Joule Invacyl Slimline Direct Unvented Hot Water Cylinder 90L 120L 150L 180L 210L
The Joule Invacyl Slimline Direct is a direct electric unvented hot water cylinder built for spaces where even the Cyclone Plus won't quite fit. With a 475 mm slimline diameter, factory-fitted 3 kW Incoloy immersion heaters, and a full G3 unvented kit included, it delivers mains-pressure hot water to single or multiple outlets — all from a cylinder manufactured in Duplex stainless steel and backed by a 25-year vessel warranty. Available in 90 L, 120 L, 150 L, 180 L and 210 L.
The cylinder body is fabricated from high-grade Duplex stainless steel — corrosion-resistant, lightweight, and proven in UK water conditions. The material handles both soft and moderately hard water without degradation. Joule's 25-year vessel warranty is transferable if the property is sold.
At 475 mm in diameter, the Invacyl Slimline Direct fits into narrow airing cupboards, apartment plant rooms and loft spaces that cannot accommodate a standard-width cylinder. This makes it a natural solution for new-build apartments and urban conversions where floor plan efficiency is critical.
The cylinder is supplied with two 3 kW Incoloy immersion heaters factory-fitted and tested at 230 V. The top immersion handles daily boost heating; the lower handles overnight Economy 7 or off-peak charging. Incoloy resists scale better than copper and is Joule's standard heater element choice.
As an unvented direct cylinder, the Invacyl connects directly to the incoming mains cold supply — no cold-water storage tank required. The result is high-pressure hot water to every outlet simultaneously: powerful showers, fast bath filling and consistent performance throughout the property.
The full G3 unvented kit is included in the box — inlet control group (strainer, PRV, expansion relief valve), expansion vessel and hose, tundish, T&P relief valve, and dual cylinder thermostat with high-limit cut-out. Safety components are branded Caleffi, with compression fittings as standard for a faster, more reliable installation.
The Invacyl Slimline Direct achieves ErP Class C — the highest achievable for a direct electric cylinder — and is compatible with smart immersion controllers. This includes solar PV diverters, time-of-use tariff optimisers, and smart home energy management systems, helping occupants use low-cost or free electricity to heat water.
The cylinder comes in a white outer casing with a plastic T&P safety cover and colour-coded tapping collars. The colour coding helps installers identify connection points at a glance, reducing errors on site and speeding up commissioning in tight spaces.
| Parameter | 90 L | 120 L | 150 L | 180 L | 210 L |
|---|---|---|---|---|---|
| Capacity (L) | 90 | 120 | 150 | 180 | 210 |
| Diameter (mm) | 475 (all models) | ||||
| Height (mm, approx) | ~936 | ~1205 | ~1470 | ~1700 | ~1930 |
| Immersion heaters | 2 × 3 kW Incoloy @ 230 V (factory-fitted) | ||||
| Max mains working pressure | 10 bar | ||||
| Operating pressure (T&P) | 7 bar | ||||
| Safety cut-out temperature | 90 °C | ||||
| ErP energy rating | Class C | ||||
| Cylinder material | Duplex stainless steel | ||||
| Safety components | Caleffi branded (T&P valve, inlet group) | ||||
| Connections | Compression fittings as standard | ||||
| Warranty | 25 years (cylinder); 1 year (controls, exp. vessel, components) | ||||
What is the difference between the Invacyl and the Cyclone Plus Direct Slim?
Can the Invacyl be used on Economy 7 or off-peak electricity?
Does the Invacyl need annual servicing?
What water quality does Joule require?
What size cylinder do I need?
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Joule Invacyl Slimline Direct Unvented Hot Water Cylinder 90L 120L 150L 180L 210L
The Joule Invacyl Slimline Direct is a direct electric unvented hot water cylinder built for spaces where even the Cyclone Plus won't quite fit. With a 475 mm slimline diameter, factory-fitted 3 kW Incoloy immersion heaters, and a full G3 unvented kit included, it delivers mains-pressure hot water to single or multiple outlets — all from a cylinder manufactured in Duplex stainless steel and backed by a 25-year vessel warranty. Available in 90 L, 120 L, 150 L, 180 L and 210 L.
The cylinder body is fabricated from high-grade Duplex stainless steel — corrosion-resistant, lightweight, and proven in UK water conditions. The material handles both soft and moderately hard water without degradation. Joule's 25-year vessel warranty is transferable if the property is sold.
At 475 mm in diameter, the Invacyl Slimline Direct fits into narrow airing cupboards, apartment plant rooms and loft spaces that cannot accommodate a standard-width cylinder. This makes it a natural solution for new-build apartments and urban conversions where floor plan efficiency is critical.
The cylinder is supplied with two 3 kW Incoloy immersion heaters factory-fitted and tested at 230 V. The top immersion handles daily boost heating; the lower handles overnight Economy 7 or off-peak charging. Incoloy resists scale better than copper and is Joule's standard heater element choice.
As an unvented direct cylinder, the Invacyl connects directly to the incoming mains cold supply — no cold-water storage tank required. The result is high-pressure hot water to every outlet simultaneously: powerful showers, fast bath filling and consistent performance throughout the property.
