Cesspit systems going bump in the night

Until recently, a few of the lighter sleepers at the Holiday Inn Express at Edinburgh Airport found that their slumbers were being interrupted by strange intermittent noises.

As engineers from pump specialist and Danfoss service partner Ritmac discovered, however, the noises were not originating from ghosts, aircrafts or even a distant heavy metal band. They were, in fact, the result of a problem with a cesspit system, and variable speed drives from the VACON range provided a convenient and costeffective solution.

On investigating the cess pump arrangements at the hotel, the Ritmac engineers found that the installation had three pumps; one controlled by a VSD, the other two by conventional electromechanical motor starters. The problem arose when the conventionally controlled pumps started, as they created a loud water hammer that could be heard throughout the hotel rooms.

Ritmac specialists felt that fitting VSDs to all the pumps, rather than only to the one with the water hammer problem would be a much better solution in the long run. In addition to the ease of maintenance; this option proved to be very affordable, thanks to VACON VSDs being competitively priced and fully self-contained.

The Ritmac team installed three VACON 100 FLOW VSDs rated at 2.2 kW. The new drives were chosen for their IP54 rating which meant that they could be installed without an outer enclosure, which saved money and installation time. As an additional benefit, 100 FLOW VSDs are optimised for pump applications and include, for example, integral PID controllers that are needed for his application as pump speed is controlled by a pressure reference.

“VACON 100 FLOW drives were the best solution for this pump application because they’re cost effective, small and very easy to commission,” said Steven Brown, business development manager of Ritmac. “We spent less than a day on site, and that included the time it took to remove the old control panel. In fact, by careful planning, we were able to reduce the actual pump downtime, while we changed from the old starters to the new drives, to well under two hours. That meant neither the hotel staff nor the guests were inconvenienced in any way by our work.”

To read the full article see the latest June edition of EiBI by registering for free here.

Follow Energyzine on Twitter. Like us on Facebook. Join us on LinkedIn.