Application

Diesel Generators for Hospitals

A hospital generator has to do something no other standby set has to do: keep oxygen flowing, operating theatres lit and life support running without an interruption that anyone notices. That sets three requirements at once — a supply restored within seconds, enough fuel on site to outlast a long outage, and no single component whose failure takes the whole essential supply down.

Sets for hospitals and clinics are normally quoted between 200 kVA and 500 kVA, often as two machines with automatic transfer and a load-shedding scheme that separates life safety, critical and equipment groups.

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Requirements

What a hospital specification has to state

Typical hospital and clinic generator requirements. National healthcare standards and the local code govern.
Item Typical requirement Why it changes the set
Load groups Life safety first, then critical, then equipment; non-essential loads shed on generator Fixes the rating, the number of sets and the changeover arrangement
Restoration time Life safety supply typically within 10 seconds; critical branches shortly after Drives engine start reliability, the starting system and the transfer logic
Autonomy Commonly 24 h or more of on-site fuel for the essential load A hospital cannot depend on a fuel delivery arriving during a regional outage
Redundancy Two sets with automatic transfer, or N+1 where the critical load justifies it Service and maintenance must not require an outage
Imaging loads MRI, CT and linear accelerators have high inrush and high harmonic content Often justifies a dedicated set or an oversized alternator
Harmonics Alternator sized for non-linear loads from scanners, LED lighting and drives Harmonic current heats the alternator beyond its kW rating
Noise Set well away from wards, with the boundary level stated at the nearest receptor Decides the enclosure and whether the plant room itself needs acoustic treatment
Vibration Isolated from the structure below theatres, imaging rooms and laboratories Prevents structure-borne noise and disturbance to sensitive equipment
Exhaust Discharged above roof level and away from any fresh-air intake or opening window Prevents exhaust being drawn into ventilation systems
Testing and maintenance Regular no-load and loaded running, with fuel quality checks A standby set that is never run under load is the most common cause of a failed start

Configurations

Configurations we quote most often

Common hospital and clinic arrangements. Each rating links to its power range page.
Rating per set Typical arrangement Fits Range page
200 kVA / 160 kW One set, or two in a small installation Clinics, day surgery units and polyclinics 200 kVA
300 kVA / 240 kW One set for essential loads, plus a small life-safety set District hospitals of 50-100 beds 300 kVA
500 kVA / 400 kW Two sets with automatic transfer and load shedding General hospitals with theatres, ICU and imaging 500 kVA
800 kVA / 640 kW and above Two or more sets in parallel Teaching hospitals and medical cities 800 kVA

Reference configuration

A worked example

This is an illustrative configuration, not a delivered project. It shows how the requirement table above turns into a specification. Replace the figures with your own load list before pricing.

Example: a 120-bed general hospital with two operating theatres, an ICU and one CT scanner.
Parameter Example value
Life safety load About 90 kW: egress lighting, fire pumps, alarms, nurse call, one lift
Critical load About 220 kW: theatres, ICU, laboratory, medical gas plant, cold rooms
Equipment load About 150 kW: chillers, water pumps, laundry, kitchen
Total essential About 460 kW, with non-essential loads shed on generator
Rating selected Two sets at 500 kVA / 400 kW, standby rating, with automatic transfer and load shedding
Largest step Chiller and water pump group started in sequence after supply restoration
Autonomy 24 h at the essential load, on bulk storage with a day tank and transfer pump
Enclosure Silent canopy sets, or open sets in an acoustically treated plant room
Imaging Scanner fed from a branch with an oversized alternator on the serving set
Testing Monthly no-load run, periodic loaded run, annual fuel quality check

Questions

Questions we are asked about hospital sets

How quickly must a hospital generator take the load?

The usual design target is that the life-safety supply is restored within about ten seconds of a mains failure, with the critical branches transferred immediately afterwards. That allows for the engine to start, reach rated voltage and frequency, and for the transfer switch to operate. Anything longer is normally treated as a design fault rather than a malfunction.

How much fuel should a hospital keep on site?

Twenty-four hours at the essential load is the common minimum, and longer where outages in the region have historically lasted days. At roughly 0.24-0.27 litres per kWh delivered, that means a hospital with 400 kW of essential load needs in the region of 2 300-2 600 litres for a full day of running — which is why fuel storage is a project in its own right, with bunding, a transfer system and quality checking.

Do imaging machines need a dedicated generator?

Not always, but they need attention. Scanners and linear accelerators combine a high inrush current with a high harmonic content, so the alternator is usually oversized for the load, and the branch protection has to be coordinated with the machine’s own requirements. Where the hospital has several imaging machines, a dedicated set for the imaging group is often the cleaner answer.

What is load shedding and why does a hospital need it?

Load shedding means deliberately dropping non-essential loads, such as some chillers or laundry equipment, so that the essential groups get the whole generator output. It lets a smaller set serve a large hospital, and it makes the transfer sequence predictable: life safety, then critical, then equipment, each one stepped on as capacity allows.

Where should the generator be installed?

As far as practical from wards, theatres and fresh-air intakes, which usually means a dedicated plant room at ground or roof level with the exhaust above roof height. The set needs its own air path in and out, and the plant room is usually acoustically treated so that the boundary level is met without an enclosure, or fitted with silent canopy sets if the room is not available.

Related

Related applications and ranges

Equipping a hospital or clinic?

Send the life safety, critical and equipment load lists, the autonomy you need and the plant room location. That is enough to fix the number of sets and the ratings.

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