Freon™ MO99
Refrigerant (R-438A)

Retrofit Guidelines
Introduction
Freon™ MO99 refrigerant has proven to be a reliable andcost-effective, non-ozone depleting retrofit refrigerant. In
many cases, systems converted to this refrigerant areoperating with the same mineral oil or alkylbenzene lubricant
that was used with the previous chlorofluorocarbon (CFC) or
hydrochlorofluorocarbon (HCFC) refrigerant. Freon™ MO99
refrigerant has shown to provide similar system performanceas when operating with the previous refrigerant. Using these
retrofit guidelines, direct expansion (DX) residential andcommercial air conditioning (AC), and medium- and lowtemperature refrigeration systems containing R-22 can beeasily and economically converted to Freon™ MO99. This
allows existing equipment to continue operating safely andeffectively for the remainder of its useful life.
Retrofit Choice for R-22 Direct Expansion Systems in
Residential and Commercial Air Conditioning, Direct
Expansion Chillers, Medium- and Low-Temperature
Refrigeration
Freon™ MO99 is a non-ozone depleting HFC refrigerant
designed to replace R-22 in existing DX residential andcommercial AC and medium- and low-temperaturerefrigeration systems. Freon™ MO99 is compatible withtraditional and new lubricants; in most cases, no changeof lubricant type during retrofit is required.
Oil return is determined by a number of operating anddesign conditions; in some complex systems, polyol ester
lubricant (POE) may need to be added. Minor equipment
modifications (e.g., seal replacement) or expansion device
adjustments may be required in some applications.
Field experience has shown that Freon™ MO99 provides
performance that meets customer requirements in mostproperly retrofitted systems. Freon™ MO99 provides similarcooling capacity and energy efficiency to R-22 in most
systems, while operating at a lower compressor discharge

temperature. Actual performance depends on systemdesign and operating conditions.
Systems using Freon™ MO99 are easy to service. Freon™
MO99 can be topped off during service, without the needto remove the entire refrigerant charge. The cause of any
refrigerant loss should be investigated and corrected assoon as possible.
Note: When servicing critically charged systems, all of therefrigerant charge should be removed. This is the samepractice recommended for R-22.
In general, Freon™ MO99 refrigerant is not recommended foruse in centrifugal compressor systems or chillers with flooded
evaporators. For system-specific guidance on working with
HFC blends in “semi-flooded” operations with low-pressurereceivers, contact Chemours or consult the OEM.
Easy Steps to Retrofit
The following provides a summary of the basic retrofit
steps for Freon™ MO99. (Detailed discussion of each stepis provided in this bulletin.)
1. Establish baseline performance with existing refrigerant(see Retrofit Checklist).
2. Remove existing refrigerant (R-22 or other) from the system
into a recovery cylinder. Weigh the amount removed.
3. Replace the filter drier and critical elastomeric seals/
gaskets.*
4. Evacuate system and check for leaks.
5. Charge with Freon™ MO99.
• Remove as a liquid only from charging cylinder.
• The initial charge amount should be approximately
85% of the standard charge for R-22. The final
charge amount will vary by system, but will beapproximately the same weight as with R-22.
*Critical seals are ones that are difficult to isolate and/or service while operating or require removal of
the entire refrigerant charge, i.e., liquid receiver level gauge, in order to replace.

Freon™ MO99

Refrigerant

6. Start up system, monitor, and adjust TXV and/or charge

Overexposure to high concentrations of refrigerant vapor

size to achieve optimum superheat.

can cause asphyxiation and cardiac arrest. Please read allsafety information before handling any refrigerant.

7. Monitor oil levels in compressor. Add oil as required tomaintain proper levels.

Refer to the Freon™ MO99 Safety Data Sheet (SDS) for

8. Label system for the refrigerant and lubricant used.

more specific safety information. Chemours Safety Bulletin
AS-1 also gives additional information for safe handling ofImportant Safety Information

refrigerants.

Like CFCs and HCFCs, Freon™ refrigerants are safe to use
when handled properly. However, any refrigerant can cause

Flammability

injury or even death when mishandled. Please review theFreon™ MO99 is nonflammable in air under normal

following guidelines and consult the product SDS, including

conditions and has an ASHRAE A1 safety classification

proper personal protective equipment recommendations,(nonflammable and low toxicity). When mixed with highbefore using any refrigerant. At a minimum, appropriate handconcentrations of air or oxygen under elevated pressure,(gloves) and eye (safety glasses) protection should be used.

however, this product, like other A1 classified HFC
refrigerants, can become combustible in the presence of an• Do not work in high concentrations of refrigerant vapors.

ignition source. This product should not be mixed with air to

Always maintain adequate ventilation in the work area.

check for system leaks.

Do not breathe vapors. Do not breathe lubricant mists
from leaking systems. Ventilate the area well after any

Filter Drier and Elastomeric Seal Information

leak before attempting to repair equipment.

Filter Drier• Do not use hand-held leak detectors to check for

Change the filter drier during the retrofit. This is a routine

breathable air in enclosed working spaces. Thesesystem maintenance practice after the system has been

detectors are not designed to determine if the air is safe

open to air. There are two types of filter driers commonly

to breathe. Use oxygen monitors to ensure adequate

used, solid core and loose filled. Replace the drier with theoxygen is available to sustain life.

same type currently in use in the system. The drier label willshow which refrigerants can be used with that drier. Select• Do not use flames or halide torches to search for leaks.

a drier specified to work with HFC refrigerants. (Many driersOpen flames (e.g., halide detection or brazing torches) cansold today are “universal” – they will work with most

release large quantities of acidic compounds in the

fluorocarbon refrigerants.) Check with your Chemours

presence of all refrigerants, and these compounds can be

distributor for the correct drier to use in your system.

hazardous. Halide torches are not effective as leakdetectors for HFC refrigerants; they detect the presence

Elastomeric Sealsof chlorine, which is not present in Freon™ MO99, and,R-22 and, to a lesser extent, R-22-containing refrigerant

consequently, these detectors will not detect theblends, interact relatively strongly with many elastomers,presence of this refrigerant. Use an electronic leakcausing significant swelling and, often, over time, adetector designed to find the refrigerants you are using.

