Kromschroder Air/gas ratio control VAG350R/NWAE 88000277

This air/gas ratio control integrates a class A solenoid shut-off valve and an EN 88 pressure ratio regulator in a sealed housing. It operates on 220–230 V AC (50–60 Hz) and has a nominal diameter of 50 mm with an Rp 2" threaded connection. Opening time is ≤ 0.5 s and closing time is 1 s. Output pressure can be adjusted from 0.5 to 100 mbar, with a maximum operating pressure of 500 mbar. The IP 65 housing, M20 cable gland, and NBR rubber seals suit it for industrial gas systems. The solenoid coil is often replaceable separately.

Parts of this type are selected by brand and series, connection size, and the control pressure range from the fan. Verify that the fan pressure signal matches the control's design range and that the gas valve body is compatible with the ratio control's mounting interface. Valve body material, diaphragm type, and presence of a zero-governor function (for low-pressure systems) also matter. Most units accept a pressure tap from the fan and output proportional gas pressure, requiring no electrical signal for the ratio function—only for the solenoid coil.

Common failure modes include a torn diaphragm, a blocked pressure impulse line, or a stuck regulating piston. These can cause unstable gas pressure, poor combustion, or failure of the valve to open. If the valve fails to open electrically, the solenoid coil should be tested—it is often replaceable separately.