Freon™ MO99™ (R-438A)
and Freon™ NU-22B™ (R-422B)
Refrigerants

Retrofit Guidelines
Introduction, Safety,
General Retrofit Procedure
Introduction
Freon™ MO99™ and Freon™ NU-22B™ refrigerants have
proven to be reliable, cost-effective, non-ozone depleting
retrofit refrigerants. In many cases, systems converted tothese refrigerants are operating with the same mineral oil
or alkylbenzene lubricant that was used with the previous
chlorofluorocarbon (CFC) or hydrochlorofluorocarbon(HCFC) refrigerant. Freon™ MO99™ and Freon™ NU-22B™
refrigerants have shown to provide similar system
performance as when operating with the previous

Field experience has shown that Freon™ MO99™ and Freon™
NU-22B™ provide performance that meets customer
requirements in most properly retrofitted systems. Freon™
MO99™ and Freon™ NU-22B™ provide similar cooling
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™ and Freon™ NU-22B™ areeasy to service. Freon™ MO99™ and Freon™ NU-22B™ can betopped off during service, without the need to remove theentire refrigerant charge. The cause of any refrigerant loss

refrigerant. Using these retrofit guidelines, direct

should be investigated and corrected as soon as possible.

expansion (DX) residential and commercial air conditioning

Note: When servicing critically charged systems, all the(AC) and medium- and low-temperature refrigeration
systems containing R-22 can be easily and economicallyconverted to Freon™ MO99™ or Freon™ NU-22B™. This allows
existing equipment to continue operating safely andrefrigerant charge should be removed. This is the samepractice recommended for R-22.
In general, Freon™ MO99™ and Freon™ NU-22B™ refrigerants

effectively for the remainder of its useful life.

are not recommended for use in centrifugal compressor

Retrofit Choice for R-22 Direct Expansion Systems in
Residential and Commercial Air Conditioning

specific guidance on working with HFC blends in “semi-Freon™ MO99™ and Freon™ NU-22B™ are non-ozone
depleting HFC refrigerants designed to replace R-22 inexisting DX residential and commercial AC systems.
Freon™ MO99™ and Freon™ NU-22B™ are compatible withtraditional and new lubricants; in most cases, no changeof lubricant type during retrofit is required.
Oil return is determined by several operating and design
conditions; in some complex systems, polyol ester (POE)
lubricant may need to be added. Minor expansion device
adjustments may be required in some applications.

systems or chillers with flooded evaporators. For systemflooded” operations with low-pressure receivers, contact
Chemours or consult the OEM.
DO NOT mix Freon™ MO99™ and Freon™ NU-22B™ in thesame system.

Freon™ MO99™ and Freon™ NU-22B™

Refrigerants

Important Safety Information

If you detect a visible change in the size or color of a flame
when using brazing torches to repair equipment, stop work

Like CFCs and HCFCs, refrigerants are safe to use when

immediately and leave the area. Ventilate the work area

handled properly. However, any refrigerant can cause injury

well, and stop any refrigerant leaks before resuming work.

or even death when mishandled. Hazards include liquid or

These flame effects may be an indication of very highvapor under pressure and frostbite from the escaping liquid,

refrigerant concentrations, and continuing to work without

and overexposure to high concentrations of refrigerant

adequate ventilation may result in injury or death.

vapor can cause asphyxiation and cardiac arrest. Please

Refer to the Freon™ MO99™ and Freon™ NU-22B™

read all safety information before handling any refrigerant.

SDS for more specific safety information. Chemours

Please review the following guidelines and consult thebulletin “Safety of Freon™ Refrigerants” also gives additional

product Safety Data Sheet (SDS), including proper personal

information for safe handling of refrigerants.

protective equipment (PPE) recommendations, before using
any refrigerant. At a minimum, appropriate hand (gloves) and

System Modificationseye (safety glasses) protection should be used.

The composition of Freon™ MO99™ and Freon™ NU-22B™

•

refrigerant have been designed to provide performance

Do not work in high concentrations of refrigerant vapors.

comparable to R-22, in terms of both capacity and energy

Always maintain adequate ventilation in the work area.

efficiency. As a result, minimal system modifications are

Do not breathe vapors. Do not breathe lubricant mists

anticipated when retrofitting properly sized systems.

from leaking systems. Ventilate the area well after any•

leak before attempting to repair equipment.

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

Do not use hand-held leak detectors to check foralternative refrigerants, such as R-407C, will require
multiple oil changes and possibly more extensive

breathable air in enclosed working spaces. These

modifications to the existing equipment. For some systems,

detectors are not designed to determine if the air is safe

the cost of conversion may be high. Freon™ MO99™ andto breathe. Use oxygen monitors to ensure adequate•

oxygen is available to sustain life.

Freon™ NU-22B™ provide the service contractor and

Do not use flames or halide torches to search for leaks.

existing systems without oil changes.

equipment owner with a cost-effective way to retrofit

Open flames (e.g., halide detection or brazing torches)

Note: Freon™ MO99™ and Freon™ NU-22B™ should not be

can release large quantities of acidic compounds in themixed with other refrigerants or additives that have notpresence of all refrigerants, and these compounds canbeen clearly specified by Chemours or the systembe hazardous. Halide torches are not effective as leakequipment manufacturer. Mixing these refrigerants with

detectors for HFC refrigerants; they detect the

CFC or HCFC refrigerants, or mixing two different

presence of chlorine, which is not present in Freon™

alternative refrigerants, may have an adverse effect on

MO99™ and Freon™ NU-22B™, and, consequently, thesesystem performance. “Topping off” a CFC or HCFC

detectors will not detect the presence of thisrefrigerant with any refrigerant is not recommended.

refrigerant. Use an electronic leak detector designed tofind the refrigerants you are using.

