Buy R438A Refrigerant (MO99) | R22 Drop-In Replacement | Free Shipping — Refrigerant Inc

R438A Refrigerant (MO99) — The Most Popular R22 Drop-In Replacement

R-438A, sold under the brand name MO99 by Mexichem (now Orbia), is widely regarded as the closest performing drop-in replacement for R22 in existing air conditioning and heat pump systems. It was specifically engineered to match R22's operating pressures, capacity, and efficiency as closely as possible, making it the go-to choice for HVAC contractors servicing older R22 systems across the country. Refrigerant Inc stocks genuine, virgin R438A/MO99 with free shipping to all 48 continental states.

Why R438A (MO99) Is the Leading R22 Replacement

Among all R22 retrofit refrigerants, MO99/R438A stands out for several reasons:

• Closest pressure match to R22 — Operating pressures are very similar to R22, meaning existing metering devices, TXVs, and system components typically work without replacement
• Minimal capacity loss — Cooling capacity is within a few percent of R22 in most applications, preserving system performance
• Compatible with existing mineral oil — Unlike some R22 alternatives, R438A has good miscibility with the alkylbenzene and mineral oils commonly found in R22 systems, reducing the need for extensive oil flushes
• Non-flammable, low toxicity — A1 safety classification, safe to handle with standard refrigerant service equipment
• No system hardware changes required — In most cases, recover the R22, recharge with MO99, and the system runs

What Systems Use R438A (MO99)?

R438A is used as a retrofit refrigerant in existing R22 systems including:

• Residential central air conditioners and heat pumps installed before 2010
• Light commercial packaged units and split systems originally charged with R22
• Older commercial rooftop units running R22

R438A is not used in new equipment — it is a service refrigerant for the existing R22 installed base.

How to Retrofit an R22 System to R438A (MO99)

1. Recover all existing R22 from the system using an EPA-certified recovery machine
2. Check system for leaks and repair as needed
3. Pull a deep vacuum (500 microns or lower) to remove moisture and non-condensables
4. Charge with R438A as a liquid to the manufacturer's recommended weight — typically the same charge weight as the original R22 specification
5. Check operating pressures against R438A PT charts and verify superheat/subcooling
6. Label the system with the new refrigerant type, charge weight, and conversion date

An oil change to POE lubricant is recommended for long-term system health but is not always required for the system to operate. Consult the MO99 retrofit guidelines from Mexichem/Orbia for your specific application.

R438A vs. Other R22 Replacements

• R438A (MO99) — Best overall pressure and capacity match to R22, most widely used in the U.S.
• RS-44b (R453A) — Designed as the closest chemical near-drop-in to R22, minimal oil change requirements
• R422B — Established retrofit option, particularly in older commercial equipment
• R22 — Still the best option for systems you want to keep running at original spec, if cost is not a constraint

Why Buy R438A (MO99) From Refrigerant Inc

• Virgin, Factory-Sealed Product — Genuine R438A/MO99, never reclaimed or gray market.
• Free Shipping to All 48 States — No freight fees added at checkout.
• Same or Next-Day Processing — Orders placed before 2PM EST ship the same day.
• Contractor & Wholesale Pricing — Volume accounts available. Call 888-593-7366.

Shipping Information

R438A ships via ground freight to all 48 continental states. Alaska and Hawaii excluded. Most orders ship within 1 business day. Transit time is typically 2–5 business days depending on location.

Frequently Asked Questions

Is MO99 the same as R438A?
Yes. MO99 is the brand name for R438A, sold by Mexichem (now Orbia). The refrigerant is identical — MO99 is simply the trademarked product name. You may see it referred to as either R438A or MO99 in service literature.

Do I need to change the oil when converting to MO99?
R438A has better mineral oil compatibility than most R22 alternatives, so many technicians convert without a full oil change and the system runs fine. However, a POE oil change is recommended for long-term compressor health, particularly on systems that will remain in service for several more years.

How much R438A do I need to charge?
Charge by weight to the original R22 nameplate specification. R438A charge weight is typically the same as the R22 charge weight for the system.

Is MO99 better than just using R22?
For systems you want to maintain at original performance, R22 is still the best option. MO99 is the best alternative when R22 cost or availability is a concern — it's the closest performing replacement available and is significantly less expensive than R22 per pound.

Can I search for "MO99 refrigerant" and find this product?
Yes — MO99 and R438A are the same refrigerant. Whether your supplier literature, equipment manufacturer, or service manual references MO99 or R438A, this is the product you need.