Elevator Machine Room Heat Load and Cooling

The heat is the INEFFICIENCY, which makes it a smaller number than people expect but a persistent one. A machine and drive at 85% efficiency converting 15 kW puts about 7,677 BTU/h into the room while running, and because elevators run intermittently the average over a peak hour is what a cooling system has to remove -- at a 40 percent duty cycle that is 3,071 BTU/h. Add 400 W of controller standby (1,365 BTU/h), lighting, and envelope gains, and a machine room on a roof in summer easily reaches 10,400 BTU/h, roughly 0.9 tons of cooling for one elevator. THE SIZING TRAP RUNS BOTH WAYS. Compute it from the machine's connected 15 kW instead of its losses and you get 51,180 BTU/h, nearly seven times too high, and buy a unit several times larger than needed. Compute it from the machine alone and you go wrong in the other direction: the controller draws standby power continuously even when the car is parked, a machine room on a roof with an uninsulated west-facing wall can gain more through the envelope than the equipment contributes, and a room shared with other equipment inherits its heat too. THE FAILURE MODE IS AN ENTRAPMENT. Modern drives monitor their own temperature and shut down to protect themselves, and an elevator that shuts down mid-trip strands passengers and needs a rescue. That is why machine room cooling in most jurisdictions is a required system rather than a comfort provision, and why it is commonly required to be on standby power alongside the elevator itself. A heat load estimate from equipment data the user supplies. The temperature-rise figure assumes the room loses no heat through its envelope, so it is a fastest-case bound rather than a prediction. Machine and drive efficiency vary with load and speed, and regenerative drives return energy to the supply rather than dissipating it, which changes the room load substantially -- manufacturer heat rejection data for the specific equipment is the authority, and duty cycle must reflect the building's actual traffic. It does not compute envelope gains or size the cooling equipment, and it does not address the code requirements for machine room ventilation, temperature and humidity limits, standby power, or the prohibition on unrelated piping and equipment in a machine room. ASME A17.1, the equipment manufacturer's environmental limits, the adopted building code, and the elevator authority having jurisdiction govern.

heat while running = input power x (1 - efficiency) x 3,412.142 BTU/h per kW; average = that x duty cycle; total = average + controller standby + lighting and envelope gains; tons = total / 12,000; temperature rise with no cooling = total / (0.018 x room volume).

Loss-based heat rejection at the exact 3,412.142 BTU per hour per kilowatt, averaged over an entered peak-hour duty cycle, by name, with ASME A17.1 and the equipment manufacturer's environmental limits named. Manufacturer heat rejection data for the specific machine and drive is the authority.

Arithmetic on equipment data the user reads off the machine and drive; no manufacturer performance table is reproduced.

Estimate. AHJ and licensed professional govern.

Field names used by the API: input_power_kw, efficiency_pct, duty_cycle_pct, controller_standby_w, other_gains_btuh, room_volume_cuft, ambient_limit_f, starting_temp_f, heat_running_btuh, heat_average_btuh, controller_btuh, total_btuh, cooling_tons, connected_overstatement

• Heat is the loss, not the connected load using connected power overstates it several times over on an efficient machineelevator drive practice
• The controller and the envelope are not optional terms standby power is continuous and a roof machine room can gain more than the equipment makeselevator machine room practice
• Over-temperature is an entrapment drives shut down to protect themselves, possibly with passengers aboardASME A17.1