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Freon™ MO99™ and Freon™ NU-22B™

Refrigerants

General Retrofit Procedure for R-22 in
Direct Expansion Residential andCommercial Air Conditioning

5.

service practices. To remove air or other noncondensable gases and any residual moisture from thesystem, evacuate the system to near full vacuum (29.9(Refer to the Retrofit Checklist at the back of this bulletin.)1.

in Hg vacuum [500 microns]), isolate the vacuum pump

Establish baseline performance with existingfrom the system, and check the vacuum reading. If therefrigerant. Collect system performance data while

system does not maintain vacuum, it is an indication thatthe old refrigerant is in the system. Check for correct

there might be a leak. Pressurize the system withrefrigerant charge and operating conditions. The

nitrogen, taking care not to exceed the system designbaseline data of temperatures and pressures at

maximum pressure, and check for leaks. Do not use

various points in the system (evaporator, condenser,

mixtures of air and refrigerant under pressure to checkcompressor suction/discharge, superheat, andfor leaks; these mixtures can be combustible. After leak

subcool) at normal operating conditions will be usefulchecking with nitrogen, remove residual nitrogen using awhen optimizing operation of the system with Freon™

vacuum pump.

MO99™ or Freon™ NU-22B™. A System Data Sheet is6.

included at the back of this bulletin to record

vapor composition in the refrigerant cylinder is different

Remove refrigerant from the system into a recovery

from the liquid composition. For this reason, Freon™

cylinder. The existing charge should be removed from

MO99™ and Freon™ NU-22B™ should be transferred fromthe system and collected in a recovery cylinder using a

the container in the liquid phase during system charging.

recovery device capable of pulling 10–15 in Hg vacuum(If the cylinder does not have a valve with a dip tube,(50–67 kPa absolute). If the recommended charge size

invert the cylinder so that the valve is underneath thefor the system is not known, weigh the amount ofcylinder.) The proper cylinder position for liquid removal

refrigerant removed. The initial quantity of Freon™

is often indicated by arrows on the cylinder and cylinder

MO99™ and Freon™ NU-22B™ to charge to the systembox. Once liquid is removed from the cylinder, thecan be estimated from this amount (see Step 6). Ensurerefrigerant can be allowed to enter the refrigerationthat any residual refrigerant dissolved in thesystem as liquid or vapor, as desired. Use the manifold

compressor oil is removed by holding the system undergauges or a throttling valve to flash the liquid to vapor,vacuum. Break the vacuum with dry nitrogen.
3.

if required.

Replace the filter drier. It is routine practice to replace

WARNING: Do not charge liquid refrigerant into

the filter drier during system maintenance.

the compressor. This will cause serious

Replacement filter driers are available that are

irreversible damage.

compatible with Freon™ MO99™ and Freon™ NU-22B™.

In general, systems will require about the same weight ofThere are two types of filter driers commonly used, solidFreon™ MO99™ or Freon™ NU-22B™ refrigerant as thecore and loose filled. Replace the drier with the same

original R-22 charge. The optimum charge will vary,

type currently in use in the system.
4.

Charge with Freon™ MO99™ or Freon™ NU-22B™.
Because 400-series refrigerants are zeotropes, thebaseline data.
2.

Evacuate system and check for leaks. Use normal

depending on the system design and operating

Replace critical elastomeric seals/gaskets. While theconditions. The initial charge should be approximately

system is empty, check and replace all critical

85% of the standard charge for R-22. After start-up

elastomeric seals (i.e., those that require removal of theand adjustment, the final charge amount will usually be

refrigerant charge to allow seal replacement). Even if

95% of the original R-22 charge. Consult the systemthey were not previously leaking, the change of swell

OEM guidelines for specific directions.

characteristics when changing to any new refrigerant

Note: These values apply, provided no changes to(e.g., R-22 to any HFC refrigerant) and the generalmechanical components of the system (which could

disturbance to the system may cause worn seals to leaksignificantly affect the system’s internal volumetricafter retrofit. A rigorous leak check regime pre- andcapacity) will be made during the retrofit. For systems

post-retrofit will minimize any refrigerant losses.

with a liquid refrigerant receiver, charge the system tothe normal refrigerant level in the receiver.

3

Freon™ MO99™ and Freon™ NU-22B™

7.

Refrigerants

Start up system and adjust charge size (for systems

WARNING: For larger systems and systems

without a liquid receiver). Start the system and let

containing compressors designed to lubricate theconditions stabilize. If the system is undercharged (asbearings by drawing oil specifically from the bottom

indicated by the level of superheat at the evaporator exitof the oil sump, such as Trane 3-D and Danfoss SM

or by the amount of subcool at the condenser exit), add

scroll compressors, please refer to the detailed oil

more Freon™ MO99™ or Freon™ NU-22B™ in small

management guidance found in section “Refrigerant

amounts (still by transferring as liquid from the charging

Migration and Oil Miscibility” under the detailed

cylinder), until the system conditions reach the desired

retrofit information.

level. See the pressure-temperature charts in this9.

bulletin to compare pressures and temperatures, toStep 4, it is possible that refrigerant leakage can occur

calculate superheat or subcooling for the refrigerant.

