Air Source Heat Pump (ASHP)

Air Source Heat Pumps

With the Governments’ announcement of £5,000 grants towards the cost of Air Source Heat Pumps (ASHP) installation, we thought our customers would be interested to have some more information about the ASHP technology.

An ASHP is, effectively, a fridge in reverse. It extracts heat from the outside air and using a compressor turns this into useable heat which can warm your home and your hot water.

There are many manufacturers of ASHP’s and correspondingly a range of prices.

In the BBC’s report on the Government’s announcement, it is suggested that the cost of installation ranges from £6,000 – £18,000.  Given the cost of equipment and labour of an install, we would respectfully comment that the lower figure is unlikely. However, the upper figure is reasonable, depending on a number of factors which we highlight below.

Currently the Government offers a Renewable Heat Incentive (RHI), details of which are below.

At this stage we believe both the RHI and the Grant are available however this needs to be confirmed by the Government.

We also understand the £5,000 grant comes from a £450M fund which has to last 3 years and hence the Grant will be available to 30,000 homes per year. We estimate approx. 1.5M boilers are changed every year and so unfortunately this scheme may only cover 1 in 50 boiler changes. We have no information on the criteria for acceptance to this scheme or if any prioritisation will be given but it will mean that 49 out of 50 homes will not get the Grant.

Things to Consider:

  1. It is possible an ASHP may not be able to deliver the heat you need to keep warm in the middle of winter as they typically have a maximum possible output of 18KW (see below).
  2. Do you have Under Floor Heating (UFH)?  ASHP’s produce heating water at 45-55C which is what UFH systems are designed to run at and so work well together. Radiators are sized per room and typically expect hot water to be delivered between 65-70C and therefore it may be the case that in order to keep the room at a temperature you are used to in the middle of Winter, more or larger radiators may be required. There are similar checks required for the pipework running to the radiators, for instance microbore pipework is likely to cause issues and may need replacing.
  3. Is the primary drive for an ASHP to save money?  Natural Gas is the lowest cost energy per KW (currently between 2.5p and 3.5p per KW), followed by Oil and LPG with Electricity being typically the highest (currently between 12p and 14p per KW) and so over the course of an entire year it is likely your heating costs with an ASHP will be the same or possibly higher than the equivalent Gas boiler.  
  4. The local Electricity provider (DNO) will want to check the property in question will not exceed their thresholds once an ASHP is installed. This often necessitates a “load check” and may result in some electrical work being required.
  5. If you have a combination Gas boiler and do not have a hot water cylinder, an ASHP installation will need to include a cylinder to store your domestic hot water, adding to the cost.
  6. There are planning considerations which need to be met.

Will an Air Source Heat Pump Work for Me?

The main question is what the heat loss for your home is. A heat loss calculation (HLC) works out how much heat your home will lose and this dictates the heat you need to put in to keep the property at a constant temperature.  An accurate HLC will need the U values of walls/windows/roof as part of the calculation.  If the HLC shows your property loses an amount of heat greater than an ASHP output and insulation will not resolve the issue then an ASHP is not for you.

For many properties the answer is insulate insulate insulate!

Insulation will keep more heat in and keep the property cooler in summer too, many measures can be done by the homeowner and give an instant benefit, this is probably the best thing that homeowners can do to help the environment and save money in the short term.

For some properties, such as very large properties, or listed properties, insulation will either not be possible or will still allow more heat to escape than an ASHP can provide.  If an ASHP is still desired, then a bivalent system is possible where an ASHP is used in milder conditions and a “peak load” boiler is used for very cold conditions. This mix and match approach works well but it is not 100% green, it does not attract the full RHI, is much more expensive and we have no details as to whether it affects the recent grant.

If the HLC shows that an ASHP can provide enough heat, then the next step will be to assess the radiators and pipework as mentioned above. If the radiators and/or pipework needs upgrading, this is achievable but will add cost to the installation.

Renewal Heat Incentive (RHI)

The RHI currently pays every 3 months (in arrears) for a total of 7 years to the homeowner.

There is an upper limit on payment, for ASHP this is 20,000 KWh per year. Payments are made up to this limit. The payments (tariffs) change year by year and can be found on the Ofgem website.

