18557-1 AERCO Boiler and Water Heater Pneumatic Bulb TSTAT RA-20/240

18557-1 AERCO Boiler and Water Heater Pneumatic Bulb TSTAT RA-20/240

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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.