8.

during or immediately after a retrofit. Experience has

WARNING: Liquid refrigerant entering theshown that some leaks will not appear until after thecompressor at any time during system operation can

new refrigerant has been charged to the system. Pay

lead to compressor oil level problems and rapid

attention to Schrader valve core seals, solenoid valves,compressor failure.

and ball valve stems on the liquid high-pressure side.

Monitor oil levels. When compressor sight glasses are

10. Label the system to clearly and permanently show thepresent, during initial operation of the system, monitor

refrigerant and oil(s) present in the system.

the level of oil in the compressor (or compressor oilmanagement system) to verify that oil is returning to thecompressor in an adequate manner.
•

If the oil level falls below the minimum allowed
level, top off to the minimum level with the existing oil
type. Do not fill to the maximum level, as the level may
rise again.

•

Should the oil return appear to be erratic, as evidenced
by large swings in oil level during the system cycle, anaddition of POE lubricant (approximately 20% of thetotal oil charge) should be made. This can be followed,
if necessary, by further small increments of POE, until
the oil level returns to normal. The exact amount of
POE needed will depend on the specific system(evaporating temperatures, physical geometry, etc.).

•

Thoroughly leak check the system. As mentioned in

It is important to ensure that, when adding POE oil tothe system, the oil level (immediately after addition) is
kept below the system mid-point (e.g., mid-sight glass)oil level. It is also important to keep accurate recordsof how much oil is added to avoid overfilling. If
concerned about overfilling with oil, a portion of theexisting mineral oil or alkylbenzene can be drained prior
to the equivalent addition of POE.

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Freon™ MO99™ and Freon™ NU-22B™

Refrigerants

Detailed Retrofit Information

Therefore, it is recommended to change elastomeric seals
and gaskets as a matter of course during a retrofit,

Flammability

particularly any system-critical seals (those which would

Freon™ MO99™ and Freon™ NU-22B™ are nonflammable in air

require removal of the refrigerant charge to allow seal

under normal conditions and have an ASHRAE A1 safety

replacement, e.g., liquid receiver, refrigerant high-pressureclassification (nonflammable and low toxicity). When mixed

side, etc.). It is also recommended to have spare seals forwith high concentrations of air or oxygen under elevatedother components available during restart of the system.

pressure, however, this product, like other A1 classified

The same type of seal can be used; it should just be a new

HFC refrigerants, can become combustible in the presence

one that has not previously been in R-22 service. A rigorousof an ignition source. This product should not be mixed withleak check regime pre- and post-retrofit will minimize any

air to check for system leaks.

refrigerant losses. Obviously, any seals found to be leaking
before the retrofit takes place should be replaced during

Filter Drier and Elastomeric Seal Information

the retrofit.

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

Lubrication and Oil Management

system maintenance practice after the system has been

Lubricants and System Oil Management

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

Lubricant selection is based on many factors, including

used, solid core and loose filled. Replace the drier with thecompressor wear characteristics, material compatibility,

same type currently in use in the system. The drier label will

and lubricant/refrigerant solubility (which can affect oil

show which refrigerants can be used with that drier. Selectreturn to the compressor). Freon™ MO99™ and Freon™

a drier specified to work with HFC refrigerants. (Many driers

NU-22B™ are compatible with traditional and newsold today are “universal”—they will work with mostlubricants.

fluorocarbon refrigerants.) Check with your Chemours

Field experience has shown that Freon™ MO99™ and Freon™

distributor for the correct drier to use in your system.

NU-22B™ will work successfully with the existing mineral (orElastomeric Seals

alkylbenzene) oil in most systems. In some poorly designed,
maintained, or operated R-22 systems, or in split systems

R-22 and, to a lesser extent, R-22-containing refrigerantwith complex piping or component arrangements where theblends, interact relatively strongly with many elastomers,

evaporator is positioned substantially lower than thecausing significant swelling and, often, over time, acondensing unit, the oil may not consistently return to themeasurable increase in hardness. Freon™ MO99 and Freon™
™

compressor. If oil return issues exist with R-22 operation, it

NU-22B™, like other HFC refrigerants, do not have as strong

is recommended that corrective actions be taken prior toof an effect on elastomers commonly used as seals in
refrigeration systems. As a result, when performing an R-22

converting to Freon™ MO99™ or Freon™ NU-22B™.

retrofit to an HFC alternative, it is possible for leaks to

When oil level sight glasses are present in the compressor,

occur at elastomeric seals that have been previously

oil levels should be monitored during initial operation with

exposed to R-22 refrigerant. This is not a problem

Freon™ MO99™ or Freon™ NU-22B™. If the oil level falls below

attributable specifically to the use of Freon MO99 or™

™

the minimum allowed, top off the oil to the minimum level

Freon™ NU-22B™. Such seal leaks have been reported whenwith the existing oil type. Do not fill to maximum, as thereplacing R-22 with other HFC refrigerants, such aslevel may rise again.

