Assessments - 5, GPA: 4.2
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26 2. Brazing WARNING 1. R-134a itself is not flammable at atmospheric pressure and temperatures up to 212°F (100°C). 2. R-134a itself is not explosive or poisonous. However, when exposed to high temperatures (open flames), R-134a can be decomposed to form hydrofluoric acid and carbonyl fluoride both of which are hazardous. 3. Do not use silver alloy or copper alloy containing arsenic. 4. Use an electronic leak detector or soap bubbles to check for leaks. Add a trace of refrigerant to the system (if using an electronic leak detector), and then raise the pressure using nitrogen gas (140 PSIG). DO NOT use R-134a as a mixture with pressurized air for leak testing. 1) Braze all fittings while purging with nitrogen gas flowing at a pressure of 3 to 4 PSIG. CAUTION 1. Always install a new drier every time the sealed refrigeration system is opened. Do not replace the drier until after all other repair or replacement has been made. 2. When brazing, protect the drier by using a wet cloth to prevent the drier from overheating. Do not allow the drier to exceed 250°F (121°C). 2) Use an electronic leak detector or soap bubbles to check for leaks. Add a trace of refrigerant to the system (if using an electronic leak detector), and then raise the pressure using nitrogen gas (140 PSIG). DO NOT use R-134a as a mixture with pressurized air for leak testing. 3. Evacuation and Recharge (R-134a) 1) Attach a vacuum pump to the system. Be sure the high-side charging hose is connected to the field-installed high-side access valve. IMPORTANT The vacuum level and vacuum pump may be the same as those for current refrigerants. However, the rubber hose and gauge manifold to be used for evacuation and refrigerant charge should be exclusively for POE oils. 2) Turn on the vacuum pump, then open the high-side valve on the gauge manifold. Never allow the oil in the vacuum pump to flow backwards. 3) Allow the vacuum pump to pull down to a 29.9" Hg vacuum. Evacuating period depends on pump capacity. 4) Close the high-side valve on the gauge manifold. 5) Disconnect the gauge manifold hose from the vacuum pump and attach it to a refrigerant service cylinder. Remember to loosen the connection and purge the air from the hose. See the nameplate for the required refrigerant charge. Hoshizaki recommends only virgin refrigerant or reclaimed refrigerant which meets the requirements of ARI Standard 700 (latest edition) be used. 27 6) A liquid charge is recommended when charging an R-134a system. Place the service cylinder on the scales; if the service cylinder is not equipped with a dip tube, invert the service cylinder, then place it on the scales. Open the high-side valve on the gauge manifold. 7) Allow the system to charge with liquid until the proper charge weight is met. 8) Close the high-side valve on the gauge manifold, then close the refrigerant access valve (if applicable). Disconnect the gauge manifold hose. 9) Cap the access valve to prevent a possible leak. B. Removal and Replacement of Compressor CAUTION 1. Always install a new drier every time the sealed refrigeration system is opened. Do not replace the drier until after all other repair or replacement has been made. 2. When brazing, protect the drier by using a wet cloth to prevent the drier from overheating. Do not allow the drier to exceed 250°F (121°C). Note: Hoshizaki recommends that compressor starting components be replaced at the same time as the compressor. Due to the ability of the POE oil in the compressor to absorb moisture quickly, the compressor must not be opened more than 15 minutes for replacement or service. 1) Move the power switch to the "OFF" position, then unplug the unit from the electrical outlet. 2) Remove the upper and lower rear panels, front panel, and louver. See Fig. 1. Remove the screws securing the control box, then gently move the box out of the way. 3) Install a temporary tap-line valve on the high side, then recover the refrigerant and store it in an approved container. 4) Remove the terminal cover on the compressor and disconnect the compressor wiring. 5) Remove the discharge and suction pipes. 6) Remove the hold-down bolts, washers, and rubber grommets. 7) Remove the compressor. 8) Attach the rubber grommets of the prior compressor to the new compressor. 9) Place the compressor in position and secure it using the bolts and washers. 10) Replace the tap-line valve with a proper, permanent access valve. 11) Remove the drier, then place the new drier in position. 12) Remove the plugs from the suction, discharge, and process pipes. 13) Braze all fittings while purging with nitrogen gas flowing at a pressure of 3 to 4 PSIG. 14) Use an electronic leak detector or soap bubbles to check for leaks. Add a trace of refrigerant to the system (if using an electronic leak detector), and then raise the pressure using nitrogen gas (140 PSIG). DO NOT use R-134a as a mixture with pressurized air for leak testing. 28 15) Evacuate the system, then charge it with refrigera...
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