Flexiheat UKHot water cylinder for heat pumps
An energy efficient domestic hot water cylinder for heat a pump ? Heat pumps are becoming more popular in the UK due to the energy efficiency that they achieve for space heating and hot water heating systems, with a high coefficient of performance (COP) by free energy extraction from the
ambient air or ground via a refrigeration cycle and this is where a hot water cylinder for heat pumps comes into play for your hot water system and reduce running costs for your domestic hot water heating via an air source heat pump heating system or ground source.
But there is one main issue when utilising heat pumps to provide hot water to your property or commercial building, and that is the water temperature that can be produced and fed to the coil or coils of the heat pump cylinder can be low as heat pump cylinders work with lower temperatures for a sustainable heating system with optimum efficiency.
These heat pump cylinders are available as an unvented cylinder (we just add a mains unvented kit) or vented cylinders (cold water tank fed) to suit your heated water requirements.
Just to be very clear these are not integrated heat pump cylinders, with a heat pump built into the cylinder, these are hot water cylinders, with increased coil size and smooth coil technology (high efficiency large diameter) for highly efficient heating of the water via an external heat pump system.
If you are looking for a hot water cylinder with an integrated air source heat pump, then we supply these, and are detailed on this dedicated webpage air source heat pump water heaters.
Hot water cylinders range specifically designed for heat pumps
To maximise the amount of heat transfer from the air source heat pump or ground source heat pump renewable energy source into the stored water, they feature a high surface area coil that is specifically built for a heat pump heating system.
The cylinder heats the water to temperature via this large heat exchanger surface area for maximum heat transfer into the heat pump hot water cylinder with a smooth coil design for complete DHW heating system performance. More heat exchanger area equates to more heated water, simple as that.
Air source heat pump systems
Air source heat pumps are the most prevalent installation in the UK which extracts energy from the outside air as a renewable heating solution and reduce reliance on fossil fuels . A standard air-to-water heat pump can, on average, achieve a flow temperature between 55°C and 60°C .
Although heat pump technology is developing at a fast pace and there are some high-temperature heat pump capacity models that can achieve 65°C to 70°C water temperatures already on the market to provide highly efficient heating with optimum efficiency.
Air source heat pump and hot water cylinder hot water system installation with heating buffer tank for a complete heating system diagram.
Ground source heat pump systems
A geothermal or ground source heat pump heating system can normally reach a maximum temperature of 55 °C.
Heat pump hot water cylinders
Our heat pump hot water cylinders high performance coil has a large heat exchange surface area to increase hot water performance, maximising thermal transfer while minimising pressure loss.
The heat pump cylinder for medium-sized to large heat pumps requires heat exchangers that can handle the higher flow rates brought on by the primary temperatures, which are usually 50°C to 55°C for an air source heat pump.
This is the main reason an existing hot water cylinder has to be replaced with a suitable new heat pump cylinder that has been specifically designed for a heat pump system, is a large surface area coil to cope with the higher flow rates, and ensures good thermal energy transfer from the hot water tank into the domestic hot water to feed your baths, showers, and hot water taps of your hot water system.
Should you wish to incorporate solar thermal into the system then we do a twin coil cylinder range, which are detailed on this webpage twin coil cylinders.
Domestic hot water heat pump cylinders product specification
With a full range of hot water cylinders for a heat pump installation, from 200 to 2,000 litres of hot water storage in our “ELC ” range, which are vitreous enamel / Glass lined tank. The surface of the heat pump cylinders storage tank that comes into contact with water is protected by vitreous enamelling, a food-grade, impermeable lining that has a porcelain appearance.
Performance data for the enamelled heat pump cylinders
The output of domestic hot water is directly related to the water temperature feeding the heat exchanger (the coil) and the flow volume to the coil of the heat pump hot water tank, as you can see from the following data chart:
For example, our 300 Litre unit, when fed with water at 55 °C to the coil with a volume of 4 m3/hr (4,000 Litres / hour) , will produce 37 kW of output, which is 910 Litres per hour when the DHW is raised from 10 °C to 45 °C. Our hot water cylinders produce high hot water heating flow rates relative to others on the UK market.
Water heating performance data at various flow temperatures and flow rates to the coil of the cylinder.
Obviously when you have a flow temperature of 55°C to the coil, you’re never going to get the DHW up to 60°C; i.e., the secondary side temperature will never be more than the flow temperature. If the flow temperature is 55°C, the maximum achievable temperature will be around 50°C, because there is always a necessary temperature differential between the two water temperatures, and no heat exchanger surface operates at 100% efficiency. So you’re going to need an immersion heater or heaters fitted to the tank to get the water temperature up to the required 60°C for anti-Legionella purposes.
This immersion heater / heaters can be powered by solar PV (Solar Photovoltaics), to reduce running costs of the DHW system.
High temperature heat pump water hot water cylinder outputs
With the development of high temperature heat pump systems, which can produce hot water temperatures of 70°C, you can achieve DHW temperatures of 60°C within the cylinder, and you won’t require an immersion heater for top-up heating.
Download the brochure for the 200 to 500 Litre low pressure drop coil designated the “HF” range , showing weight, dimensions in mm, outlets, etc., this range is typical used in domestic properties and has no inspection / clean out port here
Download the brochure for the standard 200 to 2,000 Litre high recovery hot water cylinder models, showing weight, dimensions in mm, outlets, etc. – These units have an inspection/clean-out port as standard (normally required in commercial heating or healthcare applications) here.
