Enter the heat your components put into the panel, the enclosure size, and the temperatures. The calculator returns the cooling load in watts and BTU/hr, tells you whether a filter fan can do the job, and lists the Pfannenberg air conditioners rated for that load at 95°F ambient / 95°F internal.
1. Heat inside the panel
Add up the dissipation from each drive, power supply, transformer and PLC. No data? Use the drive helper below.
A VFD rejects about 3% of its rated power as heat (40 HP x 746 W x 0.03 = 895 W). Line reactors, braking resistors and 24 V supplies add to that.
2. Enclosure
3. Temperatures
Most drives are rated to 104°F (40°C). 95°F inside gives margin. Use the hottest hour of the year for ambient, not the average.
How the calculation works
Three numbers decide the cooling load. The heat your components reject into the air inside the panel. The heat that moves through the enclosure walls, in or out, driven by the difference between ambient and internal temperature. And the safety margin you carry for a hot afternoon, a dirty filter, or a drive that runs harder than the nameplate says.
Wall heat transfer is k x A x ΔT. A is the exposed surface area of the enclosure. k is the heat transfer coefficient of the wall material, 5.5 W/m²K for painted sheet steel. ΔT is ambient minus internal. When the plant floor is hotter than the target inside the panel, the walls add heat and the air conditioner has to remove it too. When the plant is cooler, the walls help, and a filter fan may be all you need.
Watts convert to BTU/hr at 3.412 BTU/hr per watt. Air conditioner capacity is always stated at a rating point. The Pfannenberg units below are listed at 95°F ambient and 95°F internal, the common North American rating point. At higher ambient the same unit delivers less; at lower ambient it delivers more. If your conditions are far from 95/95, tell us and we size off the performance curve, not the catalog number.
Pfannenberg cooling units by capacity at 95°F / 95°F
Side mount DTS units bolt to the door or side of the enclosure. Top mount DTT units sit on the roof when the door is full or the panel is against a wall. DTI units recess into the wall and are for indoor use in narrow aisles.
| Model | Mount | Capacity 95/95 (BTU/hr) | Voltages | H x W x D (in) | Ratings |
|---|---|---|---|---|---|
| DTS 3021 / 3031 | Side | 1,200 | 115 / 230 | 15.5 x 7 x 7.5 | NEMA 12, 3R, 4, 4X |
| DTS 30X1 | Side | 3,000 | 115 / 230 / 460 | 20.2 x 10 x 10.8 | NEMA 12, 3R, 4, 4X |
| DTS 31X1 | Side | 4,000 | 115 / 230 / 460 | 29.5 x 15.6 x 9.3 | NEMA 12, 3R, 4, 4X |
| DTS 31X1 SL (slim) | Side | 5,000 | 115 / 230 / 460 | 36 x 12.1 x 12 | NEMA 12, 3R, 4, 4X |
| DTS 31X5 | Side | 7,000 | 115 / 230 / 460 | 36 x 12 x 12 | NEMA 12, 3R, 4, 4X |
| DTS 32X1 | Side | 8,500 | 115 / 230 / 460 | 47.6 x 15.6 x 10.6 | NEMA 12, 3R, 4, 4X |
| DTS 32X5 | Side | 13,000 | 115 / 230 / 460 | 53 x 16 x 11.9 | NEMA 12, 3R, 4, 4X |
| DTS 34X1C | Side | 21,000 | 230 / 460 | 57.2 x 15.8 x 19.7 | NEMA 12, 3R, 4, 4X |
| DTS 36X1C | Side | 29,000 | 230 / 460 | 57.2 x 15.8 x 19.7 | NEMA 12, 3R, 4, 4X |
| DTT 6101 | Top | 1,785 | 115 / 230 | 17.1 x 23.4 x 15.6 | NEMA 12 |
| DTT 6201 | Top | 3,570 | 115 / 230 / 460 | 17.1 x 23.4 x 15.6 | NEMA 12 |
| DTT 6301 | Top | 5,355 | 115 / 230 / 460 | 17.1 x 23.4 x 19.5 | NEMA 12 |
