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Chiller system optimization: The Hartman Loop in action at Humber

The basic set-up
About 800,000 square feet of the campus is cooled by the plant, explains Spencer Wood, Humber’s Manager of Maintenance and Operations. The new system includes three 550 ton chillers, three chilled water (CHW) pumps, three CS pumps and three cooling towers, all piped in a parallel arrangement.

What is innovative about the system is how this equipment is run.

“Variable speed chillers are actually most efficient at part load,” notes Wood. “The Hartman LOOP control system is essentially a black box control system that optimizes the operation of the chillers, the cooling towers and the pumps. So, for example, the system might run two chillers at 50 per cent load, or three cooling towers and one chiller depending on other variables.”

“The secret to this system is that it only gives a building what is required,” says Kevin Laidler, Design Build Sales Manager for SA Armstrong Limited. Laidler was involved with the implementation of the Humber College system. “Usually, chillers run on PID (proportional-integral-derivative) controller loops. In such a case, individual pieces of equipment on the loop may be running efficiently but no controls are speaking to the whole system.”

The ability to “speak” to the whole system requires the installation of differential sensors in remote locations throughout a campus so that control valves are closed in various areas, for instance, when students are not in classrooms. “The system includes an algorithm that calculates the least amount of work that is necessary to keep the facility comfortable,” explains Laidler.

Ease of use
Proof is what most facility managers want when determining the value of a new technology, and so far the Armstrong system has demonstrated its worth.

“The big number that everyone talks about when discussing chiller plant efficiency is the number of kilowatts per ton used to run it,” says Wood. “We were running at 1.3 kW per ton prior to this installation. We are now running at about 0.55 kW per ton efficiency, and looking at about $100,000 a year in financial savings.”

The system is remarkably easy to use – you basically have it installed and it monitors the campus and adjusts controls as necessary. Laidler compares it to an automatic car – you can own a stick shift, but an automatic will inevitably change gears more efficiently.

However, that very ease of use was something of a mental hurdle for the team at Humber.

“It took about a year to get used to the control system,” Wood admits. “Before, operators would tinker with machines to make them work more efficiently. Now, the system does much of that on its own. We had to get used to that.”

Of course, that doesn’t remove the need for good operators, it just changes the nature of their job.

“Programming is where we are finding efficiencies now,” notes Wood. “We’ve found that we can trim temperature set points and alter when a plant starts up in the morning – that sort of subtle change can make a big difference, and last summer we experienced those changes for the first time.”

The Humber team has also prepared for future opportunities. For instance, the system is wired so that one chiller can run off the system’s emergency generator. This means that Humber could potentially load shed and take its entire chiller off the grid for a demand response application. This hasn’t yet been done, but it is an attractive option for the future.

Ease of installation
Another interesting aspect of this particular project is that, in order to work around the College’s need to be up and running at all times, much of the system was factory designed and pre-fabricated, so that full working components could be slid into the system with relative ease.

“In a standard project, you would have pieces of the system delivered within about six weeks after ordering, and then you’d have to assemble them onsite like a jigsaw,” says Laidler. “In this case, it takes 12 weeks for delivery but a large part of it is ready to go immediately.”

And customers can see the hard savings almost immediately once the system is installed as well. It is equipped with a touch screen controller that allows you to see how efficiently the system is working at all times. The hard data can be downloaded by the customer or Armstrong at any time for review.

Thus far, the IPC system has only been installed in two facilities in Canada, but about 60 have been installed in the U.S.

“I think for some people, it seems a bit strange having your pump guy selling you chiller controls,” jokes Laidler. “That’s probably been our biggest hurdle. And in the Canadian market, customers tend to be a little more circumspect when it comes to new technologies. That said, with the installations at Humber and Seneca colleges, we are generating plenty of data that should prove that this type of system has value in this environment.”

Humber’s dedication
Meanwhile, the plant controller is only one piece of Humber’s energy management upgrades.

“Since we started working on energy efficiency in earnest back in 2005, we’ve reduced our energy use by 16.5 per cent, even while our student population has grown,” says Wood. Some of the savings have been through switching 1,000 spotlights to LEDs, going from 50 W to 6 W bulbs; retrofitting the college gym with induction lighting, which saves on both energy and maintenance; and the installation of variable speed drives on main fans so that they can be slowed at appropriate times.

But perhaps the biggest part of all of this for Wood is the importance of training.

“A lot of facilities do energy programs and then forget they ever happened,” he says. You really have to train staff. With training, you can really pick up on the momentum created by individual projects and discover new solutions.”