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New Combi Boiler Installation – 14 Steps to Avoid For The Cowboys!


There is lots to consider when you are considering a new boiler installation. This guide will take you through the process from start to finish. This is quite a difficult task describing in words what a Gas Safe engineer does every day. Not all of the points will be relevant to your particular installation but this guide will at least give you an idea of what to expect from your new boiler and what to expect from an installer coming to your house.

Things to consider:
– Your budget – grants, loans and other schemes
– Finding an installer – getting 3 quotes
– The current water pressure of your system
– Your current system – layout/design and condition, boiler siting
– Your hot water demand – bathrooms, ensuites etc
– Choosing a boiler
– Upgrading your pipework – gas and water pipework
– Adding a MagnaClean
– Adding thermostatic radiator valves/room thermostat
– Adding additional radiators
– Powerflusing your system or flushing your system
– Commissioning your system
– Filling in the benchmark/notifying building control
– Advising the customer on how to get the best efficiency from their boiler
– Installers working to best practice

Your budget – grants, loans and other schemes

There are lots of schemes available depending on your circumstances. The new Boiler Scrappage Scheme is available to all households in England who have a G rated boiler in their home. It gives £400 towards the cost of a new boiler installation. There is also a scheme called the Warm Front Scheme which provides upto £3500 towards home heating and insulation improvements. To be eligible you must be on some sort of benefit or be a low income household. It is normally a bad idea to finance your boiler installation using a credit card or bank loan. Although there are cost benefits to be gained by having a new condensing boiler these will be eaten up by repaying the loan. If your current boiler is in good working order and you are worried about it breaking down then a British Gas homecare agreement is advisable at around £19 per month. An Npower agreement which offers less benefits is also available at around £7.99 per month.

Finding an installer – getting 3 quotes

You should aim for 3 quotes. This is more than adequate to get a good idea of what you want. Each individual engineer will give you different ideas on how best to go forward. They will also have their own favourite boilers and methods of working. It is a good idea to bounce ideas and questions around to ascertain whether the engineer is actually competent in the field he will be required to work within. Unfortunately there are lots of newly qualified plumbers and gas engineers in this industry and although they are perfectly safe and ‘passed off’ to work they may not be a) able to advise you of the most efficient method going forward, b) advise you completely wrongly or c) not actually have an answer. Sometimes it may be difficult to find someone you trust; after all, this will be a huge investment.

Often using the yellow pages can be a bad idea. So can using someone who posts leaflets through the door. The best and trusted method will always be by personal recommendation. Asking the engineer lots of questions can also give you some degree of confidence. Checking their Gas Safe registration should also be a priority. Unfortunately there are lots of illegal gas engineers operating and these people are putting lives at risk. Checking someones gas safe registration is very easy. Ask to see a Gas Safe registration card. Every engineer carries a card and it amazes me that 99.5% of customers do not ask for ID. Every engineer should be proud of their qualifications and love to show them off. Do not be shy and in future make a point of it.

Once you have got your 3 quotes you need to analyse what you are getting. Quotes should be broken down as much as possible. This will give you an idea of what exactly you are paying. I don’t understand how companies can justify listing a load of materials and specifications and then adding a figure. Costs should be fixed price costs whether you are a millionnaire or on a very low budget;)

It is best to get a written contract for your own benefit. If the company doesn’t offer one then you can easily draw one up. This will protect against faults that might develop later on after the system has been installed. If installed to best practice and following all manufacturers instructions then a central heating system will only rarely breakdown due to a manufacturer component fault. That is why respected installers offer a personal guarantee on all their work, this can be upto 5 years but 3 years is normal. This is alongside normal manufacturer guarantees which can be upto 5 years parts and labour. Other ways of finding an installer can be the internet however personal recommendation is always the best method.

The current water pressure of your system

Its very important to measure your mains water pressure to ascertain whether a combi will actually work. You might not have enough pressure for a combi system to work so this will need to be measured. A competent engineer will make sure that this is one of the first things he does. If you do have low pressure then your installation options will be limited. One example is when a mains pressure of 0.8bar from a customers property is measured. A certain Vaillant boiler which gives their full hot water output at just 0.5bar would be recommended by any competent engineer. This means that this boiler would be one of a very few boilers that could be considered for this customers property. It could have been a costly mistake not testing the mains water pressure and this is one reason why this should be done as standard. Having said all of the above, problems are very very rare. Your water company can advise on what your water pressure is likely to be if you are concerned. If for say you live on a very big hill you may have reasons for concern.