There are some prerequisites required such as:

  • An accurate (within last 2 years) EPC. The EPC must meet minimum efficiency standards. If not, either apply for exemption approval or resolve the issue and re-do the EPC.
  • An MCS certificate must be available to apply for RHI.  
  • A Metering and Monitoring Service Package (MMSP) to be eligible (due to 2018 changes by BEIS).
  • The ASHP must provide space heating as a minimum. However, domestic hot water also allowed but only in conjunction with the former.
  • Swimming pools work well with an ASHP but are ineligible for the RHI.

The request for RHI must be made by the homeowner (or landlord) and not by 3rd parties.

There is an annual confirmation of compliance the homeowner is required to confirm. To include good working order and no material changes to the system.

Please note the above is based on the information available at the time of publishing.  Dated 21-10-2021.

Weather Compensation Technology Boiler Flow Temperature

Weather Compensation Technology

By taking advantage of Viessmann weather compensation technology, you can save an amazing 15% extra on your fuel bills.

Not only could you be saving money, but carbon emissions too. Which need to be net-zero by 2050, accordingly to the latest government guidelines, so a step in the right direction.

New conventional boilers offer a saving of 35%, with an opportunity to save an additional 15% if you invest in Viessmann’s weather compensating technology with very clever controls.

Technical Information:

So how does it work? In short the weather compensation controls ensure the boiler burns exactly the amount of fuel required to match the heat loss from the building.

A small temperature sensor is located on the outside of the building. This is wired into the internal controls of the boiler and information about the outside temperature is sent to the boiler controller constantly.

When the temperature changes outside the boiler responds and starts to increase or decrease the radiator temperature to compensate. This pro-active mechanism means that people inside the building won’t even notice that the temperature has changed.

So weather compensation controls enable the boiler to respond to outside temperature changes and adjust the radiator output, to maintain a constant temperature indoors.

The diagrams below shows the comparison of a heating system without weather compensation.

This also means the boiler isn’t working to hard, which in turn adds to its life span.

Condensing Effect:

Viessmann weather compensation technology enables the condensing boiler, which already has dramatically increased efficiency, by recovering latent heat in the flue. But also by enabling the boiler to operate at lower temperatures meaning it can condense for longer.


The Viessmann Vitodens 200-W weather compensating controls are very sophisticated. Giving a heat curve that can be adjusted to finely tune the household and the type of building construction. These controls also gives you the added benefit of:

  • Night set-back option.
  • Built-in 7 day programmer.
  • Built-in pump logic for optimised pump over-run to reduce power consumption.
  • Morning booster function, it lifts the flow temperature by 20% first thing in the morning to heat the house faster.

Out with the Old

Out with the Old . . and in with the New.

Out with the old and in with the new. Another new Viessmann Vitodens 200-W boiler installed and another happy customer in Abbotts Ann, Andover.

We removed an old boiler and cylinder, as the customer had concerns about storing the water in the loft. For instance the damage the water could cause if it were ever to leak.

Having experienced issues with the the old boiler, our customer from Abbotts Ann, Andover decided it was time for its replacement. So it was out with the old and in with the new!

Technical Information:

We, therefore installed a Viessmann Vitodens 200-W B2KF 26kW combination boiler, complete with horizontal flue and weather compensation. As with all of our installation we carried out a powerflush of the system. Along with the installation of a Spirotech magnetic filter to protect the boiler from debris which appears over time within all heating systems. The Viessmann Vitodens boilers have been voted Which? best buy for the last 4 years. Showing that they are loved by consumer and installer alike.

Weather Compensation:

The Viessmann 200-W is fully weather compensated, which is amazing Viessmann technology giving the boiler the ability to measure the outside temperature and adjust the boiler output accordingly. The weather compensation ensures that the radiators will feel warm, but won’t get very hot and then cool, meaning you have a steady temperature throughout. Meaning huge savings on running costs, which can be up to 15%. Not to mention the importance on being more eco-friendly.

The Viessmann 200-W 26kW combination boiler also delivers 13 litres of water a minute. Which given a standard shower needs 9 litres, gives ample hot water. With the removal of the cylinder the customer also gained more space in the cupboard.

