AE Senior Thesis on Mechanical System Redesign: Applying Chilled Water VAV and DOAS HVAC system to the Medical Office Building at Johns Hopkins Hospital in Baltimore, MD
Presentation Outline • Introduction of Building and Thesis – Current HVAC Equipment • HVAC Equipment Selection – Alternative #1, Chilled Water VAV w/ Hot Water Reheat – Alternative #2, DOAS w/ active chilled/heated beams – Parallel System Selection – Enthalpy Wheel Selection • IAQ Comparison • Economic Analysis • Breadth #1, Electrical Distribution Redesign • Breadth #2, Constructability Review • Thesis Conclusion
Building Introduction • New Medical Office Building for JHH Introduction Exist HVAC • Area of 88,000 sq ft Alt #1 VAV • Approximate cost of 15.5 million dollars Alt #2 DOAS Parallel Sys • Four floors, one below grade, three above E-Wheel • Stratified Use IAQ Comp – Basement and First Floor contain examination Economic rooms as well as phlebotomy, radiation, Breadth #1 dialysis etc. Breadth #2 Conclusions – Second and Third Floor contain mostly JHH staff offices and conference rooms. Questions
Building Location
Existing HVAC Equipment • Six rooftop DX packaged units Introduction Exist HVAC – 21,000cfm each at 10% OA Alt #1 VAV – 61 Tons of cooling each Alt #2 DOAS – Ducted together in third floor plenum to serve Parallel Sys entire building E-Wheel • Heating by terminal electric reheat VAV IAQ Comp boxes Economic Breadth #1 – 118 fan power boxes with reheating capability Breadth #2 • One 7.5 Ton FCU & ACCU Conclusions – Serves the elevator mechanical room Questions – Not considered for change in redesign
Alternative #1 VAV system with six rooftop AHUs Introduction • Chilled water used for cooling Exist HVAC – Generated at the South of Orleans Energy Plant Alt #1 VAV – Supply temperature of 38F Alt #2 DOAS – Cost of $10.33 per MMBTU Parallel Sys E-Wheel • Hot water used for terminal reheat IAQ Comp – Steam generated at the South of Orleans Energy Economic Plant Breadth #1 – Cost of $1.08 per therm Breadth #2 Conclusions Questions
Alternative #2 DOAS with three rooftop AHU s Introduction • AHU Differences Exist HVAC – 19,000cfm per unit max Alt #1 VAV – 86 Tons of cooling each Alt #2 DOAS – Temp of SA is 45 F Parallel Sys E-Wheel • Chilled water used for cooling IAQ Comp • AHUs paired with Enthalpy Wheel Economic – Lessens impact of treating all outdoor air Breadth #1 Breadth #2 • Heating and supplementary cooling Conclusions accomplished through parallel system . Questions
Trox Active Beam Section
Parallel System • Active heated and chilled beams Introduction Exist HVAC – Induces room air through a hydronic coil with high Alt #1 VAV velocity supply air within the unit Alt #2 DOAS – Mounted Flush to acoustical ceiling Parallel Sys – Four pipe system allows for heating and cooling E-Wheel • Hot water (150F) supplied from steam to water IAQ Comp HTX in lower level mechanical room Economic Breadth #1 • Cold water (60F) tapped from AHU return line Breadth #2 (52F) and mixed to proper temp. Conclusions Questions
Enthalpy Wheel • DOAS needs heat recovery/rejection device Introduction due to high volumes of OA treated Exist HVAC Alt #1 VAV • Enthalpy Wheel Modeled on Alt #2 DOAS Semco TE3-43 (Total Energy, 43”) Parallel Sys E-Wheel • 80% transfer efficiency for latent and sensible IAQ Comp energy Economic • No measured cross contamination for Breadth #1 Breadth #2 common pollutants (Georgia Tech Research Institute) Conclusions • Able to treat OA to within 2 degrees of Mixed Questions air in standard system
IAQ Comparison • MOB host to many ill patients Introduction Exist HVAC • Many spaces purposely over-ventilated Alt #1 VAV – Waiting rooms Alt #2 DOAS – Examination rooms Parallel Sys E-Wheel • Graphs of CO2 in two sample rooms IAQ Comp – Generation rate of .31 l/s Economic – VAV system at 10% OA Breadth #1 – DOAS at 100% OA Breadth #2 Conclusions Questions
CO 2 Levels in Office 3037
CO 2 Levels in Conference 3080
Economic Analysis • First Cost Introduction Exist HVAC – RS Means used for all equipment Alt #1 VAV – Parallel system priced from similar English units Alt #2 DOAS • Operating Cost Parallel Sys – HAP generated the costs for the Existing System E-Wheel and Alternative #1 IAQ Comp Economic – Alternative #2 was scaled from Alternative #1 by Breadth #1 comparing the amount of fan, pump and chilled Breadth #2 water energy used annually Conclusions Questions