Your current system – layout/design and condition, boiler siting

Your current situation could have a large affect on cost of installation. Moving a boiler can add considerable expense as routing pipework can often be very tricky. Moving a boiler nearer the gas meter can sometimes cost the same as a straight swap. This is because the gas meter pipework upgrade will require less materials and less labour. Although some re-routing of water pipes will be required. If you need to upgrade from a system to a combi boiler this will be the costliest combi boiler installation. The system layout and pipework will need altering. The hot water cylinder and tanks in the loft will need removing. If you have a back boiler this will add time and expense on as well.

This can sometimes be difficult to remove as may cause the chimney to weaken. Your installer would be able to advise whether the removal of the back boiler is best left to a contracted a builder. If there is going to be new pipework in your property then it is desirable to have this under the floorboards and out of site. It makes for a better, cleaner job. Beware of companies wishing to take shortcuts or indeed charging more for lifting carpets and floorboards. There are strict rules governing where pipes are laid in joists. The size of notches can weaken joists and limits are set for this reason. It is simply unacceptable to hang pipes loose – even pipes containing water. Floorboards should be screwed back into place and not nailed as this will just cause the floorboard to loosen over time. Carpets and other fittings should be left as found. It is normally the customers responsibility to move furniture and other items that are in the way. This is due to responsibility issues. Common sense should always prevail of course.

If you have concrete floors then this can add a lot of expense as digging into the floor can be costly. The pipes will then need to be wrapped to ensure the concrete does not perforate them and this ultimately causes a leak under your floor. Fixing this leak will mean you having to re-dig the concrete and replacing the pipework. If done correctly and in accordance with manufacturers instructions its a very simple task. An engineer who is not in the know as regards to regulations can cause severe problems. Boiler siting can also cause problems sometimes. New condensing boilers may cause pluming issues and this can cross neighbour boundaries. Pluming kits are available and can eradicate this problem. Boiler flue terminal positions can also be a problem but these will be rare. The terminal needs to be a minimum 30cm away from window or door openings to stop products of combustion re-entering the property. If there is no other alternative than to put your boiler next to a window that is not in use then it will either need blocking up, ie cementing and bricking up or it will need screws put in so that it cannot open. Although the latter method is within the scope of the regulations it would be recommended better bricking it up.

Your hot water demand – bathrooms, ensuites etc

Even the lowest output of boiler (eg a 24KW) can, if installed correctly, cope with up to 14 radiators. When determining which boiler will suit your needs you should do some research on boiler hot water output capacities. Some smaller output boilers will deliver in the region of say 9 litres of water per minute at a certain temperature. Bigger models will produce 16 litres and more. This difference will be the difference between an OK shower or a very powerful shower. It will also affect how long a bath takes to fill up. You will also see an impact if you have two bathrooms ie a main bathroom and an ensuite bathroom. Larger sized boilers will just be able to cope with two showers used simultaneously. Smaller boilers will definitely not. You need to consider how this will affect you. Further advice can be given by your chosen installer.

Choosing a boiler

Choosing a boiler can be difficult. There are so many boilers out there that only an expert can guide you through your needs and match them up with a suitable boiler. The better makes of boiler are Viessmann, Worcester and Valliant although some of the models from these manufacturers have been horrendous. These will be the earlier models and any expert will know which models to steer well clear of. The Viessmann 100 model (earlier model) has teething problems but everything has been resolved now and this is one of the leading models on the market if not the best. Of course every engineer will have his/her own preferences but if you go to any forum in the Ireland and ask if the Viessmann boilers are any good I will guarantee you wont get an expert saying anything against them.

Boilers can typically range in price from £400 (B&Q) to £1400 (top Vaillant model) Although the £400 one will last for years and years if installed properly it is open to debate whether this boiler will last 10 years and even if it does, how much money you will have to spend on repairs? A great budget boiler is the Glowworm Betacom 24KW. For the price it represents very good value. It will depend on your budget and what you feel comfortable. It is always advisable to get quotes for different boilers and you can see for yourself prices differences. The price of the boiler will include all guarantees and if there are any issues with faulty manufacturer parts etc your installer will be responsible for this. Buying your own boiler and getting an installer to fit it can present many problems.

