Optimization Strategies

Packaged Central Plants

Think your plant is running out of capacity?  Think again . . .

Before you buy another chiller, ask yourself:  Am I getting full production from the equipment I already own? And if not, why not?

You may find what other facility managers facing the same problem have: the CHW plant's low return water temperature and wasted flow are making it impossible to reach the design output. In other words, you are not getting what you paid for.

Restore Lost Cooling and Reduce Energy Usage

Before spending big money ripping up your plant, consider conversion to variable primary flow. You'll get back lost capacity and the overall kW / ton is practically guaranteed to go down at the same time. And since VP conversion typically involves only minor mechanical changes you'll have less logistical headaches and a smaller bill to boot.

How does VP Conversion make this possible?

VP flow helps compensate for low delta T, a fact of life in a typical CHW plant. Low low delta T has a direct effect on the amount of cooling a chiller can produce, since cooling is the product of flow (Q) and delta T.

In plants with traditional primary/secondary hydronic design, the constant speed primary pumps deliver a fixed flow, so cooling capacity drops in direct proportion to the decrease in actual delta T as compared to the design delta T. The result: lag chillers (along with associated CDW pumps and CT fans) must be sequenced on earlier thereby wasting significant energy. Further, maximum capacity is reduced (refer to the chart above, where a 4 degree drop in delta T limits a 1200 ton plant to only  800 tons. 

Now consider the same system after conversion to VP flow. The plant's existing pumps, chillers and towers remain in place, but a valve is installed in the bypass line. In this arrangement, the variable speed pumps can compensate for low delta T with higher flow, so the chillers can now produce more cooling. Depending on the conditions causing the low return water temperature, it is entirely possible to reach design capacity. 

That's exactly what the people at Berger Hospital found. (You can click the picture above for a case study.) In addition to getting a 50% increase in capacity, the people at Berger also found that their energy consumption went down as well. This is always the case in a conversion because the chillers run in the most efficient part of their range more often, and the lead chiller can handle the load alone for a much greater portion of the time.

Trust the Experts on Variable Primary Conversion

Several factors affect whether a CHW plant will benefit from a VP conversion, including the age and condition of the equipment, hydronic conditions, the cooling shortfall, and so on. Contact tekWorx and we will be happy to assist you in this evaluation.