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.

Commercial instantaneous water heater options for reliable commercial water heating solutions

Commercial instantaneous water heaters,are often called commercial tankless water heaters or commercal on demand water heaters as they provide domestic hot water , without storage on demand for commercial premises in an energy efficient manner.

By far the most popular type of tankless water heaters for large communal residential and commercial applications, are gas fired units due to the output you can achieve from a relatively small gas pipe size.

Flexiheat UK offer instantaneous water heaters with power ratings of up to 200kW in single units and power ratings of up to 400kW in a cascade on demand water heaters configuration.

Typical applications for these instant water heaters include hotels, gyms, healthcare,process, bars, restaurants, brewing, food production, and farming.

Benefits of Instantaneous Commercial Water Heaters

• Provide a reliable and energy efficient hot water supply for commercial premises.
• Instantaneous water heaters reduce operating costs and environmental impact with energy-efficient technology
• Increase customer satisfaction with a consistent hot water flow
• Lare power ratings / Outputs – suitable for various commercial hot water heating applications, including restaurants, hotels, and hospitals
• Cost effective / operating costs – The energy efficiency of instantaneous water heaters can be 24%–34% higher than that of traditional storage tank water heaters.Source Energy.gov
• When combined with other heating systems, a commercial water heater, in particular instantaneous water heaters, provides a comprehensive solution.
• This commercial on demand hot water heater range can provide hot water in very large volumes in an energy efficient manner for any commercial premises or to heat water for a process application.

Types of Commercial Water Heaters

Tankless water heaters: provide hot water on demand without the need for a storage tank

Instantaneous water heaters: heat water as it flows through the unit, providing a continuous hot water supply

The two types of water heaters mentioned above are identical. It’s just terminology; they are both commercial instantaneous hot water heaters.

Electric models: offer slightly greater energy efficiency and are only really suitable for smaller commercial demands due to the requirements of a 3-phase power supply and the Amps required to heat water.Also operating costs are more for electric powered water heaters.

Gas water heaters:are the most popular and cost-effective option for commercial water heaters/ instantaneous water heaters.

Product Selection and Recommendation

• Collect information about your commercial application, including hot water heating demands and power requirements (especially for electric models)
• Consider the specific needs of your commercial water heating demands when selecting a water heater

Our commercial tankless water heaters options

When a commercial instant water heater,tankless water heater or on demand water heaters have a kW rating of 50 kW or above for gas-fired units, we consider them a commercial water heater.

First we have our 50kW commercial tankless hot water heater

This commercial instant water heater benefits from a stainless steel heat exchanger featuring large 28-mm single-piece coils that provide very low pressure drops, less chance of clogging, more thermal efficiency, and easier cleaning.

This 50kW commercial instantaneous hot water heater features an inbuilt pump, which can be switched on or off depending on your system requirements, i.e., straight through on demand water heating or DHW recirculation heating system.

Internal picture of our 50kW commercial tankless hot water heater with stainless steel heat exchanger and inbuilt recirculation pump that allows a DHW recirculation system for instant hot water at the taps / showers etc.

Hot water performance i.e. flow rate of our gas fired 50kW commercial tankless hot water heater, at various temperature rises- shown as Delta T  i.e. “Δt ”

The dairy, brewing, food processing, and agricultural sectors, as well as other applications requiring high-temperature water for washdowns, pasteurization, or process water, commonly use this 50kW commercial instantaneous water heater as they are capable of producing a maximum water temperature of 85°C.

Features and benifits

• The 50kW commercial on demand hot water heater will modulate up to 10:1 for increased efficiency and lower consumption.
• Our commercial gas tankless water heater uses patented advanced burner technologies with a compact design.
• This commercial instant water heater has an integrated recirculation pump allowing the choice of direct flow through mode (draw) or a DHW recircualtion mode for immediate DHW supply.

Possible operating modes of our 50kW commercial tankless hot water heater – Direct (draw mode) with option of post circulation and DHW recirculation via the inbuilt DHW pump.

Download the SFK50 – 50kW Commercial instantaneous hot water heater manual Flexiheat UK

Please note –

If the commercial gas tankless water heater needs to operate at temperatures higher than 60 °C, the hardness of the water must be less than 150 PPM.