The full G3 unvented kit is included in the box — inlet control group (strainer, PRV, expansion relief valve), expansion vessel and hose, tundish, T&P relief valve, and dual cylinder thermostat with high-limit cut-out. Safety components are branded Caleffi, with compression fittings as standard for a faster, more reliable installation.
The Invacyl Slimline Direct achieves ErP Class C — the highest achievable for a direct electric cylinder — and is compatible with smart immersion controllers. This includes solar PV diverters, time-of-use tariff optimisers, and smart home energy management systems, helping occupants use low-cost or free electricity to heat water.
The cylinder comes in a white outer casing with a plastic T&P safety cover and colour-coded tapping collars. The colour coding helps installers identify connection points at a glance, reducing errors on site and speeding up commissioning in tight spaces.
| Parameter | 90 L | 120 L | 150 L | 180 L | 210 L |
|---|---|---|---|---|---|
| Capacity (L) | 90 | 120 | 150 | 180 | 210 |
| Diameter (mm) | 475 (all models) | ||||
| Height (mm, approx) | ~936 | ~1205 | ~1470 | ~1700 | ~1930 |
| Immersion heaters | 2 × 3 kW Incoloy @ 230 V (factory-fitted) | ||||
| Max mains working pressure | 10 bar | ||||
| Operating pressure (T&P) | 7 bar | ||||
| Safety cut-out temperature | 90 °C | ||||
| ErP energy rating | Class C | ||||
| Cylinder material | Duplex stainless steel | ||||
| Safety components | Caleffi branded (T&P valve, inlet group) | ||||
| Connections | Compression fittings as standard | ||||
| Warranty | 25 years (cylinder); 1 year (controls, exp. vessel, components) | ||||
What is the difference between the Invacyl and the Cyclone Plus Direct Slim?
Can the Invacyl be used on Economy 7 or off-peak electricity?
Does the Invacyl need annual servicing?
What water quality does Joule require?
What size cylinder do I need?
Product Information
Product Information
Shipping & Returns
Shipping & Returns
Description
The Joule Invacyl Slimline Direct is a direct electric unvented hot water cylinder built for spaces where even the Cyclone Plus won't quite fit. With a 475 mm slimline diameter, factory-fitted 3 kW Incoloy immersion heaters, and a full G3 unvented kit included, it delivers mains-pressure hot water to single or multiple outlets — all from a cylinder manufactured in Duplex stainless steel and backed by a 25-year vessel warranty. Available in 90 L, 120 L, 150 L, 180 L and 210 L.
The cylinder body is fabricated from high-grade Duplex stainless steel — corrosion-resistant, lightweight, and proven in UK water conditions. The material handles both soft and moderately hard water without degradation. Joule's 25-year vessel warranty is transferable if the property is sold.
At 475 mm in diameter, the Invacyl Slimline Direct fits into narrow airing cupboards, apartment plant rooms and loft spaces that cannot accommodate a standard-width cylinder. This makes it a natural solution for new-build apartments and urban conversions where floor plan efficiency is critical.
The cylinder is supplied with two 3 kW Incoloy immersion heaters factory-fitted and tested at 230 V. The top immersion handles daily boost heating; the lower handles overnight Economy 7 or off-peak charging. Incoloy resists scale better than copper and is Joule's standard heater element choice.
As an unvented direct cylinder, the Invacyl connects directly to the incoming mains cold supply — no cold-water storage tank required. The result is high-pressure hot water to every outlet simultaneously: powerful showers, fast bath filling and consistent performance throughout the property.
The full G3 unvented kit is included in the box — inlet control group (strainer, PRV, expansion relief valve), expansion vessel and hose, tundish, T&P relief valve, and dual cylinder thermostat with high-limit cut-out. Safety components are branded Caleffi, with compression fittings as standard for a faster, more reliable installation.
The Invacyl Slimline Direct achieves ErP Class C — the highest achievable for a direct electric cylinder — and is compatible with smart immersion controllers. This includes solar PV diverters, time-of-use tariff optimisers, and smart home energy management systems, helping occupants use low-cost or free electricity to heat water.
The cylinder comes in a white outer casing with a plastic T&P safety cover and colour-coded tapping collars. The colour coding helps installers identify connection points at a glance, reducing errors on site and speeding up commissioning in tight spaces.
| Parameter | 90 L | 120 L | 150 L | 180 L | 210 L |
|---|---|---|---|---|---|
| Capacity (L) | 90 | 120 | 150 | 180 | 210 |
| Diameter (mm) | 475 (all models) | ||||
| Height (mm, approx) | ~936 | ~1205 | ~1470 | ~1700 | ~1930 |
| Immersion heaters | 2 × 3 kW Incoloy @ 230 V (factory-fitted) | ||||
| Max mains working pressure | 10 bar | ||||
| Operating pressure (T&P) | 7 bar | ||||
| Safety cut-out temperature | 90 °C | ||||
| ErP energy rating | Class C | ||||
| Cylinder material | Duplex stainless steel | ||||
| Safety components | Caleffi branded (T&P valve, inlet group) | ||||
| Connections | Compression fittings as standard | ||||
| Warranty | 25 years (cylinder); 1 year (controls, exp. vessel, components) | ||||