measurable increase in hardness. Freon™ MO99, like other
HFC refrigerants, does not have as strong of an effect on

If you detect a visible change in the size or color of a flame

elastomers commonly used as seals in refrigeration

when using brazing torches to repair equipment, stop work

systems. As a result, when performing an R-22 retrofit toimmediately and leave the area. Ventilate the work area wellan HFC alternative, it is possible for leaks to occur atand stop any refrigerant leaks before resuming work. Theseelastomeric seals that have been previously exposed toflame effects may be an indication of very high refrigerant

R-22 refrigerant. This is not a problem attributableconcentrations, and continuing to work without adequate
ventilation may result in injury or death.

specifically to the use of Freon™ MO99. Such seal leaks

Note: Any refrigerant can be hazardous if used improperly.

refrigerants, such as R-407C or R-404A. Components

Hazards include liquid or vapor under pressure and frostbitecommonly affected are Schrader core seals, liquid levelfrom the escaping liquid.

receiver gaskets, solenoid valves, ball valves, flange seals,

have been reported when replacing R-22 with other HFC

and some shaft seals on open drive compressors. Leaks do
2

Freon™ MO99

Refrigerant

not occur in every system retrofitted, and, in practice, it isField experience has shown that Freon™ MO99 will work

difficult to predict whether such leaks will occur. (As a rule

successfully with the existing mineral (or alkylbenzene) oil inof thumb: the older the system, the higher the probability

most systems. In some poorly designed, maintained, orthat leaks will be observed after a retrofit.)

operated R-22 systems, or in split systems with complex
piping or component arrangements where the evaporator is

As a consequence, it is recommended to change

positioned substantially lower than the condensing unit, theelastomeric seals and gaskets as a matter of course during

oil may not consistently return to the compressor. If oila retrofit, particularly any system-critical seals (those which

return issues exist with R-22 operation, it is recommended

would require removal of the refrigerant charge to allowthat corrective actions be taken prior to converting toseal replacement, e.g., liquid receiver, refrigerant high-Freon™ MO99.

pressure side, etc.). It is also recommended to have spareseals for other components available during restart of the

When oil level sight glasses are present in the compressor,

system. The same type of seal can be used; it should just be

oil levels should be monitored during initial operation with thea new one that has not previously been in R-22 service. A

Freon™ MO99. If the oil level falls below the minimum

rigorous leak check regime pre- and post-retrofit willallowed, top off the oil to the minimum level with the existing

minimize any refrigerant losses. Obviously, any seals foundoil type. Do not fill to maximum, as the level may rise again.

to be leaking before the retrofit takes place should be
replaced during the retrofit.

Should the oil level fall continuously, or suffer large

General Retrofit Information

lubricant has proven effective in restoring adequate oil

oscillations during an operating cycle, addition of POE
return rates. An addition of POE lubricant (approximately

System Modifications

20% of the total oil charge) should be made. This can be

The composition of Freon™ MO99 refrigerant has been

followed, if necessary, by further small increments of POE,

designed to provide performance comparable to R-22, in

until the oil level returns to normal.

terms of both capacity and energy efficiency. As a result,minimal system modifications are anticipated when retrofitting.

When adding POE oil to the system, it is important toensure that the oil level (immediately after addition) is kept

Retrofits of R-22 systems with other non-ozone depleting

below the system mid-point (e.g., mid-sight glass) oil level. In

alternative refrigerants, such as R-407A or R-407C, will

most cases, the process of recovering R-22 at the start ofrequire multiple oil changes and possibly more extensive

the retrofit also removes some of the existing lubricant

modifications to the existing equipment. For somefrom the system. As a result, there should be sufficientsystems, the cost of conversion may be high. Freon™

space for the addition of POE, if deemed necessary. If there

MO99 provides the service contractor and equipment

is concern about over-filling the oil sump, some of theowner with a cost-effective way to retrofit an existing

existing mineral oil or alkylbenzene can be drained prior tosystem without oil changes.

the equivalent addition of POE.

Note: Freon™ MO99 should not be mixed with other

Systems with Liquid Receivers

refrigerants or additives that have not been clearly specified

When converting a refrigeration or AC system with a liquid

by Chemours or the system equipment manufacturer. Mixing

receiver from R-22 to MO99, there is a possibility ofthis refrigerant with CFC or HCFC refrigerants, or mixing two

trapping oil in the receiver by formation of a separate layer,

different alternative refrigerants, may have an adverse effectif the oil discharge rate of the compressor is high, foron system performance. “Topping off” a CFC or HCFC
refrigerant with any Freon™ refrigerant is not recommended.

example, when there is no oil separator system. Because it

Lubricants and System Oil Management

discharge rate of any compressor is, and it may change over

Lubricant selection is based on many factors, including

time, it is recommended for systems with liquid receivers

is impossible to know at any given time what the oiland no oil separators, that an addition of some POE

compressor wear characteristics, material compatibility,(approximately 20% of the total oil charge) be made during

and lubricant/refrigerant solubility (which can affect oil

the conversion. The addition of the appropriate POE for the

return to the compressor). Freon™ MO99 is compatible withsystem will assist in maintaining adequate oil solubility in

traditional and new lubricants.

the receiver in the event of a high discharge of oil from the3

Freon™ MO99

Refrigerant

compressor. There is no need to perform multiple systemchange in the compressor oil sump from mineral oil to an

flushes or remove all of the mineral oil or alkylbenzene

OEM-approved POE lubricant is recommended in thesewhen converting to MO99.

select cases to address potential refrigerant migration
concerns. The impact of refrigerant migration and

Systems that have oil separators, such as supermarket

recommendations for converting systems from R-22 toparallel racks, when converted to MO99, have typicallyFreon™ MO99 can be very equipment-specific. Consult themaintained lower oil circulation rates and have not required

OEM or contact Chemours for specific questions.

the addition of POE to maintain solubility in liquid receivers.

