Venturi Indirect Unvented Cylinder

80 | 130 | 150 | 175 | 215 | 255 | 305 |400 |500 LITRES

An indirect unvented cylinder for use with a conventional boiler with electric back-up

The Plumbing Group are at the forefront of water heating technology. We are changing the way you think about water heating installations. Our 3S Technology which replenishes the internal expansion device permanently, creating the World’s first ‘Self Sustaining System’.

There is no need for recharging. This patented device is the latest development in the expansion technology. The convenience of the internal expansion device is provided without having to service and recharge. This is of course a huge improvement to unvented water heating installations.

Venturi Indirect Unvented CylinderAvailable in nine sizes ranging from 80 litres to 500 litres. The largest model capable of satisfying the hot water demands of a property with 3 bathrooms and 3 separate shower rooms.

The indirect model has a high efficiency finned tube coil which is connected to a conventional boiler to heat the cylinder of water. The coil’s finned design gives much faster recovery times than can be achieved with plain tube coils.

All models are pressure tested to 10 bar and come complete with a temperature and pressure relief valve which is factory set at 7 bar and 90 degrees Celsius. Secondary return on 175L & above.

Venturi Indirect Unvented Cylinder

*(400L / 500L) These vessels are also available with 28mm diameter stainless steel high performance coil and outlet for high water flow.

Venturi Indirect Unvented Cylinder Heat Loss Performance

Features of a ThermaCoil Venturi Indirect Unvented Cylinder

  • 25-Year cylinder and 3-Year parts warranty
  • No risk of legionella from the expansion pipe “dead leg”.
  • Sizes 80L to 500L capacity
  • Self-sustaining air-gap system
  • Cylinder manufactured from high grade Duplex stainless steel
  • 60mm fire retardant insulation minimising heat loss
  • 100% CFC/HCFC free
  • Long life with no internal moving parts
  • Preinstalled with no additional parts required
  • No external expansion vessel, quicker installation
  • 3 Bar pressure at outlets
  • All sizes WRAS approved
  • Designed & manufactured in the UK


Venturi Indirect Unvented Cylinder Schematic

How the Venturi VXI Works

The 3S technology uses fluid dynamics to create negative pressure known as the ‘Venturi effect’. With precision design, this configuration draws enough air to recharge the air gap as the tank is filled and requires no future maintenance. A truly self-sustaining system.

Venturi Indirect

Problems with expansion in existing unvented systems

Click here to find out the benefits of using Venturi 3S Technology


Venturi VXI Product Construction – Typical

Immersion heater ☞ 3kw, 240V, 1ph, Incoloy 825, with thermostat incl. cut-out
Thermal insulation ☞ CFC/HCFC free, (ODP=0, GWP=1), 60mm fire retardant insulation*
Outer casing ☞ P200 Plastisol
Inner cylinder ☞ Duplex stainless steel
Heating coil ☞ High performance, finned
Indirect thermostat ☞ Twin thermostat with independent reset, 30-70ºC
Safety device ☞ Factory fitted with 7bar/90ºC pressure & temperature relief valve
Connections ☞ Secondary return on 175L & above

*50mm on 400L and 500L vessels

Venturi VXI Product Specification

Inlet diffuser ☞ For optimal blending of cold & hot water, see fig. 1
Expansion Technology☞ VXI – 3 bar internal expansion with 3S, All other ranges – 3 bar external expansion
Pressure test☞ Tested to 10 bar
Secondary return☞ Standard fit on models 175L & above
Approvals☞ BBA, CE, WRAS, KIWA, ISO, WRC
Guarantee☞ Internal cylinder 25 years* Ancillary components 1 year
Direct thermostat☞ Element thermostat, nominal setting 60ºC
Indirect model ☞ 22mm diameter stainless steel high performance coil & outlet with 1 immersion heater
Direct model ☞ 80L fitted with 1 immersion heater; 130 – 500L fitted with 2 immersion heaters
Manufacturing ☞ All UK using state-of-the-art robot technology
Horizontal & Slimline ☞ Suitable for roof voids & 450mmØ specification
Renewables range ☞ Solar, heat pump and buffer vessels

*Commercial cylinders carry 5 years guarantee

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