Assessments - 3, GPA: 4.3 ( )

Fabricante : Bradford-White Corp Arquivo Tamanho: 1.23 mb Arquivo Nome : Língua de Ensino:

If the protector switch should shut off unit, check the following conditions: • No water in boiler. • Restricted water flow through the boiler. • Improper wiring (boiler firing without circulator operating). • Pump failure. After correcting failure condition remove the protector switch cover and push the reset button. The protector switch may be reset after the coil surface temperature cools to .6°C (1°F). 52 5252525252 PROTECTOR SWITCH FIGURE 48 PRESSURE REDUCING VALVE The screen in the pressure reducing valve may require occasional cleaning due to foreign material in the water supply. This will restrict the flow and could reduce the effectiveness of purging and prolong filling time. To inspect the screen, close the main water supply valve ahead of the pressure reducing valve and remove the screen for cleaning, see fig’s. 1 and 2. SAFETY FLOW SWITCH For proper performance mount the switch in a section of pipe where there is a straight run of at least 5 pipe diameters on each side of the flow switch (i.e. do not locate adjacent to valves, elbows, orifices, etc.). The flow switch shall be mounted in a standard 1-1/2" x 1-1/2" x 1" tee for a 1-1/2" pipe application. For larger pipe sizes use a reducing tee in order to keep the switch as close to the pipe as possible. Install the flow switch in the branch (top) opening of the reducing tee and provide adequate paddle length in the flow stream. For example in a 2" pipe installation use a 2" x 2" x 1" reducing tee. For 2", or 3" pipe use paddle segments as supplied. For other pipe sizes (i.e. 1-1/4", 1-1/2" and 2-1/2") trim the paddle to the proper pipe size, see fig. 49. If a standard tee is used, install a face or hex bushing in the top opening. The paddle must be adjusted or trimmed to the size of the pipe in which it will be installed. CAUTION Any part of the paddle must not touch the pipe or any restrictions in the pipe. Screw the flow switch in position so the flat of the paddle is at right angles to the flow. The arrow on the side case must point in the direction of the flow. TABLE 11 - SAFETY FLOW SWITCH The safety flow switch is a safety device which must be installed at the water outlet of the unit to prevent main burner operation in the event of inadequate water flow through the unit, see fig’s. 10 through 12 and 17 through 27. An accessory package A. O. Smith No. 211480 containing a safety flow switch is available for this application. This switch may be mounted in a horizontal pipe line or a vertical pipe line with upward water flow. Do not install the switch where The safety flow switch may be field adjusted to obtain higherthe water flow is downward. minimum flow rates than those shown in table 11. Minimum Pipe RateModelNumber Contacts Closed (Flow) Contacts Open (No Flow) GPM LPS GPM LPS HWB/HW-300 5.8 0.36 3.7 0.23 HWB/HW-399 7.5 0.47 5.0 0.31 HWB/HW-420 7.5 0.47 5.0 0.31 HWB/HW-520 13.7 0.86 9.5 0.60 HWB/HW-610/670 13.7 0.86 9.5 0.60 CAUTION Paddle must be trimmed at the dotted arc. It must not touch the pipe or have any restriction when installed FIGURE 49 53 5353535353 To adjust the flow rate setting: 1. Remove the flow switch cover. 2. For higher flow rate—turn the range adjusting screw clockwise. 3. For lower flow rate—turn the range adjusting screw counter-clockwise. CAUTION The switch is factory set at approximately the minimum flow rate, see Table II. It must not be set lower than the factory setting as this may result in the switch failing to return at a “no flow” condition. 4. Replace the flow switch cover. Where units are installed in multiples, each boiler must be individually protected by a safety flow switch. SAFETY RELIEF VALVE MAINTENANCE Every six months the system safety relief valves should be checked to ensure that they are in operating condition. To check a relief valve, lift the lever at the end of the valve several times. The valve should seat properly and operate freely. CAUTION BEFORE MANUALLY OPERATING A RELIEF VALVE, MAKE SURE THAT A DRAIN LINE HAS BEEN ATTACHED TO THE VALVE TO DIRECT THE DISCHARGE TO AN OPEN DRAIN. FAILURE TO TAKE THIS PRECAUTION COULD MEAN CONTACT WITH EXTREMELY HOT WATER EXITING THE VALVE DURING THIS CHECK OPERATION. If a relief valve discharges periodically or continuously, it may be due to thermal expansion of water in a closed water supply system, or, it may be due to thermal expansion of water in a closed water supply system, or, it may be due to a faulty relief valve. Thermal expansion is the normal response of water when it is heated. In a closed system, thermal expansion will cause the system pressure to build until the relief valve actuation pressure is equaled. Then, the relief valve will open, allowing some water to escape, slightly lowering the pressure. A properly sized expansion tank should be installed. ABOVE ALL, DO NOT PLUG ANY RELIEF VALVE. THIS IS NOT A SOLUTION AND CAN CREATE A HAZARDOUS SITUATION. REPLACEMENT PARTS U.S. Models Replacement parts may be ordered through A. O. Smith d...

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