5.6. SR 10-04-2004 - Laserfiche WebLink

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. . . September], 2004 Mr. Jeffery A. Beahen Elk River Public Safety Building NRA Comm. No. 02-009 Page 3 In the Commercial/]ndustrial Custom Energy Analysis prepared by Minnegasco, Table 2 indicates the Natural Gas Summary for your building. This Table also indicates a much higher than normal usage for the 3/22/04 period. The reasons for this are unknown based on the information we have received to date. We are not sure where the balance ofthe usage readings indicated in the Table came from. The billings which you sent us do not indicate these readings. If we reduce the 3/22/04 value to a more normal amount of$2,300 as indicated in our estimates, the annual total for the building would be approximately $]4,436 which compares favorably to our estimate of $16,948. As you can see from Table A, the largest amount of gas (57%) is used by the Building Make-up Air Unit. This unit is used to supply outside (ventilation) air to the building heat pumps located throughout the building. The air is brought in from the outside and heated or cooled and ducted to the inlet of each heat pump. Based on the printouts that you sent us of the control system operational screens, it appears as though the discharge air setpoint on the unit is approximately 70oF. This means that the unit will heat the outside air with natural gas to 700F during the heating season. If heat pumps are operating in the cooling mode, the 700F discharge air may be higher than necessary. If heat pumps are in the heating mode, some of the space heating may be accomplished by the make-up air unit in lieu ofthe heat pump. We would recommend that air from the make-up air unit be discharged at approximately 600F in the heating season (outside air temperatures below 500F) and 750F in the cooling season (outside air temperatures above 500F). This should reduce the gas consumption of this unit. In addition, this unit is scheduled to operate twenty four hours per day to provide ventilation air to the building continuously. Ifthere are periods of time when the building is essential1y un-occupied, the unit could be cycled off. We were not aware that you had a problem with the heat exchanger on the Building Make-up Air Unit. This unit is designed to operate continuously. The specifications require that the unit have a one year warranty on materials and labor and a nine year extended warranty on the heat exchanger. We were concerned with the statement in your letter that said "the local (geo-thermal) provider has briefly looked at the system and their conclusions are that the pump brand/type and size are all wrong for how we intend to have the system heat and cool the building." The geo-thermal system is properly designed and matched to the building requirements. Any statement to the contrary is simply not tme. We believe that your systems are operating as intended and that the gas usage that you have experienced are in line with what we would expect based on the assumed operating profiles of the equipment. We have to keep in mind, when comparing this building to previous City Hal1 and Police Building, that this is a larger building with a significantly improved ventilation system that is currently operating twenty four hours per day. Modifications to system setpoints and operating profiles can help to reduce the costs, but this building wil1 continue to consume a significant amount of natural gas which is increasing in cost as natural gas prices continue to rise.