R-407C or R-404A. Components commonly affected are

Should the oil level fall continuously, or suffer large

Schrader core seals, liquid level receiver gaskets, solenoid

oscillations during an operating cycle, addition of POE

valves, ball valves, flange seals, and some shaft seals on

lubricant has proven effective in restoring adequate oil

open drive compressors. Leaks do not occur in every

return rates. An addition of POE lubricant (approximately

system retrofitted, and, in practice, it is difficult to predict

20% of the total oil charge) should be made. This can bewhether such leaks will occur. (As a rule of thumb: the older

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

the system, the higher the probability that leaks will be

until the oil level returns to normal.

observed after a retrofit.)5

Freon™ MO99™ and Freon™ NU-22B™

Refrigerants

When adding POE oil to the system, it is important toRefrigerant Migration and Oil Miscibility

ensure that the oil level (immediately after addition) is kept

Refrigerant migration, the movement of refrigerant (vapor

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

and/or liquid) to the compressor during off-cycles, usuallymost cases, the process of recovering R-22 at the start ofoccurs when the compressor becomes colder than the rest

the retrofit also removes some of the existing lubricantof the system, creating a driving force. This typicallyfrom the system. As a result, there should be sufficient

happens during cold weather; however, refrigerant

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

migration can occur under other conditions.

is concern about overfilling the oil sump, some of the

Systems operating with highly miscible refrigerant oil pairs

existing mineral oil or alkylbenzene can be drained prior to
the equivalent addition of POE.

(R-22/mineral oil or R-404A/POE) can dissolve a large

Systems with Liquid Receivers

sump, due to refrigerant migration during off-cycles. Uponamount of refrigerant into the oil in the compressor oil

When converting a refrigeration or AC system with a liquid

start-up, the dissolved refrigerant will rapidly flash fromreceiver from R-22 to Freon™ MO99™ or Freon™ NU-22B™,

the oil, resulting in foaming, a drop in oil pressure, andthere is a possibility of trapping oil in the receiver byreduced lubricity.

formation of a separate layer, if the oil discharge rate of theConcerns over refrigeration migration issues extend as wellcompressor is high, for example, when there is no oil

to converted systems with limited miscibility refrigerant/oil

separator system. Because it is impossible to know at any

combinations, such as /mineral oil; because, in these cases,

given time what the oil discharge rate of any compressor is,

the potential exists to form separate oil and refrigerant

and it may change over time, it is recommended forlayers in the compressor, with the refrigerant at the bottom.

systems with liquid receivers and no oil separators, that anThis potential can be reduced using properly functioning

addition of some POE (approximately 20% of the total oil

crankcase heaters. However, in compressors designed tocharge) be made during the conversion. The addition of the

lubricate the bearings by drawing oil specifically from theappropriate POE for the system will assist in maintaining

bottom of the oil sump, such as Trane 3-D and Danfoss SM

adequate oil solubility in the receiver in the event of a highscroll compressors, the refrigerant/oil combination in use

discharge of oil from the compressor. There is no need toshould be highly miscible as an added precautionary

perform multiple system flushes or remove all of themeasure to avoid the potential formation of a refrigerant

mineral oil or alkylbenzene when converting to Freon™

layer at the bottom of the compressor oil sump. Because

MO99™ or Freon™ NU-22B™.

Freon™ MO99™ and Freon™ NU-22B™ refrigerant have the

Systems that have oil separators, such as supermarket

highest miscibility with POE lubricant, a single oil change inparallel racks, when converted to Freon™ MO99™ or Freon™

the compressor oil sump from mineral oil to an OEM-

NU-22B™, have typically maintained lower oil circulation

approved POE lubricant is recommended in these selectrates and not required the addition of POE to maintaincases to address potential refrigerant migration concerns.

solubility in liquid receivers.

The impact of refrigerant migration and recommendations
for converting systems from R-22 to Freon™ MO99™ or

Enhanced Surface Tubing

Freon™ NU-22B™ can be very equipment-specific. Consult

In systems containing enhanced tube surfaces in heat

the OEM or contact Chemours for specific questions.

exchangers, large amounts of oil in circulation could
potentially inhibit heat transfer and negatively impact
system performance. If a specific system with enhanced
heat transfer tubes is suspected or known to have high oil
circulation rates, a partial charge (approximately 20%) of
POE in the existing mineral oil will provide increased
solubility of the lubricant in the refrigerant.

6

Freon™ MO99™ and Freon™ NU-22B™

Refrigerants

Direct Expansion Systems with Screw Compressors

While undesirable for reasons previously described and

The complex lubrication and oil management system

often dependent on system design, management of liquid
refrigerant in general may be accomplished by a variety of

associated with screw compressors requires special
consideration and evaluation when retrofitting to any

equipment or control strategies:

alternate refrigerant. Depending on the system design, oil•

circulation rates vary and may far exceed typical rates seen

Minimize Refrigerant Charge: Charge system withminimum amount of refrigerant required for properwith common reciprocating and scroll compressors, even

operation. Keep the tubes in condensers, evaporators,

when oil separation systems are installed.

and connecting lines to smallest practical size.