Direct Expansion Systems with Screw Compressors

Enhanced Surface Tubing

The complex lubrication and oil management system

In systems containing enhanced tube surfaces in heatassociated with screw compressors requires special

exchangers, large amounts of oil in circulation could

consideration and evaluation when retrofitting to any

potentially inhibit heat transfer and negatively impact

alternate refrigerant. Depending on the system design, oilsystem performance. If a specific system with enhanced

circulation rates vary and may far exceed typical rates seenheat transfer tubes is suspected or known to have high oilwith common reciprocating and scroll compressors, evencirculation rates, a partial charge (approximately 20%) of

when oil separation systems are installed.

POE in the existing mineral oil will provide increased
solubility of the lubricant in the refrigerant.

So that the periods of high oil circulation rates do not lead tooil logging and performance concerns, for these systems,

Refrigerant Migration and Oil Miscibility

the use of OEM-approved POE lubricant is recommended

Refrigerant migration, the movement of refrigerant (vapor

when retrofitting an R-22 system to an HFC alternative,

and/or liquid) to the compressor during off-cycles, usuallysuch as MO99. In order to ensure adequate oil returnoccurs when the compressor becomes colder than the rest

through these complex screw systems, the change from theof the system, creating a driving force. This typicallyexisting lubricant to POE should take place while the systemhappens during cold weather; however, refrigerant

is still operating with R-22. Once the system has been

migration can occur under other conditions.

converted to POE, the retrofit from R-22 to Freon™ MO99
should proceed as outlined in these guidelines.

Systems operating with highly miscible refrigerant oil pairs(R-22/mineral oil or R-404A/POE) can dissolve a large

Consultation with the chiller and screw compressor OEMs

amount of refrigerant into the oil in the compressor oil sump,

on topics beyond oil management is also recommended fordue to refrigerant migration during off-cycles. Upon start-up,

these systems. There may be additional system-specificthe dissolved refrigerant will rapidly flash from the oil, resulting

elastomeric seals in the compressor that may need to be

in foaming, a drop in oil pressure, and reduced lubricity.

replaced during the retrofit or programmed control settings
related to pressure and temperature readings that would

Concerns over refrigeration migration issues extend as wellrequire involvement of the OEM for slight set point changes.

to converted systems with limited miscibility refrigerant/oil
combinations, such as Freon™/mineral oil; because, in these

Liquid Refrigerant Control

cases, the potential exists to form separate oil and

The potential problems that poor liquid refrigerant control

refrigerant layers in the compressor, with the refrigerant at

can cause in a refrigeration or air conditioning system canthe bottom. This potential can be reduced by the use of

be severe and difficult to predict with certainty. Where

properly functioning crankcase heaters. However, inflooding, slugging, or refrigerant migration can occur,

compressors designed to lubricate the bearings by drawing

corrective action should be taken. The proper course ofoil specifically from the bottom of the oil sump, such as

action is normally dependent on the compressor type,

Trane® 3-D® and Danfoss SM scroll compressors, thesystem design, type of problem, and the refrigerant/

refrigerant/oil combination in use should be highly miscible

lubricant combination. Compressor or equipment

as an added precautionary measure to avoid the potential

manufacturers should be consulted for detailed guidance

formation of a refrigerant layer at the bottom of theon liquid control for a specific system.

compressor oil sump. Because Freon™ MO99 refrigerant
has the highest miscibility with POE lubricant, a single oil

4Freon™ MO99

Refrigerant

While undesirable for reasons previously described andFreon™ MO99 EER Comparison

often dependent on system design, management of liquid

Compressor EER (at ARI 540 Conditions - All superheat included in Capacity)

refrigerant in general may be accomplished by a variety of

Evaporator EER (10°F of suction superheat included in Capacity)equipment or control strategies:• Minimize Refrigerant Charge - Charge system withRelative EER (R-22 = 1)

minimum amount of refrigerant required for proper
operation. Keep the tubes in condensers, evaporators,
and connecting lines to smallest practical size.
• Pumpdown Cycle (Continuous or One-Time) - Isolates
the refrigerant when compressor is not in operation,
preventing refrigerant migration (see, for example,
Copeland Application Engineering Bulletin AE-1182-R24).

driving refrigerant out of the compressor.

MT

A/C

LT

MT

A/C

Application

Medium Temperature (MT): 20°F Evaporator, Seasonal Average Condenser (70% at 80°F/30% at
120°F), 10°F sub-cool liquid, 65°F return gas• Suction Line Accumulators - Provides a temporary

Air Conditioning (A/C):45°F Evaporator, 115°F Condenser, 15°F sub-cool liquid, 65°F return gas

storage vessel to trap liquid refrigerant that has flooded
back; especially important for heat pump systems.

Flood Back, Superheat, and Temperature Glide
Flood back (incomplete evaporation of liquid refrigerant in the

Liquid Control Issues During Refrigerant Conversions

evaporator), due to inadequate superheat, may be caused by(Retrofits)

an oversized or improperly adjusted TXV and can lead toWhen systems designed for a particular refrigerant gas

liquid slugging and/or bearing washout in the compressor.

need to be converted to operate on another refrigerant,
there are a few liquid control issues that require specific

For air conditioning or refrigeration systems being

attention as detailed below.

converted from R-22 to Freon™ MO99 refrigerant, themass flow rates are fairly similar, such that a TXV (valve

Freon™ MO99 Capacity Comparison

body, power-head, or nozzle/orifice) properly sized andCompressor Capacity (at ARI 540 Conditions - All superheat included in Capacity)

operating well for R-22 should not need replacement when

Evaporator Capacity (10°F of suction superheat included in Capacity)
Relative Capacity and EER (R-22 = 1)

LT

Freon™ MO99

Relative Evaporator EER

Low Temperature (LT): -25°F Evaporator, Seasonal Average Condenser (70% at 80°F/30% at 105°F),
10°F sub-cool liquid, 65°F return gas

at a temperature higher than coldest part of the system,

R-22

Relative Compressor Capacity

R-22

Relative Compressor EER

Application• Crank Case Heaters - Maintains oil in the compressor

1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0

1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0

switching to MO99.

