300 Litre Indirect Unvented Cylinder

Our 300 litre indirect unvented cylinder is the best on the UK market, manufactured in stainless steel with proven technology and quality manufacturing with the capacity to supply plenty of domestic hot water for your bathroom, shower, wet rooms, and kitchen hot water tap requirements.

This indirect unvented cylinder is “indirect,” meaning that the cylinder has a coil within the inner cylinder, which needs to be fed by a boiler, be it gas or oil. Being an unvented cylinder, you cannot use solid fuel boilers as the heat source. You must use a vented cylinder for solid fuel.

Our 300l indirect unvented cylinder does not require an external expansion vessel, as it uses a patented self-sustaining internal air gap within the cylinder to account for the hot water expansion pressure that requires minimum to no maintenance.

Unvented domestic hot water self-sustaining expansion system, so no external expansion vessel is required for our unvented hot water cylinders – Flexiheat UK

What is an indirect unvented cylinder?

An unvented hot water cylinder receives its water supply directly from the main water system, allowing it to produce hot water at a significantly higher pressure than a traditional vented cylinder due to its pressurization.

An indirect unvented cylinder is a type of hot water cylinder that uses a primary coil to heat water indirectly, providing a safe and efficient hot water supply.

Indirect unvented cylinders are designed to work with a boiler or heat source, providing a reliable and efficient domestic hot water supply.

What is a 300L indirect hot water cylinder suitable for ?

The overall amount of hot water used is also greatly influenced by personal behaviours. The amount of hot water used by two houses of the same size might range greatly, with one household needing twice as much as the other.

Understanding peak demands and making sure you have the ideal ratio of cylinder capacity to re-heat times are the most important factors.

As a general guideline, use the following average consumption values for hot water requirements per person per day:

• Low Consumption = 20–30 litres

• Average consumption = 30–50 litres.

• High consumption: 50–70 litres

source – hotwater.org.uk

As a good rule of thumb,a 4 bedrooms + 2 bathrooms/shower house should use a 300l unvented indirect cylinder.

If the property is on the lower scale of DHW usage, then you may be able to use a 250 Litre unvented indirect cylinder, please see our dedicated webpage on this size of hot water cylinder  – 250 Litre Indirect Unvented Cylinder

Key features and benefits

• The cylinder is made of high-grade stainless steel, ensuring a long product life and minimal maintenance.
• No sacrificial anode is required for a stainless steel unvented cylinder.
• Our units are manufactured and certified in accordance with the following approvals – BBA, CE, WRAS, KIWA, ISO, WRC.
• Quality manufacturing and proven technologies at a competitive price.
• We use a stainless steel indirect heating coil (heat exchanger) to speed up heat recovery and minimize heat loss.
• We use 60mm of environmentally friendly factory-injected polyurethane foam insulation on our 300 Litre cylinder to minimise heat loss and running costs.This high grade insulation is HCFC/CFC free (ODP=0, GWP=1).
• Minimal heat loss: Because these units have an ErP rating, they lose less heat, which is better for the environment.
• The pressure relief valve ensures a safe and efficient operation of these stainless steel indirect water heaters.
• It offers high flow rates for showers and baths in both residential and commercial settings, eliminating the requirement for a booster pump.

Our 300 litre indirect unvented hot water cylinders are manufactured from duplex stainless steel and thus don’t require a sacrificial anode, which results in less maintenance time and costs for our 300 litre indirect unvented cylinders.

Our indirect unvented cylinder range allows for installation in smaller spaces because it doesn’t require an external expansion vessel. On the left is our indirect unvented cylinder with no expansion vessel installed, and on the right is an indirect cylinder with an external expansion vessel system, which requires a lot more space for the associated pipework and connections.

In our own review – less space and easier installation

Hot water cylinder detail for our 300-litre indirect model

First we have the basic dimensions of our indirect unvented cylinder 300 Litres in capacity.

Our indirect hot water heater dimensions diagram

Dimensions

Heat up times, recovery times, and weights of our 300L indirect hot water cylinder—unvented model.

Technical detail showing the heat recovery times, kW output rating of the heat exchanger coil at 80C flow of our 300 Litre indirect hot water cylinder.

Download the Indirect and direct hot water cylinders in stainless steel brochure 

Download the Installation and maintenance manual for indirect and direct hot water cylinders

 Hi flow rate 300L indirect unvented cylinder option

We can also supply a 300l indirect range for high flow rates for larger domestic and commercial water heating demands; this option has 28 mm pipe connections and 28mm venturi valve rather than the standard 22 mm pipe connections and 22mm venturi valve. The stock sku for this is unit 300L Hi-Flo stainless steel indirect unvented cylinder and it has the same primary coil rating as the standard unit.

Standard indirect hot water cylinder unvented components supplied

• Temperature/Pressure Safety Relief Valve: set at 90°C and 7 bar pressure (factory fitted to the indirect unvented cylinder)
• The combination (control) valve consists of a line strainer, a non-return (check) valve, a pressure reducing valve, and an expansion relief valve. Supplied lose to be fitted to the incoming cold water mains pipework.
• 3kW Incoloy (a better material than stainless steel) immersion heater, which is single-phase 240 Volt powered, incorporating a control thermostat and re-settable safety cut-out. For back up hot water heating or a cheap economy electric power system.
• We have the option to upgrade the immersion heater to a 6kW version on this indirect unvented cylinder, which can be powered by either 1 phase or a 3 phase power supply
• The thermal cut-out is set to operate at 82°C (+/-5°C).
• Motorised valve to cut the heat source plumbing to the cylinders in the event of a high temperature cut out activation.

Warranty of our indirect unvented cylinder

Because this 300L indirect unvented hot water cylinder is manufactured in duplex high quality stainless steel, which is highly corrosion-resistant.

The hot water cylinder comes with a 25-year guarantee when used in a domestic water heating application (standard household use). If used in a commercial water heating application, then the warranty is reduced to a 5 year warranty.

G3 unvented indirect cylinder installation regulations

Section G3 of the Building Regulations (England and Wales) covers our indirect unvented cylinder range, along with Technical Standard P3 (for Scotland) and Building Regulation P5 (for Northern Ireland). Compliance can be achieved through a Competent Person Self Certification Scheme, where a heating engineer with the Unvented G3 Certificate possesses the necessary knowledge and skills to install and maintain unvented hot water storage systems, or by notifying the local authority building control department of the installation.

Do not try to install an indirect unvented cylinder unless you have the necessary certificate or qualifications. An unvented hot water cylinder can explode if not correctly fitted with all of the safety systems that they require.

Installation and maintenance considerations

Ensure the cylinder is installed by a qualified professional and follow the manufacturer installation requirements, with the tundish positioned for occupant visibility and away from electrical devices.

Regularly check and maintain the pressure relief valve to the manufacturer’s requirements.

To prevent hot water limescale buildup within the cylinder, especially in hard water areas, consider adding a scale defender.

Contact us

For more details, check stock or purchase our 300 litre indirect unvented cylinder, which is made in the United Kingdom from duplex stainless steel with quality manufacturing methods and a manufacturer 25 year warranty (for domestic use). Please contact our sales team on 01202 822221 or use our email contact form.