For example, is the boiler you are buying relatively new? It may look new, ie unopened packaging etc but it may have been sitting in a garage for 2 years. If a boiler is not installed within one year of its manufacture date it will void any warranty. Also, if any components are missing from your boiler then you will be ultimately responsible for lost time and expense. Most installers will not work this way for the above reasons as they simply do not know the history of the boiler and if a component fails after the boiler has been fitted it could cause significant problems.

Your installer will match your needs to a suitable boiler

Upgrading your pipework – gas and water pipework

Gas pipework used to be run in 15mm from the meter to the boiler. There are new rules which mean that pipework must be upgraded to 22mm as new condensing boilers are required to run on 22mm copper pipework. If the routing is simple then this can be a simple job. Sometimes carpets need to be lifted and pipework will go under floorboards. A lot of companies have fixed prices for pipework alterations and this includes fittings to give you an idea of price and labour charges.

All pipework should be clipped, there are regulations governing clipping distances for gas pipework. Pipework should always be secured and must be sleeved if passing through a cavity wall. One end must be sealed also. Your installer will bring you up to speed if you do have any concerns. If you are going from a system boiler to a combi boiler there will be lots of extra work including altering pipework and removing tanks and cylinders. This will mean more space in your airing cupboard and loft space.

Adding a MagnaClean

Some companies will not fit and guarantee their work if you do not agree to having a MagnaClean fitted. This additional work can be carried out for a very reasonable price as they would be already carrying out work in the property. More information can be found by clicking on the MagnaClean website. Unfortunately new condensing boiler have very weak heat exchangers and the MagnaClean will save them from getting damaged. This is why most companies insist on every customer having one installed.

Adding thermostatic radiator valves/room thermostat

Adding thermostatic radiator valves can significantly reduce your heating bills. It allows each radiator to be controlled individually. Why have the heat on in the whole house when you only need it in one? It is recommend not turning a valve completely off but setting it to 1. Adding TRV’s will in the long run save you lots of money and can be very cheap to install. Some companies will have offers when supplying and fitting these. Energy efficiency should be promoted whenever.

A room stat or a programmable room stat is a legal requirement. Your installer will advise what the best option for you is. A wireless stat will be more expensive but there is the advantage of no visible wiring.

Adding additional radiators

If you need to add additional radiators it is best to add these while having a new boiler installed. It will more than likely be cheaper. Some of your radiators may be undersized or very old and you should consider upgrading these.

Powerflusing your system or flushing your system

There is a huge difference between powerflushing your central heating system or just flushing your system. Powerflusing involves higher pressure and circulates fresh water and special chemicals around your system. It is normally needed on older systems as sludge and dirt builds up over years and years. This will mean that you either have cold spots or not very hot radiators. Having fresh water in a system means water can be heated up to the maximum pressure the boiler will allow and will mean hotter radiatiors which in turn means more efficiency. A powerflush is not a legal requirement when replacing your boiler but it is advisable. When a powerflush is taken with a boiler installation discounts can be given.

Normal cold and hot water flushing is a requirement when a boiler is installed. Cleanser and inhibitor is added. A hot and cold flush must be done in order to work to best practice. New boilers do not like any dirt in the system, heat exchangers can get very ‘clogged’ up and the cost of replacement can be very great.

Commissioning your system

Things that should be included in your installation and are considered best practise:

1. Flushing with Fernox or Sentinel product/filling with inhibitor from same
2. Roomstat/programmer, TRV’s (best practise, recommended)
3. Balancing and commissioning according to manufacturers instructions, important so as not to invalidate warranty.
4. Decommisioning of old boiler, tanks and all waste materials associated with installation
5. Making good eg. new and old flue openings
6. Completion of Benchmark log book, important.
7. Notification of new boiler to Building Control
8. At least 3 years guaranteed on pipework and associated fitting (the boiler manufacturer will have their own guarantees.)

The above should be in writing to protect your expensive new purchase.

Filling in the benchmark/notifying building control

Filling in the benchmark and notifying building control is part of commissioning process and a legal requirement. Pressures and temperatures need to be taken to ensure the system is correctly configured. Not filling out the benchmark and not notifying building control may cause problems if you ever decide to sell your property as proof the boiler was installed by a competent person will be required.

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