Viessmann offer a 5 year manufacturer parts and labour warranty as standard for complete piece of mind. With options to extend the warranty to 12 years if desired.

We are delighted with the work done by AHS. Their engineers are a pleasure to deal with and took great care to ensure that the installation is as neat as possible. This is the second time that we have used AHS and will certainly use them again in future requirements.

Neil Barrett.

Is the UK Hydrogen (H2) Ready?

Is hydrogen the future? Is the UK Hydrogen (H2) ready? Hydrogen has long been thought as the clean alternative to natural gas. Which could soon be used to power the appliances in our homes. To include not only boilers, but hob, cookers and fires too.

The first UK houses have been built and are set to be fuelled entirely by Hydrogen. The houses are due to be open to the public to learn more about the emerging technologies. Finding alternatives to fossil fuels and a move towards making clean energy the norm. Thus giving people a glimpse in to what the future might look like.

Hydrogen burns cleanly, producing only water as combustion. Making it ideal as a net-zero economy fuel. Hydrogen also has the benefit that it could be distributed across the country using the existing mains gas infrastructure.

The government is hoping hydrogen, as a clean and safe replacement to natural gas, will play a vital role in achieving its commitment of the UK’s contribution to climate change by 2050. By implementing their Ten Point Plan.

The Hydrogen Strategy is to be shared later in 2021, to show that the UK is indeed Hydrogen (H2) ready.

The technology is already here with the New Viessmann Vitodens 100-W & 111-W, which are now available!

Viessmann Extended Warranty

Viessmann Extended Warranty.

Viessmann have extended their warranty options of their Viessmann Vitodens range of domestic boilers. Giving Viessmann customers the reassurance that if their boiler breaks down we will be there to help. At no extra costs.

As a trained Viessmann installed and valued partner, Alexandra Heating Services, are able to undertake warranty work on behalf of Viessmann and are always happy to help.

Viessmann Vitodens 050-W

Provided with a 7 year standard warranty for Viessmann trained installers, however, new Viessmann extended warranty is now available! So you can now increase the Vitodens 050-W by 3 years. Providing a total 10 year warranty for just £120.00.

Viessmann Vitodens 100-W

Provided with a 5 year standard warranty for Viessmann trained installers, however, new Viessmann extended warranty is now available! So you can now increase the Vitodens 100-W by 3 years, 5 years or a further 7 years. Providing a total 12 year warranty for just £180.00.

Viessmann Vitodens 111-W

Provided with a 5 year standard warranty for Viessmann trained installers, however, new Viessmann extended warranty is now available! So you can now increase the Vitodens 100-W by 3 years, 5 years or a further 7 years. Providing a total 12 year warranty for just £180.00.

Viessmann Vitodens 200-W

Provided with a 7 year standard warranty for Viessmann trained installers, however, new Viessmann manufacturer’s warranty is also now available! So you can now increase the Vitodens 200-W by 5 years or a further 7 years. Providing a total 12 year warranty for just £420.00.

Viessmann Vitodens 222-F

Provided with a 7 year standard warranty for Viessmann trained installers, however, new Viessmann manufacturer’s warranty is also now available! So you can now increase the Vitodens 200-W by 5 years or a further 7 years. Providing a total 12 year warranty for just £420.00.

All prices above are including VAT.

Viessmann Vitodens 100-W Boiler

Viessmann Vitodens Boilers: (H2) Ready!

The next generation of wall hung domestic Viessmann Vitodens boilers with Wi-Fi inside, PlusBus and Hydrogen ready is coming from Viessmann.

The new Vitodens 100-W & Vitodens 111-W from Viessmann, are Hydrogen ready for the network when in place. Viessmann are know in the market place for their years of experience and innovation. Also known for the importance given to the quality of their product and rigorous checks. Giving their wall mounted boilers the Which? best buy for many years. This is due to the boilers performance, reliability and longevity too.

Main Features & Benefits of the Viessmann Vitodens Boilers:
  • MatriX Plus burner.
  • Inox-Radial heat exchanger.
  • Lambda combustion control system.
  • Wi-Fi connectivity.
  • Hydrogen ready.
  • Extendable warranty options.
MatriX Plus Burner.

