Kromschröder VAV Variable Air/Gas Ratio Control with Solenoid Valve

Kromschröder VAV is a variable air/gas ratio control (Class A) with an integrated safety solenoid valve, part of the valVario series. This page covers the VAV code only. Sibling codes in the series: VAD (spring-set constant pressure governor), VAG (fixed 1:1 ratio), VAH (flow rate regulator with solenoid valve) and VRH (flow rate regulator without solenoid valve). What sets the VAV apart: the gas/air pressure ratio is adjustable from 0.6:1 to 3:1 and combustion chamber pressure fluctuations are compensated.

Specifications

• Function: shut-off and a constant gas/air pressure ratio for modulating burners; the pressure is preset by the air control line.
• Transmission ratio V = pd:psa adjustable from 0.6:1 to 3:1 with screw V (high fire); zero point N adjustable at low fire ±1.5 mbar. Both screws can be read and set from either side and can influence each other, so the settings may need repeating.
• Outlet pressure pd: 0.5–30 mbar; air control pressure psa: 0.4–30 mbar; combustion chamber pressure psc: -20 to +20 mbar. With psc connected: (pd – psc) = V x (psa – psc) + N.
• Min. differentials psa – psc: 0.4 mbar; pd – psc: 0.5 mbar.
• Max. inlet pressure 500 mbar (ANSI/CSA version 350 mbar), always higher than psa x V + pressure loss + 1.5 mbar.
• Two 1/8″ connections for psa and psc: VAV..K (hose), VAV..E (compression fitting for 6 x 1 tube), VAV..A (NPT).
• Sizes 1–3: VAV 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 (VAV../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, VAG, VAH, VRH

• Versus VAG: the VAV ratio is adjustable 0.6:1–3:1 (VAG fixed 1:1) and adds a combustion chamber pressure connection psc; its outlet pressure range is smaller (0.5–30 mbar versus 0.5–100 mbar on the VAG).
• Versus VAD: the VAV follows an air control pressure; the VAD holds a fixed spring-set pressure.
• Versus VAH and VRH: the VAV is driven by an air pressure, whereas VAH/VRH regulate gas flow rate in proportion to air flow rate across an orifice.
• Installation: the VAV is installed in the vertical position only, black solenoid actuator upright; the other codes may be tilted up to horizontal.

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 VAV is used on modulating-controlled burners; the document shows it on a modulating forced-draught burner, with the combustion air set by a butterfly valve or the fan speed.

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.
• UL 429 (120 V AC version) and AGA (no. 5319) apply to the VAV; AGA does not apply to the 100 V AC and 200 V AC versions.
• Suitable for systems up to SIL 3 / PL e: single channel up to SIL 2 / PL d; SIL 3 / PL e with two redundant devices.

Compatibility / Installation

• Install in the vertical position only, black solenoid actuator upright.
• Keep the psa and psc impulse lines as short as possible (tube inside diameter ≥ 3.9 mm). Fit the psc line so condensate runs back into the combustion chamber and not into the regulator.
• 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 VAV with size 1-3 / DN, Rp or NPT thread or ISO flange)
• required gas/air ratio (within 0.6:1–3:1) and whether combustion chamber pressure is connected
• air control connection type (K, E or A), 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 VAV is in the matching sections.