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Hersteller: Burnham Dateigröße: 6.84 mb Dateiname: Unterrichtssprache:

Refer to Burnham RTC Return Temperature Control Manual and Tekmar Essay #021 “Mixing Methods and Sizing of Variable Speed Injection Pumps” for more information on mixing devices and boiler protection from low return water temperature. 4. A hot water boiler installed above radiation level must be provided with a low water cutoff device as part of installation. 5. A start-up strainer is recommended for all installations (new and replacement alike) to prevent system debris and sediment from ending up in the boilers where it will inhibit heat transfer and may eventually cause a cast iron section to crack from overheating. G. Alliance SL™ Water Heater (if used). Refer to Alliance SL™ Installation, Operating and Service Instructions for additional information. Install in same manner as space heating zone. WARNING Burnham Commercial recommends maintaining temperature differential (drop) across the system at 40°F or less and return water temperature at minimum of 35°F. Continued boiler operation for prolonged periods of time under conditions when temperature differential acrossthesystemexceeds40°Fand/orreturnwatertemperaturestaysbelow 35°F,mayresultinpremature boiler failure due to flue gas condensation and/or thermal shock. If the above conditions exist, to protect a boiler from sustained flue gas condensation and/or thermal shock,theabove-recommendedtemperaturesmaybemaintainedbyemployingcommonindustry-accepted mixing methods to provide boiler protection. Some common methods are boiler by-pass piping, blend pumps, primary secondary piping with a bypass, mixing valves and/or variable speed injection pumps. V. Gas Piping WARNING Failure to properly pipe gas supply to boiler may result in improper operation and damage to the boiler or structure. Always assure gas piping is absolutely leak free and of the proper size and type for the connected load. An additional gas pressure regulator may be needed. Consult gas supplier. A. Size gas Piping. Design system to provide adequate gas supply to boiler. Consider these factors: 1. Allowable pressure drop from point of delivery to boiler. Maximum allowable system pressure is . psig. Actual point of delivery pressure may be less; contact gas supplier for additional information. Minimum allowable gas valve inlet pressure is indicated on rating label. 2. Maximum gas demand. Table 5 lists boiler input rate. Also consider existing and expected future gas utilization equipment (i.e. water heater, cooking equipment). 3. Length of piping and number of fittings. Refer to Table 6 for maximum capacity of Schedule 40 pipe. Table 7 lists equivalent length for standard fittings. Table 5: Rated Input Boiler Model Rated Capacity (cubic feet per hour) Gas Connection SizeNatural LP / Propane 805H 252 100.8 1 806H 315 126 1 807H 374 149.6 1 808H 433 173.2 1 809H 491 196.4 1 810H 550 220 1 4. Specific gravity of gas. Gas piping systems for gas with a specific gravity of 0.70 or less can be sized directly from Table 6, unless authority having jurisdiction specifies a gravity factor be applied. For specific gravity greater than 0.70, apply gravity factor from Table 8. If exact specific gravity is not shown choose next higher value. For materials or conditions other than those listed above, refer to the National Fuel Gas Code, NFPA 54/ANSI Z223.1 and/or CAN/CSA B149.1 Installation Codes, or size system using standard engineering methods acceptable to authority having jurisdiction. WARNING Failure to use proper thread compounds on all gas connectors may result in leaks of flammable gas. WARNING Gas supply to boiler and system must be absolutely shut off prior to installing or servicing boiler gas piping. B. Connect boiler gas valve to gas supply system. 1. Use methods and materials in accordance with local plumbing codes and requirements of gas supplier. In absence of such requirements, follow the National Fuel Gas Code, NFPA 54/ANSI Z223.1 and/or CAN/CSA B149.1 Installation Codes. 2. Use thread (joint) compound (pipe dope) resistant to action of liquefied petroleum gas. 3. Install sediment trap, ground-joint union and manual shut-off valve upstream of boiler gas valve and outside jacket. See Figure 24. 4. All above ground gas piping upstream from manual gas valve must be electrically continuous and bonded to a grounding electrode. Do not use gas piping as a grounding electrode. Refer to the National Electrical Code, ANSI/NFPA 70 and/or CSA C22.1 Electrical Code. NOTICE USA boilers built for installation at altitudes greater than 2,000 feet above sea level have been specially orificed to reduce gas input rate 4 percent per 1,000 feet above sea level per the National Fuel Gas Code, NFPA 54/ANSI Z223.1, Section 8.1.2 and Appendix F. Canadian boilers’ orifice sizing is indicated on the rating label. High altitude boiler models are identifiable by the model number’s tenth digit on the rating label. (4=2000’ - 4500’, 5= 2000’ - 5000’) 2 Table 6: Maximum Capacity of Schedule 40 Pipe in CFH for Gas Pressure...

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