The boiler still has the MatriX Plus Burner, which wins every time. Due to its efficient operation, low pollutant and noise emissions.

Inox-Radial Heat Exchanger.

Made of stainless steel, is the real heart of the boiler and makes the real difference! It efficiently converts the energy used into heat, this component is durable and made of high quality steel. Read more about their design and comparison between steel and aluminium here.

The Inox-Radial heat exchanger benefits from a 10 year guarantee from Viessmann.

Wi-Fi Connectivity.

The new Viessmann Vitoden 100-W and 111-W boilers have a new electronic platform, which now has an integrated Wi-Fi interface. This connects the heating system directly to the internet. With the ViCare app operating the system is simple and intuitive. So you can control your home from your phone. The app gives convenient operation of the heating system and can save energy at anytime from anywhere!

Most importantly no third party controls are required and everything is contained in a single Viessmann ecosystem.

Hydrogen (H2) Ready.

Certified for 20% hydrogen (H2) content in natural gas.

Not forgetting the Viessmann extended boiler warranties now available. Heating from Viessmann doesn’t get better!

Coronavirus - COVID-19

Covid-19 Update

Our offices are open from 8am–5pm and our 24/7 cover is operational. Our engineers continue to work in line with the Governments social distancing guidelines, please inform the office of any covid-19 symptoms or testing within your household prior to an engineers visit.

Inox-Radial Stainless Steel Heat Exchanger Winchester

Heat Exchangers: Stainless Steel v’s Aluminium

Stainless steel is the key and here is why. . .

Heating technology should work together to ensure the smooth operation of the entire system – from boiler via burner, control unit and heat exchanger, to deliver the highest possible operational reliability. Today, domestic and commercial boiler technology demands the most reliable, energy efficient components. Contact us for a quotation

A key component in choosing the right system, is the heat exchanger within the boiler, as maintenance costs, durability and product lifetime should all be considered when buying a boiler. As the two most common types of heat exchanger in the UK condensing boiler market, we have examined the differences between stainless steel and aluminium to offer a comparison of quality and longevity.

Heat Exchanger (half)

Stainless Steel Heat Exchangers:

Used by Viessmann throughout its entire condensing boiler range, stainless steel heat exchangers provide a high resistance to corrosion in a wide variety of pH levels, therefore increasing the useful life of your boiler. This provides long term value for money and requires less system downtime due to maintenance.

Important points to consider:

  • Increases useful life of your boiler.
  • Less downtime due to maintenance.
  • Does not require use of system inhibitors.
  • Recommended for filling with potable water (drinking water) no inhibitors required.
  • Self-cleaning.
  • Higher grade corrosion resistant material.

Heat Exchanger (close up)

Aluminium Heat Exchangers:

A lightweight and alternative option, Aluminium heat exchangers also provide high heat transfer but require special inhibitors when maintaining the system, which if not used can result in a high risk of damage to the boiler. Annual maintenance is also vital to remove aluminium oxides, which can build up and clog the condensate line.

Important points to consider:

  • pH treatment critical to longevity of the heat exchanger.
  • Artificially softened water not permitted.
  • Aluminium material corrodes through aluminium oxide build up and erodes further at high flow rates.
  • Reduced lifetime of the heat exchanger.
  • Cheaper to manufacture than stainless steel.

Heat Exchanger Steel v's Aluminium

All Viessmann gas condensing boilers are equipped with stainless steel Inox-Radial heat exchangers. This technology brings with it an extremely high efficiency rate of 98 percent and exceptionally reliable and efficient operation during its long service life.

Viessmann guarantees the Inox-Radial heat exchanger for ten years against leaks resulting from corrosion.

Contact us for a quotation

Boiler servicing Winchester

Boiler Servicing – An Essential Investment

A study has found that watching spending has become an ingrained way of life that consumers will continue with, even when their finances improve.  It seems the recession has left behind a legacy of cautious consumers, with people needing a strong reason to part with their money.


An annual boiler service, however, needs to be seen as essential spending.  In much the same way as a homeowner would regards a service and MOT for their car.  Most people anticipate there will be ongoing costs associated with their vehicles and budget for them accordingly.

