You may think, as a homeowner, that you are an expert in boiler systems. Actually this is probably far from the truth as they are quite complex, having several different designs and fundamental layouts of boiler which are installed in normal homes. Traditional central heating systems have a hot water storage tank (in an airing cupboard) and a feed and expansion tank (located in the loft). Having a hot water storage ability allows these systems to deliver large amounts of hot water at short notice. The hot water capacity is only limited by the size of the hot water tank and the ability of the boiler to renew the hot water when depleted.

The additional components and hot water storage also contribute to reduced energy efficiency, higher installation costs and a more complex system. This means averts the traditional heating system has slightly breakdowns over its lifetime and consumes more energy to deliver the same amount of heat and hot water.

To counteract these deficiencies the combination or combi boiler was developed. This type of boiler heats hot water on demand whenever the hot water tap is turned on. This means that the supply of hot water is not limited and there are far fewer components in the central heating system.

Fewer components and no hot water storage all contribute to a lower cost installation with a better energy efficiency, resulting in lower ongoing heating costs. These directly address the issues in a traditional boiler system meaning that you will pay less for the hot water you require over the lifetime of the boiler and could well experience fewer trouble some breakdowns.

One disadvantage is that the hot water flow rate of a combi boiler will not match that of a conventional boiler. Water has to be heated on demand and hence it may take longer to run a bath although a shower will be a pleasant surprise as the hot water is delivered at mains pressure giving a high power spray.

Another issue to consider is the temperature of the hot water. This can be influenced by the temperature of the incoming cold water and the flow rate. As a result it is essential that the power of a new boiler is matched to your heating needs.

Some advanced combi boilers incorporate a small hot water cylinder. Installation is still easy with reduced components but the boiler stores some hot water to enable it to meet initial demands for hot water. This hot water reservoir is small and it will not be sufficient to fill a path but it does allow this design of boiler to provide instant hot water for most typical requirements in the home and you will not be waiting for a whole tank of hot water to finish heating before you can get sufficient hot water out to wash a view items of cutlery as an example.

If you have problems with your central heating the video guide below can give you an insight into the most common central heating problems.


71 Responses to “Boiler Systems”

  • Jane Follett:

    I live in a victorian terraced house and my neighbour had a new combi boiler fitted about 6 month ago, however, instead of it being fitted on the outer wall as before, it is attached to the party wall with my bedroom and all I can hear is the noise it makes when it is used or at night when it cools and hums all the time.

    Is there anything I can do about it? It is driving my mad and I will have to move if not.

  • Boiler Care Guide:

    We are sorry to read of the problem you are having.

    You could try fitting sound deadening materials to you adjoining wall but that disrupts your home and does not tackle the source of the problem. We must ask, have you discussed the problem with your neighbour and are they aware of the problem? Once they are aware, and if they are friendly, you can then start to explore the feasibility of amending their boiler installation to reduce the noise level.

  • Mr Steven Baker:

    I have a Heatline combi condensor boiler which is about 14 months old. The pressure is reading 2.4 bar which should not be a problem due to the built in safety features.
    I would like to know how to re-ignite the pilot light as the boiler is not firing up when the hot water tap is on.
    There are no instructions in the manual to guide me.

  • Boiler Care Guide:

    We are sorry but we do not maintain a library of technical manuals for each boiler system.

    If you telephone the technical helpline of the manufacturer of your boiler they should be able to answer your question.

  • Ayo:

    I have just bought a new house and I need to have a corgi engineer inspect the boiler and gas in the property. Does anyone offer this service and how much will it cost for a three bedroom terrace house?

  • Boiler Care Guide:

    We are pleased to advise you that the companies featured can help you. The price varies by region and hence we cannot advise you of the exact cost in this email but if you would like to call them they will be pleased to provide you with a fixed price quote.

  • andrew:

    I have a combi boiler but when I turn on the hot taps, i get no hot water and the radiators do not heat up either when the heating is on. The bolier swicthes on and goes through the motions (as if it will heat the water) but nothing happens. What can I do?