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

Pumpdown Cycle (Continuous or One-Time): Isolates
the refrigerant when compressor is not in operation,systems, the use of OEM-approved POE lubricant ispreventing refrigerant migration (see, for example,

recommended when retrofitting an R-22 system to an HFC

Copeland Application Engineering Bulletin

alternative, such as Freon™ MO99™ or Freon™ NU-22B™. To

AE-1182-R24).

ensure adequate oil return through these complex screw•

systems, the change from the existing lubricant to POE

Crank Case Heaters: Maintains oil in the compressor ata temperature higher than coldest part of the system,

should take place while the system is still operating withdriving refrigerant out of the compressor.

R-22. Once the system has been converted to POE, theretrofit from R-22 to Freon™ MO99™ or Freon™ NU-22B™

•

should proceed as outlined in these guidelines.

Suction Line Accumulators: Provides a temporarystorage vessel to trap liquid refrigerant that has flooded
back; especially important for heat pump systems.

Consultation with the chiller and screw compressor OEMs
on topics beyond oil management is also recommended for

Liquid Control Issues During Refrigerant Conversions(Retrofits)these systems. There may be additional system-specificelastomeric seals in the compressor that may need to be

When systems designed for a particular refrigerant gas

replaced during retrofit or programmed control settingsneed to be converted to operate on another refrigerant,

related to pressure and temperature readings that

there are a few liquid control issues that require specificwould require involvement of the OEM for slight set

attention as detailed below.

point changes.

System Charging and Operation

Liquid Refrigerant Control

If present, sight glasses in the liquid line can be used in

The potential problems that poor liquid refrigerant control

most cases as a guide to system charge; but, correct

can cause in a refrigeration or air conditioning system cansystem charge must be determined by measuring systembe severe and difficult to predict with certainty. Where

operating conditions (discharge and suction pressures,

flooding, slugging, or refrigerant migration can occur,suction line temperature, compressor motor amps,

corrective action should be taken. The proper course of

superheat, etc.). Attempting to charge until the sight glass

action is normally dependent on the compressor type,is “full” (bubble-free) may result in overcharging thesystem design, type of problem, and the refrigerant/

refrigerant. Please read the section on “How to Determine

lubricant combination. Compressor or equipment

Suction Pressure, Superheat, and Subcool” for details on

manufacturers should be consulted for detailed guidance

estimating when a system is full, without relying solely on

on liquid control for a specific system.

the sight glass observations.
For any of the 400-series refrigerant blends, like Freon™
MO99™ and Freon™ NU-22B™, it is reasonable to expect tosee some bubbles in the sight glass that are entrained in
the liquid, not flashing off, even once the system is properly
filled. It is also possible to have a “milky” or cloudy sightglass; this observation alone should not be cause forconcern, as it is generally a result of a light scattering

7

Freon™ MO99™ and Freon™ NU-22B™

Refrigerants

effect of the partially miscible oil in liquid refrigerant andIn these nonadjustable systems, the refrigerant charge size

typically will clear up over time. If the cloudy sight glassis critical, and extra care should be used when weighing andpersists for an extended period, it may be an indication of

charging the refrigerant. As stated in the retrofit steps,

higher oil discharge from the compressor. Details on

when charging Freon™ MO99™ or Freon™ NU-22B™ to thesemanaging systems with higher oil circulation rates

critically charged systems, begin with approximately 85%

can be found in the “Lubricants and System Oilof the original R-22 charge weight. Once conditions

Management” section.

stabilize, additional refrigerant can be added in small
increments as needed to achieve the desired superheat for

Ensuring that the correct evaporator exit and compressor

the system.

suction superheat is set is very important for reliable
system operation with Freon™ MO99™ and Freon™ NU-22B™.

During any refrigerant charging process, as system

Experience has shown that superheat (at the compressor

pressures are being monitored, if the condenser (head)

inlet) for Freon™ MO99™ and Freon™ NU-22B™ should be thepressure rises significantly above typical levels expectedsame as for the refrigerant being replaced.

with R-22, and necessary refrigerant charge weight has notbeen reached, STOP CHARGING and ensure there is not a

Flood Back, Superheat, and Temperature Glide

restriction in the flow. Fixed expansion devices are

Flood back (incomplete evaporation of liquid refrigerant indesigned with small diameters to properly meter flow; athe evaporator), due to inadequate superheat, may be

restriction in the path can lead to high condenser pressurescaused by an oversized or improperly adjusted

and/or starving of the evaporator.

thermoplastic expansion valve (TXV) and can lead to liquid

If condenser pressures remain high after verifying theslugging and/or bearing washout in the compressor.

system has no line restriction and is not overcharged, theFor air conditioning or refrigeration systems being

suction superheat should be checked. If the suction

converted from R-22 to Freon™ MO99™ or Freon™ NU-22B™

superheat is higher than typically observed with R-22, it isrefrigerant, the mass flow rates are similar, such that a TXV

possible that the existing fixed expansion device is(valve body, power-head, or nozzle/orifice) properly sizedundersized. The replacement option for each type of device

and operating well for R-22 should not need replacement

and system will vary based on design. However, in general,

when switching to Freon™ MO99™ or Freon™ NU-22B™.

fixed pistons and orifices can be replaced with an orifice ofa larger size or a TXV designed for use with R-22. Capillary

However, it may be necessary to slightly adjust the TXV,

tubes, if undersized for Freon™ MO99™ or Freon™ NU-22B™,

due to the temperature glide effect and small suction

can also be replaced with a shorter or wider tube or a TXV

pressure differences of the new refrigerant. The need for
adjustment will depend on current valve set points anddesigned for use with R-22.

