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Deep Technical Chapters · Charge & Metering
TXVs (Thermostatic Expansion Valves)
Technician
How a TXV controls feed, bulb placement, and what goes wrong with starving and flooding.
A TXV meters refrigerant to hold a constant superheat at the evaporator outlet. The bulb senses suction temperature and modulates the valve. Get the bulb placement wrong and the valve feeds wrong.
Failures
- Starving (restricted, blocked, bulb cold/loose) → high superheat
- Flooding (overfeeding, bulb too warm, oversized) → low/zero superheat
Bulb placement
Mount the bulb on a clean, horizontal suction line at the evaporator outlet, insulated, sensing pipe temperature only. A loose or warm bulb lies to the valve.
Field Rules
- 01
"Confirm bulb placement and charge before condemning a TXV."
