Kromschröder VRH Flow Rate Regulator (without Solenoid Valve)

Kromschröder VRH is a flow rate regulator that keeps the gas flow in proportion to the air flow on modulating-controlled and stage-controlled burners. Unlike the VAH it has no solenoid valve. This page covers the VRH code only. Sibling codes in the valVario series: VAH (same principle but with a solenoid valve), VAD (spring-set constant pressure governor), VAG (1:1 pressure ratio) and VAV (variable pressure ratio 0.6:1–3:1), all with an integrated solenoid valve.

Specifications

• Function: controls the gas flow rate in proportion to the air flow rate (differential pressure across a measuring orifice); no solenoid valve and no electrical connection, so it does not shut off the gas itself.
• Differential air pressure Δpsa (psa – psa-) and differential gas pressure Δpd (pd – pd-): each 0.6–50 mbar; gas:air ratio 1:1; zero point N adjustable at low fire ±5 mbar.
• Inlet pressure always higher than Δpsa + max. gas pressure at the burner + pressure loss + 5 mbar. In the horizontal position with modulating control: min. inlet pressure 80 mbar.
• Three 1/8″ connections: VRH..E (compression fitting for 6 x 1 tube) or VRH..A (NPT); measuring orifice in the air line with straight inlet and outlet sections ≥ 5 DN.
• Sizes: VRH 115 (DN 15), 120 (DN 20), 125 (DN 25), 240 (DN 40), 350 (DN 50); Rp or NPT thread, ISO 7005/ANSI flange on 240 and 350. Accessories listed in the document: screw plugs, test nipples.
• Ambient temperature -20 to +60°C; designed lifetime 10 years.

Sizes

VRH 115 (DN 15), VRH 120 (DN 20), VRH 125 (DN 25), VRH 240 (DN 40), VRH 350 (DN 50). The document has no separate dimension and weight table for the VRH.

Difference from VAD, VAG, VAV, VAH

• Versus VAH: the VRH has no solenoid valve (the manufacturer’s type code table lists the VRH as having no solenoid valve), so no power supply, no coil and no automatic gas shut-off; the VAH has them.
• Versus VAG and VAV: the VRH regulates gas flow rate from the air flow across an orifice (three connections), whereas VAG/VAV regulate gas pressure from an air control pressure.
• Versus VAD: the VRH has no integrated safety valve and no spring-set outlet pressure.
• The document gives no electrical data, opening/closing times, VRH-specific approvals or weight for the VRH.

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 VRH keeps a constant gas/air ratio on modulating-controlled and stage-controlled burners.

Standards / Certification

• VRH sizes 1–3 are named in the manufacturer’s joint declaration of conformity for VAD/VAG/VAV/VAH/VRH (directives 2014/35/EU, 2014/30/EU, 2011/65/EU, regulation (EU) 2016/426). The document gives no separate standards or approvals for the VRH, and its safety valve data (EN 161) refer to the versions with a solenoid valve.
• VRH designed lifetime: 10 years (no switching cycle count).

Compatibility / Installation

• Install vertical or tilted up to horizontal, not upside down. Fit a measuring orifice (VMO) in the air line downstream of the air control valve, with straight inlet and outlet sections ≥ 5 DN.
• Do not install a gas solenoid valve VAS between the VRH and the fine-adjusting valve VMV; the VAS could no longer act as a second safety valve there.
• Install a filter upstream; leave room for installation and adjustment.

What to send for a quote

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

• full type code (for example VRH with size 1-3 / DN, Rp or NPT thread or ISO flange)
• air flow rate/differential pressure across the measuring orifice and the gas pressure at the burner
• air control connection type (E or A)
• 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 VRH is in the matching sections.