by
Carol Ko, Staff Writer | November 15, 2013
From the November 2013 issue of HealthCare Business News magazine
Scroll compressors (also known as scroll pumps) replaced less efficient compressor designs that operate with pistons. The key to their success is a spiral-based design: two high-precision spiral scrolls that mesh together in a circular motion to compress air.
But there’s one main flaw with this system. It operates strictly under two modes, ‘on’ or ‘off,’ which usually results in imprecise cooling that either undershoots or overshoots the amount of power needed to keep the temperature within a certain range.
And because anti-recycle timers are required to prevent overheating the compressor motor, the compressor can only be switched on or off a limited number of times in an hour.
By manually positioning the scrolls, manufacturer Copeland’s digital scroll compressors are able to rapidly switch between periods of inactivity and activity without actually turning the compressor motor on or off.
In practical terms, this means that a digitally controlled slide bar will automatically register when the temperature drops two degrees and increase the power from 10 percent to 20 or 30 percent to ensure that the temperature stays within the set range.
“In the past, it was just on or off, but now it’ll detect whether it needs to increase that load up to 100 percent,” says Smith.
However, not everyone swears by digital scroll compressors. Chillers manufacturer Motivair, for example, uses Danfoss’ inverter scroll compressors instead.
Instead of repositioning the scrolls, inverter scroll compressors use a technique called variable speed drive to vary the speed of the motor depending on the load, thus saving energy when the load is at less than maximum capacity.
From an engineering standpoint, the newer variable speed drive technology wins the energy efficiency battle, though both techniques reduce power consumption and allow for better temperature modulation. “They both do exactly the same thing,” says Graham Whitmore, president of Motivair. “Danfoss just went in a different direction.”
Speaking of speed, hospitals are increasingly focused on finding chillers that are able to come back online quickly after an electrical spike or a power surge. Though traditional chillers may take as long as 15 minutes to bounce back, this downtime is less than ideal for hospitals. Chiller systems that have quick-start technology that enable them to recover in a matter of seconds are now in high demand, experts say.
Take the heat
Another trend in the general chiller market that’s only starting to make its way to the medical side is heat recovery technology.“It’s been a trend for the last 12 months or so,” says Whitmore.
