Filter fans & heat exchangers
for electrical enclosures

Which cooling for which electrical enclosure?

The cooling capacity calculator works out in one minute which solution is sufficient for your heat load — including solar load for enclosures outdoors.

Filter fans for electrical enclosures

A filter fan draws in ambient air through a filter mat, and an outlet filter on the opposite side lets the warm air escape. Fan at the bottom, outlet at the top — this way the airflow supports natural convection. For ZPAS enclosures we use filter fans of the LV series (Rübsamen & Herr) or equivalent, in 230 V or 115 V AC and 24 V DC.

Values at 50 Hz with outlet filter according to the manufacturer’s catalogue. Free-blowing, the airflow is higher (LV 800: 930 m³/h) — for sizing, the value with filter is what counts.

How many fans does the enclosure need?

The required airflow is given by V = P ÷ (0.34 × ΔT) in m³/h. With 1,500 W power loss and a permissible temperature difference of 10 K, that is around 440 m³/h — i.e. one LV 700 or two smaller fans. If one fan is not enough, the outdoor configurator automatically distributes the output across several units.

Fans with thermostat

A thermostat with a normally open contact switches the fan on when the set temperature is exceeded; a normally closed contact, by contrast, switches a heater off. The thermostats from the ZPAS accessory range work with a bimetal element, setting range 0–60 °C, switching differential around 7 K, switching capacity 6 A at 250 V AC.

Air/air heat exchanger

The heat exchanger separates internal and outside air: two fans drive the air through separate channels of a heat exchanger block, and the heat passes through the wall to the outside. This keeps dust, oil and moisture out. Its output is stated in W/K and applies per kelvin of temperature difference:

Cooling capacity (W) = specific output (W/K) × (internal temperature − outside temperature)

A unit with 35 W/K therefore manages around 525 W at a difference of 15 K. We use heat exchangers of the Aertherm XVA series (Cosmotec) with 16, 35 or 50 W/K, or equivalent. With high loads or a small temperature difference, the heat exchanger reaches its limit — then a cooling unit or, outdoors, the outdoor air conditioner is the right choice.

Fitted at the factory

ZPAS supplies electrical enclosures and outdoor enclosures with ready-installed fans, heat exchangers, cooling units and heaters — cut-outs, assembly and wiring come from the factory. The right heater also helps against condensation: more on this in the guide condensation in electrical enclosures.

Frequently asked questions about fans and heat exchangers

Filter fan or heat exchanger — which is right?

A filter fan replaces the enclosure air with filtered ambient air — inexpensive and effective as long as the surroundings are cool and clean enough. An air/air heat exchanger works with separate circuits: no outside air enters the enclosure. Both only cool to just above the ambient temperature; if it has to be cooler inside than outside, you need a cooling unit.

How much airflow does an electrical enclosure need?

Rule of thumb: airflow (m³/h) = power loss (W) ÷ (0.34 × ΔT), where ΔT is the permissible difference between internal and outside temperature. Example: 500 W at ΔT = 10 K gives around 150 m³/h. Calculate with the airflow with outlet filter, not with the free-blowing value.

Is a fan with thermostat worthwhile?

Yes. A thermostat with a normally open contact only switches the fan on when the set temperature is exceeded — this saves energy, filter changes and noise. The thermostats from the ZPAS accessory range cover 0–60 °C, with a switching differential of around 7 K and 6 A at 250 V AC.

Is the degree of protection maintained with a filter fan?

With a filter mat, the LV series filter fans achieve IP 54. For outdoor use there is an IP 55 solution (LV/GV 250–800) with a finer filter, a UV-resistant outer grille and an optional stainless steel water-jet hood.