Combination boiler or
combi boilers come being one of the most common types of boilers used in UK for
a reason. Unlike the system and conventional units, the combination boilers are
designed to be an all in one unit which produces hot water for taps and central
heating in order to cut down the use of storage tanks or cylinders, thus
occupying the least space required to house the boiler. Additionally on a
comparison, the installations are much easier and faster than any other boiler
The combi boilers
operates by using the water from the main supply that results in stronger water
pressure and ensures that you would never be lacking on hot water again. The modern
highly efficient units come, being a stainless steel condensing boiler with an
inbuilt heat exchanger that operates in order to serve the customers with hot
There are two main
reasons behind the combi boilers great and powerful efficiency i.e. these units
have high operating efficiency and low internal water volume. This means when
in summer days you don’t need space heating you are only paying to heat water
which is domestically required.
Combi boilers are
designed to be manufactured with two independent heat exchangers, one of which
carries a pipe to the radiators while the other one carries a pipe to the hot
water supply. As soon as you turn the hot tap on, your boiler fires up to heat
water and a valve gets opened to let the water flow through the network of
Combi boilers are made
to operate using a sealed or pressurized system because the water expands when
heated and thus an expansion area needs to be incorporated into the heating
system. When the heated water
in the central heating system expands, it cannot be compressed and thus
consequently presses against the expansion vessel’s internal membrane.
However, fitting an
external expansion vessel is relatively a simple thing to do.
- Identify your
old expansion vessel- For the first step you need to locate the expansion
vessel which is usually located right next to your boiler and is connected to
it. Once you are done with identifying the vessel, record the dimensions and
connections in order to ensure that you get the perfect fit in the new vessels.
- Turn everything
off- Close the shut off valve in order to turn the water supply to the heater
off and the wait for some time for the system to cool down.
- Drain the water-
Now drain out the water from the system to reduce the water pressure. This can
be done by opening the bleeder valve. You are recommended to use the bucket to
collect the water.
- Disconnect the
expansion vessel- Carefully disconnect the expansion tank and keep an eye on
the pipes and fittings that they do not get damaged while removing the
- Pressurize the
expansion vessel- When you turn off the water supply just make sure that the
pressure reading the tank is 0. Now fill the tank with air up to 12 psi or
according to the amount indicated on the manufacturer’s instructions.
- Check the
pressure- Check the pressure in the water tank using the pressure gauge.
- Teflon tape- Now
wrap a Teflon tape around the ends of the connectors except on the beginning of
- Install the new
vessel- Install the new vessel in the same position as the old one and
carefully connect it to the heater system, however ensure the connectors are
screwed on tight.
- Have a check- Now
check the system to ensure there is no leakage.