| DTT 6401 | Top | 7,161 | 115 / 230 / 460 | 17.1 x 23.4 x 19.5 | NEMA 12 |
| DTT 6601 | Top | 11,000 | 460 | 19.1 x 31.3 x 22.6 | NEMA 12 |
| DTT 6801 | Top | 14,000 | 460 | 19.1 x 31.3 x 22.6 | NEMA 12 |
| DTI 6201 | Recessed | 3,922 | 230 / 460 | 60.5 x 19.1 x 6.2 (outside) | NEMA 12 |
| DTI 6301 | Recessed | 5,286 | 230 / 460 | 60.5 x 19.1 x 6.2 (outside) | NEMA 12 |
| DTI 6401 | Recessed | 6,820 | 230 / 460 | 60.5 x 19.1 x 6.2 (outside) | NEMA 12 |
| DTI 6501 | Recessed | 8,525 | 460 | 60.5 x 19.1 x 6.2 (outside) | NEMA 12 |
| DTI 6801 | Recessed | 13,640 | 460 | 60.6 x 19.1 x 6.2 (outside) | NEMA 12 |
The X in a DTS model number is the voltage digit. Capacities are Pfannenberg catalog ratings at 95°F / 95°F. Stainless and washdown versions of most DTS sizes are available. See the Pfannenberg air conditioner collection for part numbers, or the air conditioner cross reference if you are replacing a Hoffman, Rittal, Saginaw, Thermal Edge, IceQube, Seifert or Kooltronic unit.
When a filter fan is enough
A filter fan moves plant air through the panel. It only works when the plant air is cooler than the temperature you want inside, and the panel can tolerate plant air (no washdown, no oil mist, no conductive dust). Airflow needed is CFM = BTU/hr divided by (1.08 x ΔT). A 600 W load with plant air 15°F cooler than the target needs about 126 CFM. Pfannenberg Filterfans run from 15 to 800 CFM. If the plant is within 10°F of the target, or hotter, skip the fan and size an air conditioner.
Common questions
How many BTU do I need to cool an electrical enclosure?
Add the watts of heat from every component inside, add or subtract the heat moving through the walls (k x area x temperature difference), multiply by 3.412 to get BTU/hr, then add a 20% margin. A typical 72 x 36 x 18 inch panel with a 40 HP drive lands between 3,000 and 5,000 BTU/hr at 95°F ambient.
Why is an enclosure air conditioner rated at 95°F / 95°F?
Capacity depends on the temperature on both sides of the unit. The North American rating point is 95°F outside and 95°F inside so units can be compared like for like. At 104°F ambient the same unit delivers less. Pfannenberg publishes performance curves for other conditions.
Does a bigger air conditioner hurt?
Yes. An oversized unit short cycles, runs the compressor harder, and condenses more moisture. Size to the design load with margin, not to the biggest unit that fits.
Can I use a fan instead of an air conditioner?
Only when plant air is cooler than the target inside the panel and clean enough to pass through it. If the plant hits 100°F in July, a fan cannot hold 95°F inside.
Get the load checked and quoted
Send the result from the calculator, or a photo of the panel and the drive nameplates, and we confirm the size against the Pfannenberg performance curve and quote the unit. Applied Control Inc. is the Pfannenberg representative for Michigan.
Request a QuoteBook 15 Minutes with an Application Engineer
Capacities from the Pfannenberg catalog, subject to change. The calculator gives a sizing estimate for budgeting and selection; confirm against the unit's performance curve and your enclosure's actual construction before ordering. Hoffman is a trademark of nVent. Rittal, Saginaw, Thermal Edge, IceQube, Seifert and Kooltronic are trademarks of their owners. Applied Control Inc. is not affiliated with those companies.