B1789855 – FLOWRATER PISTON (.055) (2T, R410A) (1.5T, R22)

The flowrater piston (also called a fixed orifice) controls how much refrigerant flows into your evaporator coil. If your AC isn’t cooling properly or is freezing up, the wrong size piston — or a clogged one — can be the cause. This .055″ piston is sized for 2-ton R-410A / 1.5-ton R-22 systems running R-410A and R-22.

Specs: .055″ orifice diameter, fixed orifice type, R-410A and R-22 compatible

Replaces: B1789855

Fits: Goodman and Amana condensers and heat pumps sized at 2-ton R-410A / 1.5-ton R-22

In stock at Open To Public HVAC Parts in Dallas. We test parts at the counter before you buy. Call or text (214) 340-9421.

Specs

• TypeFixed-orifice flowrater piston
• RefrigerantR-410A
• Tonnage2 tons
• Orifice.055"
• OEM CompatibilityUniversal

Cross-reference numbers

This part replaces the following OEM and aftermarket numbers:

• B1789855

Not sure if your number matches? Call (214) 340-9421 or bring the old part in — bench-testing is free.

Fits these models

• Flowrater fixed-orifice piston — fits residential AC and heat pump distributors expecting a piston-style metering device
• Common applications: Goodman GSX/GSC/CAPF, Trane CTC/4TWX, Rheem RA13/RA14/RA16 (entry-level), some Carrier / York models
• Match the orifice size to BOTH refrigerant AND tonnage per the equipment's installation manual

What does .065 mean on a flowrater piston?

.065 inches is the orifice diameter. Smaller orifice = lower refrigerant flow = sized for smaller capacity or higher-pressure refrigerant. Match to your system's data plate spec.

Why does the same orifice fit different tonnages?

Because R-410A operates at higher pressures than R-22, a smaller orifice meters MORE refrigerant on R-410A than on R-22. So a .065 piston might serve a 2.5-ton R-410A system AND a 2.5-ton R-22 system — but you need to verify on your equipment's manual.

How do I install a flowrater piston?

1. Remove the old piston (often using a piston removal tool that grips the inner orifice). 2. Apply a NEW Teflon seal (don't reuse the old one). 3. Insert the new piston in the correct direction (arrow / flow indicator faces the evaporator distributor). 4. Torque the brass nut to manufacturer spec.

Can I use a piston instead of a TXV?

On some equipment, yes — but the system loses the ability to maintain proper superheat across changing conditions. Fixed-orifice pistons are simpler but less efficient. Check your equipment's installation manual for piston-vs-TXV compatibility.