amount of superheat desired to achieve appropriate

Refrigerant Recovery Information

system performance. Detailed guidelines on measuring andMost recovery or recycle equipment used for R-22 can be

setting superheat for Freon™ MO99™ and Freon™ NU-22B™

used for Freon™ MO99™ and Freon™ NU-22B™. Use standard

can be found in the “How to Determine Suction Pressure,procedures to avoid cross-contamination when switching

Superheat, and Subcool” section. Because the mass flowfrom one refrigerant to another. Most recovery or recycle

rates and pressure-temperature curves for R-22, Freon™

machines can use the same compressor oil that was used

MO99™, and Freon™ NU-22B™ are very close, only minor

for the HCFC refrigerant. However, some modifications may

adjustments should be required for properly sized

be necessary, such as a different kind of drier or moisturecomponents. Conversion kits are available to convert someindicator. Consult the equipment manufacturer for

older nonadjustable TXVs into adjustable type, without

specific recommendations.

replacing the valve, if need be.
Freon™ MO99™ and Freon™ NU-22B™ will also work well insystems designed with fixed expansion devices, such as
capillary tubes, pistons, or other fixed orifices; in mostcases, a change in expansion device is not required.

8

Freon™ MO99™ and Freon™ NU-22B™

Refrigerants

Expected Performance After Retrofit
Operational Set Points
Freon™ MO99™ and Freon™ NU-22B™ have been designed toclosely match the pressure, temperature, enthalpy, andmass flow properties of R-22. Therefore, in most cases, theoperational set points currently used for evaporator
pressures, thermal expansion valves, condenser headpressure control, etc., will be adequate for Freon™ MO99™ orFreon™ NU-22B™. After replacing R-22 with Freon™ MO99™
or Freon™ NU-22B™, start up the system and allow it tostabilize using the existing R-22 set points. If desired, after
the system has stabilized, operating controls can be
fine-tuned to optimize system performance. Detailed
instructions for measuring and setting suction pressure,superheat, and subcooling can be found at the end of
this bulletin.
Cooling capacity and energy efficiency depend greatly on
system design, operating conditions, and the actual
condition of the equipment. Freon™ MO99™ and Freon™
NU-22B™ provide similar cooling capacity and energy
efficiency to R-22 in most systems. Actual performance
depends on system design and operating conditions.

9

Freon™ MO99™ and Freon™ NU-22B™

Refrigerants

Appendix A: Physical Properties
Table 1. Physical Properties of Freon™ MO99™ and Freon™ NU-22B™ (Properties Calculated Using REFPROP Version 10.0, NIST 2018)
Physical Property

Unit

Freon™ MO99™

Freon™ NU-22B™

R-22

Boiling Point (1 atm)

°F

–44.2

-42.4

–41.5

Vapor Pressure at 77 °F

psia

142.2

139.5

151.4

Liquid Density at 77 °F

lb/ft3

71.6

72.0

74.3

Density, Satd. Vapor at 77 °F

lb/ft3

3.03

3.28

2.76

Ozone Depletion Potential

CFC-11 = 1.0

0

0

0.05

CO2 = 1

2059

2290

1760

Global Warming Potential, AR5 Values

Table 2. Composition of Freon™ MO99™ and Freon™ NU-22B™ (wt%)
HFC-32

HFC-125

HFC-134an-butane (R-600)

i-butane (R-600a)

i-pentane (R-601a)

Freon™ MO99™

8.5

45.0

44.2

1.7

0.0

0.6

Freon™ NU-22B™

0.0

55.0

42.0

0.0

3.0

0.0

10

Freon™ MO99™ and Freon™ NU-22B™

Refrigerants

Appendix B: Checklist
Retrofit Checklist for Converting CFC or HCFC Systems to Freon™ MO99™ or Freon™ NU-22B™
1.

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.

2.

Remove existing refrigerant charge from system. Need 10–15 in Hg vacuum [50–67 kPa absolute] to remove charge.
• Use recovery cylinder. (DO NOT vent to atmosphere.)• Weigh amount removed (if possible): ___________• Break the vacuum with dry nitrogen.

3.

Replace the filter drier.
• Replace the drier with the same type currently in use in the system.

4.

Replace critical 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 in contact 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 is recommended for R-22 systems with Trane 3-D
or Danfoss SM scroll compressors.

5.

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.

6.

Charge system with Freon™ MO99™ or Freon™ NU-22B™ 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 willvary by system, but will be approximately 95% of the original R-22 charge.
• Attention should be given to critically charged systems (with fixed orifices/capillary tubes) to ensure equipment is notovercharged. (Monitor discharge pressure.)
Note: Do not charge liquid refrigerant into the compressor. This will cause serious irreversible damage.

7.

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.

8.

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 overfilling, a portion(approximately 20%) of the existing mineral oil or alkylbenzene can be drained prior to the equivalent addition of POE.

9.