  • Boiler Care Guide:

    It is very difficult to diagnose central heating systems remotely, particularly on the limited information available.

    If you have taken out a boiler service contract you should telephone the helpline number you have been provided with and an engineer will call to help remedy your problem. If you have not taken out any boiler service agreement the companies highlighted have a heating repair service which could help. If you telephone them and explain your issue you will be provided with a no obligation fixed quote for fixing the problem.

  • S Godfrey:

    My neighbor has installed a boiler in his upstairs bedroom and the outlet is near my daughters bedroom window, I am worried about how close it is. Is there a legal distance a boiler can be installed from a window.

  • Boiler Care Guide:

    The minimum distance is 300mm.

  • Lou:

    We have a back boiler and it has started to make occasional big bang noises. We are due to have it serviced, but we were thinking about having it removed and replaced with a better boiler. Can you tell me approx how much this may cost at most and how do we arrange this.

  • Boiler Care Guide:

    Advising you on cost is difficult as there are a number of outstanding questions we have, as such a quote could be very inaccurate.

    To ensure you receive an accurate quote some companies are able to send a trained heating advisor to your home to review the installation options and help to select the right boiler for your home. This visit should be free with no-obligations on your part and will also enable an accurate quotation to be developed for a new boiler.

  • Karen S:

    We curently have a non working combi boiler and to be honest it was never upto much in the water supply department. We want to convert back to a standard boiler, but we do not have room for an airing cupboard. Is it possible to have a hot water tank in the loft space? and as all radiators are insitu will these need to be replaced or will this fact reduce the cost of installation?

  • Boiler Care Guide:

    You could have an unvented hot water cylinder fitted in the loft space as this is a sealed system and there are no need for tanks. It will also give you mains pressure hot water delivery to 2, 3 or 4 taps at any one time.

  • Karen S:

    We are currently building a granny flat onto the side of our 3 bed house, for my elderly mother. Can you advise of a combi boiler that would allow us to heat the extension with having to heat the main house? Many thanks!

  • Sevin Seydi:

    We installed a large Vaillant combi boiler two years ago. It works well and is adequate for the two of us Iin quite a large house). Now however two family members are moving in, with their own kitchen and bathroom. The plumber tells us that the capacity of the boiler is technically sufficient for the calls on it, but we might keep having a conflict if two hot taps are opened at the same time. He recommends a second small boiler for one of the kitchen + bathrooms. This sounds expensive, and there are problems in siting it. I thought of having an electric immersion heater for the new demand, but then I wondered if the existing boiler might not serve an indirect unvented cylinder to supply one kitchen + bathroom. No one seems to have heard of this being done. What do you say?

  • Boiler Care Guide:

    A combi boiler cannot supply a cylinder or any kind including unvented, the flow rate will not cope with it. You should contact Valliant direct to see if the boiler model you have can cope with two draw offs – but we suspect the answer will be no. You could have a multi point water heater fitted to help with the extra bathroom/kitchen problem.

    Some companies are able to send a heating advisor to your home to review the installation options and help to select the right boiler for your home. This visit should be free with no-obligations on your part and will also enable an accurate quotation to be developed for a new boiler.

  • Lisa Cooper:

    I ahev got a potterton Performa 28 combi bolier, we have had a corgi registered guy in who has changed the fan and the pcb but still no joy, this has been going for nearly 10 weeks with no heating or hot water, could you advise on what the problem might be?

  • Boiler Care Guide:

    We are sorry but you have supplied us with little information and we are unable to provide a better diagnosis via the Internet than the CORGI registered engineer has provided through an on site visit.

  • c.lightowlers:

    My old Baxi boiler is making a lot of noise, clicking, banging and generally noisier than usual. The outside casing gets very hot and the hot water from the taps is much hotter than usual. Can you help me please.

  • Boiler Care Guide:

    If you have taken out an appropriate boiler service contract you should telephone the helpline number you have been provided with and a plumber will call to help remedy your problem. If you have not taken out any boiler service agreement you may need to telephone a local plumber and explain your issue you should be provided with a no obligation fixed quote for fixing the problem.

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