Freon™ MO99

Relative Evaporator Capacity

However, it may be necessary to slightly adjust the TXV,
due to the temperature glide effect and small suction
pressure differences of the new refrigerant. The need for
adjustment will depend on current valve set points andamount of superheat desired to achieve appropriate
system performance. Detailed guidelines on measuring andsetting superheat for Freon™ MO99 are included in aLT

MT
Application

A/C

LT

MT
Application

separate section in this document. Because the mass flow

A/C

rates and pressure-temperature curves for R-22 andMO99 are very close, only minor adjustments should be
required for properly sized components. Conversion kits areavailable to convert some older non-adjustable TXVs into
adjustable type, without replacing the valve, if need be.
Freon™ MO99 will also work well in systems designed with
fixed expansion devices, such as capillary tubes, pistons, orother fixed orifices; in most cases, a change in expansion
device is not required.
5

Freon™ MO99

Refrigerant

In these non-adjustable systems, the refrigerant charge

same compressor oil that was used for the HCFC

size is critical, and extra care should be used when weighing

refrigerant. However, some modifications may be

and charging the refrigerant. As stated in the retrofit steps,

necessary, such as a different kind of drier or a different

when charging MO99 to these critically charged systems,

moisture indicator. Consult the equipment manufacturer for

begin with approximately 85% of the original R-22 charge

specific recommendations.

weight. Once conditions stabilize, additional refrigerant canIn the United States, Chemours will take back (for reclaim)

be added in small increments as needed to achieve thedesired superheat for the system.

Freon™ MO99 refrigerant discussed in this bulletin. In other

During any refrigerant charging process, as system

details of the refrigerant reclaim program.

regions, contact your Chemours refrigerant distributor forpressures are being monitored, if the condenser (head)pressure rises significantly above typical levels expected

Expected Performance After Retrofit

with R-22, and necessary refrigerant charge weight has not

Operational Set Points

been reached, STOP CHARGING and ensure there is not aFreon™ MO99 has been designed to closely match therestriction in the flow. Fixed expansion devices arepressure, temperature, enthalpy, and mass flow properties

designed with small diameters to properly meter flow; aof R-22. Therefore, in most cases, the operational set

restriction in the path can lead to high condenser pressurespoints currently used for evaporator pressures, thermal

and/or starving of the evaporator.

expansion valves, condenser head pressure control, etc.,
will be adequate for MO99. After replacing R-22 with

If condenser pressures remain high after verifying theMO99, start up the system and allow it to stabilize using

system has no line restriction and is not overcharged, thethe existing R-22 set points. If desired, after the system

suction superheat should be checked. If the suction

has stabilized, operating controls can be fine-tuned tosuperheat is higher than typically observed with R-22, it is

optimize system performance. Detailed instructions forpossible that the existing fixed expansion device ismeasuring and setting suction pressure, superheat, andundersized. The replacement option for each type of device

sub-cooling can be found at the end of this bulletin.

and system will vary based on design. However, in general,
fixed pistons and orifices can be replaced with an orifice ofTable 1 shows approximate system performance changesa larger size or with a TXV designed for use with R-22.

following a retrofit from R-22 to MO99 and are general

Capillary tubes, if undersized for MO99, can also be

guidelines for system behavior. These values are based on

replaced with a shorter or wider tube or with a TXV

field experience, calorimeter testing, and thermodynamic

designed for use with R-22.

property data, and assume equal compressor efficiency.

Refrigerant Recovery Information

Cooling capacity and energy efficiency depend greatly on

Most recovery or recycle equipment used for R-22 can besystem design, operating conditions, and the actual

used for Freon™ MO99. Use standard procedures to avoid

condition of the equipment. Freon™ MO99 provides similarcross-contamination when switching from one refrigerantcooling capacity and energy efficiency to R-22 in mostto another. Most recovery or recycle machines can use thesystems. Actual performance depends on system designand operating conditions.

Table 1. Freon™ MO99 Compressor Calorimeter Performance Compared to R-22 in Refrigeration and Air Conditioning Systems(Performance with sub-cooling based on thermocycle calculations from calorimeter data and do not include heat transfer effects)
Low Temperature*-25 °F evaporator,
105 °F condenser,
65 °F return gas with 10 °F sub-cooling

Medium Temperature
20 °F evaporator,
120 °F condenser,
65 °F return gas with 10° F sub-cooling

A/C and High Temperature
45 °F evaporator
115 °F condenser
65°F return gas with 15°F sub-cooling

Discharge Temperature, °F

-22

-45

-31

Discharge Pressure, psi

+3

+6

+5

+ is increase and - is decrease for Freon™ MO99 vs. R-22
*R-22 assumes demand cooling with low discharge temperature of 275 °F

6Freon™ MO99

Refrigerant

Detailed Retrofit Procedure for R-22 in Direct
Expansion Residential and Commercial Air
Conditioning, Medium- and Low-Temperature
Refrigeration

replacement: liquid receiver, condenser system) as amatter of course and have spare seals for othercomponents available during the retrofit, should any seal
failure occur. A rigorous leak check regime pre- andpost-retrofit will minimize any refrigerant losses.

(Refer to the Retrofit Checklist at the back of this bulletin.)

