FRESH NEW THINKING: Given the urgency of the task at hand, the above scenarios were daunting. Additionally, the absorption chiller- heaters are not well known for thermal efficiency. Hence it became obvious that a new approach was needed. Why not try using modular electric chillers and modular gas boilers that could be transported through the building freight elevator? Very convenient, but how are we going to obtain the vast amount of new electric power needed on the top floor, and can we properly fit all the required modular equipment within the available space vacated by the old absorption machines? Tese were not easy questions to resolve but, intuitively, provided hope.
Further building surveys indicated that the existing 480 volt electric switchboards in basement had available physical and electrical spare capacity sufficient to serve the new power needs.
switchgear room up to the 21st floor, and that sufficient storage space was available to expand the existing chiller- heater room if necessary.
Tis early hope seemed to be convertible into sure promise of better design and construction strategy, as it was generally acceptable to members of the project team. It was also determined that it was feasible to run new power risers from the basement
FINAL DESIGN AND CONSTRUCTION:
he three old gas absorption chiller-heaters were replaced (in three distinct contiguous phases), each with a bank assembly of eight (8) modular electric chillers served from spare existing 800 Amp bolted pressure switches in the existing switchgear in the basement. Power feeders were extended from each bolted pressure switch to the respective modular chiller bank on 21st floor. Each chiller bank assembly was accompanied by duplex gas-fired boilers for the replacement heating. All three equipment assemblies of modular chillers/duplex boilers were located in the same floor area previously occupied by the old gas absorption chiller-heaters. No additional space was required and all equipment was able to fit properly without undue congestion. Most equipment was purchased within North America.
MODULAR CHILLER DATA: Two 35 Ton, R-410a scroll compressors (with independent refrigerant circuits) and stainless steel plate heat exchangers, 16.8 EER, 0.54 KW/Ton NPLV; Physical size 28”W x 49”D x 69”H x 2200 lbs operating weight.
MODULAR BOILER DATA: 2640 MBH output, 88% efficiency, VFD forced draft burner, 1:3 turn down ratio; Physical size 39”W x 41”D x 85”H x 2400 lbs operating weight. Other Improvements: were
replaced with smaller orifice
Te existing cooling tower target nozzles nozzles to properly help distribute
the reduced condenser water flow required by the new chiller banks.
• Te old DDC panels and sensors for the existing HVAC control system were replaced with State of the Art System that utilizes the interoperable open BACnet protocol.
• Te triplex house booster pump system for domestic water was replaced with a new modern package system with VFD controls for each pump.
• All (12) primary hydronic pumps were replaced with new pumps due to age and to suit new system requirements.
• Te cooling tower chemical feed system and fine sidestream filters at the heating and cooling hydronic mains were replaced with new equipment with pipe corrosion monitoring hardware.
• An existing 3,000 Amp building lighting switchboard with old style circuit breakers (not removed during the 1980’s renovation) was replaced with new switchboard containing modern switch and fuse construction for better reliability.
Winter 2010-11 Illinois Engineer • 9
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