Economic Analysis • Operating Cost • First Cost Introduction – Existing System Exist HVAC – Existing System Alt #1 VAV • $165,509 • $353,460 Alt #2 DOAS – VAV w/ chilled water – VAV w/ chilled water Parallel Sys • $130,004 (-35,500) • $519,881 (+166,000) E-Wheel – DOAS w/ parallel – DOAS w/ parallel IAQ Comp system system Economic • $106,603 (-58,900) • $560,514 (+207,000) Breadth #1 Breadth #2 Conclusions Questions
Payback Period Analysis • Alternative #1 vs. Existing System Introduction Exist HVAC – 4.7 years Alt #1 VAV • Alternative #2 vs. Existing System Alt #2 DOAS Parallel Sys – 3.5 years E-Wheel • Alternative #2 vs. Alternative #1 IAQ Comp – 1.7 years Economic Breadth #1 Breadth #2 Conclusions Questions
Breadth #1 Electrical Distribution System Redesign • Changing away from all electric HVAC Introduction Exist HVAC • Existing Equipment Alt #1 VAV – Two 800Amp panel boards serve the six AHUs Alt #2 DOAS – Seven 225 Amp panel boards are dedicated to the Parallel Sys fan powered VAV boxes E-Wheel • DOAS w/ Parallel System IAQ Comp Economic – Supported equipment lowered to three water Breadth #1 pumps and a three AHU fans Breadth #2 – Require only two 100 Amp panel boards Conclusions • Cost savings of $21,860 Questions
Breadth #2 Constructability Review • Chilled Water and Steam Piping Introduction Constructability Exist HVAC Alt #1 VAV – Connection of the MOB to the South of Orleans Alt #2 DOAS Energy Plant Parallel Sys – Feasibility E-Wheel – Location of piping IAQ Comp – Impact on Construction Economic Breadth #1 Breadth #2 Conclusions Questions
MOB Block Layout
Pipe Location Options • Option one, Buried Piping Introduction Exist HVAC – Formerly vacant block facilitates installation Alt #1 VAV – Will not impact construction of loading dock Alt #2 DOAS • Option two, Above Ground Piping Parallel Sys Recommended E-Wheel IAQ Comp – No conflict with existing buried utilities Economic – Piping is accessible Breadth #1 – Installation cost may be lower without excavation Breadth #2 Conclusions Questions
Schedule Impact of Piping • Minimal schedule impact for the following Introduction reasons Exist HVAC Alt #1 VAV – Easy to coordinate construction since the whole Alt #2 DOAS was block planned as one extension of the JHH Parallel Sys campus E-Wheel – Source of Chilled Water and Steam is very close IAQ Comp to the MOB Economic – Structure between the Energy Plant and the MOB Breadth #1 is very utilitarian Breadth #2 Conclusions Questions
Thesis Conclusions • Alternative #1 Chilled water VAV w/ hot water Introduction reheat Exist HVAC Alt #1 VAV – Initially more expensive but lower operating cost Alt #2 DOAS yields a pay back period of only 4.7 years Parallel Sys – Can use same number and layout for AHUs and E-Wheel VAV boxes IAQ Comp Economic Breadth #1 Breadth #2 Conclusions Questions
Thesis Conclusions • Alternative #2 DOAS with parallel system Introduction Exist HVAC – Highest first cost but lowest operating cost of all Alt #1 VAV systems considered, yields a pay back period of Alt #2 DOAS 3.5 years Parallel Sys – Uses only three AHUs E-Wheel – Paired with enthalpy wheel and parallel system IAQ Comp – Capable of significantly improving IAQ Economic Breadth #1 Breadth #2 Conclusions Questions
Thesis Conclusions • Enthalpy Wheel Introduction Exist HVAC – Lowers overall cooling need dramatically Alt #1 VAV – No risk of cross contamination Alt #2 DOAS • Parallel System Parallel Sys E-Wheel – Active heated and chilled beams IAQ Comp – Can either heat or cool a space Economic • Electrical System Redesign Breadth #1 – With deletion of all electrical HVAC equipment Breadth #2 panel boards drop from nine to two in number Conclusions Questions – Cost savings of $21,860 in equipment
Thesis Conclusions • Constructability Review of steam and chilled Introduction water piping from the energy plant to the MOB Exist HVAC Alt #1 VAV – Minimal schedule impact Alt #2 DOAS – Two easily constructed options Parallel Sys – Block development facilitates coordination with E-Wheel surrounding buildings IAQ Comp Economic Breadth #1 Breadth #2 Conclusions Questions
Questions
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