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Zeonda™ - Circulation Method - practical
application
3-pipe or 4-pipe system
For the consultant and the developer
For the fitter
Adaptation of existing water systems
New construction
Ahead of alterations of a building
Economy in both installation and operation phases
Products
Checklists and other form
3-pipe or 4-pipe
system
A 3-pipe system consists of a cold water
pipe and a hot water pipe plus a common circulation pipe.
All mixers are fitted with a return pipe through which a small
quantity of cold and hot water is drawn to the circulation
pipe. The circulation water is therefore a mixture of cold
and hot water. Normally the amount of cold recirculation water
is small, so there is no significant cooling of the hot water.
Flows are adjusted so that the circulation water is never
colder than 57°C.
A 4-pipe system has separate circulation
pipes for cold and hot water. Here all mixers have two return
pipes. Cold circulation water passes through an exchanger
in the sub-station that is connected to a cooler, and in this
way the whole cold water system in the building is kept below
20°C. Hot circulation water passes through an exchanger
in the sub-station that is linked to the district heating
network or to the property’s own furnace. A 4-pipe system
provides better temperature control and energy costs can therefore
be reduced significantly.
Connection diagrams for 3-pipe
and 4-pipe systems
VV = Warm Water VVC = Warm Water Circulation KV = Cold Water
KVC = Cold Water Circulation
FJV = District Heating Network KylVVX = Coolant Recovery System
For the consultant
and the developer
The consultant’s role is to design
a system that is as legionella-safe as possible. This is done
by bearing the following principles in mind:
- Never any stationary water
- Never cold water warmer than 20°C
- Never water colder than 57°C in the
circulation pipe
- Never water colder than 60°C delivered
from the heating station
- Never unsuitable storage tanks
- Never unsuitable choices of materials
The principles may be simple, but they still
require thought and careful attention in design work.
(1) Never having any stationary water means,
for instance, that there must never be any unused branch pipes,
not even temporarily. All possible instances of stationary
water must be eliminated. In the event of phased expansion
all branch pipes must be arranged so that water circulates
in them. Unconnected branches must never be longer than 40
per cent of pipe diameter. The hot water distribution unit
is fitted with a link to the circulation distribution unit.
If pipes that remain unused still have to be installed for
technical reasons, then they must be equipped with circulation
or be emptied. Towel driers should not be connected to the
hot water recirculation pipe, as they are a cooling source
that can reduce the hot water recirculation temperature below
a suitable level and can also be blocked, thereby forming
dead end pipes. Shower hoses should be drained automatically
using vacuum valves and should be short so that they cannot
be hung in such a way that the hose assumes a U shape. Check
that the shower handle is not designed with inner pockets.
(2) Never having cold water warmer than
20°C requires particular care when cold and hot water
pipes are placed together. The insulation and placement method
chosen must prevent unintentional heating of cold water ever
taking place. Take this into account when pipes are cast in
building elements.
 (3)
Never having water colder than 57°C in the circulation
pipe also means that the insulation and placement method must
be chosen with due care and consideration so that cooling
does not take place. Hot water recirculation pipes must be
insulated. It can be an advantage to use co-insulated double
pipes to transport hot water along with the circulation pipe.
(4) Never have water colder than 60°C delivered from the
heating station. The flow temperature must be adjusted so
that water in the hot water recirculation pipe is never colder
than 57 °C.
(5) Never have storage tanks where water
can be stationary and remain in the temperature range 20-60°C.
Avoid the stationary water volume in a pressure tank associated
with booster plants by using a specially designed flow valve
for connection to the tank.
(6) Never selecting unsuitable materials
means that the materials shown in the table below must not
be used anywhere in the installation where there is contact
with water. Attention should also be given to small details
like washers, O-ring gaskets, sealings, etc. in fittings and
pumps. The material chosen should also withstand repeated
decontamination work over a reasonable useful life. For instance,
50 autoclaving treatments should apply to shower hoses.
RISK-GENERATING APPROACHES AND UNSUITABLE
MATERIALS:
- Parts of plant containing gaskets made
of EPDM rubber
- Shower handles designed with inner pockets
- Water-saving aerated washers
- Expansion vessels for pressure tanks
- Towel driers connected to hot water recirculation
- Uninsulated pipes no matter whether for
hot water or cold water
- Unsuitable connection to fire water points
For the fitter
The task of the fitter is not just to build
the systems so that the criteria set out above are realised
or the completed plant.
The fitter is also responsible for the plant
during the actual construction period. Frequently the construction
period is long and there can be stationary water in the pipes.
It is important to give attention to this and either to arrange
circulation in the pipes or to empty them.
It is also important that the pipes are
cleaned and flushed with hot water before being used. In pipe
assembly consideration must be given to the expansion that
may take place during hot water decontamination and the necessary
expansion potential must be built in.
Adaptation
of existing water systems
Inventory procedure:
- Study of documentation and drawings
- Inspection of water supply system
concerning
- Temperatures
- Cold and hot water temperatures
at connection point/calorifiers as well as at different
tap points, especially the worst located tap point
- Temperature of any hot water
recirculation pipe at the calorifier
- Mixer
- Type and design concerning inner
pockets
- Materials in gaskets, etc
- Pumps
- Materials in washers, packing
boxes, etc
- Pipe and fitting materials
- Materials in pipes, fittings
and gaskets
- Dead end pipes.
