1、DAEN-ECE-E Engineer Technical Letter 1110-3-373 3515789 0023695 358 W U.S. Army Corps of Engineers Washington, D.C. 20314-1000 DEPARTMENT OF THE ARMY (R-47-0 I ETL 1110-3-373 20 February 1987 Engineering and Design HEAT DISTRIBUTION SYSTEMS OUTSIDE OF BUILDINGS 1. Purpose. This letter updates criter
2、ia for heat distribution systems. 2. Applicability. This letter applies to all HQUSACE/OCE elements and field operating activities (FOA) having military construction design responsibility. 3. Background. The Office of the Secretary of Defense (OSD) has revised the policy for the selection and design
3、 of underground heat distribution systems (UGHDS). Now, OSD allows the selection of the type of UGHDS to be based on life-cycle cost. In order to clarify these requirements, this letter indicates the appropriate guide specifications and updates the procedures for project and design managers in the s
4、election of and basis for the design of central heat distribution systems. It also requires a life-cycle cost analysis (LCCA) to be used to make the selection of aboveground, shallow concrete trench, and direct buried conduit distribution systems based on the optimum routing for each. 4. Design Guid
5、ance. the guide specifications which apply are as follows: a. Criteria. The three basic types of systems to be considered and (1) Aboveground, high or low profile systems. CEGS-15711, Aboveground Heat Distribution Systems. (2) Shallow concrete trench systems. CEGS-15709, Heat Distribution Systems Ou
6、tside of Buildings Concrete Shallow Trench Systems. (3) Direct Buried Conduit Systems. (a) Chilled water, low temperature water, and dual temperature systems. CEGS-15704, Underground (Chilled Water) (and) (Low Temperature Hot Water) (Dual Temperature) Distribution Systems. Provided by IHSNot for Res
7、aleNo reproduction or networking permitted without license from IHS-,-,-m 3515789 0023bb 2Y m ETL 1110-3-373 20 Feb 87 (b) Medium and high temperature systems. CEGS-15705, Underground (Heat Distribution System) (and) (Condensate Return System) (Prefabricated or Pre-Engineered Types). b. Procedure. (
8、1) Results of an auditable LCCA shall be used to determine system selection. All systems with site criteria compatible with project site characteristics shall be included in the LCCA. (2) System selection. For each type of system to be considered, select the system design parameters (e.g., temperatu
9、re, aboveground or underground, etc.) that will provide the lowest life-cycle cost and that will satisfy end use conditions. Comparative life-cycle cost analysis for different systems shall be based on optimum user-acceptable routing for each type of system. (3) Route selection. System configuration
10、 shall be coordinated with the facility master plan. The route selected has considerable impact on system selection. Often, the type of system will be determined by the available route, i-e., aboveground systems are generally not acceptable if they will create obstructions to traffic or are unsightl
11、y. Shallow concrete trench systems may not be an alternative if the concrete covers are unacceptable, for example, across a parade ground. Large numbers of obstructions along the system profile will greatly increase the cost of underground systems. However, previous studies indicate that for smaller
12、 pipe sizes, the direct buried conduit system has a lower life-cycle cost than shallow concrete trench systems. Attention should be given to unusually severe or complex installation conditions which adversely impact the life-cycle cost advantage of any system. (4) Site surveys. For underground syste
13、ms, a site survey and soil borings, in accordance with the criteria contained in the specifications referenced in paragraph 3 above, is required to determine soil types, soil resistivity, ground water conditions, and the location of obstructions along the proposed route of the new system, as appropr
14、iate. This information is required to determine the applicability of shallow concrete trench and direct buried conduit type system, to establish the site classification for medium and high temperature direct buried conduit systems, and to develop accurate plans and specifications. Class A site condi
15、tions shall not be assumed. The requirement for Class A system in Classes BI Cl and D sites do not improve system performance but may increase initial construction cost unnecessarily. Extensive obstructions may require re-evaluation of the selected route. Soil resistivity will determine the requirem
16、ent for cathodic protection. (5) Design. (a) When aboveground, shallow concrete trench, or chilled waterllow temperatureldual temperature systems are selected, the design agent will 2603 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-m 3535789 0023b
