Sea Frost BG 2000 - Manual (Page 24)

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3. The sight glass will show a stream of foam indicating a partial charge.
4. Introduce liquid refrigerant (liquid is supplied by keeping the cylinder inverted) at
a controlled pressure regulated by slightly opening the blue hand wheel valve.
Keep the low side pressure no more than 15 PSIG above the indicated operating
pressure. Add refrigerant for 30 seconds then turn off the supply and observe
the sight glass and cooling operation for 2 minutes before adding refrigerant the
same way again. Repeat this filling and observing. At the time the return line
frosts the sight glass should be clearing. Let the system operate for 30 minutes
with a mostly clear glass before adding a small shot for good measure (4 oz).
Do not exceed the 24 oz maximum charge amount regardless of the sight glass
reading. Compare pressures with the pressure trends page 32. When a
sufficient amount of refrigerant has been added to the system (A new system
holds 24 oz. maximum) the sight glass will clear, indicating sufficient charge.
When charging a hot system, (cabinet and plates over 80 degrees F) the sight
glass will usually clear as the return line at the valve becomes frosted.
5. When observation and test operation have been completed, disconnect the
gauges. Replace the service port caps.
6. Re-check all connection points for leaks.
7. Spray the acrylic coating, or similar rust inhibitor, on all the components and
fittings while they are clean and dry.
READING THE SIGHT GLASS
A clear sight glass when the compressor is operating signifies a sufficiently charged
SEA FROST BG 2000 System. To determine the meaning of "clear", notice the
appearance of the RFD sight glass when the system is at rest with the compressor off.
This is a "clear" glass.
SPECIAL WARNING: A clear sight glass can also indicate a completely EMPTY
system. Any time the compressor is started, a white stream of foam should
appear in the sight glass indicating that refrigerant is present. This foam may
disappear quite quickly, but IF NO FOAM IS EVIDENT, the system is empty. DO
NOT OPERATE THE SYSTEM if empty. Operation in this mode will ruin the
compressor. Turn off the main breaker to prevent operation until system can be
properly leak tested and recharged.