In short. A generator site survey answers one question: can this set be delivered, placed, ventilated, exhausted, fuelled, connected, protected, operated and maintained at this location? It records measurements, routes, equipment labels and photographs tied to positions, and it lists what could not be inspected. Done before quotation, it prevents the site from redesigning the project after the set has been bought.
Why the survey comes before the quotation
Most of the cost surprises in generator projects are not in the set. They are in the crane that cannot reach the roof, the cable route that turns out to be 90 metres instead of 30, the room that cannot pass the radiator airflow, the exhaust that must climb four floors, and the neighbour’s window three metres from the proposed discharge. Every one of those is visible to a surveyor who walks the route with a tape and a camera, and invisible to anyone pricing from a kVA figure and a pin on a map. The survey turns the site into a design basis, and the design basis into a quotation that holds.
Survey the whole journey, not the empty space
A set is delivered, lifted, positioned, connected, fuelled, maintained for fifteen years and eventually removed. The survey follows that journey. Can a truck with a 3 tonne or 12 tonne set enter the compound and turn? Is there crane access, or must the set be skidded through a door and a corridor? Does the floor or roof slab take the static and dynamic load? Will the doors of the canopy open fully in the proposed position? Can a technician reach the radiator cap, the oil drain and the alternator terminals once the cables are in? Can a fuel tanker get close enough to refuel without hoses crossing a public road? The position that satisfies all of these is often not the one marked on the architect’s drawing.
What a complete survey records
| Area | Record | Why it matters |
|---|---|---|
| Access and handling | Gate width, turning space, door and corridor dimensions, crane standing area, floor or slab loading | Decides transport, lifting method and whether the set can reach the position at all |
| Position and foundation | Dimensions, level, drainage, ground bearing or slab capacity, distance to walls and property line | Foundation design, clearances for airflow and service |
| Ventilation | Existing openings with free area, orientation, obstructions, prevailing wind, adjacent air intakes | Radiator airflow and recirculation risk |
| Exhaust | Possible route, length, bends, penetrations, building height, nearest windows and intakes | Backpressure budget and CPCB stack height |
| Fuel | Tanker access, bulk tank position, bund space, pipe route to day tank, drainage nearby | Autonomy, PESO and fire-safety requirements |
| Electrical connection | Switchboard location, incoming breaker and busbar details, fault level, available space for ATS or AMF, metering | Cable sizing, protection coordination, transfer scheme |
| Cable route | Length, method (trench, tray, duct), bends, crossings, mechanical protection, termination space | Voltage drop, cable size and installation cost |
| Earthing and neutral | Existing earth pits, their resistance if known, neutral arrangement at the main board | Neutral switching decision, earth fault protection |
| Environment | Noise-sensitive neighbours, flooding history, dust, corrosion, security | Enclosure choice, plinth height, weather protection |
| Documentation | Drawings available, drawing versus reality differences, items not inspected | Makes assumptions visible |
Electrical findings that change the design
The survey must establish where the generator will connect and what is already there: switchboard make, incoming breaker rating and type, busbar rating, spare ways, and the transformer rating and impedance if the fault level is not documented. A generator’s fault contribution is much lower than the utility’s, so protection that works on utility supply may not operate on generator supply, and the survey gathers the data the protection review needs. Note the neutral arrangement, because it decides whether the transfer switch must be four-pole, and find the earth pits and their test records. Cable route length drives cable size directly, which is why the route is measured and not estimated; the arithmetic is in generator cable sizing.
Indoor and outdoor positions
An indoor position gives weather protection and security but needs the room to pass radiator airflow, combustion air and room heat, and the exhaust to leave the building. The survey measures the room, its openings and their free area, and looks for the recirculation traps described in generator-room ventilation; the full checklist is at indoor installation. An outdoor canopied set needs a plinth above flood level, drainage, clearances at inlet and discharge, shade where possible, and attention to monsoon rain driving into louvres; see outdoor installation. Rooftop positions add structural loading, vibration transmission to occupied floors below and the hardest lifting problem of all, and they need a structural engineer’s confirmation before the set is ordered.
Rental and emergency surveys
A temporary power project needs the same questions answered faster. Where will the trailer stand, how will cables run safely to the connection point without crossing traffic, where is fuel delivered, and who can isolate the board for connection? An emergency may not allow a full survey, but it never removes the need to know the connection point, the fault level and the earthing before a cable is landed. Planned outages are the best time to survey, because the board can be opened safely while the utility is off; see rental and temporary power.
Making the survey usable
Photographs are tied to a position on a sketch and captioned with what they show. Measurements are written against the sketch, not remembered. Equipment labels are photographed legibly. Items that could not be inspected, such as a locked transformer yard or a slab whose reinforcement is unknown, are listed as open points with an owner. The record then says which observations affect equipment selection, which affect installation planning and which need specialist input from a structural, civil or protection engineer. A survey that ends in a list of decisions and open points feeds straight into design support and installation planning; a folder of unlabelled photos feeds nothing.
Common mistakes
- Surveying only the proposed footprint and not the route to it; the set arrives and cannot pass the gate, the stair or the slab.
- Estimating cable length from a plan instead of walking the route; the real route is longer, the cable size rises and the voltage drop is checked too late.
- Ignoring the neighbours and the nearest windows; the exhaust discharge and noise generate complaints that force a relocation after installation.
- Assuming the existing switchboard can accept the generator connection; there is no spare way, no space for an ATS and no record of fault level.
- Leaving uninspected items unrecorded; a structural or access assumption becomes a hidden design input and surfaces on delivery day.
What to send us
Before the visit, send the site address and a plan or satellite view marked with the proposed position, the kVA class under consideration, drawings of the main switchboard and single-line diagram if available, photos of the access route and the proposed location, and any operating restrictions such as permitted visit hours or shutdown windows. Tell us whether the application assessment is complete. Use the generator sales enquiry for new sets, and the survey report will be the basis of the quotation.
Questions engineers ask
How much space does a diesel generator need?
The set’s footprint plus the manufacturer’s clearances for airflow and service, which for a canopied set is typically at least 1 to 1.5 metres on the inlet and service sides and a free discharge, and for a room enough width to open doors and remove the radiator. The survey measures the actual position rather than relying on a rule.
Can a generator be installed on a roof?
Often, but only after a structural engineer confirms the slab for static weight and running vibration, a lifting method is confirmed, and vibration isolation and exhaust routing are designed. Rooftop sets need the most careful surveys because every mistake is expensive to correct at height.
What should be ready before the surveyor arrives?
Access to the proposed position and the main switchboard, any drawings and single-line diagrams, someone who knows the plant’s operations and restrictions, and permission to photograph. If the board can be safely opened with the supply isolated, that gives the best electrical information.
Does a rental generator need a site survey?
For anything beyond a small set on a short hire, yes. The survey confirms where the trailer stands, how cables reach the board safely, how fuel is delivered and what the connection and earthing arrangement will be. It takes an hour and prevents most of the problems seen on hire sites.
Technical content reviewed by Srinivas Reddy, Managing Partner, Reddy Generators. Last updated 19 October 2026.