17、97 120 m provide complete plans and specifications. materials and system requirements included in CEGS-15711. (1) Aboveground high or low profile systems. Base the design on the (2) Shallow concrete trench systems. Base the design on the materials and system requirements included in CEGS-15709. (3)
18、Underground chilled water, low temperature hot water, and dual temperature distribution systems. Base the design on the materials and system requirements included in CEGS-15704. (b) When underground medium and high temperature direct buried, prefabricated conduit systems (including condensate return
19、s) are the design agent will provide general routing, pipe size, profiles, allowable heat loss, locations and design of manholes, known underground obstructions, and easements for a distance of 25 feet on each side of the proposed system centerline, as required in CEGS-15705. The system supplier wil
20、l provide the design details of the conduit system between manholes; between manholes and building walls, including system wall penetrations, and expansion compensation as described in the approved product brochure. (i) Fiberglass reinforced plastic (FRP) condensate systems. Prefabricated insulated
21、FRP condensate return systems are included in approved manufacturers brochures. This product may be specified at the users option in Class A sites, as defined in CEGS-15705. The system shall be a contractors option in sites identified as Class BI C, or D. (2) Because experience indicates that conden
22、sate lines fail at a greater rate than do the steam lines, condensate lines shall not be installed within the same conduit as the steam line. (c) Modifications to guide specifications shall be only made when techncially required. Modifications shall be those which meet the technical requirement at t
23、he lowest life-cycle cost. c. Life-cycle cost analysis. (i) Preparation of the contracting documents will be accomplished using the “Invitation for Bid“ format with fixed price and work scope. The project designerlmanager will make the determination on the type of distribution system to be used, in
24、accordance with the criteria stated in paragraph 3 above, and the results of an audiable life-cycle cost analysis. The LCCA shall be conducted in strict compliance with the economic studies criteria and standards established by the appropriate military service, i.e. ETL 1110-3-332, Economic Studies,
25、 for Army projects and Air Force Regulation (AFR) 88-15, Criteria and Standards for Air Force Construction, for Air Force projects. (2) The designer shall perform a comprehensive engineering analysis to determine the functional life and maintenance requirements of the system under consideration. Thi
26、s analysis shall be a part of the LCCA and all data including historical references, engineering 2604 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-3515789 0023b98 Ob7 calculations, etc., shall be clearly and completely documented. The analysis sha
27、ll be made a part of the design documentation and included in the project file. This file is subject to public review at bid opening. (3) All system types should have a minimum life of 25 years when properly installed and maintained; therefore, the end point of the analysis period shall be 25 years
28、after the projected beneficial occupancy date (BOD) for the project. A 25-year life expectancy for direct buried conduit system is based on tests required for system approval. Documentation shall be included in the design analysis to justify a system life other than 25 years. (4) When comparing syst
29、ems, the designer shall use the same total heat loss for each system. Insulation thickness for each system shall be selected to achieve the required heat loss. These thicknesses shall be used in the operating and capital cost components of the LCCA. (5) If using a computer aided LCCA, only those com
30、puter programs certified by the headquarters of the appropriate military service, as being in strict compliance with the economic studies criteria and standards stated above, shall be used in the LCCA. The life-cycle-cost-in design (LCCID) program developed by the U.S. Army .Construction Engineering
31、 Laboratory (CERL) is acceptable to all services. This program is available through CERLs agent, the BLAST Support Office, University of Illinois, Champaign, Illinois, 61801 telephone (217) 333-3977. 5. Action to be Taken. The above guidance is effective immediately for projects that have not reache
32、d design completion of 35 percent and for projects with design initiated after the date of issuance of this ETL. Any project beyond design completion of 35 percent may be modified at the designers option to use these criteria. 6. Implemenation. This letter will have routine application as defined in paragraph 6c, ER 1110-345-100. FOR THE COMMANDER: WILLIAM N. McCORMICK, JR. Chief, Engineering Division Directorate of Engineering and Construct ion 2605 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
