18557-1 AERCO Boiler and Water Heater Pneumatic Bulb TSTAT RA-20/240 Normal Stocking Item in Our Warehouse AERCO 18557‑1 is the OEM Pneumatic Bulb Thermostat (RA‑20/240) used on AERCO boilers and water heaters. Grounded documentation and distributor listings confirm its identity, specifications, and application. AERCO 18557‑1 Pneumatic Bulb Thermostat (RA‑20/240) — OEM reverse‑acting pneumatic temperature controller for AERCO boilers and water heaters. Features a remote liquid‑filled sensing bulb for accurate hydronic temperature regulation and stable pneumatic control. Required for heat exchangers equipped with anticipator temperature‑control systems. 🔧 Core Identity & Function Part Number: 18557‑1 Component: Pneumatic Bulb Thermostat Series: RA‑20/240 OEM: AERCO This thermostat is a reverse‑acting pneumatic temperature controller. As temperature rises, its output air pressure decreases, and vice‑versa. It uses a remote, liquid‑filled sensing bulb designed specifically for AERCO heat exchangers. It is used when the heat exchanger includes an anticipator temperature‑control system. 📐 Technical Specifications (Grounded) From AERCO Instruction AC‑103: Temperature range: −20°F to +240°F Max bulb temperature: 310°F Max controller case temperature: 150°F ambient Air supply: 20–30 PSIG Air consumption: 0.008 SCFM Air capacity: Up to 16 SCFM for mains sizing Action: Reverse‑acting pneumatic control Sensor: Remote averaging liquid‑filled bulb Applications Used in: AERCO boilers and water heaters Pneumatic building‑automation loops Hydronic heating plants Industrial HVAC temperature‑regulation systems Important installation note: 18557‑1 must be used only on AERCO heat exchangers equipped with an anticipator system.
