Combi boilers were designed for small properties and flats. They save space because you do not need any form of water storage, so the cupboard where the hot water tank use to be can now be used for extra storage, and as we all know we all need extra storage these days. You also don't need a cold water storage tank in the loft area.
Combi boilers now have a higher hot water output compared to when they were first introduced. The first models gave you around 9.8 litres of hot water at a 30 degree rise, but the true output was around 8 litres at a 40 degrees rise, which is what we all need for the water to be hot enough to use.
When the first Combi boilers were fitted, most were fitted with the gas supply being to small, most were fitted with a 15 m gas supply, when they should have been fitted with a 22 m supply. They worked but the hot water always was lower than the speciation. Even today some are still fitted with an undersized gas supply. They all should have a 22 m supply within one meter of the boiler.
With today's Combi boilers some now produce up to 20 litres of hot water, which is a big improvement on the earlier models. These boilers have come a long way from the first ones.
With any Combi boilers you need a decent incoming water supply, if your water pressure is not very good then a Combi is not for you. There are now booster pumps that you can fit to the water mains, but these are expensive and produce around 12 litres of water, also they can be very noisy.
If you have a heating system in your property and are thinking of converting over to a Combi boiler, there are a few things you have to consider. The first is, is your system low pressure, to find out you should have a small tank in the loft, this is normally fitted beside the big cold water tank.
If you have the small water tank, this supplies water to the heating system, so the heating is working on low pressure. If you now want to fit a Combi boiler and remove all the tanks you may be at risk of a leak, because Combi boilers work on high pressure and your pipe work may have been ok on low pressure, but now you are putting extra pressure on the system, leaks can happen. Not always but they do happen.
As a guideline if you're heating system is over 10 years old you are more at risk of a leak. The worst part is sometimes the leak does not show up straight away, it could take a couple of months to appear. Then you have the task of finding it so it can be repaired. You will know if you have a leak because you will notice the pressure on the boiler will keep dropping and you will need to top it up.
If you already have a system that is pressurised then fitting a Combi boiler should cause you no problems, unless you need to top up the system pressure regular.
The other annoying problem that we come across a lot is, when someone is using the hot water let say in the bathroom, when someone opens the hot tap in the kitchen, the bathroom supply reduces sometimes down to a dribble, this common, even with the high output models.
These are just a few of the things we come across as installers of Combi boilers, in general they are a good boiler, but it can take a little time to get tousle to them. You have a constant supply of hot water, you will never run out.
When you open the hot tap the boiler then gives priory to the hot water, you may find that the heating side goes a little cool, but as soon as the tap is closed the heating will come back on and reheat to your desired temperature.
All in all, Combi boilers work well and give you more storage space.
One last thing before we end, Combies and all boilers need to be serviced at least once a year, gone are the days when you could leave the boiler till you were ready to have it serviced. Today's boilers have so many different parts that need to be checked. Ask your local gas safe engineer to book you in his dairy for a regular service, if you don't you could find yourself with an expensive repair bill, even the need to replace the boiler.