In short. A generator general-arrangement drawing, CAD file or BIM model turns an equipment selection into a buildable installation. It fixes the footprint, connection points, access zones and lifting arrangements, and lets architects and services engineers coordinate ventilation, exhaust, fuel, cabling and structure. It must match the confirmed model, options and revision, and it never replaces engineering checks on airflow, loading, acoustics or protection.
Drawings are coordination tools
The value of a GA drawing is not the outline of the machine; it is how that outline fits with everything around it. A generator room in a Hyderabad commercial building has to fit radiator air, exhaust routes, fuel day tanks, cable trenches, a door large enough for the set and space to change a starter motor. Most of the expensive problems we see on retrofit jobs started with a layout drawn around the generator footprint alone.
What a useful GA package shows
- Overall dimensions, footprint and operating weight, with mounting and anti-vibration positions.
- Radiator air inlet and discharge faces, and the canopy or enclosure openings.
- Exhaust outlet position, size and flange details.
- Fuel supply and return connections, and the base tank details where fitted.
- Power cable entry and the breaker or terminal box position.
- Control cable entry and the controller location.
- Service zones and door swings for maintenance access.
- Lifting points and handling instructions where the manufacturer documents them.
The drawing must correspond to the confirmed equipment configuration. A generic family drawing should not be used as a final construction drawing for a different model or option set, because canopy, tank and radiator options change dimensions and connection positions.
Clearances and room layout
Allow working space on all sides that need maintenance access, and plan a route to bring in or remove the set, including the largest single component. For containerised or canopied sets outdoors, keep discharge air from recirculating into the inlet, and keep exhaust away from building openings and fresh-air intakes. Our installation planning and site survey services check these points on site before the layout is fixed.
Ventilation sizing from the drawing
A room installation needs air for combustion, air for the radiator and air to remove heat radiated from the engine and alternator. The radiator and combustion flows come from manufacturer data; the room heat removal can be checked with a simple balance.
Q = H / (ρ × cp × ΔT)
Here Q is the ventilation airflow in m³/s, H is the heat radiated into the room in kW from the datasheet, ρ is air density in kg/m³, cp is the specific heat of air (about 1.005 kJ/kg K) and ΔT is the allowed temperature rise in the room in kelvin.
Example (illustrative): a set radiating 30 kW into its room, with air density 1.15 kg/m³ at Hyderabad summer conditions and an allowed rise of 10 K, needs about 30 / (1.15 × 1.005 × 10), or roughly 2.6 m³/s, for heat removal alone. Radiator and combustion air are added according to the manufacturer’s figures, and louvre and attenuator pressure drop must stay within the radiator fan’s allowance.
BIM and multidisciplinary coordination
A BIM model lets structural, mechanical, electrical and fire teams see the generator alongside ducts, trays, pipes and beams. It supports clash detection and maintainability reviews. Geometric coordination, however, does not verify electrical ratings, floor loading, airflow, acoustic performance, exhaust backpressure or protection. Those still need engineering calculations using manufacturer data.
| Interface | What the model coordinates | What still needs engineering |
|---|---|---|
| Structure | Plinth position and size, openings | Static and dynamic loading, vibration isolation |
| Ventilation | Louvre and duct positions | Airflow, pressure drop, recirculation |
| Exhaust | Route, supports, penetrations | Backpressure, thermal expansion, discharge height |
| Fuel | Tank and pipe routes | Pipe sizing, venting, statutory storage limits |
| Electrical | Cable tray and trench routes | Cable size, voltage drop, fault level, protection |
| Acoustics | Attenuator and barrier space | Noise levels at boundaries and receivers |
Linking CAD with electrical documents
Physical and electrical design depend on each other. Cable length set by the layout affects voltage drop; equipment position affects ventilation and access; exhaust routing affects backpressure and heat. CAD resources should link to the single-line diagram, cable schedule, earthing layout, control philosophy and wiring diagrams. Check equipment data against the relevant datasheet before the drawing is issued for construction.
Revision control and as-built records
Preliminary, tender, coordination, construction and as-built drawings serve different purposes and are not interchangeable. Every drawing should carry its revision and issue status, and superseded revisions should be withdrawn from site. Changes made during installation should be captured so the final record reflects what was built. An accurate as-built set saves time on every later service visit, relocation or upgrade.
Common mistakes
- Laying out the room around the set footprint only. Radiator air recirculates and the set derates or shuts down on high temperature.
- Using a family GA for a set with different options. Exhaust, fuel or cable connections end up in the wrong place.
- Treating a BIM clash check as engineering approval. Backpressure, floor loading or airflow problems pass unnoticed.
- Forgetting the removal route. A major overhaul later needs walls broken or the set cut apart.
- Leaving superseded drawings on site. Contractors build to an old revision and rework follows.
What to send us
Send the proposed model and options, or for an existing set the nameplate photo, together with architectural plans of the room or area, photographs, door and access dimensions and the drawing format you need. Note any constraints such as floor level, nearby openings and noise limits. Use the application engineering enquiry and we will confirm what drawing data is available for that configuration.
Questions engineers ask
Can you supply BIM objects for generators?
Availability depends on the manufacturer and model. Where a native model is not available, a GA drawing can be used to build a coordination block. Either way, it must match the confirmed configuration.
How much space should be left around a generator?
Enough for maintenance on all serviced sides, door swings and component removal, as stated in the manufacturer’s installation guidance. Also plan a route to remove the whole set. Clearances set by fire and electrical rules apply in addition.
Does the GA drawing show ventilation airflow?
Usually it shows air inlet and outlet faces, while airflow and allowable restriction come from the datasheet. Room ventilation design combines both with a heat balance.
Why do as-built drawings matter for a generator?
They show what was actually installed, including site changes. Service engineers, auditors and future project teams rely on them. Without them, every later job starts with a survey.
Technical content reviewed by Srinivas Reddy, Managing Partner, Reddy Generators. Last updated 19 October 2026.