The amount of carbonate, calcium, and magnesium minerals in water is measured to determine its hardness –  75 to 150 ppm is regarded moderately hard for reference.

Also on the other scale, do not soften the water to levels lower than 50 PPM, it turns acidic at these levels and may decrease the instant hot water heater’s lifespan by corroding parts of it.

Larger industrial and commercial instantaneous water heaters

In order to consistently satisfy instantaneous large capacity commercial and industrial domestic hot water (DHW) demands, we developed the “SFKG” family of floor-standing, high-efficiency condensing gas water heaters.These are an industrial tankless hot water heater range with very large domestic hot water heating performance.

Large instantaneous gas water heaters- condensing in cascade in one self-contained floor standing unit ,150kW or 200kW from Flexiheat UK

Instantaneous water heaters – ideal for both new and existing buildings with domestic hot water systems, such as hotels, restaurants, schools, hospitals, apartment buildings, and spas and leisure centres, that require instant water heaters.

High capacity instantaneous DHW systems

A compact single floor-standing gas fired commercial water with either three (150 kW model) or four (200 kW model) load-balanced 50 kW stainless steel heat exchangers within the casing that guarantees even wear along with integrated redundancy as standard.

SFKG – our Industrial on demand hot water heater range in 150kW or 200kW single units – 400kW in casacde.

Multiple heat exchangers within one water heater casing will consistently ensure operational continuation in the event of maintenance or malfunctions.

With built-in redundancy that ensures service continuity and multiple (three for the 150kW model or four for the 200kW model) integrated heat exchangers providing load balancing for optimum long-life operation.

Designed to provide hot water for both new and existing buildings domestic hot water systems, such as hotels, restaurants, schools, hospitals, apartment buildings, spas, leisure centres, or any other businesses that require high levels of hot water for their customers.

Download the  SFKG150 and 200kW Gas instantaneous commercial water heaters brochure from Flexiheat UK

Features and benefits

• Compact floor-standing configuration instant water heaters which are condensing water heaters.
• 107.50% energy efficient at full power and 112% energy efficient at minimum power.
• Both LPG and natural gas versions are available of these instant water heaters.
• High-capacity instantaneous production of domestic hot water for commercial or industrial use.
• Multiple stainless steel heat exchangers (the SKFG150 has three and the SFKG200 has four) provide built-in redundancy.
• A high-efficiency pre-mix burner provides a large modulation range; the 150kW model has a 30:1 modulation range, and the 200kW model has a 40:1 modulation range.
• 5 year warranty on the heat exchanger (subject to terms and conditions), 2 year warranty on all other parts for these commercial water heaters.
• The heat exchangers’ large 28 mm diameter ensures very low pressure drops, lower risks of clogging, greater thermal efficiency, and greater ease of cleaning.
• We recommend softening the water to a maximum hardness of 100 ppm if the total hardness of the water supply exceeds 150 ppm if the water heaters are water heating at a water temperature above 60 °C.
• Maximum working pressure 8 bar (10 bar at special request), minimum working pressure 0.5 bar for this range of commercial water heaters.

Industrial instant hot water heater / Industrial inline water heater providing energy efficient and cost effective domestic hot water heating for industrial hot water heating systems.

150kW Industrial tankless water heater, gas-fired – hot water performance flow rate data – at various Delta T

This 150kW industrial and commercial on demand gas water heater delivers exceptional instant hot water performance. A standard shower head has a flow rate of 7 litres per minute. In the winter, the temperature of the cold water mains is 10 degrees Celsius for the majority of the UK, while the showering temperature is 40 degrees Celsius, resulting in a temperature rise of 30 degrees. This 150kW commercial instantaneous hot water heater will supply 10 showers with continuous hot water if you have the water flow rate and gas supply required.

200kW Industrial tankless water heater, gas-fired – hot water performance flow rate data – at various Delta T

Just to give you an idea of the incredible instant hot water performance of this 200kW industrial and commercial on demand gas water heater. A standard shower head has a flow rate of 7 litres a minute. In the winter the cold-water mains temperature is 10 Degrees C for the majority of the UK, and the showering temperature is 40C, thus a temperature rise of 30C. This 150kW commercial instantaneous hot water heater will supply 14 showers with continuous hot water, if you have the water flow rate and gas supply required.

