As you may have read in one of the previous posts, combi (or combination) boilers possess a lot of benefits over the more conventional, every day boilers. Despite their many advantages they still have their own drawbacks (although few), and these will vary depending of the quality/price. In most stores you get what you pay for, the higher the value the greater the quality, just remember to compare the market before purchasing.
1. Potential heat exchanger scaling
Over time if you are supplied with hard water from your water company it is highly likely that the DHW (domestic hot water) heat exchanger will scale. This is the same however for all boilers, but you will find the newer models of combi boiler will have been designed to further reduce the risk of scaling.
This presents you with two options in the future, one to replace the equipment which can work out quite expensive, or two to replace the boiler completely.
If you look to replace the necessary parts, just bear in mind that this will reoccur in the future and may be worth upgrading the boiler to reduce the risk of scaling further. The other natural solution would be to change to a soft water supplier to again reduce the potential.
2. Electric immersion heaters are a no go
If a boiler were to some point fail with a regular water tank installed you have the opportunity to purchase an electric immersion heater just for emergency purposes. This can save you money for example if it occurs over the weekend or bank holiday when most plumbers would be charging more.
If a combi boiler were to go wrong for some reason, as there is no tank with this type of central heating system it is not possible to use an immersion heater and a plumber call out could well be required.
3. Gas pipe incompatibility
Due to regulations when installing combi boilers, some incompatibilities with the diameter of the gas pipe could occur and this may need to be upgraded as a result.
4. Shower or a bath person?
Combi boilers provide highly pressurized water to both hot and cold taps, but older models tend to have a slower rate of hot water than more modern boilers. As a result there will be plenty of water for a shower but a bath will take a lot longer to fill up.
5. No instant hot water
Combi boilers still suffer from the same problems as other boilers, although they are a lot better at producing near ‘instant hot water’ than most. If the boiler is positioned quite a way from the tap being used, it can take a good few minutes before the hot water will come through. This isn’t so much a problem for showers or baths, but if you are only using it to quickly wash your hands or face it can become a hindrance.
Overall however Combi boilers have a fairly limited number of disadvantages which are going to impact performance when compared to other types of boilers.