Hoshizaki M029-897 service manual Brazing, Evacuation and Recharge R-404A

2. Brazing

WARNING

•R-404A itself is not flammable at atmospheric pressure and temperatures up to 176°F (80°C).

•R-404A itself is not explosive or poisonous. However, when exposed to high temperatures (open flames), R-404A can be decomposed to form hydrofluoric acid and carbonyl fluoride both of which are hazardous.

•Do not use silver alloy or copper alloy containing arsenic.

1)Braze all fittings while purging with nitrogen gas flowing at a pressure of 3 to 4 PSIG. Note: Because the pipes in the evaporator case are specially coated to resist corrosion,

it is important to make connections outside the evaporator case when possible. If it is necessary to braze inside the evaporator case, use sandpaper to remove the coating from the brazing connections before unbrazing the components.

NOTICE

•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. Install the new drier with the arrow on the drier in the direction of the refrigerant flow.

•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-404A as a mixture with pressurized air for leak testing.

3.Evacuation and Recharge (R-404A)

1)Attach a vacuum pump to the system. Be sure to connect the charging hoses to both high and low-side refrigerant access valves.

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. Open the gauge manifold valves. 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 low-side valve and high-side valve on the gauge manifold.

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