4. Evacuate system and check for leaks. Use normal

1. Establish baseline performance with existing

service practices. To remove air or other non-refrigerant. Collect system performance data while thecondensable gases and any residual moisture from theold refrigerant is in the system. Check for correct

system, evacuate the system to near full vacuum (29.9

refrigerant charge and operating conditions. The

in Hg vacuum [500 microns] or less than 10 kPa), isolate

baseline data of temperatures and pressures at various

the vacuum pump from the system, and observe thepoints in the system (evaporator, condenser, compressor

vacuum reading. If the system does not maintainsuction and discharge, superheat, and sub-cool) at

vacuum, it is an indication that there might be a leak.

normal operating conditions will be useful when

Pressurize the system with nitrogen, taking care not to

optimizing operation of the system with Freon™ MO99.

exceed the system design maximum pressure, andA System Data Sheet is included at the back of thischeck for leaks. Do not use mixtures of air andbulletin to record baseline data.

refrigerant under pressure to check for leaks; thesemixtures can be combustible. After leak checking with

2. Remove refrigerant from the system into a recovery

nitrogen, remove residual nitrogen using a vacuum pump.

cylinder. The existing charge should be removed fromthe system and collected in a recovery cylinder using a

5. Charge with Freon™ MO99. Because MO99™ is arecovery device capable of pulling 10–15 in Hg vacuum

near-azeotrope, the vapor composition in the refrigerant(50–67 kPa absolute). If the recommended charge size forcylinder is different from the liquid composition. For thisthe system is not known, weigh the amount of refrigerant

reason, Freon™ MO99 should be transferred from theremoved. The initial quantity of Freon™ MO99 to charge tocontainer in the liquid phase during system charging. (Ifthe system can be estimated from this amount (see Stepthe cylinder does not have a valve with a dip tube, invert5). Ensure that any residual refrigerant dissolved in thethe cylinder so that the valve is underneath the cylinder.)compressor oil is removed by holding the system under

The proper cylinder position for liquid removal is often

vacuum. Break the vacuum with dry nitrogen.

indicated by arrows on the cylinder and cylinder box.
Once liquid is removed from the cylinder, the refrigerant

3. Replace the filter drier/elastomeric seals/gaskets.

can be allowed to enter the refrigeration system as liquid

It is routine practice to replace the filter drier during

or vapor, as desired. Use the manifold gauges or asystem maintenance. Replacement filter driers arethrottling valve to flash the liquid to vapor, if required.

available that are compatible with Freon™ MO99. While
the system is empty, check and replace any elastomeric

WARNING: Do not charge liquid refrigerant into theseals that may be near the end of their serviceable life.

compressor. This will cause serious irreversible damage.

Even if they were not previously leaking, the change ofswell characteristics when changing to any new

In general, refrigeration systems will require about the samerefrigerant (e.g., R-22 to any HFC refrigerant) and theweight of Freon™ MO99 refrigerant as the original R-22

general disturbance to the system may cause worn seals

charge. The optimum charge will vary, depending on theto leak after retrofit. Components commonly affected

system design and operating conditions. The initial charge

are Schrader core seals, liquid level receiver gaskets,should be approximately 85% of the standard charge forsolenoid valves, ball valves, flange seals, and some shaft

R-22. After start-up and adjustment, the final charge

seals on open drive compressors; but, all external seals

amount will usually be 95% of the original R-22 charge.

in contact with the refrigerant should be viewed as aConsult the system OEM guidelines for specific directions.

potential leak source post-retrofit. Field experience has
shown that the older the system, the greater theNote: These values apply, provided no changes tolikelihood of seal and gasket leaks. It is recommended tomechanical components of the system (which couldchange any system-critical seals (e.g., those that requiresignificantly affect the system’s internal volumetricremoval of the refrigerant charge to allow sealcapacity) will be made during the retrofit. For systems

7

Freon™ MO99

Refrigerantwith a liquid refrigerant receiver, charge the system to

WARNING: Liquid refrigerant entering the compressor

the normal refrigerant level in the receiver.

at any time during system operation can lead to compressor oil level problems and rapid compressor failure.

6. Start up system and adjust charge size (for systems
without a liquid receiver). Start the system and let

7. Monitor oil levels. When compressor sight glasses areconditions stabilize. If the system is undercharged (aspresent, during initial operation of the system, monitor

indicated by the level of superheat at the evaporator exit

the level of oil in the compressor (or compressor oilor by the amount of sub-cool at the condenser exit), add

management system) to verify that oil is returning to themore Freon™ MO99 in small amounts (still bycompressor in an adequate manner.

transferring as liquid from the charging cylinder), until• If the oil level falls below the minimum allowed level,

the system conditions reach the desired level. See the

top off to the minimum level with the existing oilpressure-temperature charts in this bulletin to compare

type. Do not fill to the maximum level, as the levelpressures and temperatures, in order to calculate

may rise again.

superheat or sub-cooling for the refrigerant.

• Should the oil return appear to be erratic, as

If present, sight glasses in the liquid line can be used inevidenced by large swings in oil level during themost cases as a guide to system charge; but, correct

refrigeration system cycle, an addition of POE

system charge must be determined by measuring

lubricant (approximately 20% of the total oil charge)

system operating conditions (discharge and suction

should be made. This can be followed, if necessary, bypressures, suction line temperature, compressor motor

further small increments of POE, until the oil levelamps, superheat, etc.). Attempting to charge until the

returns to normal. The exact amount of POE neededsight glass is “full” (bubble-free) may result inwill depend on the specific system (evaporating

overcharging the refrigerant. Please read the section ontemperatures, physical geometry, etc.).

“How to Determine Suction Pressure, Superheat, and
Sub-Cool” for details on estimating when a system is full,• It is important to ensure that, when adding POE oil towithout relying solely on the sight glass observations.

the system, the oil level (immediately after addition) is
kept below the system mid-point (e.g., mid-sight glass)

For any of the 400-series refrigerant blends, like MO99,

oil level. It is also important to keep accurate records

it is reasonable to expect to see some bubbles in theof how much oil is added to avoid over-filling. Ifsight glass that are entrained in the liquid, not flashingconcerned about over-filling with oil, a portion of theoff, even once the system is properly filled. It is also

existing mineral oil or alkylbenzene can be drained

possible to have a “milky” or cloudy sight glass; thisprior to the equivalent addition of POE.

observation alone should not be cause for concern, as it
is generally a result of a light scattering effect of the

8. Thoroughly leak check the system. As mentioned inpartially miscible oil in liquid refrigerant and typically will

Step 3, it is possible that refrigerant leakage can occur

clear up over time. If the cloudy sight glass persists for an

during or immediately after a retrofit. Experience has

extended period of time, it may be an indication of higher

shown that some leaks will not appear until after the newoil discharge from the compressor. Details on managing

refrigerant has been charged to the system. Pay

systems with higher oil circulation rates can be found inparticular attention to Schrader valve core seals,

the Lubricants and System Oil Management section.

solenoid valves, and ball valve stems on the liquid highpressure side.