- Distributors
- Occurrence, type and design
- Insulation
- Type and thickness as well as
condition
- Hot water recirculation system
- Occurrence, type, insulation,
flow and temperature
- Heating system
- Type of calorfication, technical
data
- Any storage tanks, high-pressure
tanks
- Size, temperature, placing, etc
- Water analysis
- Only carried out if there is doubt
about water quality, and the level of the analysis is
geared to the circumstances
- Check occurrence of legionella bacteria
in the water phase if there is suspicion of cases of
illness and before carrying out extensive installation
work in renovations
- Documentation of inventory result
Action programme
- Choice of 3-pipe or 4-pipe system
- Removal of dead end pipes
- Replacement of mixers with Zeonda™
mixers
- Replacement of unsuitable materials in
other parts of the system
- Installation/supplementary installation
of circulation pipes
- Installation of frequency-controlled
pumps for circulation
- Installation of sampling equipment,
Zeonda™ - Biofilm Chamber model
Installation procedure
- Water-filled pipes must be filled from
the sub-station with cold water under 20°C and hot water
above 60°C (Note: water in the hot water recirculation
pipe must maintain at least 57°C)
- Branches must be empty or fitted with
circulation
- Sampling points must be mounted at accessible
places
Decontamination must be carried out in connection with commissioning
- Operating instructions must be
framed in a clear and instructive way and must be communicated
to operating personnel
New construction
For the consultant and the developer
In the outline design phase it is specified that the facility
will be built according to the Zeonda™ - Circulation Method
and a choice of 3-pipe system or the 4-pipe system is made.
In addition, future monitoring and control requirements are
also described. In the system document phase the locations
of main components, such as the heat exchanger and sub-stations,
are shown. The system configuration is described and temperatures
and flows are fixed. Preliminary calculations are made of
power and energy requirements. In addition, the principles
for assembly work are laid down. In detailed design work the
pipe systems are placed and dimensioned. Equipment and products
are selected and located. Pressure falls are calculated and
values are determined for settings. Accessibility is checked,
and coordination with other installations takes place. The
control system is designed. Choose the 4-pipe system!
For the contractor
Assembly work is carried in such a way that pockets where
water can be stationary are avoided. Distribution pipes with
short branches are chosen; branches must not be longer than
40 per cent of pipe diameter. If water is used in pressure
tests or similar work during the assembly phase, the components
involved must be emptied after test or connected to the circulation
system. The utmost cleanliness is sought so that no foreign
objects enter the pipe system. Pipe ends must always be plugged.
Pipes must be mounted so that they are accessible for service
and inspection. After assembly and testing the pipe system
must be decontaminated. Adjustments must be made to obtain
the correct flows and temperatures in the system. Operation
and maintenance instructions describing the design and care
of the system and operating data are framed.
Ahead of alterations
of a building
Inventory procedure and action programme,
see the Zeonda™ - Circulation Method in the adaptation
of existing water systems. Link.
Outline design and installation
- In the outline design phase the present
situation and the demands on the new system are examined
- The system phase describes what alterations
are to be made to existing systems. Placings are selected
for our equipment, and power and energy requirements are
calculated. Temperatures are also specified.
- Detailed design then describes
the placing of new pipes and what has to be removed
Procedure for renovation of water supply
systems
- Dimensioning of pipes and pumps
- Securing pressures in the system
Economy in
both installation and operation phases
The Zeonda™ - Circulation Method is
a continuous decontamination method that prevents legionella
growth in an effective and environment-friendly way. In the
outline design phase a total cost for both installation and
operation should be calculated. In comparisons with hot water
flushing, which is an acute method in common use today, account
should be taken of the high water and heating costs and that
fact that this method is very labour-intensive. Nor does the
decontamination have any lasting effect. In comparison with
alternative methods for continuous water treatment account
should be taken both of the long-term decontamination effect
and of environmental impacts on people, pipe systems and nature.
Investment costs and operating costs should be weighed against
one another.
When the Zeonda™ - Circulation Method
is installed in a building, additional costs may be incurred
for:
- Possible cost increase for Zeonda™
mixers compared with conventional mixers
- Circulation pipes from mixers to hot
water recirculation
- Installation of biofilm chambers
- In a 4-pipe system with cold water
recirculation, costs for installation of equipment to maintain
cold water cooled
Normally, operation of the Zeonda™
system requires no work effort by operating staff and no costs
for chemicals or similar purposes. The decontamination of
the whole system at commissioning after interruptions or new
installation, for instance, can be handled solely from the
sub-station and requires no personnel placed out in the system.
Products
Products linked to the method
- Specially patented mixers with circulation
through both cold and hot water and with automatic draining
- Spiral shower hoses that drain automatically
after use
- Sampling equipment in the form
of a biofilm chamber
Checklists
and other form
Checklists and other forms will be posted
on our website as they are finalised.
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