Kromschröder VAG Air/Gas Ratio Control with Solenoid Valve

Kromschröder VAG is an air/gas ratio control (Class A) with an integrated safety solenoid valve; it holds the gas pressure in a fixed 1:1 ratio to an air control pressure. This page covers the VAG code only. Sibling codes in the valVario series: VAD (spring-set constant pressure governor), VAV (variable ratio 0.6:1–3:1), VAH (flow rate regulator with solenoid valve) and VRH (flow rate regulator without solenoid valve). The VAG’s own traits are the fixed 1:1 ratio and the VAG..N variant, which can be used as a zero governor for gas engines.

Specifications

• Function: shut-off and a constant 1:1 gas/air pressure ratio for modulating burners; with the VAS 1 bypass valve also for stage-controlled burners. The pressure is preset by the air control line.
• Outlet pressure pd: 0.5–100 mbar; air control pressure psa: 0.5–100 mbar. On excess-air burners pd and psa may be below 0.5 mbar, but no situation jeopardising safety may arise and CO formation must be avoided.
• Gas:air ratio 1:1; zero point N adjustable at low fire ±5 mbar; turndown up to 10:1.
• Inlet pressure always higher than the air control pressure + pressure loss + 5 mbar; max. 500 mbar (ANSI/CSA version 350 mbar). In the horizontal position with modulating control: min. inlet pressure 80 mbar.
• Air control connection: VAG..K (1/8″ hose, 3.9 mm inside, 6.1 mm outside), VAG..E (compression fitting for 6 x 1 tube), VAG..A (1/8″ NPT), VAG..N (zero governor with breathing orifice).
• Sizes 1–3: VAG 115, 120, 125, 240, 350 (DN 15, 20, 25, 40, 50), Rp or NPT thread, ISO 7005/ANSI flange on 240 and 350. Voltage 230, 200, 120, 100 V AC or 24 V DC.
• Opening ≤ 1 s, closing < 1 s (VAG../N); aluminium housing, NBR seal; -20 to +60°C; IP 65.

Dimensions and weight (Rp thread version)

The NPT version (NPT thread, ANSI flange) has its own dimension table in the document (section 9.2). ISO flanges exist on sizes 240 and 350 only.

Difference from VAD, VAV, VAH, VRH

• Versus VAD: the VAG follows the air control pressure (1:1 ratio); the VAD holds a fixed spring-set outlet pressure.
• Versus VAV: the VAG has a fixed 1:1 ratio and one air control connection; the VAV is adjustable 0.6:1–3:1 and adds a connection for combustion chamber pressure compensation (psc).
• Versus VAH and VRH: the VAG is driven by an air pressure, whereas VAH/VRH regulate gas flow rate in proportion to air flow rate across an orifice (3 connections). The VRH has no solenoid valve.
• Variant only on the VAG: VAG..N is a zero governor with breathing orifice, usable for gas engines.

Applications

The valVario series is used in gas control and safety systems in the iron, steel, glass and ceramics industries, and in residential or commercial heat generation such as the packaging, paper and food industries. The VAG keeps a constant air/gas ratio on modulating burners, or on stage-controlled burners together with the VAS 1 bypass valve; the VAG..N serves as a zero governor for gas engines. The document shows an aluminium age-hardening furnace (low air pressure protection) and a melting furnace (stoichiometric combustion over the whole capacity range) as examples.

Standards / Certification

• Class A control to EN 88-1:2011+A1:2016; Class A, Group 2 safety valve to EN 13611 and EN 161:2011+A3:2013; EN 126:2012; EN 1854:2010 (declaration of conformity for VAD/VAG/VAV/VAH/VRH sizes 1–3). UKCA: BS EN 88-1, EN 126, EN 161.
• FM (Class 7400 and 7411), ANSI Z21.21 / CSA 6.5 (ANSI/CSA), UL 429 (120 V AC version), AGA (no. 5319); not applicable to the 100 V AC and 200 V AC versions.
• Suitable for systems up to SIL 3 (EN 61508) / PL e (ISO 13849): single channel up to SIL 2 / PL d; SIL 3 / PL e with two redundant devices.

Compatibility / Installation

• Keep the air control impulse line psa as short as possible, impulse tube inside diameter ≥ 3.9 mm (0.15″), so the valve reacts quickly to load changes.
• Black solenoid actuator vertical or tilted up to horizontal, not upside down; install a filter upstream; leave 25 cm above the actuator.
• Accessories: bypass/pilot gas valve VAS 1 (staged burners), pressure switch DG..C, test nipples, closed position switch.

What to send for a quote

To quote quickly and against the right code, please send:

• full type code (for example VAG with size 1-3 / DN, Rp or NPT thread or ISO flange)
• air control connection type (K hose, E compression fitting, A 1/8″ NPT or N zero governor)
• outlet and air control pressure ranges, coil voltage (230, 200, 120, 100 V AC or 24 V DC)
• gas type (natural gas, gaseous LPG, biogas, hydrogen or clean air), inlet pressure and required flow rate
• quantity

CAD replies with a quote within 24 working hours.

Technical documentation (datasheet)

Kromschröder: Technical Information VAD, VAG, VAH, VAV, VRH, VCD, VCG, VCV, VCH (English, edition 08.23). This is the manufacturer’s single document for the whole series; the data for VAG is in the matching sections.