Ensuring that the correct evaporator exit andcompressor suction superheat is set is very important

9. Label the system to clearly and permanently show thefor reliable system operation with Freon™ MO99.

refrigerant and oil(s) present in the system.

Experience has shown that superheat (at thecompressor inlet) for Freon™ MO99 should be the same
as for the refrigerant being replaced.

8

Freon™ MO99

Refrigerant

Pressure-Temperature Charts (Appendix B)

Superheat

How to Read the Pressure-Temperature Chart

In many cases, the superheat settings used for R-22 will
provide adequate performance when using MO99.

The following pages contain pressure-temperature charts

However, if it is determined an adjustment is needed, refer

for the refrigerants discussed in this bulletin. Twoto the P-T chart (Appendix B) and proceed as follows: First,

temperatures are shown for MO99 at a given pressure:measure the suction pressure, and using the saturated• Saturated Liquid Temperature (Bubble Point)—In thevapor pressure (dew point) table for Freon™ MO99,

condenser, this is the point at which the last bit of vapor

determine the saturated vapor temperature corresponding

has condensed. This temperature-pressure should beto that measured pressure. Next, measure the suctionused when determining the system sub-cooling as welltemperature at the evaporator exit (for evaporator

as the temperature-pressure value of product stored in asuperheat) or at the compressor inlet (for suction

refrigerant cylinder.

superheat) and subtract the previously determined dew• Saturated Vapor Temperature (Dew Point)—In the

point temperature for Freon™ MO99, to give the amount of

evaporator, this is the temperature at which the lastvapor superheat. Adjust TXV, if necessary, to increase ordrop of liquid has just boiled. Above this temperature,

decrease superheat. In general, the superheat for MO99

the refrigerant will be superheated vapor. This

operation should be similar to that used previously during

pressure-temperature should be used in determining

R-22 operation.

the system superheat.

Sub-Cool

How to Determine Suction Pressure, Superheat, andUsing the saturated liquid pressure (bubble point) tables in

Sub-Cool

P-T Chart Appendix B, for Freon™ MO99, determine theSuction Pressure

saturated liquid temperature for the measured condensing

In many cases, the evaporator pressure setting used forpressure (usually the high-side pressure). Measure therefrigerant liquid line temperature and subtract it from theR-22 will provide adequate performance when using

previously determined bubble point temperature forMO99. However, if it is determined some adjustment isFreon™ MO99 to give the amount of liquid sub-cool.

needed, refer to Appendix A (Average Evaporator [Table 5]
and Average Condenser Set Points [Table 4]) and proceed
as follows: Determine the expected average evaporator
temperature using R-22 (from the baseline data you
collected prior to the retrofit). Find the same expectedevaporator temperature in the Saturated Vapor (Dew Point)column for Freon™ MO99. Note the corresponding pressure
for this temperature. This is the approximate suction
pressure at which the system should operate.

9

Freon™ MO99

Refrigerant

Retrofit Checklist for Converting CFC or HCFC Systems to Freon™ MO99
h Establish baseline performance with existing refrigerant.
• Use the System Data sheet provided in this bulletin.
• Note the oil type in use and system operating data (if system is operating properly).
• Check for existing leaks and repair.
h Remove existing refrigerant charge from system. (Need 10–15 in Hg vacuum [50–67 kPa absolute] toremove charge.)• Use recovery cylinder. (DO NOT vent to atmosphere.)• Weigh amount removed (if possible).: ___________• Break the vacuum with dry nitrogen.
h Replace the filter drier and elastomeric seals/gaskets ; check oil/add POE lubricant where applicable (see below):• Check and replace elastomeric seals and gaskets that cannot be replaced without removal of refrigerant.
– Components commonly affected are Schrader core seals, liquid level receiver gaskets, solenoid
valves, ball valves, flange seals, or shaft seals on open drive compressors; but, all external seals incontact with the refrigerant should be viewed as a potential post-retrofit leak source.
• Check that oil is in good condition; replace if necessary. (NOTE: Add 20% POE lubricant to R-22
systems with liquid receivers or with known or potential oil return issues).
- One time change to POE lubricant in compressor oil sump recommended for R-22 systems with
Trane® 3-D® or Danfoss SM scroll compressors.
h Evacuate system and check for leaks.
• Does the system hold a vacuum?
• Break vacuum with dry nitrogen; pressurize to below the system design pressure.
• Does the system hold pressure?
• Check for any leaks, and make repairs as necessary.
h Charge system with Freon™ MO99 refrigerant.
• Remove liquid only from cylinder.
• The initial charge amount should be approximately 85% of the standard charge for R-22. The final
charge amount will vary by system, but will be approximately the same weight as with R-22.
• Particular attention should be given to critically charged systems (with fixed orifices/capillary tubes) toensure equipment is not overcharged. (Monitor discharge pressure.)
NOTE: Do not charge liquid refrigerant into the compressor. This will cause serious irreversible damage.
h Adjust TXV and/or refrigerant charge in small increments to achieve the same superheat as the original
system. If adjustment is not possible or adequate, replace expansion device.
h Monitor oil levels in compressor.
• If the oil level falls below the minimum, top off to the minimum level with the existing oil type.
• If the oil level continuously falls or large oscillations occur during operation, add approximately 20% of
an equivalent POE, or more if needed, until oil return becomes normal.
• If a sudden surge in oil level occurs (e.g., during/just after defrost), or if there is concern about over-filling,a portion (approximately 20%) of the existing mineral oil or alkylbenzene can be drained prior to theequivalent addition of POE.
h Label system clearly. Ensure System Data sheet is completed and filed securely.