Residential vs. Commercial Applications

The design of commercial water heaters meets the higher hot water demands of commercial water heating requirements.

Residential water heaters are often not suitable for commercial use due to lower power ratings and flow rates required to heat water in domestic applications.

We provide a comprehensive range of gas on demand water heaters to provide hot water for homes, apartments, and smaller projects. You can find more information about these on our dedicated webpage: instantaneous gas water heaters

Hydrogen ready water heating equipment

We have designed all of our commercial instantaneous hot water heaters to be hydrogen-ready and capable of operating on a 20% hydrogen blend, facilitating a seamless transition to zero-carbon emissions.

Commercial Water Heater Installation and Maintenance

• Ensure proper installation by a qualified gas safe heating engineer to ensure safe and efficient operation.
• Regular maintenance is necessary to extend the lifespan of any commercial water heaters and prevent costly repairs or downtime.
• Consider the installation and maintenance requirements of the commercial water heater, such as clearances, flue system requirements, etc.

Contact us

When you specify and install a Flexiheat energy efficient commercial and industrial on demand water heater, you can be confident that you will be getting the most durable, trouble-free water heater available.

Should you require further assistance or information on our commercial instantaneous water heater range, then please contact our sales team on 01202 822221 or click here for our email contact form.

Electric Multipoint Water Heaters for Instant Hot Water

Electric multipoint water heaters are an excellent solution for supplying hot water to multiple points with an instantaneous water heater.Thus the term “multipoint instantaneous water heater”

Our multi-point electric water heaters have state-of-the-art heating technology, allowing for precise temperature regulation to provide personalised comfort. Typically, our units with a rating output of up to 27 kW come with digital displays and adjustable temperature settings for easy water temperature monitoring and adjustment.

This multipoint instantaneous water heater range is typically used in domestic and commercial applications such as shops, factories, student accommodation, etc., supplying hot water for one outlet or multiple outlets, depending on the flow rate of the shower or taps (sink taps for dishwashing, food preparation, etc. or toilet-type taps) being used.

You will require a three phase power supply to this multipoint instantaneous water heater range – you needs the Amps to heat water on demand.

What is an Instantaneous Electric Water Heater?

• An instantaneous electric water heater is a type of water heater that provides hot water on demand, without the need for a storage tank.
• A multi point electric water heater heats water instantly, using electricity, and supplies it to various points of use, such as sinks, showers, and basins depending on the flow rates required.
• Instantaneous electric water heaters are ideal for residential and commercial applications where water heating is required quickly and efficiently with energy savings compared to storage water heaters.

Benefits of Multipoint Water Heaters

• An electric multi point water heater,which is a tankless heater provides hot water on demand, eliminating the need for storage water heaters.
• Energy-efficient, as they only heat water when needed.This instantaneous water heater range all have a ErP “A” energy rating.
• Lower utility bills because there is no standby heat loss that you have with a storage tank system.
• Suitable for multiple points of use, such as sinks, showers, and basins or to provide instant hot water for an appliance such as a dishwasher or washing machine.
• Compact design, ideal for compact spaces or remote areas for point of use such as a sink or shower that require instant hot water.
• These wall mounted multipoint electric water heaters can be used in commercial water heating settings, such as offices, restaurants,student accommodation and hotels, as well as larger households.

Key features to consider for instantaneous electric water heating

• Look for an instantaneous water heater with a suitable power rating (the kW rating) to meet your hot water needs.
• Safety features: Ensure the multipoint hot water heater has features such as a high temperature cut out, which is a safety cut out for overheating protection.
• Multiple points: Consider a water heater that can supply hot water to multiple hot water outlets / points of use.
• Check the flow rate of the multipoint electric water heater to ensure it meets your hot water needs.

Choosing the Right Size and Type

Consider the number of points of use and the flow rate required.

Choose a water heater with a suitable power rating (in kW) to meet your instant hot water needs.

Overview of the product, including its features such as wall mounted etc and benefits.

