Combination boilers (also known as combi boilers) are the most popular boilers in the UK.
With a combination boiler you have one unit which supplies both your heating and hot water, there are no separate tanks.
Advantages of a combi boiler:
Hot water supplied on demand.
No hot water cylinder ... Read review
Advantages: Good where there is a lack of space. Disadvantages: Not always the best option.
Combination boilers (also known as combi boilers) are the most popular boilers in the UK.
With a combination boiler you have one unit which supplies both your heating and hot water, there are no separate tanks.
Advantages of a combi boiler:
Hot water supplied on demand.
No hot water cylinder required thus saving space which is why a lot of people choose to have a combi.
Hot water supplied ... ...Most combi boilers can only supply one tap at any one time.
You will be left with no hot water if the boiler was to break down.
Not the best option for larger homes.
Cannot supply hot water and heating simultaneously.
With a combi boiler, the water is supplied on demand, which means when you open a hot water tap the boiler will fire up to heat the cold water entering the boiler, the water ... more
Combination boilers (also known as combi boilers) are the most popular boilers in the UK.
With a combination boiler you have one unit which supplies both your heating and hot water, there are no separate tanks.
Advantages of a combi boiler:
Hot water supplied on demand.
No hot water cylinder required thus saving space which is why a lot of people choose to have a combi.
Hot water supplied at mains pressure.
Disadvantages:
Most combi boilers can only supply one tap at any one time.
You will be left with no hot water if the boiler was to break down.
Not the best option for larger homes.
Cannot supply hot water and heating simultaneously.
With a combi boiler, the water is supplied on demand, which means when you open a hot water tap the boiler will fire up to heat the cold water entering the boiler, the water is heated by what is known as a "plate heat exchanger". Cold water enters the heat exchanger from one connection, as the water passes through the heat exchanger heat is transferred from the boiler to the water.
In total there are 4 connections on a plate heat exchanger:
1. Cold water in. 2.Hot water out. 3.Hot water heated by the boiler is fed into the heat exchanger. 4.The water returns to the boiler to get heated again.
See the picture to understand it better.
The amount of hot water a combi boiler can produce is dependant on the hot water output which is measure in kilowatts; the higher the kw rating the more water can be heated resulting in a better flow rate.
A 24kw combi boiler can supply hot water at approximately 9-10 l/min, this is good for a single hot water tap or a not so powerful shower, these combi boilers are usually fitted in flats. A bath would take very long to fill with this kind of boiler.
A 30kw combi boiler can supply hot water at approximately 12-13 l/min, you can have a decent shower with this combi boiler but if two taps/showers were being used the flow would be very disappointing. Not ideal for filling a bath either.
You do get more powerful combi boilers with outputs of about 40kw which supplies hot water at 17 l/min, I don't usually fit these boilers unless space is at a premium.
A very good high output combi boiler would be the Vaillant ecoTEC plus 937; this boiler has two tanks at the back which supply hot water at up to 20 l/min for 10 minutes, this is great for filling baths and nice powerful showers, once the water in the tank is finished the boiler can supply hot water at 15.7 l/min which is still quite good. The tanks take 2 minutes to fully recharge. You can run two showers or taps but the performance can't be matched to an unvented cylinder. This boiler is rather large - see picture.
If hot water requirements are high than an unvented cylinder with a regular or system boiler is usually the best option. These can supply two showers at once too.
Let's imagine it is a very cold winters day and the heating is on, someone decides to take a nice long shower, while this person is showering the radiators will start to cool down as well as your house, this is quite a big disadvantage especially in larger homes with high heat losses.
Things to watch out for:
If a combi boiler can supply 15l /min the cold water flow rate of your house cannot be below 15 l/min.
High performance combi boilers cannot usually modulate very low for CH which can result in a slight drop in efficiency.
Installers wanting to put a combi boiler in in a house where two showers a likely to be run, if you have the space get a cylinder instead of a combi boiler.
If you live in hard water area the plate heat exchanger can scale up quickly, it is a good idea to have a scale reducer fitted such as a Combimate. A lot of boiler manufacturers guarantee the heat exchanger for five years though.
Installers using existing 22mm hot water pipework (if you had a cylinder), the hot water pipework with a combi should be all in 15mm pipe.