200 to 2,000 Litre Glass lined heat pump cylinders brochure from Flexiheat UK
Immersion heater sizing for top up water heating
To determine the flow rate achievable with a known kW rating and temperature rise, you can use the following formula:
Flow Rate (Litres/minute) = (kW Rating) / (Specific Heat of Water (4.2 kJ/kg·°C) Temperature Rise (in °C) 60 (seconds/minute)
Explanation:
- kW Rating: The power output of the heating device i.e. the immersion heater.
- Specific Heat of Water (4.2 kJ/kg·°C): The amount of energy needed to raise the temperature of 1 kg of water by 1 °C.
- Temperature Rise (in °C): The difference between the desired outlet temperature and the inlet temperature.
- 60 (seconds/minute): Conversion factor to express flow rate in litres per minute.
Let’s say you have a 3kW immersion heater and want a temperature rise of 10°C.
- Calculate Flow Rate in Liters/Second:
- (3 kW) / (4.2 kJ/kg·°C X 10°C) = 0.07 litres/second
- Convert to Liters/Minute:
- 0.07 litres/second X 60 seconds/minute = 4.28 litres/minute
Thus, in one hour, a 3 kW immersion heater will heat 257.14 litres of water from 50°C to the required 60°C; a 6 kW immersion heater will double this volume to 514.28 litres; and a 9 kW immersion heater will heat up to 771.42 litres, and so on.
200 to 500 Litre low pressure drop hot water cylinders have one immersion heater port
The 200 ,300 and 500 Litre heat pump cylinders with one immersion heater port can be fitted with a 3kW,6kW or 9kW immersion heater. These can be powered by energy efficient PV solar panels (a renewable energy) if you have the electrical capacity.
“HF” series of low pressure drop hot water cylinders from 200 to 500 Litres for domestic properties with one immersion heater port.
The standard range have a inspection / clean out flange at the bottom of the hot water cylinder, that we can add an additional immersion heater port.
Inspection or clean out flange for our hot water cylinders with immersion heater tapping.
So you can install an immersion heater in tapping “4” and in the inspection / clean out flange at the bottom of the cylinder.
The heat pump cylinders with the additional clean out / inspection port can be fitted with
200 and 300 Litre models – 9kW in the immersion port and 9kW in the inspection flange = total 18kW of immersion heater power.
400, 500, 800 and 1,000 Litre models – 12kW in the immersion port and 12kW in the inspection flange = total 24kW of immersion heater power.
1,500 and 2,000 Litre models – 18kW in the immersion port and 18kW in the inspection flange = total 36kW of immersion heater power.
Stainless steel hot water cylinders option
or our stainless steel heat pump cylinders option, which is designated the “S ELC ” range. These are manufactured in 316L stainless steel, which is chemically pickled and passivated, giving the best corrosion resistance and life cycle costs for these water heaters. This range must be fitted in soft water areas.
Stainless steel cylinders should be used in Scotland, south-west and north-west of England and the west of Wales where water is particularly soft.
Glass lined versions are not suitable for very soft or soft water areas.
Performance data for the stainless steel cylinder option is the same as the glass lined range
These stainless steel heat pump cylinders are detailed on the following brochure
Stainless Steel cylinders for domestic hot water production from heat pumps brochure – Flexiheat UK
Our range benefits from:
Anti-Legionella Design:
Our high-efficiency coils are made to generate heat from the lowest point in these heat pump cylinders. This increased coil size making them compatible with a wider range of heating sources and keeps there from being cold spots inside the hot water cylinders where bacteria like Legionella could build up, produce and grow.
Energy efficiency
With low heat loss due to our superior insulation which is rigid Polyurethane thermal injected insulation , (CFC/HCFC-free, 0.025 W/mºK), they are rated either ErP “B” or “C” for heat loss according to the EU 812/2013 ErP building regulations and environmental requirements, depending on the size of the hot water cylinders.
Larger hot water heat pump cylinders
Domestic hot water tanks for heat pump use, from 1,500 to 6,000 Litre capacity. With a detachable coils system for DHW production via an external energy source, such as a air source heat pump. They can be fitted with immersion electric elements or ceramic electric elements just like direct hot water cylinders, as backup heating, which can be powered by solar PV or other renewable energy sources for long term efficiency.
Our “SB” heat pump cylinder range with a twin coils heat exchanger to provide highly efficient heating.
SB range of larger capacity hot water heat pump cylinders
With side and top 400mm manholes to access the interior of the storage tank for inspection, cleaning, and maintenance tasks. Thermally insulated with rigid highly efficient thermal injected insulation , 80 mm-thick, PU polyurethane foam, with insulated 400mm side manhole.
DHW production figures and kW ratings for our SB range of calorifiers
The heat pump coils have large surface areas for optimal heat transfer, with low resistance, and are positioned within the heat pump cylinder to ensure low temperatures on the return circuit for ground source or air source heat pumps.
Contact Flexiheat UK for your hot water heat pump cylinder requirements
With the largest range of heat pump cylinders on the UK market, please don’t hesitate to contact our sales team direct on 01202 822221, or click here for our email contact form to get a current price, general information, stock situation or delivery times.
Flexiheat UK
Flexiheat UK