Gather the actual enclosure data
Use the enclosure's external width, height and depth in metres, the heat actually dissipated inside it, the surrounding ambient temperature and a heat-transfer coefficient suited to the material, finish and air conditions. The coefficient is an explicit input so the calculator does not assume that every enclosure behaves like a particular sheet-steel product.
Select the installation arrangement from the manufacturer's seven effective-area branches. A single enclosure against a wall, an end enclosure and an enclosure in the middle of a suite expose different amounts of surface to the surrounding air.
Area and heat-balance method
The model uses Q = k × A × (Ti − Ta), rearranged as temperature rise ΔT = Q ÷ (k × A). Q is internal dissipated heat in watts, k is the supplied heat-transfer coefficient, A is the effective area in square metres, Ti is estimated internal temperature and Ta is ambient temperature.
The effective area follows nVent HOFFMAN's installation branches. For example, a single enclosure free-standing on all sides uses A = 1.8H(W + D) + 1.4WD. Other arrangements use their corresponding branch shown in the selector. Arithmetic retains full precision; displayed values use three decimals or scientific notation for very small or large values.
Worked example
For W = 0.6 m, H = 0.8 m, D = 0.3 m, 110 W of internal heat, ambient 25°C and k = 5.5 W/(m²·K), the free-standing area is 1.548 m². The estimated rise is 12.920 K and the internal temperature is 37.920°C.
These numbers describe the supplied model inputs only. They are not a product rating, a maximum permitted temperature or an installation acceptance result.
What the estimate cannot certify
The result is a bulk steady-state estimate. It does not predict component hot spots, air stratification, local radiation, solar gains, condensation, transient overloads or the temperature rating of any device. Confirm the actual product construction, manufacturer instructions and operating limits separately.
Do not use the result to select a breaker, conductor, enclosure, fan, heat exchanger or air conditioner. It also makes no Canadian Electrical Code, provincial, territorial or AHJ determination.
Common questions
Can I use a generic coefficient?
Only when it is appropriate to the actual enclosure material, surface and air conditions. The calculator does not supply a default because changing the coefficient changes the temperature result directly.
Should equipment input power be entered as heat?
Enter the portion dissipated as heat inside the enclosure at the operating condition. Output power, transferred mechanical power and heat released outside the enclosure should not be counted as internal loss without a matching energy balance.
Does a lower result mean the enclosure is acceptable?
No. It is a model estimate only. Component ratings, product construction, hot spots, installation conditions and applicable requirements still need separate verification.
Related tools
Source and scope
nVent HOFFMAN, Calculating heat dissipation in nVent HOFFMAN enclosures, printed p. 3 (heat balance), p. 5 (seven installation-area branches), and p. 6 (published enclosure heat table). The coefficient remains an explicit input; the paper's example/table is not used as a coefficient default. Source checked November 10, 2026.
This implementation requires the coefficient as an explicit user input and does not import a product table, material default or temperature limit. Inputs and results stay in this page without saving or transmission. Report a problem or suggest a source; values are not attached automatically.