400 Litre Direct Unvented Cylinder 

Our 400 Litre direct unvented cylinder is built with corrosion-resistant duplex stainless steel and is reasonably priced. This unvented hot water cylinder for mains pressure hot water was created with high flow rates and a long product life in mind, utilising proven technology and a quality manufacturing method.

Flexiheat UK offers a 25-year warranty for household usage on this 400 Litre unvented direct cylinder in stainless steel. These hot water cylinders are heated by 100% energy-efficient immersion heaters (100% heat transfer) and provide water heating for bathrooms and showers.

When gas or oil is unavailable or individuals prefer to heat their water with carbon-free electricity, electric water heating is commonly used thus the term direct models.

Patented unvented hot water expansion system

The innovative internal hot water expansion mechanism, which employs a venturi valve to keep an air pocket within the stainless steel cylinder, eliminates the need for an external expansion vessel.

This unvented system has a long product life because it has no moving parts, lowering operating and lifetime expenses.

Internal air gap system for our direct unvented hot water cylinders: no external expansion vessel is required because this is a self-sustaining air gap in our unvented hot water cylinder range that requires little to no maintenance and ensures mains pressure hot water flow throughout the property regardless of the heat source feeding the unvented hot water cylinder.

Our direct unvented hot water cylinders use an internal air gap and venturi valve technology, which eliminates the need for an external expansion vessel and requires minimal maintenance.

As a result, our 400 litre electric hot water system requires less space, pipes, and plumbing connections, simplifying the installation process and saving installation costs and time.

What applications is a 400L direct unvented cylinder appropriate for?

A basic guideline is that 400 litre direct unvented hot water cylinders are appropriate for larger residences, such as a 4-bedroom house with two bathrooms/showers or more, or for properties with a high need for hot water.

People’s hot water consumption habits, however, can differ from one another. 

Please see the recovery time data for our 400L unvented direct cylinder below to determine whether this is the right electric water heater for your requirements.

This 400 Litre volume direct unvented cylinder is a popular seller in this range; however, if you require a higher volume cylinder, please visit the following webpage: direct unvented cylinder range.

Hot water heating and recovery times for a our direct unvented cylinder 400 Litres from Flexiheat UK

Our 400 Litre direct-pressurised hot water cylinders in high-grade stainless steel come standard with 2 x 3kW immersion heaters.

Our 400 Litre unvented electric powered direct cylinder has the following hot water heat-up time and recovery rates with the standard  2 x 3kW immersion heaters installed:

 

 

If you need a different size direct unvented hot water cylinder, we have a whole variety from 80 to 500 Litres, which are explained on this page: Unvented Direct Cylinder in Stainless Steel variety.

Upgraded immersion heater options.

We can upgrade the immersion heaters to higher outputs for faster heat recovery on both the 2 and 3 immersion model options.

This 400-litre direct unvented cylinder can also be equipped with 3 x 3 kW immersion electric heaters, for a total kW output of 9 kW and a recovery time of 180 minutes from 10°C to 65°C (or 3 hours).

If desired, we can deliver this 400 Ltr direct unvented cylinder with 3 x 6 kW immersion heaters. These heaters can be connected to either a single phase at 240 volts (32 amps per heater) or three phases (10.66 amps per phase), for a total power output of 18 kW. This system heats the water from cold (10°C) to 65°C in 86 minutes for the 400 litres of volume.

We must also change the basic temperature and pressure relief valve to a higher output model, as the normal valve is rated for 10kW of power.

All our unvented hot water cylinders are pressure tested at the factory, with a maximum working pressure of 5.5 bar and a test pressure of 10 bar.

If you want a bigger output of up to 36 kW for a 400 Litre direct water heater, please consult this webpage: Commercial electric water heater range.

Unvented Direct Cylinder 400 Litres: Features and Benefits.

Improved Venturi valve technology automatically supplies the internal air gap of the unvented cylinder.

The dual immersion cylinder comes standard with 2 x 3 kW immersion heaters but may be upgraded to 3 × 3 kW or 3 × 6 kW.

Our direct unvented hot water cylinders with an inbuilt expansion system do not require any external expansion vessels to be installed.

Our direct unvented hot water cylinders, which have an integrated expansion mechanism, do not require external expansion vessels to be fitted, making installation in compact places easier.

 

• 3-bar water pressure at the outflow (subject to entering pressure)
• Direct distribution of hot water under mains pressure enables high flow rates.
• 100% Heat transfer with electric immersion heaters
• There is no expansion vessel or moving parts, which ensures minimum maintenance.
• ErP “C” heat loss rating indicates lower energy heat loss and consumption.
• Benefits from an updated design and high-quality manufacture for better performance at low flows.
• Our 400 litre direct electric unvented cylinder includes a DHW secondary return connector.
• This 400l electric hot water system comes standard with 22mm connectors (which produce 40 litres per minute), but it may also be ordered with a 28mm-diameter stainless steel inlet and output for higher flow rates (56 litres per minute).
• This unvented direct hot water cylinder includes 60mm of fire retardant insulation to decrease heat loss.

Dimensions for a 400-litre unvented straight cylinder

Our 400-litre stainless steel unvented cylinder has the following dimensions:

 

The dimensions in millimetres for the extremely corrosion-resistant duplex stainless steel 400 Ltr capacity direct unvented cylinder are as follows:

 

 

 

The full brochure and installation manuals are here (Which cover both the direct models and indirect models ) :

Download the Hot Water cylinders direct and indirect unvented brochure from Flexiheat UK

Download the intallation and technical manual for our direct and indirect hot water cylinders.

Approvals for unvented direct cylinders of 400 Litre in capacity 

The 400 Ltr direct unvented cylinder we sell has been certified by CE, BBA, and WRAS, which are independent organisations that ensure hot water heating products are safe and comply with regulations, as well as ISO, KIWA, and WRC certifications, demonstrating that our stainless steel direct cylinders are manufactured to high standards.

Warranty for the 400 Litre Hot Water Cylinder

We are so confident in the quality of our 400 Litre unvented direct cylinders that they come with a 25-year warranty for use in residential applications such as homes and apartments. The guarantee covers the stainless steel hot water cylinder for 25 years, while other parts, such as immersion heaters and control thermostats, are covered for one year from the date of purchase.

Contact Flexiheat UK

Please contact us at 01202 822221 if you have any queries or use site contact email form for more information or specifics, the current stock situation, or a price on the best 400 litre direct unvented cylinder/400Ltr unvented direct cylinder models on the UK market. We manufacturer these models from high-grade duplex stainless steel, which has a 25-year warranty for residential customers (5 years for commercial use), a low heat loss rating, and WRAS independent approvals.