We have compiled a number of questions in our FAQ on the topic AkoTec solar heating systems for you. The questions
are divided into different sections: General, Tubes, Installation and Financing.

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Where can I purchase AkoTec collectors? Please do not hesitate to contact us and fill out the planning sheet. We will forward you to our
What different sizes are available? We can offer Solar Keymark certificated collectors with 5, 10, 20 and 30 tubes.
Which medium flows through the collectors? A water glycol mixture flows through the collectors and serves as a heat transfer medium. This
fluid does not freeze up to a certain temperature.
Is it possible to use a low-cost antifreeze
No, it is not possible because the AkoTec antifreeze fluid is a highly temperature
resistant glycol. The entitlement to the warranty would be cancelled when using another fluid.
Is it recommended to pump the chlorine water
from a pool heater directly through the collectors?
No, the copper of the manifold may be damaged by chlorine content and corrodes
faster. We recommend the use of swimming pool heat exchangers to prevent corrosion.
Is it possible to operate the collectors with water? When operating the collectors with water, the water must be prepared, decalcified
and desalinated. Furthermore a closed circuit must be existent and not an open drain back.
What are direct flow and heat pipe collectors?
Where is the difference?
The main difference is the tube. As the name suggests, the direct flow tube is flowed
through directly by the heat transfer medium. Only the manifold of the heat pipe,
however, is flowed through by the fluid. The tube has an own circuit.
The direct flow collector has various mounting options: pitched roof, flat roof, facade
and balcony, elevation. When mounting the heat pipe mind an angle between 5 °-75 ° and
vertical tube position. The collectors must be assembled elevated within that angle or
on a pitched roof only.
Do AkoTec collectors overheat? An overheating can be avoided through a professional system planning and a sufficiently
dimensioned storage tank. We recommend for systems with an irregular heat consumption
(regular heat consumption: process heat, pool heating) and especially for private
applications the heat pipe collectors. They possess an overheating protection, optionally
at 100 °C or 160 °C depending on the product version.
What happens with surplus energy? Either you choose the heat pipe with the automatically shut down function or you have to
plan a big dimensioned storage tank for saving the surplus energy.
Do building insurances include
hail damages?
AkoTec collectors are hail tested. Please contact your insurance agent.
Are vacuum tube collectors suitable for
upgrading a single-family house?
AkoTec collectors suite for upgrading existing heating systems as well as
supporting conventional heating systems.
How is the efficiency factor of AkoTec
full vacuum tube collectors in comparison
to flat collectors?
At the zero point, the efficiency factors are almost equally. More important is
a height of the efficiency factor at the operating point. At an average temperature
of 80 °C the efficiency factor of flat collectors amount 30 %. The AkoTec full vacuum
tube collectors have with 55 % a significantly higher performance.
(Get to know more about this topic in our comparison of the efficiency factors!)
How is the performance
during the winter time?
The collectors produce yields even during the winter time and in diffuse light.
This is due to the inner pipe system which is 100 % vacuum isolated. The vacuum
tube has no heat loss and does not cool down in contrary to common flat collectors.
How are the flow temperatures? The collectors reach up to 120 °C under optimum sun radiation.
Do the tubes pollute? No, the tubes are coated with a nano powder silicon dioxide and repel dirt.
When do the collectors begin to work? The vacuum tube collectors produce yields even in diffuse sun light. Yields are
generated from a sun radiation of 250 Watt.


How is the performance of one tube? The tubes with one side coating have a performance of 80 Watt (df) and 75 Watt (hp)
(data from Narva). In connection with a reflecting area the double coated tubes can
generate up to 110 Watt performance.
Which tube types are available? As the name suggests, the direct flow tube is flowed through directly by the heat transfer
medium. Only the manifold of the heat pipe, however, is flowed through by the fluid. The
tube has an own circuit. The direct flow collector is very versatile in relation to its
mounting options. Everything is possible – from pitched roof, to flat roof mounting, to
facade or balcony mounting up to elevation. Please mind that the heat pipe must be
elevated between an angle of 5 ° – 75 °. Therefore the collectors can only be assembled
elevated in that angle or on a pitched roof. The tubes are available on request in the
following lengths: 0,8 m, 1,5 m and 1,75 m. The standard length is 2m.
What is the absorber and the coating made of? The absorber plate is made of copper and coated with Titan-Nitrit-Oxyd. In fact there are
multiple layers. See (TINOX energy Cu): http://www.almecosolar.com/Brochure/tinox_energy_new_de.pdf
What is the difference between Standard and Power Tubes? In contrary to Standard Tubes, Power Tubes are double coated and used for reflector collectors
or if the collector is mounted on a reflecting area such as a bright facade or a tin. It is
possible to generate up to 40 % more energy yields by using the reflections of the sun light.
Does the tube lose its vacuum? No, as long as the tube is not damaged it does not lose its vacuum and 25 years of stable energy
yields are ensured.
How is it ensured that the vacuum stays durably? This is ensured by the innovative and sturdy NARVA glass-to-metal connection which does not punish
the glass through movements. Therefore the glass-to-metal connection resists to powerful axial and
transverse forces effortlessly.

