Electrical switch room were historically designed to house large Motor Control Centres with DOL / Star Delta motor starters. With the process and energy benefits Variable Speed Drives delivers the motor starter retrofit market is bigger than the new drive application UK market. But this is a problem as the drives are bigger and take up more room and we are seeing our clients switch rooms full to capacity, so what is the solution?

Drives fitted outdoors need to be protected from the elements, as the electronics may otherwise become damaged by water as well as by elevated temperatures. At Quantum Controls we have designed a weatherproof enclosure system with our Variable Speed Drives. The range goes from 1.5kW – 800kW so if your switch room if full to bursting point we have a ready made solution suitable for mounting direct onto your plant or even outside. The complete range of VSDs is available in our VSD Guide, which is completely free for our UK customers. Claim your Guide today!

The required protection is often sought by selecting a high protection class for the drive enclosure, such as IP66, but this does not necessarily address the issue.

IP stands for “Ingress Protection”, where a higher number denotes higher protection, so it is easy to assume that the highest number available will provide the best protection.

Installers may even be under the impression that the location does not matter as the drive is so well protected, but this is not correct.

A high IP rating will protect against water jets or water splashing, but drives fitted outdoors are normally located on rooftops, typically for for controlling air-handling units, where splashing water is not often a problem. Instead, it is the moisture in the air, sealed inside the drive enclosure, that has the potential to damage the drive electronics.

The IP rating of the drive has no effect on the air drawn in by the unit’s cooling fan and, in fact, can a cooling fan operate properly against water jets?. If damp air circulates inside the drive enclosure and the internal heat sink cools down, enough for the temperature to drop below the dew point, condensation will form, which could damage the electronics.

The IP numbers have specific meanings. The first digit denotes protection against solid objects and the second against liquids. For IP66, for instance, number 6 in the first position means “totally protected against dust ingress” and in the second position “protected against high pressure water jets from any direction” – not a particularly relevant feature in a rooftop location.

Another enemy outdoors is direct sunshine, which can elevate the temperature inside the drive. This will add to the heat the electronics produce when working; this is not much, but it may be sufficient to raise the temperature inside by 10 degrees compared to the outside. If the unit is totally sealed, cooling could become an issue. The drive’s components and heatsink have been designed to remove heat from the drive assuming an adequate volume of cooling air is available.

If the drive internal conditions cause the drive electronics to work at a higher temperature than for which it was designed,the service life will be reduced : ’Rule of Thumb’ 10 degress above design equates to half lifetime, and the availability of the equipment could be affected.

Frequently, the drives are built into the air handling units, in which case there is no need for a high IP rating. Alternatively, a separate outdoor enclosure can be used complete with a weather proof cowling for the drives, with anti-condensation heaters that help keep the water vapour in the air above the Dew point. Thermostats in the enclosure also ensure that the internal air temperature is properly controlled in warm weather, with fans and filters to help draw clean air into the cabinet.

The AHU enclosure should be protected to IP56. Drives inside such an enclosure need only be protected to IP21, which means less costly drives can be used. Savings can be made by placing several drives into one enclosure.

Because a drive is rated at IP66 it is for a specific internal situation e.g. food and beverage sites, this does not mean that an IP66 enclosure is weatherproof: to do this would require the IP rating to be given as IP66W. Beware of being ‘beguiled’ by specmanship, understand where an IP66 enclosure is appropriate, and where more consideration is required if the drive is required to be sited at an external position.

We have designed a weatherproof enclosure system with our Variable Speed Drives. The range goes from 1.5kW – 800kW so if your switch room if full to bursting point we have a ready made solution suitable for mounting direct onto your plant or even outside.

These weather units are available for sale or to hire and have provided a solution to many of our clients space problems when installing new machinery, or simply wanting to upgrade existing DOL starters to VSD control for process improvement and energy saving. If your switch rooms are full to capacity our new weather proof enclosure system allows you to put your drives outdoors and in environments previously not suited for Variable Speed Drives. For more information request your Free Rental Guide today or email us at sales@quantum-controls.co.uk