An annual boiler service provides some important benefits; it will ensure the boiler is safe, is performing efficiently and reliably, and maintains the manufacturer’s warranty.


The number one reason for a homeowner to have their gas boiler serviced regularly is safety.

Unfortunately, consumer awareness of carbon monoxide (CO) poisoning is thought to be generally low across the UK.  It is important for heating engineers to explain to their customers that unsafe gas appliances – those that have been incorrectly fitted, badly repaired or poorly maintained – can produce this highly poisonous gas.

According to the Department of Health, 50 people die each year from CO poisoning and another 4,000 are treated in hospital.  It is thought the true number is likely to be much higher, as the early symptoms can easily be mistaken for flu or tiredness.


Another benefit of regular servicing extends the service life of your heating system and ensures reliable, trouble-free operation.  This is the only way to make sure that the energy from the fuel is used efficiently and cleanly, thus protecting the environment and saving on heating bills and the likelihood of breakdown, saving the homeowner money and minimising disruption without compromising high heating and hot water convenience.

Again, it is useful to draw on a car analogy.  A homeowner will understand that things like replacing filters and spark plugs are essential to keep their vehicle in top condition, and that avoiding a scheduled service may have a detrimental effect on the way the car works, leaving them out of pocket in the long run.  The same rules apply here, the boiler, burner and control unit form a system like that of a car engine which is essentially runs for many more hours than a car.  If your car was in operation for the same amount of time as your boiler, it would cover more than 60,000 miles in a year.  All car owners know that they need to have a service carried out at regular intervals.  Therefore your heating system should be serviced at least once a year, much like your car.


An annual service is usually a condition of a boiler warranty – which is another important reason why you as the homeowner should invest.  Today, boilers come with lengthy warranties, which should be seen as a sign of reliability, but the working parts still need to be checked annually.

Call us today to book your service on 01722 417873.

Sited: McCallum Layton study.  HVP Magazine May 2016.

Written by ‘The Girl in the Office’.

Coronavirus - COVID-19

COVID-19 Update: Our Pledge to you

As the government has placed us on their key worker list, we will be carrying out emergency works, to include breakdowns, repairs, required maintenance, water leaks, oil leaks and gas leaks.  Therefore being on hand to help our customers who have no heating and/or hot water in these difficult times.

In these strange and unprecedented times Alexandra Heating Services takes its responsibilities for the health and safety of our customers and our employees very seriously taking special care to follow the government guidelines to include social distancing and PPE to be worn by our engineers.

Our Pledge to You.

Please note that all appointments are made for emergencies only. To include a lack of heating, hot water or a gas, water, oil leak. As I am sure you can appreciate boiler services will be postponed until the current COVID-19 crisis has subsided.

Our Office will have asked you if any members of the household are showing any of the symptoms of COVID-19.  Please ensure you inform the office if any symptoms become apparent after making the appointment.

On arrival our engineer will knock on the door and will stand back 2 metres to introduce themselves. They  will be wearing gloves and potentially a protective face mask. Following the current guidance they will be unable to shake hands, please do not take offence.

They will ask you the same questions that you have been asked when booking your appointment to confirm that your circumstances have not changed from when the booking was made.

Social Distancing.

Our engineer will ask where the boiler/cylinder is located and confirm what the problem is.  Our engineer will ask you to step back so they can adhere to the 2 metre social distancing rule and go directly to the area of concern.

Please do not follow the engineer or enter the room with them.  Please do not offer our engineer a drink, however well meaning.  Our engineer may use antiseptic wipes to clean the area where he is working.

If the engineer has questions they may call you on the telephone so as to keep a safe distance.

Once the works are completed our engineer will shout out that he has finished, place his single use plastic gloves in your waste bin. He will then wait outside the front door to explain the works completed. Along with explaining any potential next actions required.

Please inform the office if you find the above unacceptable before our engineer attends your property.

Our Thanks.

We hugely appreciate your cooperation in helping ensure our engineers remain safe which in turn will help us keep our customers safe. Then we can ensure we will continue providing this vital service to the local community.

We look forward to normal service being resumed as soon as we are safe to do so and we would like to thank everyone for your support to our local business in these difficult times.