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<br /> <br /> <br /> <br /> <br />EXH Cit <br />Converting the Electric Rooftop Unit to Natural Gas Heat <br />y <br /> <br />IBI <br /> <br />H <br /> <br />a <br />T <br />Energy Calculations - Variable Frequency Drives Optimization <br />ll <br /> <br />BASELINE PROPOSED SAVINGS <br />HVACHRS <br />D <br /> <br /> <br />Ai <br />Proposed Proposed Proposed <br />SUPPLY O.A. Measured Baseline Affected Proposed Baseline Fan Energy Ventilation Cooling Fan Energy Ventilation Cooling Fan Energy Ventilation Ventilation Cooling <br /> <br />S.F. CFM O.A. CFM % Flow <br />AHU # AREA SERVED CFM CFM KW Hrs/Wk Hrs/Wk Hrs/Wk % Flow KWH kWh KWH KWH Therms KWH KWH Therms kWh KWH <br />r <br /> <br /> <br />Ha <br />AHU-7 Offices - Elec 14,000 3000 16.13 55.00 55 55 70% 14,000 3,000 70% 15,825 18,097 2,700 15,825 686 2,700 0 -686 18,097 0 <br /> <br />nd <br />15,825 686 2,700 15,825 18,097 2,700 0 -686 18,097 0 <br />TOTAL <br /> <br />l <br /> <br />er <br />Assumptions <br /> <br />R <br />ep <br />lacemen <br />UT <br />F <br /> <br />I <br />L <br />AC <br />VARIABLES CALCULATIONS <br />I <br />See Table Above ...PRESENT HRS/WK OF SYSTEM OPERATION (HVACHRS) <br />T <br />PROPOSED O.A. CFM <br />t <br />0 ...HRS/WK OF SCHEDULED FOR WARMUP/COOLDOWN (WUCD) <br />Fan Law #2: S.P.n/S.P.o = (CFMn/CFMo)^2 <br />Y <br />: <br />IL <br /> <br />52 ...WKS/YR OF AIR SYSTEM OPERATION (WPY) <br />therfore: CFMn = CFMo * SQRT(S.P.n/S.P.o) <br /> <br />See Table Above …Measured KW / Data Logger KW (FANKW) <br />PROPOSED KW <br />SA <br />I <br />T <br />...ELECTRICITY UNIT ($) COST/KWHR (ELECCOST) Fan Law #3 BHPn/BHPo = (CFMn/CFMo)^3 (BHP is proportionate to KW); CFMn=CFMo * (S.P.n / S.P.o) <br />4977 ...HEATING HRS/YR FROM WEATHER DATA (HHPY) therfore: (CFMn/CFMo)^3 = KWn/Kwo <br />Y <br />V <br />See Table Above ...TOTAL SUPPLY FAN CFM (CFM) <br />FAN ENERGY (KWH/YR.) <br /> <br />See Table Above …TOTAL OA CFM (OACFM) <br />Basseline = (WINTER KW * HVACHRS * (HHPY/168)) + (SUMMER KW * HVACHRS * (52-(HHPY/168))) O <br />I <br />N <br />62 ...UNOCCUPIED HRS. SPACE HEATING SETPOINT (HTSPUNOC) <br />Proposed = (PROPOSED WINTER KW * HVACHRS * (HHPY/168)) + (PROPOSED SUMMER KW * HVACHRS * (52-(HHPY/168))) <br />P <br />27.9 ...AVERAGE O.A. TEMP. DURING HEATING SEASON (AVEDBT) <br />FAN ENERGY COST ($/YR.) <br />G <br />...$/BTU COST OF HEATING ENERGY (HEATCOST) <br />= FAN ENERGY * ELECCOST <br />ER <br />0.9 …BOILER EFFICIENCY (BTU) <br />VENTILATION (BTU/YR.) <br />S <br />1.4 …CHILLER EFFICIENCY IN KW/TON (KWTON) <br />Basseline = ((BIN-DELTA T-HRS) * OACFM * 1.08) + (0.4 * (BIN-DELTA T-HRS) * TOTAL-CFM * 1.08) EXH <br /> <br />AT <br />2462 ...COOLING HRS/YR FROM WEATHER DATA (CHPY) <br />Proposed = ((BIN-DELTA T-HRS) * PROPOSED OACFM * 1.08) + (0.4 * (BIN-DELTA T-HRS) * PROPOSED TOTAL-CFM * 1.08) <br />CA <br />14.7 ...COOLING WEEKS PER YEAR (CWPY) = (CHPY/168) <br />VENTILATION COST ($/YR.) <br />6.2 …COOLING ENTHALPY DELTA (ENTHALPY) <br />= VENTILATION COST * HEATCOST <br />I <br />55 …MIXED AIR TEMPERATURE SETPOINT (MAT) L <br />COOLING (KWH/YR.) <br />N <br />I <br /> <br />BI <br />Basseline = (HVACHRS * CWPY * OACFM * 4.5 * ENTHALPY / 12,000) * KWTON C <br />G <br />Proposed = (HVACHRS * CWPY * PROPOSED OACFM * 4.5 * ENTHALPY / 12,000) * KWTON <br />ULA <br />COOLING COST ($/YR.) T <br /> <br />= COOLING COST * ELECCOST <br />PA <br /> <br /> <br />D <br /> <br />T <br />RA <br />I <br />O <br />M <br />N <br /> E <br />ME <br />T <br />ER <br />T <br />HODS <br /> <br />& <br /> <br />S <br /> <br />Pa <br />g <br />e <br /> <br />10 <br /> <br />o <br />f <br /> <br />27 <br /> <br /> <br />