Common misconception:
Combi boilers are more efficient because your not keeping a cylinder hot all day.
This not true, with a cylinder set up the boiler heats the cylinder and then remains off for quite a long time because newer cylinders have exceptional insulation, with a combi boiler the boiler goes into full power as soon as you open a tap which does use a considerable amount of gas. The cylinder can stay hot for up to three days if you don't use any hot water.
Also the boiler can condense quite a lot when heating a cylinder AND you don't usually keep the cylinder on all day so you are not wasting gas in keeping the cylinder "hot all day".Conclusion:
Combi boilers are best suited for smaller houses with one shower, not ideal for filling a bath or very powerful showers.
Combi's are great where there is a lack of space.
I have put the quality to excellent because I assume you will get a decent one fitted such as a Vaillant.
Advantages: Easy to install Disadvantages: For smaller properties only
...is what 50% of a combination boiler is. Albeit all tangled up with a conventional boiler and covered in a large enamel spayed aluminium box. Except for the Ideal Response, which is rather smaller. By the way, if you are offered an Ideal Response, the ideal response to the question is ‘no thanks’ I’d rather stick my head up an elephant’s bottom. Trust me, an elephant’s bum is much more desirable.
Is a combo suitable for you? Well not if you want ... ...more than one hot tap at a time. A combo heats the water as you use it, and so is limited to the amount it can heat. It will raise the temperature about 40 degrees Celcius. So in the winter, it may be a case of turning the tap down a bit to get the desired temperature.
Whilst it is heating the water, it is not heating the central heating. Not normally a problem, unless you have a dripping tap or two, which could prevent the heating from coming on ...
botmission 23.06.2003
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Ciao members have rated this review on average: very helpful Review of Combination Boiler System
Advantages: Hot water on demand. Cheaper bills, Great showers Disadvantages: Central heating is slow to perform. A little more expensive to install.
Just as winter was starting, our boiler decided to pack up. I managed to conclude that the problem was with the pump but as the boiler was about 30 years old and some (we inherited it when we moved in) we decided that the best investment was in a new one. The decision was helped by the various shaking heads and lack of definite price estimates for repair from the succession of engineers who had a look. We had also spent about £350 reparing it the ... ...go for. The system being pretty old, also needed new hot,cold and header tanks as well as a few rads. We therefore decided to spend a bit more on the boiler and went for a new Bosch condensing/combination version. We knew that the water pressure would be the key to it working effectively. We were advised by two companies that the pressure was fine and by a third that it wasn't. Once we were clear that we would be happy with only being able to run ...
smithid 07.03.2004 (08.03.2004)
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Ciao members have rated this review on average: helpful Review of Combination Boiler System
Advantages: Lower bills, more space and instant hot water Disadvantages: Can't use a shower pump
When our heating system broke down, it was deemed unrepairable and condemmed. We were told by neighbours the water pressure was too low for a combi. We have proved them wrong. We have had both our water tanks removed, giving extra space, the combi is in a convenient location. Our gas bills have dramatically reduced, we don't have to wait for water to heat up for a bath or to wash a few dishes. The heating comes on instantly and is extremly easy to ... ...that is set and is not connected by wires, a bit like a remote control. Price included two mens labour who also cleaned up the mess and bricked up the orginal flu hole. Very reliable system, would recomment to any one.
For those who want more information, our boiler was a Worcester Boiler that cost £650, they also offer an excellent service contract, which is cheaper than British Gas. They installed it all in one day, not too much mess and gave ...
helbru 25.05.2004 (26.05.2004)
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Ciao members have rated this review on average: somewhat helpful Review of Combination Boiler System
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whatever model took your fancy, fit it, and jump under that refreshing spray?WRONG!
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Advantages: Cheap. Easy to Install. Replacement parts readily available. Disadvantages: Its not a power shower. Cannot be used with a combi boiler
nothing about plumbing we asked a local one to do the honours, which took a couple of hours and then we were ready with our shiny new Gem 88. It is not suitable for people with combinationboilers installed in their house but is fine with the gravity fed systems that most people still have. The shower has adjustable fittings from 149mm to 154mm meaning that it should fit onto any pipe configuration if you already have a shower installed. The shower also uses Mira's anti lime scale technology meaning it is safe to use even in areas with very hard water supplies.
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