or upgrades.

Which hospital loads need backup power?

Not every load in a hospital is equal. A good design separates loads by how quickly they must be restored, then sizes the generator and UPS around that.

In practice, most Malaysian hospitals wire selected outlets and circuits as “essential power”. During the 2021 Hospital Sultan Ismail outage, ICU and NICU ventilators stayed on because they were plugged directly into essential power outlets fed by the generators.

Standards and requirements in Malaysia

The core Malaysian standard is MS IEC 60364-7-710, which adopts IEC 60364-7-710 for electrical installations in medical locations. It covers hospitals, private clinics, medical and dental practices, health care centres and dedicated medical rooms. MS 2366:2010 gives guidance on applying it to Group 2 locations such as operating theatres and ICUs, and is used alongside it.

Changeover classes

The standard groups safety supplies by the maximum time allowed before power returns:

The 15-second class is where the diesel generator set does most of its work. A properly specified genset must start, reach rated voltage and frequency, and accept load within that window.

Run time

Under IEC 60364-7-710, equipment on the 15-second safety supply must be backed by a source able to sustain it for at least 24 hours. This can be reduced to a minimum of 3 hours only where medical needs can be covered and the building can be safely evacuated within that time. For most hospitals, this means planning fuel storage for at least 24 hours at full essential load.

Other requirements to check

• Separate distribution: the general supply and the safety supply need separate distribution boards.
• Medical IT systems: Group 2 locations use an unearthed (IT) system, fed from two independent sources with automatic changeover.
• Approvals: generator installations are subject to Energy Commission (Suruhanjaya Tenaga) requirements, fire authority (Bomba) requirements for fuel storage and plant rooms, and environmental rules on noise and emissions. Ministry of Health requirements apply to public hospitals, and private facilities are licensed under the Private Healthcare Facilities and Services Act 1998.

Requirements change and vary by project. Always confirm the current edition and local approvals with your consulting engineer.

How to size a hospital generator

Sizing starts from the essential load list, not the hospital’s total connected load. Oversizing wastes capital and causes light-load problems; undersizing risks a trip at the worst moment.

1. List every essential load. Group them by the classes above and note running kW for each.
2. Add motor starting loads. Chillers, AHUs, medical air compressors, vacuum pumps, fire pumps and lifts draw several times their running current at start-up. Stagger their starts with load-step sequencing where possible.
3. Allow for non-linear loads. UPS systems, imaging equipment and VFDs create harmonics. These often call for an oversized alternator, even if the engine is sized correctly.
4. Convert kW to kVA. Most generator sets are rated at 0.8 power factor, so kVA = kW ÷ 0.8.
5. Add a margin for growth. Hospitals expand. A 20–25% margin covers new wards and equipment without a full replacement.
6. Choose the rating. Hospital emergency systems normally use standby-rated generators, because the generator is the alternate source and runs only during outages and tests. Where outages are frequent or long, consider a prime rating.

Worked example: a 200-bed private hospital has 640 kW of essential load. At 0.8 power factor that is 800 kVA. With a 25% growth margin, the target is about 1,000 kVA, which could be one 1,000 kVA set or two 500 kVA sets in parallel for redundancy.

Avoid running generators at very light loads for long periods. Diesel engines that run lightly loaded can suffer wet stacking, where unburnt fuel builds up in the exhaust. Regular load bank testing helps prevent this (see below).

Redundancy, ATS and fuel autonomy

A single generator is a single point of failure. If it fails to start, or is down for service when the grid trips, the hospital has nothing but its UPS batteries.

Build in redundancy

• N+1 configuration: install one more generator than the essential load needs. If the load needs two 1,000 kVA sets, install three. Any one can fail or be serviced without loss of supply.
• Paralleling: multiple sets synchronised on a common bus share load and add capacity in steps. This also keeps each engine better loaded at low demand.
• Mobile backup: keep a connection point for a truck-mounted or rental generator. It covers major overhauls, extended outages and emergencies such as floods.

