söndag 19 oktober 2014

4.2 Measure 2:

4.2 Measure 2: Type I Exhaust Hood Airflow Limitations Equipment and electrical costs of each case were compared. Only the hoods, exhaust fans, and makeup fans were used. Similar comparisons could include differences in duct sizes, diffuser size and counts, and the conditioning energy. As these additional comparisons would reveal the same differences as the values used, they were not included. Table 4below compares the equipment costs between an exhaust and makeup air system using an unlisted hood versus a listed hood. The unlisted 10’ canopy wall hood for heavy duty used requires an exhaust rate of 550 cfm per linear foot of the leading edge of the hood. A similar listed hood requires an exhaust rate of 385 cfm per linear foot. The hood costs per the vendor we consulted are the same. The explanation for this is that the hoods have similar amounts of sheet metal and require similar amounts of labor to construct. The only difference between them is the vendor’s expense to test their hood designs for listing. It was explained that most cataloged commercial hoods are listed which creates cost competition so there is no economic benefit to pursue an unlisted hood. The exhaust fans and makeup air fans cost data reflect fans sized for the specific hood cfm. In the scenario developed, there is a $5,676 difference in the equipment. Table 5 below compares the power and electrical costs to exhaust and makeup the different air rates. The electrical costs assumed 5,400 hours of operation a year and an average electrical rate of $0.15 per kilowatt-hour. The annual electrical cost difference between the systems is $1,523. The data shows that listed hoods cost the same as unlisted hoods but the fans cost more for system with the higher exhaust rate. Subsequent, the energy costs are also more for the system with the higher exhaust rate.

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