10Freon™ MO99

Refrigerant

System Data SheetType of System/Location:____________________________________________________________________________________________________________________________________
Equipment Mfg.:_______________________________________________________

Compressor Mfg.:_______________________________________________________

Model No.: _______________________________________________________________

Model No.:__________________________________________________________________

Serial No.:_________________________________________________________________

Serial No.:___________________________________________________________________

Date of Manufacture:_______________________________________________

Date of Manufacture:_________________________________________________

Original Charge Size: _______________________________________________

Lubricant Type:___________________________________________________________

Lubricant Charge Size:_____________________________________________

Drier Mfg.:__________________________________________________________________

Drier Type:________________________________________________________________

Condenser Cooling Medium:_______________________________________

Expansion Device (check one):h Capillary Tube:______________________________________________________h Expansion Valve:_____________________________________________________

If Expansion Valve:
Manufacturer:___________________________________________________________

Model No.:__________________________________________________________________

Control/Set Point:_____________________________________________________

Location of Sensor:____________________________________________________

Other System Controls (e.g., head pressure control):_______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Date/Time
Refrigerant
Charge Size (lb)
Ambient Temperature (°F)
Compressor
Suction Temperature (°F)
Suction Pressure (psig)
Discharge Temperature (°F)
Discharge Pressure (psig)
Evaporator
Coil Air/H2O In T (°F)

Coil Air/H2O Out T (°F)

Operating Service Temperature (°F)
Condenser
Coil Air/H2O In T (°F)

Coil Air/H2O Out T (°F)

Superheat and Sub-Cool (derived values)
Refrigerant T at Superheat Ctl. Pt. (°F)
Calculated Superheat (°F)
Expansion Device Inlet T (°F)
Calculated Sub-Cool (°F)
Motor Amps (if rack: total)

11

Freon™ MO99

Refrigerant

Appendix A
Table 2. Physical Properties of Freon™ MO99
(Properties calculated using REFPROP version 9.0, NIST 2010)
Physical Property

Unit

Freon™ MO99

R-22

Boiling Point (1 atm)

°F

–44.2

–41.4

Vapor Pressure at 77 °F

psia

162.0

151.4

Liquid Density at 77 °F

lb/ft3

71.6

74.3

Density, Satd. Vapor at 77 °F

lb/ft

3.03

2.76

Ozone Depletion Potential

CFC-11 = 1.0

0

0.05

CO2 = 1

2059

1760

Global Warming Potential, AR5 Values

3

Table 3. Composition of Freon™ MO99 (Wt%)
Freon™ MO99

HFC-32

HFC-125

HFC-134an-butane (R-600)

i-pentane (R-601a)

8.5

45

44.2

1.7

0.6

12

Freon™ MO99

Refrigerant

Table 4. Condenser Pressure Set Points

Table 5. Evaporator Suction Pressure Set Points

Based on 20 °F Evaporator, 10 °F Sub-Cooling

Based on 105 °F Condenser, 95 °F Sub-Cooling

R-22,
psig

Avg
Condenser
Temp., °F

Freon™
MO99,
psig

R-22,
psig

Avg
Condenser
Temp., °F

Freon™
MO99,
psig

R-22,
psig

Avg.
Evaporator
Temp., °F

Freon™
MO99,
psig

R-22,
psig

Avg.
Evaporator
Temp., °F

Freon™
MO99,
psig

143.4

80

143.9

229.6

111

232.7

7.6

-25

5.2

33.8

11

30.7

145.7

81

146.3

232.9

112

236.1

8.1

-24

5.7

34.8

12

31.7

148.0

82

148.7

236.2

113

239.5

8.6

-23

6.1

35.8

13

32.7

150.4

83

151.1

239.5

114

243.0

9.1

-22

6.6

36.9

14

33.7

152.8

84

153.6

242.9

115

246.5

9.6

-21

7.1

37.9

15

34.7

155.3

85

156.1

246.3

116

250.0

10.1

-20

7.6

39.0

16

35.8

157.8

86

158.6

249.7

117

253.6

10.7

-19

8.1

40.0

17

36.9

160.3

87

161.2

253.2

118

257.1

11.2

-18

8.6

41.1

18

37.9

162.8

88

163.8

256.7

119

260.8

11.8

-17

9.2

42.2

19

39.0

165.4

89

166.4

260.2

120

264.4

12.4

-16

9.7

43.3

20

40.2

168.0

90

169.1

263.7

121

268.1

13.0

-15

10.3

44.5

21

41.3

170.6

91

171.8

267.3

122

271.8

13.6

-14

10.9

45.6

22

42.4

173.2

92

174.6

270.9

123

275.5

14.2

-13

11.5

46.8

23

43.6

175.9

93

177.3

274.6

124

279.3

14.9

-12

12.1

47.9

24

44.8

178.7

94

180.1

278.3

125

283.1

15.5

-11

12.8

49.1

25

46.0

181.4

95

183.0

282.0

126

287.0

16.2

-10

13.4

50.3

26

47.2

184.2

96

185.8

285.7

127

290.9

16.9

-9

14.1

51.5

27

48.4

187.0

97

188.7

289.5

128

294.8

17.6

-8

14.8

52.8

28

49.6

189.8

98

191.7

293.3

129

298.7

18.3

-7

15.5

54.0

29

50.9

192.7

99

194.6

297.1

130

302.7

19.1

-6

16.2

55.3

30

52.2

195.6

100

197.6

300.9

131

306.7

19.8

-5

16.9

56.6

31

53.4

198.6

101

200.6

304.8

132

310.7

20.6

-4

17.7

57.9

32

54.7

201.5

102

203.7

308.8

133

314.8

21.4

-3

18.4

59.2

33

56.1

204.5

103

206.8

312.7

134

318.9

22.2

-2

19.2

60.5

34

57.4

207.5

104

209.9

316.7

135

323.0

23.0

-1

20.0

61.8

35

58.7

210.6

105

213.1

320.7

136

327.2

23.8

0

20.8

63.2

36

60.1

213.7

106

216.3

324.8

137

331.4

24.6

1

21.6

64.5

37

61.5

216.8

107

219.5

328.8

138

335.7

25.5

2

22.5

65.9

38

62.9

220.0

108

222.8

332.9

139

339.9

26.4

3

23.3

67.3

39

64.3

223.2

109

226.1

337.1

140

344.2

27.2

4

24.2

68.7

40

65.7

226.4

110

229.4

28.1

5

25.1

70.1

41

67.1

29.0

6

26.0

71.6

42

68.9

30.0

7

26.9

73.0

43

70.0

30.9

8

27.8

74.5

44

71.5

31.9

9

28.7

76.0

45

73.0

32.8

10

29.7

In general, the condensing pressure of R-22 and MO99 arevery close and will require minimal adjustment to control
set points. After converting from R-22 to MO99, thecondensing pressure can be determined by locating thedesired average condenser temperature (or R-22 pressure
setting) on this chart and determining the new set point