The NARVA solution is protected by patent law:
What is the difference between Sydney tubes and full vacuum tubes? The Sydney tubes have a glass tube as protection of the inner tubing. Therefore the tubing system is
in the atmosphere and ages. The Power decreases already after 2 years. The tubing system of the
NARVA tube is vacuum isolated. Materials do not age inside of vacuum. This is why our collectors
generate stable energy yields over 25 years.


Are the mounting options of heat pipe and direct flow identic? No, the heat pipe collector needs to be assembled between an angle of 5° – 75° and with vertical tubes
to ensure that the condensed fluid flows back in the tube. In contrary the direct flow collector can be
assembled on a flat roof, facade/balcony and elevated. Even the position of the tube is freely selectable.
Which mounting options are possible with the direct flow collector? The direct flow collector is mountable on a flat roof, facade, balcony and elevated. Even the position of
the tube is freely selectable.
Which collector is suitable for facade and balcony mounting? The direct flow collectors are perfectly suitable for balcony and facade mounting because they can be
assembled flat on a wall with horizontal tubes. The heat pipe collectors can be assembled on a
facade/balcony too but they have to be elevated to an angle between 5° – 75° with vertical tubes.
What type of mounting is recommended in snow areas? We recommend the facade mounting.
How is the flow ensured when mounting the collector horizontally? The flow works despite horizontal mounting because the fluid is pumped through the collector with a pump.
Is it possible to use the collectors as an in-roof system or brick replacement? Yes, we can offer an in-roof solution for our collectors, that are mounted like a roof window.
How do I change the tubes? Direct flow system: It is particularly important to empty the whole system because the tube is tethered
wet. Afterwards take off the housing cover and remove the spring clips. Now you can dismount the tube
easily. Heat pipe system: Remove the housing and pull the tube 10 cm back. Take out the tube backwards.
It is not necessary to empty the system because the tube is dry tethered.
How close to a boarder can I mount the collector on a flat roof? Please mind a minimum distance of 15 cm.
What is the maximum pressure for the collectors? The collector can be perfused with a maximum pressure of 10 Bar.
Where is the flow and where the return? From the heat generator the flow is always hotter side and the return the colder side. The collector is
the heat generator in a solar system. The installation of flow and return is freely selectable.
Where has the sensor pocket to be mounted? The sensor must be mounted at the flow.
What does the reflector consist of? It consists of a white coated plastic aluminium plate.
Is it necessary to mount the air vent on the highest position in the solar system? It is not necessary to mount the air vent on the highest point of the system when the system is filled with
a filling pump. The filling pump flushes air inclusions out of the system. We recommend installing air vents
on large systems (more than 15 KW/120 tubes).The solar fluid gases a bit out on heating because it can
absorb less air in hot state than in cold state. The air vent is used as an air buffer container and the solar
fluid includes the air again in cold state. The air vent must not be provided with automatical air vents.
How long does it take to remove air inclusions completely with a flushing and filling pump? This depends on the flushing and filling pump. We recommend a flushing time of 30 – 45 minutes in a
single-family house.
How need fittings to be sealed, teflon tape or hemp? We recommend the use of Solar-Fermit with hemp to seal the fittings properly. Teflon tape is not suitable because of the high thermal load.
The heat pipe collectors can be elevated up to an angle of 5 °, is this sufficient? In theory it is sufficient but on construction site it must be planned 10 ° because the tolerances are larger
and so the 5 ° can be fulfilled.


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