Project Brief

165 Halsey Street in Newark is a carrier hotel, and zColo, a Zayo Group company, runs colocation suites across its fifth floor. Those suites are cooled by 31 Liebert CRAC units, 8 to 30 tons each and installed between 1998 and 2010, all rejecting heat through a glycol loop to dry coolers on the roof. KeRi was brought in by Boon Energy, the owner's energy consultant, first to find out why the system was not holding up and then to fix it.

The first phase was diagnosis. The roof condenser water system had never been documented, so KeRi drew the existing conditions, inventoried every CRAC unit by tag, model, capacity, and install date, reviewed the dry-cooler selections against what was actually connected, and totalled the load: 652 tons of nominal CRAC capacity moving 2,056 GPM and pushing 8,856,960 BTU/hr, about 738 tons, back to the roof. KeRi then wrote the balancing requirements and had the loop tested against them. The report told the story: units designed for 67 GPM were measuring 38 to 46, one balancing port was blocked outright, and several had no usable flow curve.

The fix was a rebuilt pump room. New 6 inch condenser water supply and return tied into the existing 8 inch mains, an 816 GPM air separator on its own service bypass so it can be maintained without draining the loop, a new bladder expansion tank, a reduced pressure zone backflow preventer on the make-up water, and epoxy containment rolled 6 inches up the wall with a sump pump in case a pump ever leaks. The eleven roof dry coolers, 80 to 240 GPM each, were tied together on 8 inch glycol mains with differential pressure sensing, and every unit, pump, and dry cooler was to be re-balanced to its design flow.

None of it could stop the floor. The drawings say so in as many words: system shut down is not allowed. So the set carries a ten step sequence. The new piping and air separator were prefabricated complete with isolation valves before anything existing was opened, the plant ran on its backup pumps while the primary pumps were isolated, every isolation valve was exercised and proven before anyone relied on it, and strainers were cleaned one pump at a time so the loop never lost more than a single pump. Controls were integrated back to the landlord's building management system.

MEP Engineering Scope

What We Engineered

Condenser water and dry-cooler engineering for the colocation floor:

• Existing conditions documentation for the roof condenser water system
• Full CRAC and dry-cooler inventory with heat rejection totalled across the floor
• Water flow balancing requirements, specifications, and independent hydronic testing
• Rebuilt pump room with air separator, expansion tank, backflow prevention, and leak containment
• A ten step construction sequence that kept the plant running throughout
• Controls integrated to the landlord's building management system, with commissioning and training

How the Work Ran

The Challenge

A colocation floor cannot go warm. Thirty-one CRAC units spanning twelve years of installations were all rejecting heat to one glycol loop and a roof full of dry coolers, and the system was not keeping up, but nobody had documentation of what was actually up there. Testing showed units drawing well under their design flow, one balancing port blocked, and several units with no usable flow curve. Whatever the fix turned out to be, it had to be installed around tenants whose cabinets could not be allowed to lose cooling, and the drawings carried the constraint in plain words: system shut down is not allowed.

Our Solution

KeRi documented the plant first, inventorying every CRAC unit and dry cooler and totalling 8,856,960 BTU/hr of heat rejection so the loop could be judged against a real number rather than an assumption, then wrote balancing requirements and had the system independently tested against them. The rebuild that followed replaced the pump room piping with a new air separator on a maintenance bypass, an expansion tank, backflow prevention, and epoxy leak containment, tied the eleven roof dry coolers together on 8 inch mains with differential pressure sensing, and put every unit back to its design flow. The whole installation was sequenced in ten steps around the live floor: prefabricate first, run on backup pumps, prove every isolation valve before trusting it, and clean strainers one pump at a time.