Review of the product’s performance, including its flow rate at your required water temperature increases , the maximum water temperature it can produce, and energy efficiency.

Flow rates for hot water fixtures

Standard shower head: 7 to 8 litres per minute flow rate

Standard shower head 7 to 8 litres a minute of flow @ 40C

A standard shower head requires 7 or 8 litres of hot water per minute, whereas European Water Label “green band” water-saving shower heads require 6 litres per minute. Think of this standard as an “ErP” rating for bathroom products, taps, etc.

Kitchen sink taps: 4 to 6 litres per minute

The “spray taps” for basins and sinks range in capacity from 2 to 4 litres per minute.

Be careful to check the flow rates on your spray taps, as all our instantaneous water heater units require a minimum flow of 2.5 litres per minute to operate.

Modern bath mixer taps have an approximate demand rate of 12 litres per minute.

Please note:

Please be aware that drench showers can have massive flow requirements, ranging from 15 litres to pretty much any flow rate; 30 litres per minute for a drench type shower is not uncommon. For these water heating applications,a large instantaneous water heater will be required or even a direct storage unvented DHW cylinder due to the high volume of water required to feed this type of shower.

Product range

These instant water heaters feature four power ratings or output ranges in a single unit. The 27kW and 36kW electric multipoint water heater, on the other hand, only offers a single power setting.

For instance, you can choose between the 17kW, 18kW, 21kW, or 24kW power outputs on our 17kW to 24kW instantaneous water heater.

This affects the draw-off point flow rate; therefore, at 17 kW, it will produce 8.1 litres; at 24 kW, it will produce 11.6 litres a minute, at the standard temperature rise of 30 °C, for daily use in the winter period, as that’s when you want hot water the most, as you can see in the following data table.

Please note that our instantaneous water heater range requires a minimum flow rate of 2.5 l/min to start heating the water. They will not operate if the flow is lower than this point.

For a given kW output from the hot water heater – as the water temperature increases, the flow rate decreases is the basic rule of physics.

The 9kW to 27kW have a digital display for easy monitoring and precise temperature control.

The digital display on our 9kW to 27kW instantaneous water heater range

Download the 9kW to 27kW multipoint instantaneous water heater range manual

and our 36kW instantaneous water heater has a tradtional temperature dial and is really suited to commercial settings.

36 kW Electric instant water heater – with a manual temperature control dial

Download the 36kW Electric multipoint instantaneous water heater manual 

Installation and safety considerations

1. Make sure a qualified electrician installs the water heater.
2. Follow the manufacturer’s installation guides and instructions to ensure the warranty.
3. Ensure the instantaneous water heater is located (wall mounted) in an area with adequate space to service or inspect the water heater and as close as possible to the water outlets being served.
4. The water heater must not be installed in a site that is exposed to the danger of an explosion and where the temperature might drop below zero C, as the water in the heater will freeze and damage the water heater, which will invalidate the warranty.
5. Check the water heater’s safety features, such as the high temperature cut out i.e., a safety cut out to prevent overheating.
6. No pressure relief valve is generally required on an instantaneous water heater unless the water pressure can get above the 10 bar the 9kW to 27kW models are rated for.The 36kW water heater is rated to a maximum water pressure of 6 bar.
7. No Expansion vessel is required for an instantaneous water heater, as they supply instant hot water there is no hot water storage to account for unlike tank-type water heaters.

Energy Efficiency and Running Costs

Instantaneous electric water heaters are energy-efficient, as they only heat water when needed they reduce your water heating energy consumption.

Look for a water heater with a high energy efficiency rating- Our electric multipoint instantaneous water heaters have an “A” energy rating.

Consider the running costs of the water heater, including electricity consumption and maintenance costs.

Contact us

Should you require further assistance, check stock (we normally have the units on the shelf for the next working day delivery or select express delivery times i.e. timed, weekend saturday delivery etc), or get prices on our energy-efficient and cost-effective electric multipoint water heaters with accurate factory fitted temperature control and supplying hot water with no standby heat loss, then please call our sales team on 01202 822221 or click here for our email contact form, as we deal with both the public and trade customers.