Label system clearly. Ensure System Data Sheet is completed and filed securely.
11Freon™ MO99™ and Freon™ NU-22B™

Refrigerants

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): Capillary Tube:______________________________________________________________

 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 Subcool (derived values)
Refrigerant T at Superheat Ctl. Pt. (°F)
Calculated Superheat (°F)
Expansion Device Inlet T (°F)
Calculated Subcool (°F)
Motor Amps (If Rack: Total)

12

Freon™ MO99™ and Freon™ NU-22B™

Refrigerants

Appendix C: Pressure-Temperature
Information

Superheat

How to Read the Pressure-Temperature Chartprovide adequate performance when using Freon™ MO99™

In many cases, the superheat settings used for R-22 willor Freon™ NU-22B™. However, if it is determined an

Appendix C (Table 5) contains pressure-temperatureadjustment is needed, refer to the P-T chart (Appendix C

charts for the refrigerants discussed in this bulletin. Two[Table 5]) and proceed as follows: First, measure thetemperatures are shown for Freon™ MO99™ and Freon™

suction pressure, and using the saturated vapor pressure

NU-22B™ at a given pressure:••(dew point) table for Freon™ MO99™ or Freon™ NU-22B™,

Saturated Liquid Temperature (Bubble Point)—In thedetermine the saturated vapor temperature corresponding

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

to that measured pressure. Next, measure the suction

has condensed. This temperature-pressure should betemperature at the evaporator exit (for evaporator

used when determining the system subcooling as wellsuperheat) or at the compressor inlet (for suction

as the temperature-pressure value of product stored insuperheat), and subtract the previously determined dew

a refrigerant cylinder.

point temperature for Freon™ MO99™ or Freon™ NU-22B™ togive the amount of vapor superheat. Adjust TXV, if

Saturated Vapor Temperature (Dew Point)—In thenecessary, to increase or decrease superheat. In general,

evaporator, this is the temperature at which the last

the superheat for Freon™ MO99™ or Freon™ NU-22B™

drop of liquid has just boiled. Above this temperature,operation should be similar to that used previously during

the refrigerant will be superheated vapor. This pressure-R-22 operation.

temperature should be used in determining the system

Subcool

superheat.

Using the saturated liquid pressure (bubble point) tables in

How to Determine Suction Pressure, Superheat,and Subcool

P-T Chart Appendix C (Table 5) for Freon™ MO99™ or Freon™
NU-22B™, determine the saturated liquid temperature for

Suction Pressure

the measured condensing pressure (usually the high-side

In many cases, the evaporator pressure setting used forpressure). Measure the refrigerant liquid line temperature

R-22 will provide adequate performance when using Freon™

and subtract it from the previously determined bubble point

MO99™ or Freon™ NU-22B™. However, if it is determined

temperature for Freon™ MO99™ or Freon™ NU-22B™ to givesome adjustment is needed, refer to Appendix C (“Average

the amount of liquid subcool.

Condenser Set Points” [Table 3] and “Average Evaporator
Set Points” [Table 4]) and proceed as follows: Determine theexpected average evaporator temperature using R-22
(from the baseline data you collected prior to the retrofit).
Find the same expected evaporator temperature in the
Saturated Vapor (Dew Point) column for Freon™ MO99™ orFreon™ NU-22B™. Note the corresponding pressure for thistemperature. This is the approximate suction pressure atwhich the system should operate.

13

Freon™ MO99™ and Freon™ NU-22B™

Refrigerants

Table 3. Condenser Pressure Set Points (Based on 20 °F Evaporator, 10 °F Subcooling)
R-22, psig

Average Condenser Temperature, °F

Freon™ MO99™, psig

Freon™ NU-22B™, psig

143.4

80

143.9

145.4

148.0

82

148.7

150.2

152.8

84

153.6

155.1

157.8

86

158.6

160.1

162.8

88

163.8

165.2

168.0

90

169.1

170.4

173.2

92

174.6

175.7

178.7

94

180.1

181.2

184.2

96

185.8

186.7

189.8

98

191.7

192.4

195.6

100

197.6

198.2

201.5

102

203.7

204.1

207.5

104

209.9

210.2

213.7

106

216.3

216.3

220.0

108

222.8

222.6

226.4

110

229.4

229.0

232.9

112

236.1

235.6

239.5

114

243.0

242.3

246.3

116

250.0

249.1

253.2

118

257.1

256.0

260.2

120

264.4

263.1

267.3

122

271.8

270.3

274.6

124

279.3

277.7

282.0

126

287.0

285.2

289.5

128

294.8

292.8

297.1

130

302.7

300.6

304.8

132

310.7

308.6

312.7

134

318.9

316.6

320.7

136

327.2

324.9

328.8

138

335.7

333.3

337.1

140

344.2

341.8

In general, the condensing pressure of R-22, Freon™ MO99™, and Freon™ NU-22B™ are very close and will require minimal
adjustment to control set points. After converting from R-22 to Freon™ MO99™ or Freon™ NU-22B™, the condensing pressure
can be determined by locating the desired average condenser temperature (or R-22 pressure setting) in Table 3 anddetermining the new set point required for equivalent operation with Freon™ MO99™ or Freon™ NU-22B™.

