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Domestic
hot water Copper Cylinders by Gledhill
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| You may find the terminology used to
describe a hot water cylinder a little confusing.
Direct....
Indirect.... Combination..... Solar.... What does this mean? Click on
your question below -
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....It all depends where the
cylinder gets it's heat from.
Please note:
Information contained on this page is intended to assist with your
understanding of cylinders and terminology. It does not represent a definitive
description of each and every product available. If in any doubt, please call
for assistance - we will be pleased to help.
A DIRECT CYLINDER |
| A Direct Cylinder is heated by a source
located within the cylinder - such as an electrical immersion heater. Because
the Immersion Heater is heating the water 'directly' the cylinder is called a
'Direct Cylinder'. In a direct cylinder there are no other external heat
sources. The diagram
shows a 'direct' cylinder with two side mounted immersion heaters.
Please note: Variants may
include:
- a side mounted single
immersion heater boss
- a top mounted single
immersion heater boss
- one side mounted and one top
mounted heater boss
- two side mounted heater
bosses
- more than two heater bosses
You should specify the
number of heater bosses you require and their desired position. The diagram
is only intended for the purpose of explanation.
Immersion heater elements are not normally fitted
or included in the price of a cylinder and should be specified if required. |
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| An
INDIRECT CYLINDER |
| Although heat is imparted to the cylinder by an
internal heat exchanger, the heat source is actually remote - such as a gas
boiler, solar panel, wood burning stove, Aga etc. etc.. It is therefore deemed
that such a cylinder is 'Indirect'. Indirect
cylinders may be fitted with immersion heaters as a supplementary heat source,
but they are still known as 'Indirect'.
An Immersion heater boss may be
fitted through the top of the cylinder. You should specify your requirement.
Immersion heater elements are not normally
fitted or included in the price of a cylinder and should be specified if
required. |
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COMBINATION CYLINDERS |
| A gravity-fed household copper cylinder is
supplied typically from a tank sited above the cylinder - often
located in the loft. The higher above the cylinder, the greater the 'head' of
water and hence the higher the gravity pressure. (Please refer to Section on
Grades of Cylinder to understand more)
Where the property is unable to accommodate a header tank (for example in an
apartment or flat) the header can be accommodated literally on top of the
cylinder and is built into the unit. The cylinder therefore combines the
'header' and the 'storage' elements and becomes a COMBINATION cylinder.
Note: The output water pressure from a
combination cylinder is often poor due to the small distance (head) between the
header, the cylinder and the outlet (i.e. A tap).
Combination Cylinders may be Direct, Indirect or Economy
7. They simply combine the header function.
Immersion heater elements are not normally fitted
or included in the price of a cylinder and should be specified if required. |
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| SOLAR
CYLINDERS |
| This is a cylinder that has been configured
to accept solar energy. Cylinders we provide can often have an additional
'solar coil' fitted in order to add solar energy to the cylinder when
available. The 'solar coil' is a particularly high
efficiency heat exchanger designed to add as much of the relatively low solar
gain.
Solar coils may be added to standard cylinders to
supplement energy input.
Also see:
Renewable energy systems (such as solar,
heat pumps, geothermal etc) are becoming popular. However, it continues to be
relatively expensive to install - albeit you recover the cost over the long
term.
Many discerning householders are now fitting cylinders that are 'solar
ready' in order that future addition of a solar (or any other renewable
energy) system will present minimal disruption and eliminate the need to
change major hardware - enabling an easily expandable system. |
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| ECONOMY 7
Cylinders |
| An Economy 7 cylinder is designed to
exploit 'off-peak' electricity - typically available throughout the night. Because you are heating your cylinder
overnight it is important to not to loose the stored heat. Economy 7 cylinders
are therefore fitted with an extra thick jacket of insulation - typically 60mm
thick, as opposed to the 30mm jacket on a standard cylinder.
Economy 7 cylinders are available as direct and
indirect
models.
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Configuring or Specifying a Cylinder to your own design
To fully configure a cylinder to your requirement also
see information about heat exchangers -
Gledhill cylinders are fitted with a 30mm jacket of
rockwool insulation (with the exception of the Economy 7 models that have a
60mm jacket). At your request it is possible to have a 60mm thick jacket
fitted to any cylinder - greatly enhancing the performance of the insulation
and improving economy.
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| Grades of
cylinder |
| Domestic Cylinders are available in three
grades. The grades refer to the pressure of water they can withstand from the
header tank (the pressure created by the height of the header tank above the
cylinder).
In simple terms, this translates to
the gauge (thickness) of copper used in construction. Do not confuse a
gravity
cylinder with mains pressure or unvented cylinders. Connection of mains
pressure water to any cylinder designed for a gravity feed can be extremely
dangerous. |
Grade 1 - Can withstand a
25 metre head of water |
| Grade 2 - Can withstand a 15 metre
head of water |
| Grade 3 - Can withstand a 10 metre
head of water It is possible to supply a gravity
cylinder that will withstand a 31 metre head. This is achieved by doming the
bottom of the cylinder. These cylinders sit in a ring mount. Please specify
the working head of the system into which the cylinder will be installed.
A normal domestic cylinder is
usually a Grade 3. (All prices quoted on this website refer to Grade 3
cylinders unless otherwise stated) |
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How are cylinders insulated? |
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Insulation is absolutely essential on a 'hot water' cylinder. It is
ridiculous to consider heating a large volume of water only to let it go
cold again. Many older properties will indeed have an un-lagged cylinder,
but their owners are simply burning money each and every day as they warm
the water then allow the heat to escape. It is almost a blessing when an old
cylinder fails, as the replacement will invariably arrive lagged and go on
to demonstrate the difference in efficiency over the following years. |
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But the term 'insulation' can be a little misleading. Many manufacturers try
to utilise the spray-on properties of a polyurethane foam as a quick (if not
entirely clean or green) and cheap method of apply an insulating layer to the body of a
cylinder. Indeed, there are so many about these days that one could be
excused in thinking this is a best or only way the job might be done. But
no, it is simply the cheapest, easiest, quickest way. But chemical foam insulation is not all it's cracked up to be.
Studies have revealed that chemical foam insulation can lose up to 40% of
its efficiency in a relatively short period of time as it oxidises through
repetitive cycles of warming and cooling. So the advantages of using such a
material (namely cost and convenience for the manufacturer) result in
eventual waste to the end user. But of course, you
are now the owner of said object and unlikely to have the means to check
efficiency, so as the problem goes unnoticed up go your running costs. |
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The foam utilised to insulate cylinders is similar in composition to the
foam that used to be used in furniture, yes the stuff that gives off noxious
and lethal fumes in the unfortunate event of a fire, so the potential
repercussions are worthy of serious consideration.
All Gledhill cylinders are fully insulated to British Standard using a
premium insulation based on the mineral rockwool. |
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Patented as Flexilag,
the insulating medium comprises either a 30mm or 60mm (depending on
the cylinder specification) slab of rockwool sandwiched between two
reflective aluminium layers. This is held in position by a
tight-fitting heavy-duty polythene jacket. The result is a premium
quality insulation giving superb heat retention and minimal standing
losses. |
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| Gledhill are proud to boast that
their cylinders use clean bio-degradable rockwool Flexilag to keep your
water warm. |
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When you chose to change your cylinder opt for the natural premium choice -
Flexilag. |
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