Multi point water heater ( Including combination
"combi" boilers.)
In the majority of houses in this country,
there are two different types of hot water
system.
The Combination boiler that
heats radiators in the central heating system
and also give you hot water all from the same
boiler. The other is the more traditional system
where home owner will see two separate appliance
the boiler and the hot
water tank.
Different ways of heating the domestic hot
water need to be understood in order for the
home owner to identify theirs and effect any
maintenance needed. It will also be necessary to
asses any type of shower you may wish to
install.
The types of domestic water heating can be
broken down into two categories. 1. Hot water is
stored in a cylinder. 2. Cold water is heated on
demand.
Stored hot water:
This category, although the hot
water is always stored in a cylinder or tank,
can be further divided into three categories.
Immersion:
An immersion heater
is an electric element which screws into the hot
water tank. This element is wired to the mains
electrical supply via an isolating switch, a
thermostat to control the temperature, and
sometimes a timer which enables you set the
times you wish to have the water heated. Using a
timer, together with a well insulated tank, it
is possible to heat the water when electricity
rates are at their cheapest ( Economy, 7 between
12 midnight and 7 am), and use it during the
day. It is worth remembering that the hot water
from an immersion heater is always drawn from
the top of the cylinder, where it has risen over
the cold water underneath (convection current).
The cold water, fed to the tank from underneath,
gives the hot water the pressure it needs to
leave the cylinder, from the top, when required
by the taps. Some tanks can contain two
elements, giving you a choice as to how much
water you want to heat up at any one time. It is
quite rare nowadays for the immersion heater to
be the only method of domestic water heating in
a home and the immersion is generally used as a
back up to one, or both, of the following two
methods.
All materials and tools
necessary for the maintenance of your hot water
system are available at
www.paceplumbing.co.uk
Direct boiler system:
In older houses, with a direct
system, the hot water may be stored in a square
galvanised tank. The principle is the same.
Using the diagram above as a reference, another
cold water pipe runs from the base of the
cylinder to the boiler. The boiler heats the
water and returns it to the tank higher up. When
hot water is drawn from the tank, it is replaced
by cold from the cold tank, which in turn is fed
to the boiler. This is direct heating of the
water by either a) the immersion or b) the
boiler. The hot water is simply stored in the
tank.
To identify a direct water
system you will find the end of the vent pipe
fixed above your cold water tank. This allows
for any stem expansion in the cylinder to flow
directly into the cold tank and not damage the
cylinder or cause air locks in the system.
All materials and tools
necessary for the maintenance of your hot water
system are available atwww.paceplumbing.co.uk
Indirect boiler system:
With an indirect water system,
the copper hot water cylinder contains a coil of
pipe. This coil forms part of a run of pipework
attached to the boiler. It is heated directly by
the boiler. Indirectly, it heats the water in
the cylinder. The coil, or "heat exchanger"
forms part of the central heating circuit, and
its water heating abilities are purely a
by-product of its main function, which is to
heat the radiators
This heating is called the "primary" circuit,
the pipes running to and from the boiler are
called the primary flow and return. The hot
water tank operates in exactly the same way as
the direct system.
To identify an indirect system,
you will see two water tanks in your loft. The
second, smaller one, is the feed for the primary
circuit. It will top up the system when
necessary and will also have a vent pipe over
the top. The level of water in this tank will be
considerably lower to allow the water to rise as
it expands when it gets hot without overflowing.
Both of the boiler systems above
are called "vented" systems. Because of this
vent pie, they are open to atmospheric pressure
and operate as "low pressure" systems. They both
call for cold water from a cold tank stored,
generally, in the roof space. Because they are
low pressure, sometimes the flow from the taps
etc is not as great as one might like and pumps
can be introduced, both for the domestic hot
water and the heating, to give greater flow.
Unvented system
In 1989 unvented systems were
allowed into general use.
All materials and tools necessary
for the maintenance of your hot water system are
available at
www.paceplumbing.co.uk
The unvented system operates
purely from mains water. The principles of
heating are the same, but because everything is
under the pressure of the mains water, flow
rates are much better...Many safety devices are
built into this system to accommodate for the
greater pressure and expansion of the water.
Although a small tank may be found in the loft
for venting and feeding your central heating, No
cold water storage tank is necessary.
Hot water cylinder capacity
varies between 25 gallons to 50 gallons for
normal domestic supply, with the larger being
enough to supply an average family for a day.
Most cylinders are made from thin copper and you
should make sure your cylinder is well lagged to
prevent heat loss. Pre-lagged cylinders are
available, which are coated with foamed
polyurethane.
All materials and tools
necessary for the maintenance of your hot water
system are available at
www.paceplumbing.co.uk
Thermal store system:
A revolutionary new concept
(British development) which reverses the
indirect principle detailed above. The boiler heats
the water and sends it to a cylinder, and then
on to the central heating. On its way it heats,
in the cylinder, via a very efficient heat
exchanger, the mains fed water for the taps. An
integral feed and expansion tank can be
incorporated on top of the main tank. This
system is so efficient, a thermostatic
(cold/hot) mixer valve is built into the
pipework before the hot reaches the taps or
shower. For the two part tank to be viable, the
system must be installed at the highest possible
level in the house, however it can be installed
with the feed tank separately installed in the
loft. This system is now available with its own
dedicated boiler allowing the central heating to
be switched off in summer. The ultimate in
combination systems.
All materials and tools
necessary for the maintenance of your hot water
system are available at
www.paceplumbing.co.uk
Single point water heater:
Single point water heaters come
in both gas and electricity "flavour" and are
sited, generally, next to the point they serve.
In the case of an electric heater (an electric
shower is an example) They must be wired to the
mains via an isolating switch. A heater up to
3kw can be plugged into an ordinary 13 amp
socket, but that socket must not be in reach of
the water outlet. Above 3kw, the heater must be
wired directly to the fusebox with a double pole
isolating switch in the circuit. In the kitchen,
this switch may be wall mounted, again, out of
reach from the sink, but in the bathroom it must
either be a cord operated switch on the ceiling,
or an isolating switch outside the room.
Differing cable sizes are needed for differently
rated heater and checks should be made for the
particular heater you wish to install.
Single point gas heaters of the
old "Ascot" type are based on a thermostat
sensing the arrival of cold water into its
reservoir when water is asked for from a tap. As
soon as the tap is open, fresh cold water comes
in to replace that being drawn from the tap.
This triggers the ignition of the burners which
heat the water. The hot water rises to the top
and is available immediately.
All materials and tools
necessary for the maintenance of your hot water
system are available at
www.paceplumbing.co.uk
Multi point water heater: (Including combination
boilers)
The most common of these is a
combination boiler. These heaters operate on the
same principle as above, but can serve many
points (taps, washing machine, etc) as well as,
in the case of a combination boiler, supplying
the hot water for a central heating
system
An ordinary multi point heater will only supply
water to the domestic water system but can be
installed in conjunction with an ordinary
central heating boiler.
A combination boiler combines
the functions of a central heating boiler and an
instantaneous multi point water heater, giving
priority to the supply of domestic hot water.
Combination boilers can be direct or indirect in
much the same way as the cylinders above, using
calorifiers (heat producers) to heat water
passing through them.
All materials and tools
necessary for the maintenance of your hot water
system are available at
www.paceplumbing.co.uk
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a great way to ensure that your carpets or
hard floor surfaces are fully protected for
the duration of your DIY work or indeed any
refurbishment or alteration work that
results in heavy foot traffic or spillage
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