14

Freon™ MO99™ and Freon™ NU-22B™

Refrigerants

Table 4. Evaporator Suction Pressure Set Points (Based on 105 °F Condenser, 95 °F Liquid Line)
R-22, psig

Average Evaporator Temperature, °F

Freon™ MO99™, psig

Freon™ NU-22B™, psig

10.1

-20

7.6

5.7

11.2

-18

8.6

6.7

12.4

-16

9.7

7.8

13.6

-14

10.9

8.9

14.9

-12

12.1

10.1

16.2

-10

13.4

11.3

17.6

-8

14.8

12.5

19.1

-6

16.2

13.8

20.6

-4

17.7

15.2

22.2

-2

19.2

16.6

23.8

0

20.8

18.0

25.5

2

22.5

19.5

27.2

4

24.2

21.1

29.0

6

26.0

22.7

30.9

8

27.8

24.4

32.8

10

29.7

26.1

34.8

12

31.7

27.8

36.9

14

33.7

29.7

39.0

16

35.8

31.6

41.1

18

37.9

33.5

43.3

20

40.2

35.5

45.6

22

42.4

37.6

47.9

24

44.8

39.7

50.3

26

47.2

41.9

52.8

28

49.6

44.2

55.3

30

52.2

46.6

57.9

32

54.7

49.0

60.5

34

57.4

51.5

63.2

36

60.1

54.0

65.9

38

62.9

56.7

68.7

40

65.7

59.4

71.6

42

68.9

62.1

74.5

44

71.5

65.0

77.6

46

69.3

67.9

After converting from R-22 to Freon™ MO99™ or Freon™ NU-22B™, the evaporator temperature can be set by locating thedesired average evaporator temperature (or R-22 evaporator pressure) in Table 4 and determining the new set point
required for Freon™ MO99™ or Freon™ NU-22B™, in order to achieve an equivalent average evaporator temperature.
15

Freon™ MO99™ and Freon™ NU-22B™

Refrigerants

Table 5. Freon™ MO99™ and Freon™ NU-22B™ Pressure-Temperature Data (ENG)
R-22

Freon™ MO99™

Freon™ NU-22B™

Pressure, psig

Saturated Temp.,ºF

Saturated Liquid
Temp. (Bubble Point),°F

Saturated Vapor
Temp. (Dew Point), °F

Saturated Liquid
Temp. (Bubble Point),°F

Saturated Vapor
Temp. (Dew Point), °F

-6
-5
-4
-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

-60.5
-56.7
-53.3
-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

-63.0
-59.3
-55.8
-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

-51.5
-47.8
-44.5
-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

-61.5
-57.7
-54.2
-50.9
-47.9
-45.1
-42.4
-39.8
-37.4
-35.1
-32.9
-30.7
-28.7
-26.7
-24.8
-23.0
-21.2
-17.8
-14.6
-11.6
-8.7
-6.0
-3.4
-0.8
1.6
3.9
6.1
8.3
10.4
12.5
14.4
16.4
18.2
20.0
21.8
23.5
25.2
26.9
28.5
30.1
31.6
33.1
34.6
36.1
37.5
38.9
40.2
43.6
46.8
49.8
52.8

-51.1
-47.4
-44.0
-40.9
-38.0
-35.2
-32.6
-30.1
-27.8
-25.5
-23.4
-21.3
-19.4
-17.5
-15.6
-13.9
-12.1
-8.9
-5.8
-2.8
-0.1
2.6
5.1
7.6
9.9
12.2
14.4
16.5
18.5
20.5
22.4
24.2
26.0
27.8
29.5
31.2
32.8
34.4
36.0
37.5
39.0
40.5
41.9
43.3
44.7
46.0
47.4
50.6
53.7
56.7
59.5

16

Freon™ MO99™ and Freon™ NU-22B™

Refrigerants

Table 5. Freon™ MO99™ and Freon™ NU-22B™ Pressure-Temperature Data (ENG)—Continued
R-22

Freon™ MO99™

Pressure, psig

Saturated Temp.,ºF

Saturated Liquid
Temp. (Bubble Point),°F

95
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

56.4
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

52.2
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

Freon™ NU-22B™

Saturated Vapor
Temp. (Dew Point), °F

Saturated Liquid
Temp. (Bubble Point),°F

Saturated Vapor
Temp. (Dew Point), °F

61.2
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

55.6
58.4
61.1
63.6
66.1
68.6
71.0
73.3
75.5
77.7
79.8
81.9
84.0
86.0
87.9
89.9
91.7
93.6
95.4
97.2
98.9
100.6
102.3
103.9
105.6
107.2
108.8
110.3
111.8
113.3
114.8
116.3
117.7
119.1
120.5
121.9
123.3
124.6
126.0
127.3
128.6
129.9
132.4
134.8
137.2
139.6
141.9
144.1
146.3
148.5
150.6
152.7

62.3
64.9
67.5
70.0
72.4
74.8
77.1
79.3
81.5
83.6
85.7
87.7
89.7
91.6
93.5
95.4
97.2
99.0
100.7
102.4
104.1
105.8
107.4
109.0
110.6
112.1
113.6
115.1
116.6
118.0
119.5
120.9
122.3
123.6
125.0
126.3
127.6
128.9
130.2
131.5
132.7
133.9
136.4
138.7
141.0
143.3
145.5
147.6
149.7
151.8
153.8
155.8

17

Freon™ MO99™ and Freon™ NU-22B™

Refrigerants

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, attheir own risk. Because conditions of use are outside our control, Chemours makes no warranties, express or implied, and assumes no liability in connection with any use of thisinformation. Nothing herein is to be taken as a license to operate under, or a recommendation to infringe, any patents or patent applications.
© 2019 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 trademarksof The Chemours Company.
Replaces: K-22217-2
C-10862 (6/19)