Automatic transfer switch (ATS)

The ATS detects mains failure, signals the generator to start and transfers load once the set is stable. It is what turns a generator into a 15-second safety supply. Specify an ATS with:

• adjustable start and transfer delays to ignore momentary dips
• closed-transition or soft retransfer to avoid a second break when mains returns
• monitoring and alarms linked to the building management system
• separate ATS units for life-safety, critical and equipment branches, so a fault on one does not take down the others

Fuel autonomy

Plan for at least 24 hours of fuel at full essential load, in line with the run-time requirement above. Many hospitals choose 48–72 hours to cover flood-season access problems. Fuel storage design, bund walls and refilling arrangements must meet Bomba and environmental requirements. Treat or polish stored diesel regularly, because degraded fuel is a common cause of start failure.

Choosing the right generator type

The right configuration depends on capacity, available space, noise limits and how the hospital site is laid out. HSP Power Systems supplies four configurations:

A few site factors to weigh:

• Noise: hospitals sit near wards and residential areas. Canopy and containerised sets with acoustic treatment keep noise down, and exhaust silencers should be rated for the location.
• Location and flooding: place generators and fuel tanks above flood level. Basement plant rooms are a known risk during floods.
• Ventilation and exhaust: open sets need well-designed air intake and discharge so the room does not overheat. Keep exhaust away from air intakes, windows and helipads.
• Access: leave room for service, major overhauls and future replacement, and a clear route for fuel deliveries.

Testing and maintenance

A generator that has never been tested under load is an assumption, not a backup. Most hospital generator failures come from poor maintenance: flat batteries, stale fuel, coolant leaks or a faulty ATS.

Load bank testing is especially important for hospitals, because the real load during a monthly test is often well below the generator’s rating. A load bank adds a controlled artificial load to prove the set can carry its full rating and to burn off carbon from light-load running. HSP provides load bank testing from 10 kW to 5,000 kW.

Keep a logbook of every test, run hour and repair. It is your evidence for audits and licensing inspections. For more on maintenance, see our guides on extending diesel generator lifespan and preventive maintenance vs reactive repairs.

Hospital backup power checklist

• Essential loads listed and grouped by changeover class (0, 0.5, 15, >15 s)
• UPS in place for Class 0 and Class 0.5 locations (theatres, ICU, recovery)
• Generator sized on essential load, motor starting and harmonics, plus 20–25% growth margin
• Standby-rated generator, with N+1 redundancy or paralleled sets
• ATS units separated by branch and linked to the BMS
• Fuel for at least 24 hours at full essential load
• Generators and fuel above flood level, with good ventilation and exhaust routing
• Connection point for a mobile generator
• Monthly load runs, annual load bank test and full mains-failure simulation, all logged
• Design confirmed against MS IEC 60364-7-710, MS 2366 and local approvals

Talk to HSP Power Systems

Since 1988, HSP Power Systems has supplied diesel generator sets for industrial, commercial and critical facilities across Malaysia, including healthcare. We supply open, canopy, containerised and truck-mounted gensets from 15 kVA to 4,125 kVA, plus rental power and load bank testing for commissioning and annual checks.

Planning a new hospital, an extension or a generator upgrade? Speak to our power specialists for a recommendation based on your essential load, site and run-time requirements.

Frequently asked questions

What standard covers hospital electrical installations in Malaysia? 

MS IEC 60364-7-710 covers electrical installations in medical locations, and MS 2366:2010 gives guidance for Group 2 locations such as operating theatres and ICUs.

How fast must a hospital generator take over? 

For most safety loads, within 15 seconds. Operating theatres and ICUs need power back within 0.5 seconds, which is achieved by a UPS that carries the load until the generator takes over.

How long should a hospital generator be able to run? 

At least 24 hours on the safety supply under IEC 60364-7-710. Many hospitals plan for 48–72 hours of fuel.

What size generator does a hospital need? 

It depends on the essential load, not the total load. A small clinic may need under 100 kVA; a large hospital may need several megawatts across paralleled sets.

Should a hospital buy or rent a generator? 

Permanent standby power should be owned and maintained on site. Rental generators are useful for temporary cover during overhauls, extensions or emergencies.

How often should a hospital generator be tested? 

Run it under load monthly and carry out a full load bank test at least once a year.