Carrier 23XL Specifiche Scaricare il pdf (Pagina 48)

Standing Vacuum Test — When performing the stand-

ing vacuum test or machine dehydration, use a manometer

or a wet bulb indicator. Dial gages cannot indicate the small

amount of leakage acceptable during a short period of time.

1. Attach an absolute pressure manometer or wet bulb in-

dicator to the machine.

2. Evacuate the vessel using a vacuum pump or the pum-

pout unit (see Pumpout and Refrigerant Transfer Proce-

dures section on page 61) to the pressure level speciﬁed

by the EPA under 40 CFR Part 82.

3. Valve off the pump to hold the vacuum and record the

manometer or indicator reading.

4. a. If the leakage rate is less than 0.05 in. Hg (.17 kPa) in

24 hours, the machine is sufficiently tight.

b. If the leakage rate exceeds 0.05 in. Hg (.17 kPa) in 24

hours, repressurize the vessel and test for leaks. If re-

frigerant is available in the other vessel, pressurize by

following Steps2-10ofReturn Refrigerant To Nor-

mal Operating Conditions section, on page 63. If not,

use nitrogen and a refrigerant tracer. Raise the vessel

pressure in increments until the leak is detected. If

refrigerant is used, the maximum gas pressure is ap-

proximately 120 psig (827 kPa) [70 psig (483 kPa)] at

normal ambient temperature. If nitrogen is used,

limit the leak test pressure to 230 psig (1585 kPa)

maximum.

5. Repair leak, retest, and proceed with dehydration.

Machine Dehydration — Dehydration is recom-

mended if the machine has been open for a considerable pe-

riod of time, if the machine is known to contain moisture, or

if there has been a complete loss of machine holding charge

or refrigerant pressure.

Do not start or megohm test the compressor motor if the

machine is under dehydration vacuum. Insulation break-

down and severe damage may result.

Dehydration is readily accomplished at room tempera-

tures. Use of a cold trap (Fig. 35) may substantially reduce

the time required to complete the dehydration. The higher

the room temperature, the faster dehydration takes place. At

low room temperatures, a very deep vacuum is required for

boiling off any moisture. If low ambient temperatures are

involved, contact a qualiﬁed service representative for the

dehydration techniques required.

Perform dehydration as follows:

1. Connect a high capacity vacuum pump (5 cfm

[.002 m

/s] or larger is recommended) to the refrigerant

charging valve (Fig. 2A and 2B). Tubing from the pump

to the machine should be as short and as large a diameter

as possible to provide least resistance to gas ﬂow.

2. Use an absolute pressure manometer or a wet bulb vacuum

indicator to measure the vacuum. Open the shutoff valve

to the vacuum indicator only when taking a reading. Leave

the valve open for 3 minutes to allow the indicator vacuum

to equalize with the machine vacuum.

3. Open all isolation valves, if present, if the entire machine

is to be dehydrated.

4. With the machine ambient temperature at 60 F (15.6 C)

or higher, operate the vacuum pump until the manometer

reads 29.8 in. Hg (.7 kPa absolute), ref 30 in. bar, or a

vacuum indicator reads 35 F (1.7 C). Operate the pump

an additional 2 hours.

Do not apply greater vacuum than 29.82 in. Hg vac

(.4 kPa absolute) or go below 33 F (.56 C) on the wet

bulb vacuum indicator. At this temperature/pressure, iso-

lated pockets of moisture can turn into ice. The slow rate

of evaporation (sublimination) of ice at these low

temperatures/pressures greatly increases dehydration time.

5. Valve off the vacuum pump, stop the pump, and record

the instrument reading.

6. After a 2-hour wait, take another instrument reading. If

the reading has not changed, dehydration is complete. If

the reading indicates vacuum loss, repeat Steps 4 and 5.

7. If the reading continues to change after several attempts,

perform a leak test up to the maximum 230 psig (1585

kPa) pressure. Locate and repair the leak, and repeat de-

hydration.

Inspect Water Piping — Refer to piping diagrams pro-

vided in the certiﬁed drawings, and the piping instructions

in the 23XL Installation Instructions manual. Inspect the pip-

ing to the cooler and condenser. Be sure that ﬂow directions

are correct and that all piping speciﬁcations have been met.

Piping systems must be properly vented, with no stress on

water box nozzles and covers. Water ﬂows through the cooler

and condenser must meet job requirements. Measure the pres-

sure drop across cooler and across condenser.

Water must be within design limits, clean, and treated

to ensure proper machine performance and reduce the

potential of tubing damage due to corrosion, scaling, or

erosion. Carrier assumes no responsibility for chiller dam-

age resulting from untreated or improperly treated

water.

Check Optional Pumpout Compressor Water Pip-

ing —

If the optional storage tank and/or pumpout system

are installed, check to ensure the pumpout condenser water

has been piped in. Check for ﬁeld-supplied shutoff valves

and controls as speciﬁed in the job data. Check for refrig-

erant leaks on ﬁeld-installed piping. Refer to the Pumpout

and Refrigerant Transfer Procedures section on page 61.

Check Relief Devices — Be sure that relief devices

have been piped to the outdoors in compliance with the lat-

est edition of ANSI/ASHRAE Standard 15 and applicable

local safety codes. Piping connections must allow for access

to the valve mechanism for periodic inspection and leak

testing.

Fig. 35 — Dehydration Cold Trap

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