After converting from R-22 to MO99, the evaporator

required for equivalent operation with MO99.

temperature can be set by locating the desired average
evaporator temperature (or R-22 evaporator pressure) on
this chart and determining the new set point required for
MO99, in order to achieve an equivalent average
evaporator temperature.

13

Freon™ MO99

Refrigerant

Appendix B. Freon™ MO99 Pressure-Temperature Data (Eng)
R-22

Freon™ MO99

R-22

Pressure,
psig

Saturated
Temp.,ºF

Saturated Liquid(Bubble Point) Temp.,°F

Saturated Vapor(Dew Point) Temp.,
°F

-6

-60.5

-63.0

-51.5

-5
-4

-56.7
-53.3

-59.3
-55.8

-47.8
-44.5

-3
-2
-1
0
1
2
3
4
5
6
7
8
9
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
60
62
64
66
68
70
75
80
85
90
95

-50.0
-47.0
-44.1
-41.4
-38.9
-36.5
-34.2
-32.0
-29.8
-27.8
-25.8
-24.0
-22.1
-20.4
-17.0
-13.8
-10.8
-7.9
-5.2
-2.5
0.0
2.4
4.7
6.9
9.1
11.2
13.2
15.2
17.1
19.0
20.8
22.6
24.3
26.0
27.6
29.2
30.8
32.4
33.9
35.3
36.8
38.2
39.6
41.0
44.3
47.5
50.6
53.5
56.4

-52.6
-49.6
-46.8
-44.2
-41.7
-39.3
-37.0
-34.8
-32.7
-30.7
-28.8
-26.9
-25.1
-23.4
-20.1
-16.9
-13.9
-11.1
-8.4
-5.8
-3.4
-1.0
1.3
3.5
5.7
7.7
9.7
11.7
13.6
15.4
17.2
18.9
20.6
22.3
23.9
25.5
27.0
28.6
30.1
31.5
32.9
34.3
35.7
37.1
40.3
43.5
46.5
49.4
52.2

-41.3
-38.4
-35.6
-33.0
-30.6
-28.2
-26.0
-23.9
-21.8
-19.8
-18.0
-16.1
-14.4
-12.6
-9.4
-6.3
-3.4
-0.6
2.0
4.6
7.0
9.3
11.6
13.7
15.8
17.8
19.8
21.7
23.5
25.3
27.1
28.8
30.4
32.1
33.7
35.2
36.7
38.2
39.6
41.1
42.5
43.8
45.2
46.5
49.7
52.7
55.7
58.5
61.2

14

Freon™ MO99

Pressure,
psig

Saturated
Temp.,ºF

Saturated Liquid(Bubble Point) Temp.,°F

Saturated Vapor(Dew Point) Temp.,
°F

100
105
110
115
120
125
130
135
140
145
150
155
160
165
170
175
180
185
190
195
200
205
210
215
220
225
230
235
240
245
250
255
260
265
270
275
280
285
290
295
300
310
320
330
340
350
360
370
380
390
400

59.1
61.8
64.4
66.9
69.3
71.7
74.0
76.2
78.4
80.6
82.7
84.7
86.7
88.7
90.6
92.5
94.3
96.2
97.9
99.7
101.4
103.1
104.8
106.4
108.0
109.6
111.1
112.7
114.2
115.7
117.1
118.6
120.0
121.4
122.8
124.2
125.5
126.9
128.2
129.5
130.8
133.3
135.8
138.2
140.6
142.9
145.2
147.5
149.6
151.8
153.9

54.9
57.5
60.1
62.6
65.0
67.3
69.6
71.8
73.9
76.0
78.1
80.1
82.1
84.0
85.9
87.8
89.6
91.4
93.1
94.8
96.5
98.2
99.8
101.4
103.0
104.6
106.1
107.6
109.1
110.5
112.0
113.4
114.8
116.2
117.6
118.9
120.3
121.6
122.9
124.2
125.4
127.9
130.4
132.7
135.1
137.4
139.6
141.8
143.9
146.1
148.1

63.9
66.4
68.9
71.3
73.6
75.9
78.1
80.3
82.4
84.4
86.4
88.4
90.3
92.1
94.0
95.8
97.5
99.2
100.9
102.6
104.2
105.8
107.4
108.9
110.5
112.0
113.4
114.9
116.3
117.7
119.1
120.5
121.8
123.1
124.4
125.7
127.0
128.3
129.5
130.7
131.9
134.3
136.6
138.9
141.1
143.3
145.4
147.5
149.5
151.5
153.4

Freon™ MO99

Refrigerant

For more information on Freon™ refrigerants, visit freon.com
The information set forth herein is furnished free of charge and based on technical data that Chemours believes to be reliable. It is intended for use by persons having technical skill, at their own risk. Because
conditions of use are outside our control, Chemours makes no warranties, expressed or implied, and assumes no liability in connection with any use of this information. Nothing herein is to be taken as a license tooperate under, or a recommendation to infringe, any patents or patent applications.
© 2016 The Chemours Company FC, LLC. Freon™ and any associated logos are trademarks or copyrights of The Chemours Company FC, LLC. Chemours™ and the Chemours Logo are trademarks of The Chemours Company.
Replaces: K-22217-2
C-10862 (8/16)